2023-10-17 03:46:05

by Anshul Dalal

[permalink] [raw]
Subject: [PATCH v5 1/2] dt-bindings: input: bindings for Adafruit Seesaw Gamepad

Adds bindings for the Adafruit Seesaw Gamepad.

The gamepad functions as an i2c device with the default address of 0x50
and has an IRQ pin that can be enabled in the driver to allow for a rising
edge trigger on each button press or joystick movement.

Product page:
https://www.adafruit.com/product/5743
Arduino driver:
https://github.com/adafruit/Adafruit_Seesaw

Reviewed-by: Conor Dooley <[email protected]>
Reviewed-by: Krzysztof Kozlowski <[email protected]>
Signed-off-by: Anshul Dalal <[email protected]>
---

Changes for v5:
- Added link to the datasheet

Changes for v4:
- Fixed the URI for the id field
- Added `interrupts` property

Changes for v3:
- Updated id field to reflect updated file name from previous version
- Added `reg` property

Changes for v2:
- Renamed file to `adafruit,seesaw-gamepad.yaml`
- Removed quotes for `$id` and `$schema`
- Removed "Bindings for" from the description
- Changed node name to the generic name "joystick"
- Changed compatible to 'adafruit,seesaw-gamepad' instead of
'adafruit,seesaw_gamepad'

.../input/adafruit,seesaw-gamepad.yaml | 60 +++++++++++++++++++
1 file changed, 60 insertions(+)
create mode 100644 Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml

diff --git a/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml b/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
new file mode 100644
index 000000000000..3f0d1c5a3b9b
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
@@ -0,0 +1,60 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id: http://devicetree.org/schemas/input/adafruit,seesaw-gamepad.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: Adafruit Mini I2C Gamepad with seesaw
+
+maintainers:
+ - Anshul Dalal <[email protected]>
+
+description: |
+ Adafruit Mini I2C Gamepad
+
+ +-----------------------------+
+ | ___ |
+ | / \ (X) |
+ | | S | __ __ (Y) (A) |
+ | \___/ |ST| |SE| (B) |
+ | |
+ +-----------------------------+
+
+ S -> 10-bit percision bidirectional analog joystick
+ ST -> Start
+ SE -> Select
+ X, A, B, Y -> Digital action buttons
+
+ Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
+ Product page: https://www.adafruit.com/product/5743
+ Arduino Driver: https://github.com/adafruit/Adafruit_Seesaw
+
+properties:
+ compatible:
+ const: adafruit,seesaw-gamepad
+
+ reg:
+ maxItems: 1
+
+ interrupts:
+ maxItems: 1
+ description:
+ The gamepad's IRQ pin triggers a rising edge if interrupts are enabled.
+
+required:
+ - compatible
+ - reg
+
+additionalProperties: false
+
+examples:
+ - |
+ i2c {
+ #address-cells = <1>;
+ #size-cells = <0>;
+
+ joystick@50 {
+ compatible = "adafruit,seesaw-gamepad";
+ reg = <0x50>;
+ };
+ };
--
2.42.0


2023-10-17 03:46:20

by Anshul Dalal

[permalink] [raw]
Subject: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Adds a driver for a mini gamepad that communicates over i2c, the gamepad
has bidirectional thumb stick input and six buttons.

The gamepad chip utilizes the open framework from Adafruit called 'Seesaw'
to transmit the ADC data for the joystick and digital pin state for the
buttons. I have only implemented the functionality required to receive the
thumb stick and button state.

Steps in reading the gamepad state over i2c:
1. Reset the registers
2. Set the pin mode of the pins specified by the `BUTTON_MASK` to input
`BUTTON_MASK`: A bit-map for the six digital pins internally
connected to the joystick buttons.
3. Enable internal pullup resistors for the `BUTTON_MASK`
4. Bulk set the pin state HIGH for `BUTTON_MASK`
5. Poll the device for button and joystick state done by:
`seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)`

Product page:
https://www.adafruit.com/product/5743
Arduino driver:
https://github.com/adafruit/Adafruit_Seesaw

Driver tested on RPi Zero 2W

Reviewed-by: Thomas Weißschuh <[email protected]>
Signed-off-by: Anshul Dalal <[email protected]>
---

Changes for v5:
- Added link to the datasheet
- Added debug log message when `seesaw_read_data` fails

Changes for v4:
- Changed `1UL << BUTTON_` to BIT(BUTTON_)
- Removed `hardware_id` field from `struct seesaw_gamepad`
- Removed redundant checks for the number of bytes written and received by
`i2c_master_send` and `i2c_master_recv`
- Used `get_unaligned_be32` to instantiate `u32 result` from `read_buf`
- Changed `result & (1UL << BUTTON_)` to
`test_bit(BUTTON_, (long *)&result)`
- Changed `KBUILD_MODNAME` in id-tables to `SEESAW_DEVICE_NAME`
- Fixed formatting issues
- Changed button reporting:
Since the gamepad had the action buttons in a non-standard layout:
(X)
(Y) (A)
(B)
Therefore moved to using generic directional action button event codes
instead of BTN_[ABXY].

Changes for v3:
- no updates

Changes for v2:
adafruit-seesaw.c:
- Renamed file from 'adafruit_seesaw.c'
- Changed device name from 'seesaw_gamepad' to 'seesaw-gamepad'
- Changed count parameter for receiving joystick x on line 118:
`2` to `sizeof(write_buf)`
- Fixed invalid buffer size on line 123 and 126:
`data->y` to `sizeof(data->y)`
- Added comment for the `mdelay(10)` on line 169
- Changed inconsistent indentation on line 271
Kconfig:
- Fixed indentation for the help text
- Updated module name
Makefile:
- Updated module object file name
MAINTAINERS:
- Updated file name for the driver and bindings

MAINTAINERS | 7 +
drivers/input/joystick/Kconfig | 9 +
drivers/input/joystick/Makefile | 1 +
drivers/input/joystick/adafruit-seesaw.c | 273 +++++++++++++++++++++++
4 files changed, 290 insertions(+)
create mode 100644 drivers/input/joystick/adafruit-seesaw.c

diff --git a/MAINTAINERS b/MAINTAINERS
index 6c4cce45a09d..a314f9b48e21 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -441,6 +441,13 @@ W: http://wiki.analog.com/AD7879
W: https://ez.analog.com/linux-software-drivers
F: drivers/input/touchscreen/ad7879.c

+ADAFRUIT MINI I2C GAMEPAD
+M: Anshul Dalal <[email protected]>
+L: [email protected]
+S: Maintained
+F: Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
+F: drivers/input/joystick/adafruit-seesaw.c
+
ADDRESS SPACE LAYOUT RANDOMIZATION (ASLR)
M: Jiri Kosina <[email protected]>
S: Maintained
diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
index ac6925ce8366..df9cd1830b29 100644
--- a/drivers/input/joystick/Kconfig
+++ b/drivers/input/joystick/Kconfig
@@ -412,4 +412,13 @@ config JOYSTICK_SENSEHAT
To compile this driver as a module, choose M here: the
module will be called sensehat_joystick.

+config JOYSTICK_SEESAW
+ tristate "Adafruit Mini I2C Gamepad with Seesaw"
+ depends on I2C
+ help
+ Say Y here if you want to use the Adafruit Mini I2C Gamepad.
+
+ To compile this driver as a module, choose M here: the module will be
+ called adafruit-seesaw.
+
endif
diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
index 3937535f0098..9976f596a920 100644
--- a/drivers/input/joystick/Makefile
+++ b/drivers/input/joystick/Makefile
@@ -28,6 +28,7 @@ obj-$(CONFIG_JOYSTICK_N64) += n64joy.o
obj-$(CONFIG_JOYSTICK_PSXPAD_SPI) += psxpad-spi.o
obj-$(CONFIG_JOYSTICK_PXRC) += pxrc.o
obj-$(CONFIG_JOYSTICK_QWIIC) += qwiic-joystick.o
+obj-$(CONFIG_JOYSTICK_SEESAW) += adafruit-seesaw.o
obj-$(CONFIG_JOYSTICK_SENSEHAT) += sensehat-joystick.o
obj-$(CONFIG_JOYSTICK_SIDEWINDER) += sidewinder.o
obj-$(CONFIG_JOYSTICK_SPACEBALL) += spaceball.o
diff --git a/drivers/input/joystick/adafruit-seesaw.c b/drivers/input/joystick/adafruit-seesaw.c
new file mode 100644
index 000000000000..2a1eae8d2861
--- /dev/null
+++ b/drivers/input/joystick/adafruit-seesaw.c
@@ -0,0 +1,273 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 Anshul Dalal <[email protected]>
+ *
+ * Driver for Adafruit Mini I2C Gamepad
+ *
+ * Based on the work of:
+ * Oleh Kravchenko (Sparkfun Qwiic Joystick driver)
+ *
+ * Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
+ * Product page: https://www.adafruit.com/product/5743
+ * Firmware and hardware sources: https://github.com/adafruit/Adafruit_Seesaw
+ */
+
+#include <asm-generic/unaligned.h>
+#include <linux/bits.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+/* clang-format off */
+#define SEESAW_DEVICE_NAME "seesaw-gamepad"
+
+#define SEESAW_STATUS_BASE 0
+#define SEESAW_GPIO_BASE 1
+#define SEESAW_ADC_BASE 9
+
+#define SEESAW_GPIO_DIRCLR_BULK 3
+#define SEESAW_GPIO_BULK 4
+#define SEESAW_GPIO_BULK_SET 5
+#define SEESAW_GPIO_PULLENSET 11
+
+#define SEESAW_STATUS_HW_ID 1
+#define SEESAW_STATUS_SWRST 127
+
+#define SEESAW_ADC_OFFSET 7
+
+#define BUTTON_A 5
+#define BUTTON_B 1
+#define BUTTON_X 6
+#define BUTTON_Y 2
+#define BUTTON_START 16
+#define BUTTON_SELECT 0
+
+#define ANALOG_X 14
+#define ANALOG_Y 15
+
+#define SEESAW_JOYSTICK_MAX_AXIS 1023
+#define SEESAW_JOYSTICK_FUZZ 2
+#define SEESAW_JOYSTICK_FLAT 4
+
+#define SEESAW_GAMEPAD_POLL_INTERVAL 16
+#define SEESAW_GAMEPAD_POLL_MIN 8
+#define SEESAW_GAMEPAD_POLL_MAX 32
+/* clang-format on */
+
+u32 BUTTON_MASK = BIT(BUTTON_A) | BIT(BUTTON_B) | BIT(BUTTON_X) |
+ BIT(BUTTON_Y) | BIT(BUTTON_START) | BIT(BUTTON_SELECT);
+
+struct seesaw_gamepad {
+ char physical_path[32];
+ struct input_dev *input_dev;
+ struct i2c_client *i2c_client;
+};
+
+struct seesaw_data {
+ __be16 x;
+ __be16 y;
+ u8 button_a, button_b, button_x, button_y, button_start, button_select;
+};
+
+static int seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)
+{
+ int err;
+ unsigned char write_buf[2] = { SEESAW_GPIO_BASE, SEESAW_GPIO_BULK };
+ unsigned char read_buf[4];
+
+ err = i2c_master_send(client, write_buf, sizeof(write_buf));
+ if (err < 0)
+ return err;
+ err = i2c_master_recv(client, read_buf, sizeof(read_buf));
+ if (err < 0)
+ return err;
+
+ u32 result = get_unaligned_be32(&read_buf);
+
+ data->button_a = !test_bit(BUTTON_A, (long *)&result);
+ data->button_b = !test_bit(BUTTON_B, (long *)&result);
+ data->button_x = !test_bit(BUTTON_X, (long *)&result);
+ data->button_y = !test_bit(BUTTON_Y, (long *)&result);
+ data->button_start = !test_bit(BUTTON_START, (long *)&result);
+ data->button_select = !test_bit(BUTTON_SELECT, (long *)&result);
+
+ write_buf[0] = SEESAW_ADC_BASE;
+ write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_X;
+ err = i2c_master_send(client, write_buf, sizeof(write_buf));
+ if (err < 0)
+ return err;
+ err = i2c_master_recv(client, (char *)&data->x, sizeof(data->x));
+ if (err < 0)
+ return err;
+ /*
+ * ADC reads left as max and right as 0, must be reversed since kernel
+ * expects reports in opposite order.
+ */
+ data->x = SEESAW_JOYSTICK_MAX_AXIS - be16_to_cpu(data->x);
+
+ write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_Y;
+ err = i2c_master_send(client, write_buf, sizeof(write_buf));
+ if (err < 0)
+ return err;
+ err = i2c_master_recv(client, (char *)&data->y, sizeof(data->y));
+ if (err < 0)
+ return err;
+ data->y = be16_to_cpu(data->y);
+
+ return 0;
+}
+
+static void seesaw_poll(struct input_dev *input)
+{
+ struct seesaw_gamepad *private = input_get_drvdata(input);
+ struct seesaw_data data;
+ int err;
+
+ err = seesaw_read_data(private->i2c_client, &data);
+ if (err != 0) {
+ dev_dbg(&input->dev, "failed to read joystick state: %d\n",
+ err);
+ return;
+ }
+
+ input_report_abs(input, ABS_X, data.x);
+ input_report_abs(input, ABS_Y, data.y);
+ input_report_key(input, BTN_EAST, data.button_a);
+ input_report_key(input, BTN_SOUTH, data.button_b);
+ input_report_key(input, BTN_NORTH, data.button_x);
+ input_report_key(input, BTN_WEST, data.button_y);
+ input_report_key(input, BTN_START, data.button_start);
+ input_report_key(input, BTN_SELECT, data.button_select);
+ input_sync(input);
+}
+
+static int seesaw_probe(struct i2c_client *client)
+{
+ int err;
+ struct seesaw_gamepad *private;
+ unsigned char register_reset[] = { SEESAW_STATUS_BASE,
+ SEESAW_STATUS_SWRST, 0xFF };
+ unsigned char get_hw_id[] = { SEESAW_STATUS_BASE, SEESAW_STATUS_HW_ID };
+
+ err = i2c_master_send(client, register_reset, sizeof(register_reset));
+ if (err < 0)
+ return err;
+
+ /* Wait for the registers to reset before proceeding */
+ mdelay(10);
+
+ private = devm_kzalloc(&client->dev, sizeof(*private), GFP_KERNEL);
+ if (!private)
+ return -ENOMEM;
+
+ err = i2c_master_send(client, get_hw_id, sizeof(get_hw_id));
+ if (err < 0)
+ return err;
+
+ unsigned char hardware_id;
+
+ err = i2c_master_recv(client, &hardware_id, 1);
+ if (err < 0)
+ return err;
+
+ dev_dbg(&client->dev, "Adafruit Seesaw Gamepad, Hardware ID: %02x\n",
+ hardware_id);
+
+ private->i2c_client = client;
+ scnprintf(private->physical_path, sizeof(private->physical_path),
+ "i2c/%s", dev_name(&client->dev));
+ i2c_set_clientdata(client, private);
+
+ private->input_dev = devm_input_allocate_device(&client->dev);
+ if (!private->input_dev)
+ return -ENOMEM;
+
+ private->input_dev->id.bustype = BUS_I2C;
+ private->input_dev->name = "Adafruit Seesaw Gamepad";
+ private->input_dev->phys = private->physical_path;
+ input_set_drvdata(private->input_dev, private);
+ input_set_abs_params(private->input_dev, ABS_X, 0,
+ SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
+ SEESAW_JOYSTICK_FLAT);
+ input_set_abs_params(private->input_dev, ABS_Y, 0,
+ SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
+ SEESAW_JOYSTICK_FLAT);
+ input_set_capability(private->input_dev, EV_KEY, BTN_EAST);
+ input_set_capability(private->input_dev, EV_KEY, BTN_SOUTH);
+ input_set_capability(private->input_dev, EV_KEY, BTN_NORTH);
+ input_set_capability(private->input_dev, EV_KEY, BTN_WEST);
+ input_set_capability(private->input_dev, EV_KEY, BTN_START);
+ input_set_capability(private->input_dev, EV_KEY, BTN_SELECT);
+
+ err = input_setup_polling(private->input_dev, seesaw_poll);
+ if (err) {
+ dev_err(&client->dev, "failed to set up polling: %d\n", err);
+ return err;
+ }
+
+ input_set_poll_interval(private->input_dev,
+ SEESAW_GAMEPAD_POLL_INTERVAL);
+ input_set_max_poll_interval(private->input_dev,
+ SEESAW_GAMEPAD_POLL_MAX);
+ input_set_min_poll_interval(private->input_dev,
+ SEESAW_GAMEPAD_POLL_MIN);
+
+ err = input_register_device(private->input_dev);
+ if (err) {
+ dev_err(&client->dev, "failed to register joystick: %d\n", err);
+ return err;
+ }
+
+ /* Set Pin Mode to input and enable pull-up resistors */
+ unsigned char pin_mode[] = { SEESAW_GPIO_BASE, SEESAW_GPIO_DIRCLR_BULK,
+ BUTTON_MASK >> 24, BUTTON_MASK >> 16,
+ BUTTON_MASK >> 8, BUTTON_MASK };
+ err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
+ if (err < 0)
+ return err;
+ pin_mode[1] = SEESAW_GPIO_PULLENSET;
+ err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
+ if (err < 0)
+ return err;
+ pin_mode[1] = SEESAW_GPIO_BULK_SET;
+ err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
+ if (err < 0)
+ return err;
+
+ return 0;
+}
+
+#ifdef CONFIG_OF
+static const struct of_device_id of_seesaw_match[] = {
+ {
+ .compatible = "adafruit,seesaw-gamepad",
+ },
+ { /* Sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, of_seesaw_match);
+#endif /* CONFIG_OF */
+
+/* clang-format off */
+static const struct i2c_device_id seesaw_id_table[] = {
+ { SEESAW_DEVICE_NAME, 0 },
+ { /* Sentinel */ }
+};
+/* clang-format on */
+
+MODULE_DEVICE_TABLE(i2c, seesaw_id_table);
+
+static struct i2c_driver seesaw_driver = {
+ .driver = {
+ .name = SEESAW_DEVICE_NAME,
+ .of_match_table = of_match_ptr(of_seesaw_match),
+ },
+ .id_table = seesaw_id_table,
+ .probe = seesaw_probe,
+};
+module_i2c_driver(seesaw_driver);
+
+MODULE_AUTHOR("Anshul Dalal <[email protected]>");
+MODULE_DESCRIPTION("Adafruit Mini I2C Gamepad driver");
+MODULE_LICENSE("GPL");
--
2.42.0

2023-10-19 00:12:13

by kernel test robot

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hi Anshul,

kernel test robot noticed the following build warnings:

[auto build test WARNING on dtor-input/next]
[also build test WARNING on dtor-input/for-linus hid/for-next linus/master v6.6-rc6 next-20231018]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/Anshul-Dalal/input-joystick-driver-for-Adafruit-Seesaw-Gamepad/20231017-160635
base: https://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git next
patch link: https://lore.kernel.org/r/20231017034356.1436677-2-anshulusr%40gmail.com
patch subject: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad
config: sparc-allyesconfig (https://download.01.org/0day-ci/archive/20231019/[email protected]/config)
compiler: sparc64-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20231019/[email protected]/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/

All warnings (new ones prefixed by >>):

In file included from include/linux/thread_info.h:27,
from arch/sparc/include/asm/current.h:15,
from include/linux/sched.h:12,
from include/linux/delay.h:23,
from drivers/input/joystick/adafruit-seesaw.c:17:
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
>> include/linux/bitops.h:52:11: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
52 | __builtin_constant_p(*(const unsigned long *)(addr))) ? \
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
include/linux/bitops.h:61:41: note: in expansion of macro 'bitop'
61 | #define test_bit(nr, addr) bitop(_test_bit, nr, addr)
| ^~~~~
drivers/input/joystick/adafruit-seesaw.c:89:27: note: in expansion of macro 'test_bit'
89 | data->button_a = !test_bit(BUTTON_A, (long *)&result);
| ^~~~~~~~
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~
In file included from include/linux/bitops.h:34:
In function 'generic_test_bit',
inlined from 'seesaw_read_data' at drivers/input/joystick/adafruit-seesaw.c:89:20:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~
In function 'generic_test_bit',
inlined from 'seesaw_read_data' at drivers/input/joystick/adafruit-seesaw.c:90:20:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~
In function 'generic_test_bit',
inlined from 'seesaw_read_data' at drivers/input/joystick/adafruit-seesaw.c:91:20:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~
In function 'generic_test_bit',
inlined from 'seesaw_read_data' at drivers/input/joystick/adafruit-seesaw.c:92:20:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~
In function 'generic_test_bit',
inlined from 'seesaw_read_data' at drivers/input/joystick/adafruit-seesaw.c:93:24:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~
In function 'generic_test_bit',
inlined from 'seesaw_read_data' at drivers/input/joystick/adafruit-seesaw.c:94:25:
>> include/asm-generic/bitops/generic-non-atomic.h:128:27: warning: array subscript 'long unsigned int[0]' is partly outside array bounds of 'u32[1]' {aka 'unsigned int[1]'} [-Warray-bounds=]
128 | return 1UL & (addr[BIT_WORD(nr)] >> (nr & (BITS_PER_LONG-1)));
| ~~~~^~~~~~~~~~~~~~
drivers/input/joystick/adafruit-seesaw.c: In function 'seesaw_read_data':
drivers/input/joystick/adafruit-seesaw.c:87:13: note: object 'result' of size 4
87 | u32 result = get_unaligned_be32(&read_buf);
| ^~~~~~


vim +52 include/linux/bitops.h

0e862838f29014 Alexander Lobakin 2022-06-24 35
b03fc1173c0c2b Alexander Lobakin 2022-06-24 36 /*
b03fc1173c0c2b Alexander Lobakin 2022-06-24 37 * Many architecture-specific non-atomic bitops contain inline asm code and due
b03fc1173c0c2b Alexander Lobakin 2022-06-24 38 * to that the compiler can't optimize them to compile-time expressions or
b03fc1173c0c2b Alexander Lobakin 2022-06-24 39 * constants. In contrary, generic_*() helpers are defined in pure C and
b03fc1173c0c2b Alexander Lobakin 2022-06-24 40 * compilers optimize them just well.
b03fc1173c0c2b Alexander Lobakin 2022-06-24 41 * Therefore, to make `unsigned long foo = 0; __set_bit(BAR, &foo)` effectively
b03fc1173c0c2b Alexander Lobakin 2022-06-24 42 * equal to `unsigned long foo = BIT(BAR)`, pick the generic C alternative when
b03fc1173c0c2b Alexander Lobakin 2022-06-24 43 * the arguments can be resolved at compile time. That expression itself is a
b03fc1173c0c2b Alexander Lobakin 2022-06-24 44 * constant and doesn't bring any functional changes to the rest of cases.
b03fc1173c0c2b Alexander Lobakin 2022-06-24 45 * The casts to `uintptr_t` are needed to mitigate `-Waddress` warnings when
b03fc1173c0c2b Alexander Lobakin 2022-06-24 46 * passing a bitmap from .bss or .data (-> `!!addr` is always true).
b03fc1173c0c2b Alexander Lobakin 2022-06-24 47 */
e69eb9c460f128 Alexander Lobakin 2022-06-24 48 #define bitop(op, nr, addr) \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 49 ((__builtin_constant_p(nr) && \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 50 __builtin_constant_p((uintptr_t)(addr) != (uintptr_t)NULL) && \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 51 (uintptr_t)(addr) != (uintptr_t)NULL && \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 @52 __builtin_constant_p(*(const unsigned long *)(addr))) ? \
b03fc1173c0c2b Alexander Lobakin 2022-06-24 53 const##op(nr, addr) : op(nr, addr))
e69eb9c460f128 Alexander Lobakin 2022-06-24 54

--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

2023-10-22 23:55:20

by Jeff LaBundy

[permalink] [raw]
Subject: Re: [PATCH v5 1/2] dt-bindings: input: bindings for Adafruit Seesaw Gamepad

Hi Anshul,

On Tue, Oct 17, 2023 at 09:13:44AM +0530, Anshul Dalal wrote:
> Adds bindings for the Adafruit Seesaw Gamepad.
>
> The gamepad functions as an i2c device with the default address of 0x50
> and has an IRQ pin that can be enabled in the driver to allow for a rising
> edge trigger on each button press or joystick movement.
>
> Product page:
> https://www.adafruit.com/product/5743
> Arduino driver:
> https://github.com/adafruit/Adafruit_Seesaw
>
> Reviewed-by: Conor Dooley <[email protected]>
> Reviewed-by: Krzysztof Kozlowski <[email protected]>
> Signed-off-by: Anshul Dalal <[email protected]>

Perhaps this ship has sailed, but is there any reason this simple device
cannot be added to Documentation/devicetree/bindings/trivial-devices.yaml
as opposed to having its own binding?

It has no vendor-specific properties, and the only properties are the
standard properties already understood by the I2C core. In case I have
misunderstood, please let me know.

> ---
>
> Changes for v5:
> - Added link to the datasheet
>
> Changes for v4:
> - Fixed the URI for the id field
> - Added `interrupts` property
>
> Changes for v3:
> - Updated id field to reflect updated file name from previous version
> - Added `reg` property
>
> Changes for v2:
> - Renamed file to `adafruit,seesaw-gamepad.yaml`
> - Removed quotes for `$id` and `$schema`
> - Removed "Bindings for" from the description
> - Changed node name to the generic name "joystick"
> - Changed compatible to 'adafruit,seesaw-gamepad' instead of
> 'adafruit,seesaw_gamepad'
>
> .../input/adafruit,seesaw-gamepad.yaml | 60 +++++++++++++++++++
> 1 file changed, 60 insertions(+)
> create mode 100644 Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
>
> diff --git a/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml b/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
> new file mode 100644
> index 000000000000..3f0d1c5a3b9b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
> @@ -0,0 +1,60 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/input/adafruit,seesaw-gamepad.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Adafruit Mini I2C Gamepad with seesaw
> +
> +maintainers:
> + - Anshul Dalal <[email protected]>
> +
> +description: |
> + Adafruit Mini I2C Gamepad
> +
> + +-----------------------------+
> + | ___ |
> + | / \ (X) |
> + | | S | __ __ (Y) (A) |
> + | \___/ |ST| |SE| (B) |
> + | |
> + +-----------------------------+
> +
> + S -> 10-bit percision bidirectional analog joystick
> + ST -> Start
> + SE -> Select
> + X, A, B, Y -> Digital action buttons
> +
> + Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
> + Product page: https://www.adafruit.com/product/5743
> + Arduino Driver: https://github.com/adafruit/Adafruit_Seesaw
> +
> +properties:
> + compatible:
> + const: adafruit,seesaw-gamepad
> +
> + reg:
> + maxItems: 1
> +
> + interrupts:
> + maxItems: 1
> + description:
> + The gamepad's IRQ pin triggers a rising edge if interrupts are enabled.
> +
> +required:
> + - compatible
> + - reg
> +
> +additionalProperties: false
> +
> +examples:
> + - |
> + i2c {
> + #address-cells = <1>;
> + #size-cells = <0>;
> +
> + joystick@50 {
> + compatible = "adafruit,seesaw-gamepad";
> + reg = <0x50>;
> + };
> + };
> --
> 2.42.0
>

Kind regards,
Jeff LaBundy

2023-10-22 23:55:25

by Jeff LaBundy

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hi Anshul,

On Tue, Oct 17, 2023 at 09:13:45AM +0530, Anshul Dalal wrote:
> Adds a driver for a mini gamepad that communicates over i2c, the gamepad
> has bidirectional thumb stick input and six buttons.
>
> The gamepad chip utilizes the open framework from Adafruit called 'Seesaw'
> to transmit the ADC data for the joystick and digital pin state for the
> buttons. I have only implemented the functionality required to receive the
> thumb stick and button state.
>
> Steps in reading the gamepad state over i2c:
> 1. Reset the registers
> 2. Set the pin mode of the pins specified by the `BUTTON_MASK` to input
> `BUTTON_MASK`: A bit-map for the six digital pins internally
> connected to the joystick buttons.
> 3. Enable internal pullup resistors for the `BUTTON_MASK`
> 4. Bulk set the pin state HIGH for `BUTTON_MASK`
> 5. Poll the device for button and joystick state done by:
> `seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)`
>
> Product page:
> https://www.adafruit.com/product/5743
> Arduino driver:
> https://github.com/adafruit/Adafruit_Seesaw
>
> Driver tested on RPi Zero 2W
>
> Reviewed-by: Thomas Wei?schuh <[email protected]>
> Signed-off-by: Anshul Dalal <[email protected]>
> ---
>
> Changes for v5:
> - Added link to the datasheet
> - Added debug log message when `seesaw_read_data` fails
>
> Changes for v4:
> - Changed `1UL << BUTTON_` to BIT(BUTTON_)
> - Removed `hardware_id` field from `struct seesaw_gamepad`
> - Removed redundant checks for the number of bytes written and received by
> `i2c_master_send` and `i2c_master_recv`
> - Used `get_unaligned_be32` to instantiate `u32 result` from `read_buf`
> - Changed `result & (1UL << BUTTON_)` to
> `test_bit(BUTTON_, (long *)&result)`
> - Changed `KBUILD_MODNAME` in id-tables to `SEESAW_DEVICE_NAME`
> - Fixed formatting issues
> - Changed button reporting:
> Since the gamepad had the action buttons in a non-standard layout:
> (X)
> (Y) (A)
> (B)
> Therefore moved to using generic directional action button event codes
> instead of BTN_[ABXY].
>
> Changes for v3:
> - no updates
>
> Changes for v2:
> adafruit-seesaw.c:
> - Renamed file from 'adafruit_seesaw.c'
> - Changed device name from 'seesaw_gamepad' to 'seesaw-gamepad'
> - Changed count parameter for receiving joystick x on line 118:
> `2` to `sizeof(write_buf)`
> - Fixed invalid buffer size on line 123 and 126:
> `data->y` to `sizeof(data->y)`
> - Added comment for the `mdelay(10)` on line 169
> - Changed inconsistent indentation on line 271
> Kconfig:
> - Fixed indentation for the help text
> - Updated module name
> Makefile:
> - Updated module object file name
> MAINTAINERS:
> - Updated file name for the driver and bindings
>
> MAINTAINERS | 7 +
> drivers/input/joystick/Kconfig | 9 +
> drivers/input/joystick/Makefile | 1 +
> drivers/input/joystick/adafruit-seesaw.c | 273 +++++++++++++++++++++++
> 4 files changed, 290 insertions(+)
> create mode 100644 drivers/input/joystick/adafruit-seesaw.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 6c4cce45a09d..a314f9b48e21 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -441,6 +441,13 @@ W: http://wiki.analog.com/AD7879
> W: https://ez.analog.com/linux-software-drivers
> F: drivers/input/touchscreen/ad7879.c
>
> +ADAFRUIT MINI I2C GAMEPAD
> +M: Anshul Dalal <[email protected]>
> +L: [email protected]
> +S: Maintained
> +F: Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
> +F: drivers/input/joystick/adafruit-seesaw.c
> +
> ADDRESS SPACE LAYOUT RANDOMIZATION (ASLR)
> M: Jiri Kosina <[email protected]>
> S: Maintained
> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
> index ac6925ce8366..df9cd1830b29 100644
> --- a/drivers/input/joystick/Kconfig
> +++ b/drivers/input/joystick/Kconfig
> @@ -412,4 +412,13 @@ config JOYSTICK_SENSEHAT
> To compile this driver as a module, choose M here: the
> module will be called sensehat_joystick.
>
> +config JOYSTICK_SEESAW
> + tristate "Adafruit Mini I2C Gamepad with Seesaw"
> + depends on I2C
> + help
> + Say Y here if you want to use the Adafruit Mini I2C Gamepad.
> +
> + To compile this driver as a module, choose M here: the module will be
> + called adafruit-seesaw.
> +
> endif
> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
> index 3937535f0098..9976f596a920 100644
> --- a/drivers/input/joystick/Makefile
> +++ b/drivers/input/joystick/Makefile
> @@ -28,6 +28,7 @@ obj-$(CONFIG_JOYSTICK_N64) += n64joy.o
> obj-$(CONFIG_JOYSTICK_PSXPAD_SPI) += psxpad-spi.o
> obj-$(CONFIG_JOYSTICK_PXRC) += pxrc.o
> obj-$(CONFIG_JOYSTICK_QWIIC) += qwiic-joystick.o
> +obj-$(CONFIG_JOYSTICK_SEESAW) += adafruit-seesaw.o
> obj-$(CONFIG_JOYSTICK_SENSEHAT) += sensehat-joystick.o
> obj-$(CONFIG_JOYSTICK_SIDEWINDER) += sidewinder.o
> obj-$(CONFIG_JOYSTICK_SPACEBALL) += spaceball.o
> diff --git a/drivers/input/joystick/adafruit-seesaw.c b/drivers/input/joystick/adafruit-seesaw.c
> new file mode 100644
> index 000000000000..2a1eae8d2861
> --- /dev/null
> +++ b/drivers/input/joystick/adafruit-seesaw.c
> @@ -0,0 +1,273 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2023 Anshul Dalal <[email protected]>
> + *
> + * Driver for Adafruit Mini I2C Gamepad
> + *
> + * Based on the work of:
> + * Oleh Kravchenko (Sparkfun Qwiic Joystick driver)
> + *
> + * Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
> + * Product page: https://www.adafruit.com/product/5743
> + * Firmware and hardware sources: https://github.com/adafruit/Adafruit_Seesaw
> + */
> +
> +#include <asm-generic/unaligned.h>
> +#include <linux/bits.h>
> +#include <linux/delay.h>
> +#include <linux/i2c.h>
> +#include <linux/input.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +
> +/* clang-format off */

I don't think we need this directive; at least, no other input drivers have
it, or really any drivers for that matter.

> +#define SEESAW_DEVICE_NAME "seesaw-gamepad"
> +
> +#define SEESAW_STATUS_BASE 0
> +#define SEESAW_GPIO_BASE 1
> +#define SEESAW_ADC_BASE 9
> +
> +#define SEESAW_GPIO_DIRCLR_BULK 3
> +#define SEESAW_GPIO_BULK 4
> +#define SEESAW_GPIO_BULK_SET 5
> +#define SEESAW_GPIO_PULLENSET 11
> +
> +#define SEESAW_STATUS_HW_ID 1
> +#define SEESAW_STATUS_SWRST 127
> +
> +#define SEESAW_ADC_OFFSET 7
> +
> +#define BUTTON_A 5
> +#define BUTTON_B 1
> +#define BUTTON_X 6
> +#define BUTTON_Y 2
> +#define BUTTON_START 16
> +#define BUTTON_SELECT 0

Please namespace these (e.g. SEESAW_BUTTON_A) to make it clear they refer
to device-specific bits and not standard keycodes (e.g. BTN_A). In fact,
these seem better off as part of an array of structs; more on that below.

> +
> +#define ANALOG_X 14
> +#define ANALOG_Y 15

Please namespace these as well.

> +
> +#define SEESAW_JOYSTICK_MAX_AXIS 1023
> +#define SEESAW_JOYSTICK_FUZZ 2
> +#define SEESAW_JOYSTICK_FLAT 4
> +
> +#define SEESAW_GAMEPAD_POLL_INTERVAL 16
> +#define SEESAW_GAMEPAD_POLL_MIN 8
> +#define SEESAW_GAMEPAD_POLL_MAX 32
> +/* clang-format on */
> +
> +u32 BUTTON_MASK = BIT(BUTTON_A) | BIT(BUTTON_B) | BIT(BUTTON_X) |
> + BIT(BUTTON_Y) | BIT(BUTTON_START) | BIT(BUTTON_SELECT);
> +
> +struct seesaw_gamepad {
> + char physical_path[32];
> + struct input_dev *input_dev;
> + struct i2c_client *i2c_client;
> +};
> +
> +struct seesaw_data {
> + __be16 x;
> + __be16 y;
> + u8 button_a, button_b, button_x, button_y, button_start, button_select;

Please keep these each on a separate line.

> +};

Please declare this struct as __packed, as that is how it appears to be used.

> +
> +static int seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)
> +{
> + int err;

Please use 'ret' for return variables that can indicate a positive value on success.

> + unsigned char write_buf[2] = { SEESAW_GPIO_BASE, SEESAW_GPIO_BULK };
> + unsigned char read_buf[4];

Please use standard kernel type definitions (i.e. u8 in this case).

> +
> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
> + if (err < 0)
> + return err;

You correctly return err (or rather, ret) for negative values, but you should also
check that ret matches the size of the data sent. For 0 <= ret < sizeof(writebuf),
return -EIO.

> + err = i2c_master_recv(client, read_buf, sizeof(read_buf));
> + if (err < 0)
> + return err;

And here.

> +
> + u32 result = get_unaligned_be32(&read_buf);

Please do not mix declarations and code; all declarations must be at the
top of the function.

> +
> + data->button_a = !test_bit(BUTTON_A, (long *)&result);
> + data->button_b = !test_bit(BUTTON_B, (long *)&result);
> + data->button_x = !test_bit(BUTTON_X, (long *)&result);
> + data->button_y = !test_bit(BUTTON_Y, (long *)&result);
> + data->button_start = !test_bit(BUTTON_START, (long *)&result);
> + data->button_select = !test_bit(BUTTON_SELECT, (long *)&result);
> +
> + write_buf[0] = SEESAW_ADC_BASE;
> + write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_X;
> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
> + if (err < 0)
> + return err;
> + err = i2c_master_recv(client, (char *)&data->x, sizeof(data->x));
> + if (err < 0)
> + return err;

This is starting to look like a 16-bit register map. To that end, please
consider using regmap instead of open-coding each of these standard write-
then-read operations.

Using regmap would also save you the trouble of managing the endianness
yourself, as well as having to check for incomplete transfers since its
functions return zero or a negative error code only.

> + /*
> + * ADC reads left as max and right as 0, must be reversed since kernel
> + * expects reports in opposite order.
> + */
> + data->x = SEESAW_JOYSTICK_MAX_AXIS - be16_to_cpu(data->x);
> +
> + write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_Y;
> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
> + if (err < 0)
> + return err;
> + err = i2c_master_recv(client, (char *)&data->y, sizeof(data->y));
> + if (err < 0)
> + return err;
> + data->y = be16_to_cpu(data->y);
> +
> + return 0;
> +}
> +
> +static void seesaw_poll(struct input_dev *input)
> +{
> + struct seesaw_gamepad *private = input_get_drvdata(input);
> + struct seesaw_data data;
> + int err;
> +
> + err = seesaw_read_data(private->i2c_client, &data);
> + if (err != 0) {
> + dev_dbg(&input->dev, "failed to read joystick state: %d\n",
> + err);

This should be dev_err_ratelimited().

> + return;
> + }
> +
> + input_report_abs(input, ABS_X, data.x);
> + input_report_abs(input, ABS_Y, data.y);
> + input_report_key(input, BTN_EAST, data.button_a);
> + input_report_key(input, BTN_SOUTH, data.button_b);
> + input_report_key(input, BTN_NORTH, data.button_x);
> + input_report_key(input, BTN_WEST, data.button_y);
> + input_report_key(input, BTN_START, data.button_start);
> + input_report_key(input, BTN_SELECT, data.button_select);

I think you can make this much cleaner and smaller by defining an array
of structs, each with a key code and bit position. You can then simply
iterate over the array and call input_report_key() once per element as
in the following:

struct seesaw_btn_desc {
unsigned int code;
unsigned int shift;
};

static const struct seesaw_btn_desc seesaw_btns[] = {
{
.code = BTN_EAST,
.mask = 5,
},
[...]
};

And then:

btn_status = ...;

for (i = 0; i < ARRAY_SIZE(seesaw_btns); i++)
input_report_key(input, seesaw_btns[i].code,
btn_status & seesaw_btns[i].mask);

This would also make it easier to quickly discern what keycodes are mapped
to which bits in the register.

> + input_sync(input);
> +}
> +
> +static int seesaw_probe(struct i2c_client *client)
> +{
> + int err;
> + struct seesaw_gamepad *private;

I'd rather this be called something like 'seesaw' rather than private.

> + unsigned char register_reset[] = { SEESAW_STATUS_BASE,
> + SEESAW_STATUS_SWRST, 0xFF };
> + unsigned char get_hw_id[] = { SEESAW_STATUS_BASE, SEESAW_STATUS_HW_ID };
> +
> + err = i2c_master_send(client, register_reset, sizeof(register_reset));
> + if (err < 0)
> + return err;
> +
> + /* Wait for the registers to reset before proceeding */
> + mdelay(10);
> +
> + private = devm_kzalloc(&client->dev, sizeof(*private), GFP_KERNEL);
> + if (!private)
> + return -ENOMEM;
> +
> + err = i2c_master_send(client, get_hw_id, sizeof(get_hw_id));
> + if (err < 0)
> + return err;
> +
> + unsigned char hardware_id;

Same comment as earlier with regard to mixed declarations.

> +
> + err = i2c_master_recv(client, &hardware_id, 1);
> + if (err < 0)
> + return err;
> +
> + dev_dbg(&client->dev, "Adafruit Seesaw Gamepad, Hardware ID: %02x\n",
> + hardware_id);
> +
> + private->i2c_client = client;
> + scnprintf(private->physical_path, sizeof(private->physical_path),
> + "i2c/%s", dev_name(&client->dev));

This seems overly complex; can we not simply set input_dev->phys to the
literal "i2c/seesaw-gamepad"? Why to copy at runtime and incur the cost
of carrying 'physical_path' throughout the life of the module?

> + i2c_set_clientdata(client, private);
> +
> + private->input_dev = devm_input_allocate_device(&client->dev);
> + if (!private->input_dev)
> + return -ENOMEM;
> +
> + private->input_dev->id.bustype = BUS_I2C;
> + private->input_dev->name = "Adafruit Seesaw Gamepad";
> + private->input_dev->phys = private->physical_path;
> + input_set_drvdata(private->input_dev, private);
> + input_set_abs_params(private->input_dev, ABS_X, 0,
> + SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
> + SEESAW_JOYSTICK_FLAT);
> + input_set_abs_params(private->input_dev, ABS_Y, 0,
> + SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
> + SEESAW_JOYSTICK_FLAT);
> + input_set_capability(private->input_dev, EV_KEY, BTN_EAST);
> + input_set_capability(private->input_dev, EV_KEY, BTN_SOUTH);
> + input_set_capability(private->input_dev, EV_KEY, BTN_NORTH);
> + input_set_capability(private->input_dev, EV_KEY, BTN_WEST);
> + input_set_capability(private->input_dev, EV_KEY, BTN_START);
> + input_set_capability(private->input_dev, EV_KEY, BTN_SELECT);

Same comment with regard to creating an array of structs, and hence only
having to call input_set_capability() from within a small loop.

> +
> + err = input_setup_polling(private->input_dev, seesaw_poll);
> + if (err) {
> + dev_err(&client->dev, "failed to set up polling: %d\n", err);
> + return err;
> + }
> +
> + input_set_poll_interval(private->input_dev,
> + SEESAW_GAMEPAD_POLL_INTERVAL);
> + input_set_max_poll_interval(private->input_dev,
> + SEESAW_GAMEPAD_POLL_MAX);
> + input_set_min_poll_interval(private->input_dev,
> + SEESAW_GAMEPAD_POLL_MIN);
> +
> + err = input_register_device(private->input_dev);
> + if (err) {
> + dev_err(&client->dev, "failed to register joystick: %d\n", err);
> + return err;
> + }
> +
> + /* Set Pin Mode to input and enable pull-up resistors */
> + unsigned char pin_mode[] = { SEESAW_GPIO_BASE, SEESAW_GPIO_DIRCLR_BULK,
> + BUTTON_MASK >> 24, BUTTON_MASK >> 16,
> + BUTTON_MASK >> 8, BUTTON_MASK };
> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
> + if (err < 0)
> + return err;
> + pin_mode[1] = SEESAW_GPIO_PULLENSET;
> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
> + if (err < 0)
> + return err;
> + pin_mode[1] = SEESAW_GPIO_BULK_SET;
> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
> + if (err < 0)
> + return err;

Please configure the HW before the input device is live and being polled.

> +
> + return 0;
> +}
> +
> +#ifdef CONFIG_OF
> +static const struct of_device_id of_seesaw_match[] = {
> + {
> + .compatible = "adafruit,seesaw-gamepad",
> + },
> + { /* Sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, of_seesaw_match);
> +#endif /* CONFIG_OF */

Please correct me if I am wrong, but it does not seem that OF support is
required by this driver. There are no properties beyond the standard ones
understood by the I2C core, which can match based on the ID table below.

> +
> +/* clang-format off */
> +static const struct i2c_device_id seesaw_id_table[] = {
> + { SEESAW_DEVICE_NAME, 0 },
> + { /* Sentinel */ }
> +};
> +/* clang-format on */

Again, I don't see any need for these directives.

> +

Nit: unnecessary NL.

> +MODULE_DEVICE_TABLE(i2c, seesaw_id_table);
> +
> +static struct i2c_driver seesaw_driver = {
> + .driver = {
> + .name = SEESAW_DEVICE_NAME,
> + .of_match_table = of_match_ptr(of_seesaw_match),
> + },
> + .id_table = seesaw_id_table,
> + .probe = seesaw_probe,
> +};
> +module_i2c_driver(seesaw_driver);
> +
> +MODULE_AUTHOR("Anshul Dalal <[email protected]>");
> +MODULE_DESCRIPTION("Adafruit Mini I2C Gamepad driver");
> +MODULE_LICENSE("GPL");
> --
> 2.42.0
>

Kind regards,
Jeff LaBundy

2023-10-23 05:56:37

by Thomas Weißschuh

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hi Jeff,

Oct 23, 2023 01:42:47 Jeff LaBundy <[email protected]>:

> Hi Anshul,
>
> On Tue, Oct 17, 2023 at 09:13:45AM +0530, Anshul Dalal wrote:
>> Adds a driver for a mini gamepad that communicates over i2c, the gamepad
>> has bidirectional thumb stick input and six buttons.
>>
>> The gamepad chip utilizes the open framework from Adafruit called 'Seesaw'
>> to transmit the ADC data for the joystick and digital pin state for the
>> buttons. I have only implemented the functionality required to receive the
>> thumb stick and button state.
>>
>> Steps in reading the gamepad state over i2c:
>>   1. Reset the registers
>>   2. Set the pin mode of the pins specified by the `BUTTON_MASK` to input
>>       `BUTTON_MASK`: A bit-map for the six digital pins internally
>>        connected to the joystick buttons.
>>   3. Enable internal pullup resistors for the `BUTTON_MASK`
>>   4. Bulk set the pin state HIGH for `BUTTON_MASK`
>>   5. Poll the device for button and joystick state done by:
>>       `seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)`
>>
>> Product page:
>>   https://www.adafruit.com/product/5743
>> Arduino driver:
>>   https://github.com/adafruit/Adafruit_Seesaw
>>
>> Driver tested on RPi Zero 2W
>>
>> Reviewed-by: Thomas Weißschuh <[email protected]>
>> Signed-off-by: Anshul Dalal <[email protected]>
>> ---
>>
>> Changes for v5:
>> - Added link to the datasheet
>> - Added debug log message when `seesaw_read_data` fails
>>
>> Changes for v4:
>> - Changed `1UL << BUTTON_` to BIT(BUTTON_)
>> - Removed `hardware_id` field from `struct seesaw_gamepad`
>> - Removed redundant checks for the number of bytes written and received by
>>   `i2c_master_send` and `i2c_master_recv`
>> - Used `get_unaligned_be32` to instantiate `u32 result` from `read_buf`
>> - Changed  `result & (1UL << BUTTON_)` to
>>   `test_bit(BUTTON_, (long *)&result)`
>> - Changed `KBUILD_MODNAME` in id-tables to `SEESAW_DEVICE_NAME`
>> - Fixed formatting issues
>> - Changed button reporting:
>>     Since the gamepad had the action buttons in a non-standard layout:
>>          (X)
>>       (Y)   (A)
>>          (B)
>>     Therefore moved to using generic directional action button event codes
>>     instead of BTN_[ABXY].
>>
>> Changes for v3:
>> - no updates
>>
>> Changes for v2:
>> adafruit-seesaw.c:
>> - Renamed file from 'adafruit_seesaw.c'
>> - Changed device name from 'seesaw_gamepad' to 'seesaw-gamepad'
>> - Changed count parameter for receiving joystick x on line 118:
>>     `2` to `sizeof(write_buf)`
>> - Fixed invalid buffer size on line 123 and 126:
>>     `data->y` to `sizeof(data->y)`
>> - Added comment for the `mdelay(10)` on line 169
>> - Changed inconsistent indentation on line 271
>> Kconfig:
>> - Fixed indentation for the help text
>> - Updated module name
>> Makefile:
>> - Updated module object file name
>> MAINTAINERS:
>> - Updated file name for the driver and bindings
>>
>> MAINTAINERS                              |   7 +
>> drivers/input/joystick/Kconfig           |   9 +
>> drivers/input/joystick/Makefile          |   1 +
>> drivers/input/joystick/adafruit-seesaw.c | 273 +++++++++++++++++++++++
>> 4 files changed, 290 insertions(+)
>> create mode 100644 drivers/input/joystick/adafruit-seesaw.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 6c4cce45a09d..a314f9b48e21 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -441,6 +441,13 @@ W: http://wiki.analog.com/AD7879
>> W: https://ez.analog.com/linux-software-drivers
>> F: drivers/input/touchscreen/ad7879.c
>>
>> +ADAFRUIT MINI I2C GAMEPAD
>> +M: Anshul Dalal <[email protected]>
>> +L: [email protected]
>> +S: Maintained
>> +F: Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
>> +F: drivers/input/joystick/adafruit-seesaw.c
>> +
>> ADDRESS SPACE LAYOUT RANDOMIZATION (ASLR)
>> M: Jiri Kosina <[email protected]>
>> S: Maintained
>> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
>> index ac6925ce8366..df9cd1830b29 100644
>> --- a/drivers/input/joystick/Kconfig
>> +++ b/drivers/input/joystick/Kconfig
>> @@ -412,4 +412,13 @@ config JOYSTICK_SENSEHAT
>>       To compile this driver as a module, choose M here: the
>>       module will be called sensehat_joystick.
>>
>> +config JOYSTICK_SEESAW
>> +   tristate "Adafruit Mini I2C Gamepad with Seesaw"
>> +   depends on I2C
>> +   help
>> +     Say Y here if you want to use the Adafruit Mini I2C Gamepad.
>> +
>> +     To compile this driver as a module, choose M here: the module will be
>> +     called adafruit-seesaw.
>> +
>> endif
>> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
>> index 3937535f0098..9976f596a920 100644
>> --- a/drivers/input/joystick/Makefile
>> +++ b/drivers/input/joystick/Makefile
>> @@ -28,6 +28,7 @@ obj-$(CONFIG_JOYSTICK_N64)        += n64joy.o
>> obj-$(CONFIG_JOYSTICK_PSXPAD_SPI)  += psxpad-spi.o
>> obj-$(CONFIG_JOYSTICK_PXRC)        += pxrc.o
>> obj-$(CONFIG_JOYSTICK_QWIIC)       += qwiic-joystick.o
>> +obj-$(CONFIG_JOYSTICK_SEESAW)      += adafruit-seesaw.o
>> obj-$(CONFIG_JOYSTICK_SENSEHAT)    += sensehat-joystick.o
>> obj-$(CONFIG_JOYSTICK_SIDEWINDER)  += sidewinder.o
>> obj-$(CONFIG_JOYSTICK_SPACEBALL)   += spaceball.o
>> diff --git a/drivers/input/joystick/adafruit-seesaw.c b/drivers/input/joystick/adafruit-seesaw.c
>> new file mode 100644
>> index 000000000000..2a1eae8d2861
>> --- /dev/null
>> +++ b/drivers/input/joystick/adafruit-seesaw.c
>> @@ -0,0 +1,273 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * Copyright (C) 2023 Anshul Dalal <[email protected]>
>> + *
>> + * Driver for Adafruit Mini I2C Gamepad
>> + *
>> + * Based on the work of:
>> + * Oleh Kravchenko (Sparkfun Qwiic Joystick driver)
>> + *
>> + * Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
>> + * Product page: https://www.adafruit.com/product/5743
>> + * Firmware and hardware sources: https://github.com/adafruit/Adafruit_Seesaw
>> + */
>> +
>> +#include <asm-generic/unaligned.h>
>> +#include <linux/bits.h>
>> +#include <linux/delay.h>
>> +#include <linux/i2c.h>
>> +#include <linux/input.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +
>> +/* clang-format off */
>
> I don't think we need this directive; at least, no other input drivers have
> it, or really any drivers for that matter.
>
>> +#define SEESAW_DEVICE_NAME "seesaw-gamepad"
>> +
>> +#define SEESAW_STATUS_BASE 0
>> +#define SEESAW_GPIO_BASE   1
>> +#define SEESAW_ADC_BASE        9
>> +
>> +#define SEESAW_GPIO_DIRCLR_BULK    3
>> +#define SEESAW_GPIO_BULK   4
>> +#define SEESAW_GPIO_BULK_SET   5
>> +#define SEESAW_GPIO_PULLENSET  11
>> +
>> +#define SEESAW_STATUS_HW_ID    1
>> +#define SEESAW_STATUS_SWRST    127
>> +
>> +#define SEESAW_ADC_OFFSET  7
>> +
>> +#define BUTTON_A   5
>> +#define BUTTON_B   1
>> +#define BUTTON_X   6
>> +#define BUTTON_Y   2
>> +#define BUTTON_START   16
>> +#define BUTTON_SELECT  0
>
> Please namespace these (e.g. SEESAW_BUTTON_A) to make it clear they refer
> to device-specific bits and not standard keycodes (e.g. BTN_A). In fact,
> these seem better off as part of an array of structs; more on that below.
>
>> +
>> +#define ANALOG_X   14
>> +#define ANALOG_Y   15
>
> Please namespace these as well.
>
>> +
>> +#define SEESAW_JOYSTICK_MAX_AXIS   1023
>> +#define SEESAW_JOYSTICK_FUZZ       2
>> +#define SEESAW_JOYSTICK_FLAT       4
>> +
>> +#define SEESAW_GAMEPAD_POLL_INTERVAL   16
>> +#define SEESAW_GAMEPAD_POLL_MIN        8
>> +#define SEESAW_GAMEPAD_POLL_MAX        32
>> +/* clang-format on */
>> +
>> +u32 BUTTON_MASK = BIT(BUTTON_A) | BIT(BUTTON_B) | BIT(BUTTON_X) |
>> +         BIT(BUTTON_Y) | BIT(BUTTON_START) | BIT(BUTTON_SELECT);
>> +
>> +struct seesaw_gamepad {
>> +   char physical_path[32];
>> +   struct input_dev *input_dev;
>> +   struct i2c_client *i2c_client;
>> +};
>> +
>> +struct seesaw_data {
>> +   __be16 x;
>> +   __be16 y;
>> +   u8 button_a, button_b, button_x, button_y, button_start, button_select;
>
> Please keep these each on a separate line.
>
>> +};
>
> Please declare this struct as __packed, as that is how it appears to be used.
>
>> +
>> +static int seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)
>> +{
>> +   int err;
>
> Please use 'ret' for return variables that can indicate a positive value on success.
>
>> +   unsigned char write_buf[2] = { SEESAW_GPIO_BASE, SEESAW_GPIO_BULK };
>> +   unsigned char read_buf[4];
>
> Please use standard kernel type definitions (i.e. u8 in this case).
>
>> +
>> +   err = i2c_master_send(client, write_buf, sizeof(write_buf));
>> +   if (err < 0)
>> +       return err;
>
> You correctly return err (or rather, ret) for negative values, but you should also
> check that ret matches the size of the data sent. For 0 <= ret < sizeof(writebuf),
> return -EIO.

The driver did this originally.
I then requested it to be removed as this case
can never happen.
i2c_master_send will either return size of(writebuf) or an error.

>> +   err = i2c_master_recv(client, read_buf, sizeof(read_buf));
>> +   if (err < 0)
>> +       return err;
>
> And here.
>
>> +
>> +   u32 result = get_unaligned_be32(&read_buf);
>
> Please do not mix declarations and code; all declarations must be at the
> top of the function.
>
>> +
>> +   data->button_a = !test_bit(BUTTON_A, (long *)&result);
>> +   data->button_b = !test_bit(BUTTON_B, (long *)&result);
>> +   data->button_x = !test_bit(BUTTON_X, (long *)&result);
>> +   data->button_y = !test_bit(BUTTON_Y, (long *)&result);
>> +   data->button_start = !test_bit(BUTTON_START, (long *)&result);
>> +   data->button_select = !test_bit(BUTTON_SELECT, (long *)&result);
>> +
>> +   write_buf[0] = SEESAW_ADC_BASE;
>> +   write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_X;
>> +   err = i2c_master_send(client, write_buf, sizeof(write_buf));
>> +   if (err < 0)
>> +       return err;
>> +   err = i2c_master_recv(client, (char *)&data->x, sizeof(data->x));
>> +   if (err < 0)
>> +       return err;
>
> This is starting to look like a 16-bit register map. To that end, please
> consider using regmap instead of open-coding each of these standard write-
> then-read operations.
>
> Using regmap would also save you the trouble of managing the endianness
> yourself, as well as having to check for incomplete transfers since its
> functions return zero or a negative error code only.
>
>> +   /*
>> +    * ADC reads left as max and right as 0, must be reversed since kernel
>> +    * expects reports in opposite order.
>> +    */
>> +   data->x = SEESAW_JOYSTICK_MAX_AXIS - be16_to_cpu(data->x);
>> +
>> +   write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_Y;
>> +   err = i2c_master_send(client, write_buf, sizeof(write_buf));
>> +   if (err < 0)
>> +       return err;
>> +   err = i2c_master_recv(client, (char *)&data->y, sizeof(data->y));
>> +   if (err < 0)
>> +       return err;
>> +   data->y = be16_to_cpu(data->y);
>> +
>> +   return 0;
>> +}
>> +
>> +static void seesaw_poll(struct input_dev *input)
>> +{
>> +   struct seesaw_gamepad *private = input_get_drvdata(input);
>> +   struct seesaw_data data;
>> +   int err;
>> +
>> +   err = seesaw_read_data(private->i2c_client, &data);
>> +   if (err != 0) {
>> +       dev_dbg(&input->dev, "failed to read joystick state: %d\n",
>> +           err);
>
> This should be dev_err_ratelimited().
>
>> +       return;
>> +   }
>> +
>> +   input_report_abs(input, ABS_X, data.x);
>> +   input_report_abs(input, ABS_Y, data.y);
>> +   input_report_key(input, BTN_EAST, data.button_a);
>> +   input_report_key(input, BTN_SOUTH, data.button_b);
>> +   input_report_key(input, BTN_NORTH, data.button_x);
>> +   input_report_key(input, BTN_WEST, data.button_y);
>> +   input_report_key(input, BTN_START, data.button_start);
>> +   input_report_key(input, BTN_SELECT, data.button_select);
>
> I think you can make this much cleaner and smaller by defining an array
> of structs, each with a key code and bit position. You can then simply
> iterate over the array and call input_report_key() once per element as
> in the following:
>
> struct seesaw_btn_desc {
>     unsigned int code;
>     unsigned int shift;
> };
>
> static const struct seesaw_btn_desc seesaw_btns[] = {
>     {
>         .code = BTN_EAST,
>         .mask = 5,
>     },
>     [...]
> };
>
> And then:
>
>     btn_status = ...;
>
>     for (i = 0; i < ARRAY_SIZE(seesaw_btns); i++)
>         input_report_key(input, seesaw_btns[i].code,
>                  btn_status & seesaw_btns[i].mask);
>
> This would also make it easier to quickly discern what keycodes are mapped
> to which bits in the register.
>
>> +   input_sync(input);
>> +}
>> +
>> +static int seesaw_probe(struct i2c_client *client)
>> +{
>> +   int err;
>> +   struct seesaw_gamepad *private;
>
> I'd rather this be called something like 'seesaw' rather than private.
>
>> +   unsigned char register_reset[] = { SEESAW_STATUS_BASE,
>> +                      SEESAW_STATUS_SWRST, 0xFF };
>> +   unsigned char get_hw_id[] = { SEESAW_STATUS_BASE, SEESAW_STATUS_HW_ID };
>> +
>> +   err = i2c_master_send(client, register_reset, sizeof(register_reset));
>> +   if (err < 0)
>> +       return err;
>> +
>> +   /* Wait for the registers to reset before proceeding */
>> +   mdelay(10);
>> +
>> +   private = devm_kzalloc(&client->dev, sizeof(*private), GFP_KERNEL);
>> +   if (!private)
>> +       return -ENOMEM;
>> +
>> +   err = i2c_master_send(client, get_hw_id, sizeof(get_hw_id));
>> +   if (err < 0)
>> +       return err;
>> +
>> +   unsigned char hardware_id;
>
> Same comment as earlier with regard to mixed declarations.
>
>> +
>> +   err = i2c_master_recv(client, &hardware_id, 1);
>> +   if (err < 0)
>> +       return err;
>> +
>> +   dev_dbg(&client->dev, "Adafruit Seesaw Gamepad, Hardware ID: %02x\n",
>> +       hardware_id);
>> +
>> +   private->i2c_client = client;
>> +   scnprintf(private->physical_path, sizeof(private->physical_path),
>> +         "i2c/%s", dev_name(&client->dev));
>
> This seems overly complex; can we not simply set input_dev->phys to the
> literal "i2c/seesaw-gamepad"? Why to copy at runtime and incur the cost
> of carrying 'physical_path' throughout the life of the module?
>
>> +   i2c_set_clientdata(client, private);
>> +
>> +   private->input_dev = devm_input_allocate_device(&client->dev);
>> +   if (!private->input_dev)
>> +       return -ENOMEM;
>> +
>> +   private->input_dev->id.bustype = BUS_I2C;
>> +   private->input_dev->name = "Adafruit Seesaw Gamepad";
>> +   private->input_dev->phys = private->physical_path;
>> +   input_set_drvdata(private->input_dev, private);
>> +   input_set_abs_params(private->input_dev, ABS_X, 0,
>> +                SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
>> +                SEESAW_JOYSTICK_FLAT);
>> +   input_set_abs_params(private->input_dev, ABS_Y, 0,
>> +                SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
>> +                SEESAW_JOYSTICK_FLAT);
>> +   input_set_capability(private->input_dev, EV_KEY, BTN_EAST);
>> +   input_set_capability(private->input_dev, EV_KEY, BTN_SOUTH);
>> +   input_set_capability(private->input_dev, EV_KEY, BTN_NORTH);
>> +   input_set_capability(private->input_dev, EV_KEY, BTN_WEST);
>> +   input_set_capability(private->input_dev, EV_KEY, BTN_START);
>> +   input_set_capability(private->input_dev, EV_KEY, BTN_SELECT);
>
> Same comment with regard to creating an array of structs, and hence only
> having to call input_set_capability() from within a small loop.
>
>> +
>> +   err = input_setup_polling(private->input_dev, seesaw_poll);
>> +   if (err) {
>> +       dev_err(&client->dev, "failed to set up polling: %d\n", err);
>> +       return err;
>> +   }
>> +
>> +   input_set_poll_interval(private->input_dev,
>> +               SEESAW_GAMEPAD_POLL_INTERVAL);
>> +   input_set_max_poll_interval(private->input_dev,
>> +                   SEESAW_GAMEPAD_POLL_MAX);
>> +   input_set_min_poll_interval(private->input_dev,
>> +                   SEESAW_GAMEPAD_POLL_MIN);
>> +
>> +   err = input_register_device(private->input_dev);
>> +   if (err) {
>> +       dev_err(&client->dev, "failed to register joystick: %d\n", err);
>> +       return err;
>> +   }
>> +
>> +   /* Set Pin Mode to input and enable pull-up resistors */
>> +   unsigned char pin_mode[] = { SEESAW_GPIO_BASE,  SEESAW_GPIO_DIRCLR_BULK,
>> +                    BUTTON_MASK >> 24, BUTTON_MASK >> 16,
>> +                    BUTTON_MASK >> 8,  BUTTON_MASK };
>> +   err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
>> +   if (err < 0)
>> +       return err;
>> +   pin_mode[1] = SEESAW_GPIO_PULLENSET;
>> +   err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
>> +   if (err < 0)
>> +       return err;
>> +   pin_mode[1] = SEESAW_GPIO_BULK_SET;
>> +   err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
>> +   if (err < 0)
>> +       return err;
>
> Please configure the HW before the input device is live and being polled.
>
>> +
>> +   return 0;
>> +}
>> +
>> +#ifdef CONFIG_OF
>> +static const struct of_device_id of_seesaw_match[] = {
>> +   {
>> +       .compatible = "adafruit,seesaw-gamepad",
>> +   },
>> +   { /* Sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, of_seesaw_match);
>> +#endif /* CONFIG_OF */
>
> Please correct me if I am wrong, but it does not seem that OF support is
> required by this driver. There are no properties beyond the standard ones
> understood by the I2C core, which can match based on the ID table below.
>
>> +
>> +/* clang-format off */
>> +static const struct i2c_device_id seesaw_id_table[] = {
>> +   { SEESAW_DEVICE_NAME, 0 },
>> +   { /* Sentinel */ }
>> +};
>> +/* clang-format on */
>
> Again, I don't see any need for these directives.
>
>> +
>
> Nit: unnecessary NL.
>
>> +MODULE_DEVICE_TABLE(i2c, seesaw_id_table);
>> +
>> +static struct i2c_driver seesaw_driver = {
>> +   .driver = {
>> +       .name = SEESAW_DEVICE_NAME,
>> +       .of_match_table = of_match_ptr(of_seesaw_match),
>> +   },
>> +   .id_table = seesaw_id_table,
>> +   .probe = seesaw_probe,
>> +};
>> +module_i2c_driver(seesaw_driver);
>> +
>> +MODULE_AUTHOR("Anshul Dalal <[email protected]>");
>> +MODULE_DESCRIPTION("Adafruit Mini I2C Gamepad driver");
>> +MODULE_LICENSE("GPL");
>> --
>> 2.42.0
>>
>
> Kind regards,
> Jeff LaBundy

2023-10-23 11:59:43

by Anshul Dalal

[permalink] [raw]
Subject: Re: [PATCH v5 1/2] dt-bindings: input: bindings for Adafruit Seesaw Gamepad

Hello Jeff,

On 10/23/23 05:17, Jeff LaBundy wrote:
> Hi Anshul,
>
> On Tue, Oct 17, 2023 at 09:13:44AM +0530, Anshul Dalal wrote:
>> Adds bindings for the Adafruit Seesaw Gamepad.
>>
>> The gamepad functions as an i2c device with the default address of 0x50
>> and has an IRQ pin that can be enabled in the driver to allow for a rising
>> edge trigger on each button press or joystick movement.
>>
>> Product page:
>> https://www.adafruit.com/product/5743
>> Arduino driver:
>> https://github.com/adafruit/Adafruit_Seesaw
>>
>> Reviewed-by: Conor Dooley <[email protected]>
>> Reviewed-by: Krzysztof Kozlowski <[email protected]>
>> Signed-off-by: Anshul Dalal <[email protected]>
>
> Perhaps this ship has sailed, but is there any reason this simple device
> cannot be added to Documentation/devicetree/bindings/trivial-devices.yaml
> as opposed to having its own binding?
>
> It has no vendor-specific properties, and the only properties are the
> standard properties already understood by the I2C core. In case I have
> misunderstood, please let me know.
>

The driver currently implements only a subset of the functionality in
the Adafruit Seesaw specification. I eventually plan on adding adding
full support for the Seesaw framework in the form of a driver for the
atsamd09 seesaw breakout board:
https://learn.adafruit.com/adafruit-seesaw-atsamd09-breakout

Then I think it would be better for this driver to use the newly exposed
seesaw APIs by the atsamd09 driver instead of relying on kernel's i2c APIs.

I would also like to add support for the provided interrupt pin later
down the line which is documented in the binding along with description
of the non-standard action button layout.

Above were my reasons for going for a standalone binding, please let me
know if you disagree.

>> ---
>>
>> Changes for v5:
>> - Added link to the datasheet
>>
>> Changes for v4:
>> - Fixed the URI for the id field
>> - Added `interrupts` property
>>
>> Changes for v3:
>> - Updated id field to reflect updated file name from previous version
>> - Added `reg` property
>>
>> Changes for v2:
>> - Renamed file to `adafruit,seesaw-gamepad.yaml`
>> - Removed quotes for `$id` and `$schema`
>> - Removed "Bindings for" from the description
>> - Changed node name to the generic name "joystick"
>> - Changed compatible to 'adafruit,seesaw-gamepad' instead of
>> 'adafruit,seesaw_gamepad'
>>
>> .../input/adafruit,seesaw-gamepad.yaml | 60 +++++++++++++++++++
>> 1 file changed, 60 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml b/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
>> new file mode 100644
>> index 000000000000..3f0d1c5a3b9b
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
>> @@ -0,0 +1,60 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/input/adafruit,seesaw-gamepad.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Adafruit Mini I2C Gamepad with seesaw
>> +
>> +maintainers:
>> + - Anshul Dalal <[email protected]>
>> +
>> +description: |
>> + Adafruit Mini I2C Gamepad
>> +
>> + +-----------------------------+
>> + | ___ |
>> + | / \ (X) |
>> + | | S | __ __ (Y) (A) |
>> + | \___/ |ST| |SE| (B) |
>> + | |
>> + +-----------------------------+
>> +
>> + S -> 10-bit percision bidirectional analog joystick
>> + ST -> Start
>> + SE -> Select
>> + X, A, B, Y -> Digital action buttons
>> +
>> + Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
>> + Product page: https://www.adafruit.com/product/5743
>> + Arduino Driver: https://github.com/adafruit/Adafruit_Seesaw
>> +
>> +properties:
>> + compatible:
>> + const: adafruit,seesaw-gamepad
>> +
>> + reg:
>> + maxItems: 1
>> +
>> + interrupts:
>> + maxItems: 1
>> + description:
>> + The gamepad's IRQ pin triggers a rising edge if interrupts are enabled.
>> +
>> +required:
>> + - compatible
>> + - reg
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> + - |
>> + i2c {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + joystick@50 {
>> + compatible = "adafruit,seesaw-gamepad";
>> + reg = <0x50>;
>> + };
>> + };
>> --
>> 2.42.0
>>
>
> Kind regards,
> Jeff LaBundy

Thank you,
Anshul Dalal

2023-10-23 18:53:49

by Jeff LaBundy

[permalink] [raw]
Subject: Re: [PATCH v5 1/2] dt-bindings: input: bindings for Adafruit Seesaw Gamepad

Hi Anshul,

Thank you for this additional information.

On Mon, Oct 23, 2023 at 05:28:10PM +0530, Anshul Dalal wrote:
> Hello Jeff,
>
> On 10/23/23 05:17, Jeff LaBundy wrote:
> > Hi Anshul,
> >
> > On Tue, Oct 17, 2023 at 09:13:44AM +0530, Anshul Dalal wrote:
> >> Adds bindings for the Adafruit Seesaw Gamepad.
> >>
> >> The gamepad functions as an i2c device with the default address of 0x50
> >> and has an IRQ pin that can be enabled in the driver to allow for a rising
> >> edge trigger on each button press or joystick movement.
> >>
> >> Product page:
> >> https://www.adafruit.com/product/5743
> >> Arduino driver:
> >> https://github.com/adafruit/Adafruit_Seesaw
> >>
> >> Reviewed-by: Conor Dooley <[email protected]>
> >> Reviewed-by: Krzysztof Kozlowski <[email protected]>
> >> Signed-off-by: Anshul Dalal <[email protected]>
> >
> > Perhaps this ship has sailed, but is there any reason this simple device
> > cannot be added to Documentation/devicetree/bindings/trivial-devices.yaml
> > as opposed to having its own binding?
> >
> > It has no vendor-specific properties, and the only properties are the
> > standard properties already understood by the I2C core. In case I have
> > misunderstood, please let me know.
> >
>
> The driver currently implements only a subset of the functionality in
> the Adafruit Seesaw specification. I eventually plan on adding adding
> full support for the Seesaw framework in the form of a driver for the
> atsamd09 seesaw breakout board:
> https://learn.adafruit.com/adafruit-seesaw-atsamd09-breakout
>
> Then I think it would be better for this driver to use the newly exposed
> seesaw APIs by the atsamd09 driver instead of relying on kernel's i2c APIs.

The underlying functions used to implement I2C communication are orthogonal
to the binding. Whether you use the kernel's core I2C support, regmap, or
your own wrappers built on top of either have no bearing on whether or not
a binding is necessary.

The binding is used to define device tree properties that describe the
hardware and its constraints. Classic examples are things such as clock
frequency, regulator voltage, etc. Drivers often translate device tree
properties into register settings.

In the case of this device, the only thing the driver needs to know about
the hardware are its compatible string and I2C client address, both of
which are already supported in the common trivial devices binding [1].

> I would also like to add support for the provided interrupt pin later
> down the line which is documented in the binding along with description
> of the non-standard action button layout.

The trivial devices binding includes interrupts as well; please see [1].
My opinion is that the device's own documentation is responsible for
describing the product and anything unique about its physical layout.

> Above were my reasons for going for a standalone binding, please let me
> know if you disagree.

I don't see any need for a binding for this device because it has no vendor-
specific properties, and the only properties it does have are covered by
existing infrastructure.

My feedback is that this patch can be replaced with at most a two-line patch
to [1]. This is just my $.02; it is ultimately up to the maintainers. The
existing binding, albeit unnecessary, is nicely written either way :)

Kind regards,
Jeff LaBundy

[1] Documentation/devicetree/bindings/trivial-devices.yaml

2023-10-23 21:25:14

by Jeff LaBundy

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hi Thomas,

On Mon, Oct 23, 2023 at 07:55:52AM +0200, Thomas Wei?schuh wrote:

[...]

> >> +?? err = i2c_master_send(client, write_buf, sizeof(write_buf));
> >> +?? if (err < 0)
> >> +?????? return err;
> >
> > You correctly return err (or rather, ret) for negative values, but you should also
> > check that ret matches the size of the data sent. For 0 <= ret < sizeof(writebuf),
> > return -EIO.
>
> The driver did this originally.
> I then requested it to be removed as this case
> can never happen.
> i2c_master_send will either return size of(writebuf) or an error.

Great catch; indeed you are correct. Apologies for having missed this
in the change log; this is good to know in the future.

That being said, it's a moot point IMO; this driver seems like a good
candidate for regmap. If regmap cannot be made to work here for some
reason, then I'd like to at least see some wrapper functions to avoid
duplicate code and manual assignments to a buffer.

Kind regards,
Jeff LaBundy

2023-10-24 15:57:21

by Thomas Weißschuh

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hi Jeff,

Oct 23, 2023 23:24:55 Jeff LaBundy <[email protected]>:
> On Mon, Oct 23, 2023 at 07:55:52AM +0200, Thomas Weißschuh  wrote:
>
> [...]
>
>>>> +   err = i2c_master_send(client, write_buf, sizeof(write_buf));
>>>> +   if (err < 0)
>>>> +       return err;
>>>
>>> You correctly return err (or rather, ret) for negative values, but you should also
>>> check that ret matches the size of the data sent. For 0 <= ret < sizeof(writebuf),
>>> return -EIO.
>>
>> The driver did this originally.
>> I then requested it to be removed as this case
>> can never happen.
>> i2c_master_send will either return size of(writebuf) or an error.
>
> Great catch; indeed you are correct. Apologies for having missed this
> in the change log; this is good to know in the future.

I guess it would make sense to also adapt the
function documentation to be more explicit
about this invariant.
No need to complicate every caller unnecessarily.

I can send a patch somewhere next week, but
if you want to send one I'll be happy to review it.

> That being said, it's a moot point IMO; this driver seems like a good
> candidate for regmap. If regmap cannot be made to work here for some
> reason, then I'd like to at least see some wrapper functions to avoid
> duplicate code and manual assignments to a buffer.

Ack.

Thomas

2023-10-25 10:21:41

by Anshul Dalal

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hello Jeff,
Thanks for the review, I plan on addressing the changes you requested in
the next version of the patch. Though I had a few questions:

On 10/23/23 05:12, Jeff LaBundy wrote:
> Hi Anshul,
>
> On Tue, Oct 17, 2023 at 09:13:45AM +0530, Anshul Dalal wrote:
>> Adds a driver for a mini gamepad that communicates over i2c, the gamepad
>> has bidirectional thumb stick input and six buttons.
>>
>> The gamepad chip utilizes the open framework from Adafruit called 'Seesaw'
>> to transmit the ADC data for the joystick and digital pin state for the
>> buttons. I have only implemented the functionality required to receive the
>> thumb stick and button state.
>>
>> Steps in reading the gamepad state over i2c:
>> 1. Reset the registers
>> 2. Set the pin mode of the pins specified by the `BUTTON_MASK` to input
>> `BUTTON_MASK`: A bit-map for the six digital pins internally
>> connected to the joystick buttons.
>> 3. Enable internal pullup resistors for the `BUTTON_MASK`
>> 4. Bulk set the pin state HIGH for `BUTTON_MASK`
>> 5. Poll the device for button and joystick state done by:
>> `seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)`
>>
>> Product page:
>> https://www.adafruit.com/product/5743
>> Arduino driver:
>> https://github.com/adafruit/Adafruit_Seesaw
>>
>> Driver tested on RPi Zero 2W
>>
>> Reviewed-by: Thomas Weißschuh <[email protected]>
>> Signed-off-by: Anshul Dalal <[email protected]>
>> ---
>>
>> Changes for v5:
>> - Added link to the datasheet
>> - Added debug log message when `seesaw_read_data` fails
>>
>> Changes for v4:
>> - Changed `1UL << BUTTON_` to BIT(BUTTON_)
>> - Removed `hardware_id` field from `struct seesaw_gamepad`
>> - Removed redundant checks for the number of bytes written and received by
>> `i2c_master_send` and `i2c_master_recv`
>> - Used `get_unaligned_be32` to instantiate `u32 result` from `read_buf`
>> - Changed `result & (1UL << BUTTON_)` to
>> `test_bit(BUTTON_, (long *)&result)`
>> - Changed `KBUILD_MODNAME` in id-tables to `SEESAW_DEVICE_NAME`
>> - Fixed formatting issues
>> - Changed button reporting:
>> Since the gamepad had the action buttons in a non-standard layout:
>> (X)
>> (Y) (A)
>> (B)
>> Therefore moved to using generic directional action button event codes
>> instead of BTN_[ABXY].
>>
>> Changes for v3:
>> - no updates
>>
>> Changes for v2:
>> adafruit-seesaw.c:
>> - Renamed file from 'adafruit_seesaw.c'
>> - Changed device name from 'seesaw_gamepad' to 'seesaw-gamepad'
>> - Changed count parameter for receiving joystick x on line 118:
>> `2` to `sizeof(write_buf)`
>> - Fixed invalid buffer size on line 123 and 126:
>> `data->y` to `sizeof(data->y)`
>> - Added comment for the `mdelay(10)` on line 169
>> - Changed inconsistent indentation on line 271
>> Kconfig:
>> - Fixed indentation for the help text
>> - Updated module name
>> Makefile:
>> - Updated module object file name
>> MAINTAINERS:
>> - Updated file name for the driver and bindings
>>
>> MAINTAINERS | 7 +
>> drivers/input/joystick/Kconfig | 9 +
>> drivers/input/joystick/Makefile | 1 +
>> drivers/input/joystick/adafruit-seesaw.c | 273 +++++++++++++++++++++++
>> 4 files changed, 290 insertions(+)
>> create mode 100644 drivers/input/joystick/adafruit-seesaw.c
>>
>> diff --git a/MAINTAINERS b/MAINTAINERS
>> index 6c4cce45a09d..a314f9b48e21 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -441,6 +441,13 @@ W: http://wiki.analog.com/AD7879
>> W: https://ez.analog.com/linux-software-drivers
>> F: drivers/input/touchscreen/ad7879.c
>>
>> +ADAFRUIT MINI I2C GAMEPAD
>> +M: Anshul Dalal <[email protected]>
>> +L: [email protected]
>> +S: Maintained
>> +F: Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
>> +F: drivers/input/joystick/adafruit-seesaw.c
>> +
>> ADDRESS SPACE LAYOUT RANDOMIZATION (ASLR)
>> M: Jiri Kosina <[email protected]>
>> S: Maintained
>> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
>> index ac6925ce8366..df9cd1830b29 100644
>> --- a/drivers/input/joystick/Kconfig
>> +++ b/drivers/input/joystick/Kconfig
>> @@ -412,4 +412,13 @@ config JOYSTICK_SENSEHAT
>> To compile this driver as a module, choose M here: the
>> module will be called sensehat_joystick.
>>
>> +config JOYSTICK_SEESAW
>> + tristate "Adafruit Mini I2C Gamepad with Seesaw"
>> + depends on I2C
>> + help
>> + Say Y here if you want to use the Adafruit Mini I2C Gamepad.
>> +
>> + To compile this driver as a module, choose M here: the module will be
>> + called adafruit-seesaw.
>> +
>> endif
>> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
>> index 3937535f0098..9976f596a920 100644
>> --- a/drivers/input/joystick/Makefile
>> +++ b/drivers/input/joystick/Makefile
>> @@ -28,6 +28,7 @@ obj-$(CONFIG_JOYSTICK_N64) += n64joy.o
>> obj-$(CONFIG_JOYSTICK_PSXPAD_SPI) += psxpad-spi.o
>> obj-$(CONFIG_JOYSTICK_PXRC) += pxrc.o
>> obj-$(CONFIG_JOYSTICK_QWIIC) += qwiic-joystick.o
>> +obj-$(CONFIG_JOYSTICK_SEESAW) += adafruit-seesaw.o
>> obj-$(CONFIG_JOYSTICK_SENSEHAT) += sensehat-joystick.o
>> obj-$(CONFIG_JOYSTICK_SIDEWINDER) += sidewinder.o
>> obj-$(CONFIG_JOYSTICK_SPACEBALL) += spaceball.o
>> diff --git a/drivers/input/joystick/adafruit-seesaw.c b/drivers/input/joystick/adafruit-seesaw.c
>> new file mode 100644
>> index 000000000000..2a1eae8d2861
>> --- /dev/null
>> +++ b/drivers/input/joystick/adafruit-seesaw.c
>> @@ -0,0 +1,273 @@
>> +// SPDX-License-Identifier: GPL-2.0-or-later
>> +/*
>> + * Copyright (C) 2023 Anshul Dalal <[email protected]>
>> + *
>> + * Driver for Adafruit Mini I2C Gamepad
>> + *
>> + * Based on the work of:
>> + * Oleh Kravchenko (Sparkfun Qwiic Joystick driver)
>> + *
>> + * Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
>> + * Product page: https://www.adafruit.com/product/5743
>> + * Firmware and hardware sources: https://github.com/adafruit/Adafruit_Seesaw
>> + */
>> +
>> +#include <asm-generic/unaligned.h>
>> +#include <linux/bits.h>
>> +#include <linux/delay.h>
>> +#include <linux/i2c.h>
>> +#include <linux/input.h>
>> +#include <linux/kernel.h>
>> +#include <linux/module.h>
>> +
>> +/* clang-format off */
>
> I don't think we need this directive; at least, no other input drivers have
> it, or really any drivers for that matter.
>
>> +#define SEESAW_DEVICE_NAME "seesaw-gamepad"
>> +
>> +#define SEESAW_STATUS_BASE 0
>> +#define SEESAW_GPIO_BASE 1
>> +#define SEESAW_ADC_BASE 9
>> +
>> +#define SEESAW_GPIO_DIRCLR_BULK 3
>> +#define SEESAW_GPIO_BULK 4
>> +#define SEESAW_GPIO_BULK_SET 5
>> +#define SEESAW_GPIO_PULLENSET 11
>> +
>> +#define SEESAW_STATUS_HW_ID 1
>> +#define SEESAW_STATUS_SWRST 127
>> +
>> +#define SEESAW_ADC_OFFSET 7
>> +
>> +#define BUTTON_A 5
>> +#define BUTTON_B 1
>> +#define BUTTON_X 6
>> +#define BUTTON_Y 2
>> +#define BUTTON_START 16
>> +#define BUTTON_SELECT 0
>
> Please namespace these (e.g. SEESAW_BUTTON_A) to make it clear they refer
> to device-specific bits and not standard keycodes (e.g. BTN_A). In fact,
> these seem better off as part of an array of structs; more on that below.
>
>> +
>> +#define ANALOG_X 14
>> +#define ANALOG_Y 15
>
> Please namespace these as well.
>
>> +
>> +#define SEESAW_JOYSTICK_MAX_AXIS 1023
>> +#define SEESAW_JOYSTICK_FUZZ 2
>> +#define SEESAW_JOYSTICK_FLAT 4
>> +
>> +#define SEESAW_GAMEPAD_POLL_INTERVAL 16
>> +#define SEESAW_GAMEPAD_POLL_MIN 8
>> +#define SEESAW_GAMEPAD_POLL_MAX 32
>> +/* clang-format on */
>> +
>> +u32 BUTTON_MASK = BIT(BUTTON_A) | BIT(BUTTON_B) | BIT(BUTTON_X) |
>> + BIT(BUTTON_Y) | BIT(BUTTON_START) | BIT(BUTTON_SELECT);
>> +
>> +struct seesaw_gamepad {
>> + char physical_path[32];
>> + struct input_dev *input_dev;
>> + struct i2c_client *i2c_client;
>> +};
>> +
>> +struct seesaw_data {
>> + __be16 x;
>> + __be16 y;
>> + u8 button_a, button_b, button_x, button_y, button_start, button_select;
>
> Please keep these each on a separate line.
>
>> +};
>
> Please declare this struct as __packed, as that is how it appears to be used.
>
>> +
>> +static int seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)
>> +{
>> + int err;
>
> Please use 'ret' for return variables that can indicate a positive value on success.
>
>> + unsigned char write_buf[2] = { SEESAW_GPIO_BASE, SEESAW_GPIO_BULK };
>> + unsigned char read_buf[4];
>
> Please use standard kernel type definitions (i.e. u8 in this case).
>
>> +
>> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
>> + if (err < 0)
>> + return err;
>
> You correctly return err (or rather, ret) for negative values, but you should also
> check that ret matches the size of the data sent. For 0 <= ret < sizeof(writebuf),
> return -EIO.
>
>> + err = i2c_master_recv(client, read_buf, sizeof(read_buf));
>> + if (err < 0)
>> + return err;
>
> And here.
>
>> +
>> + u32 result = get_unaligned_be32(&read_buf);
>
> Please do not mix declarations and code; all declarations must be at the
> top of the function.
>
>> +
>> + data->button_a = !test_bit(BUTTON_A, (long *)&result);
>> + data->button_b = !test_bit(BUTTON_B, (long *)&result);
>> + data->button_x = !test_bit(BUTTON_X, (long *)&result);
>> + data->button_y = !test_bit(BUTTON_Y, (long *)&result);
>> + data->button_start = !test_bit(BUTTON_START, (long *)&result);
>> + data->button_select = !test_bit(BUTTON_SELECT, (long *)&result);
>> +
>> + write_buf[0] = SEESAW_ADC_BASE;
>> + write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_X;
>> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
>> + if (err < 0)
>> + return err;
>> + err = i2c_master_recv(client, (char *)&data->x, sizeof(data->x));
>> + if (err < 0)
>> + return err;
>
> This is starting to look like a 16-bit register map. To that end, please
> consider using regmap instead of open-coding each of these standard write-
> then-read operations.
>
> Using regmap would also save you the trouble of managing the endianness
> yourself, as well as having to check for incomplete transfers since its
> functions return zero or a negative error code only.
>
In this driver there are only two places a 16-bit regmap could be used,
for getting the joystick X and Y values. I see minimal utility in adding
the boilerplate necessary to use the more sophisticated regmap API in
this case.

As for the handling of endianness, if I am not mistaken the
`be16_to_cpu` macro should manage it.

If you prefer I could add the following function to reduce code duplication:

int seesaw_get_analog(int pin) {
__be16 result;
u8 write_buf[2] = { SEESAW_ADC_BASE, SEESAW_ADC_OFFSET + pin };
int ret;
ret = i2c_master_send(client, write_buf, sizeof(write_buf));
if (ret < 0)
return ret;
ret = i2c_master_recv(client, (char *)&result, sizeof(result));
if (ret < 0)
return ret;
return result;
}

>> + /*
>> + * ADC reads left as max and right as 0, must be reversed since kernel
>> + * expects reports in opposite order.
>> + */
>> + data->x = SEESAW_JOYSTICK_MAX_AXIS - be16_to_cpu(data->x);
>> +
>> + write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_Y;
>> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
>> + if (err < 0)
>> + return err;
>> + err = i2c_master_recv(client, (char *)&data->y, sizeof(data->y));
>> + if (err < 0)
>> + return err;
>> + data->y = be16_to_cpu(data->y);
>> +
>> + return 0;
>> +}
>> +
>> +static void seesaw_poll(struct input_dev *input)
>> +{
>> + struct seesaw_gamepad *private = input_get_drvdata(input);
>> + struct seesaw_data data;
>> + int err;
>> +
>> + err = seesaw_read_data(private->i2c_client, &data);
>> + if (err != 0) {
>> + dev_dbg(&input->dev, "failed to read joystick state: %d\n",
>> + err);
>
> This should be dev_err_ratelimited().
>
>> + return;
>> + }
>> +
>> + input_report_abs(input, ABS_X, data.x);
>> + input_report_abs(input, ABS_Y, data.y);
>> + input_report_key(input, BTN_EAST, data.button_a);
>> + input_report_key(input, BTN_SOUTH, data.button_b);
>> + input_report_key(input, BTN_NORTH, data.button_x);
>> + input_report_key(input, BTN_WEST, data.button_y);
>> + input_report_key(input, BTN_START, data.button_start);
>> + input_report_key(input, BTN_SELECT, data.button_select);
>
> I think you can make this much cleaner and smaller by defining an array
> of structs, each with a key code and bit position. You can then simply
> iterate over the array and call input_report_key() once per element as
> in the following:
>
> struct seesaw_btn_desc {
> unsigned int code;
> unsigned int shift;
> };
>
> static const struct seesaw_btn_desc seesaw_btns[] = {
> {
> .code = BTN_EAST,
> .mask = 5,
> },
> [...]
> };
>
> And then:
>
> btn_status = ...;
>
> for (i = 0; i < ARRAY_SIZE(seesaw_btns); i++)
> input_report_key(input, seesaw_btns[i].code,
> btn_status & seesaw_btns[i].mask);
>
> This would also make it easier to quickly discern what keycodes are mapped
> to which bits in the register.
>
>> + input_sync(input);
>> +}
>> +
>> +static int seesaw_probe(struct i2c_client *client)
>> +{
>> + int err;
>> + struct seesaw_gamepad *private;
>
> I'd rather this be called something like 'seesaw' rather than private.
>
>> + unsigned char register_reset[] = { SEESAW_STATUS_BASE,
>> + SEESAW_STATUS_SWRST, 0xFF };
>> + unsigned char get_hw_id[] = { SEESAW_STATUS_BASE, SEESAW_STATUS_HW_ID };
>> +
>> + err = i2c_master_send(client, register_reset, sizeof(register_reset));
>> + if (err < 0)
>> + return err;
>> +
>> + /* Wait for the registers to reset before proceeding */
>> + mdelay(10);
>> +
>> + private = devm_kzalloc(&client->dev, sizeof(*private), GFP_KERNEL);
>> + if (!private)
>> + return -ENOMEM;
>> +
>> + err = i2c_master_send(client, get_hw_id, sizeof(get_hw_id));
>> + if (err < 0)
>> + return err;
>> +
>> + unsigned char hardware_id;
>
> Same comment as earlier with regard to mixed declarations.
>
>> +
>> + err = i2c_master_recv(client, &hardware_id, 1);
>> + if (err < 0)
>> + return err;
>> +
>> + dev_dbg(&client->dev, "Adafruit Seesaw Gamepad, Hardware ID: %02x\n",
>> + hardware_id);
>> +
>> + private->i2c_client = client;
>> + scnprintf(private->physical_path, sizeof(private->physical_path),
>> + "i2c/%s", dev_name(&client->dev));
>
> This seems overly complex; can we not simply set input_dev->phys to the
> literal "i2c/seesaw-gamepad"? Why to copy at runtime and incur the cost
> of carrying 'physical_path' throughout the life of the module?
>
>> + i2c_set_clientdata(client, private);
>> +
>> + private->input_dev = devm_input_allocate_device(&client->dev);
>> + if (!private->input_dev)
>> + return -ENOMEM;
>> +
>> + private->input_dev->id.bustype = BUS_I2C;
>> + private->input_dev->name = "Adafruit Seesaw Gamepad";
>> + private->input_dev->phys = private->physical_path;
>> + input_set_drvdata(private->input_dev, private);
>> + input_set_abs_params(private->input_dev, ABS_X, 0,
>> + SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
>> + SEESAW_JOYSTICK_FLAT);
>> + input_set_abs_params(private->input_dev, ABS_Y, 0,
>> + SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
>> + SEESAW_JOYSTICK_FLAT);
>> + input_set_capability(private->input_dev, EV_KEY, BTN_EAST);
>> + input_set_capability(private->input_dev, EV_KEY, BTN_SOUTH);
>> + input_set_capability(private->input_dev, EV_KEY, BTN_NORTH);
>> + input_set_capability(private->input_dev, EV_KEY, BTN_WEST);
>> + input_set_capability(private->input_dev, EV_KEY, BTN_START);
>> + input_set_capability(private->input_dev, EV_KEY, BTN_SELECT);
>
> Same comment with regard to creating an array of structs, and hence only
> having to call input_set_capability() from within a small loop.
>
>> +
>> + err = input_setup_polling(private->input_dev, seesaw_poll);
>> + if (err) {
>> + dev_err(&client->dev, "failed to set up polling: %d\n", err);
>> + return err;
>> + }
>> +
>> + input_set_poll_interval(private->input_dev,
>> + SEESAW_GAMEPAD_POLL_INTERVAL);
>> + input_set_max_poll_interval(private->input_dev,
>> + SEESAW_GAMEPAD_POLL_MAX);
>> + input_set_min_poll_interval(private->input_dev,
>> + SEESAW_GAMEPAD_POLL_MIN);
>> +
>> + err = input_register_device(private->input_dev);
>> + if (err) {
>> + dev_err(&client->dev, "failed to register joystick: %d\n", err);
>> + return err;
>> + }
>> +
>> + /* Set Pin Mode to input and enable pull-up resistors */
>> + unsigned char pin_mode[] = { SEESAW_GPIO_BASE, SEESAW_GPIO_DIRCLR_BULK,
>> + BUTTON_MASK >> 24, BUTTON_MASK >> 16,
>> + BUTTON_MASK >> 8, BUTTON_MASK };
>> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
>> + if (err < 0)
>> + return err;
>> + pin_mode[1] = SEESAW_GPIO_PULLENSET;
>> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
>> + if (err < 0)
>> + return err;
>> + pin_mode[1] = SEESAW_GPIO_BULK_SET;
>> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
>> + if (err < 0)
>> + return err;
>
> Please configure the HW before the input device is live and being polled.
>

Could you elaborate on what you meant by this. To my knowledge, the
device is ready to be polled right after the pin state for the
`BUTTON_MASK` is configured. That is also how it's done in the Arduino
driver provided by the manufacturer. Please clarify if I'm missing
something here.

>> +
>> + return 0;
>> +}
>> +
>> +#ifdef CONFIG_OF
>> +static const struct of_device_id of_seesaw_match[] = {
>> + {
>> + .compatible = "adafruit,seesaw-gamepad",
>> + },
>> + { /* Sentinel */ }
>> +};
>> +MODULE_DEVICE_TABLE(of, of_seesaw_match);
>> +#endif /* CONFIG_OF */
>
> Please correct me if I am wrong, but it does not seem that OF support is
> required by this driver. There are no properties beyond the standard ones
> understood by the I2C core, which can match based on the ID table below.
>
>> +
>> +/* clang-format off */
>> +static const struct i2c_device_id seesaw_id_table[] = {
>> + { SEESAW_DEVICE_NAME, 0 },
>> + { /* Sentinel */ }
>> +};
>> +/* clang-format on */
>
> Again, I don't see any need for these directives.
>
>> +
>
> Nit: unnecessary NL.
>
>> +MODULE_DEVICE_TABLE(i2c, seesaw_id_table);
>> +
>> +static struct i2c_driver seesaw_driver = {
>> + .driver = {
>> + .name = SEESAW_DEVICE_NAME,
>> + .of_match_table = of_match_ptr(of_seesaw_match),
>> + },
>> + .id_table = seesaw_id_table,
>> + .probe = seesaw_probe,
>> +};
>> +module_i2c_driver(seesaw_driver);
>> +
>> +MODULE_AUTHOR("Anshul Dalal <[email protected]>");
>> +MODULE_DESCRIPTION("Adafruit Mini I2C Gamepad driver");
>> +MODULE_LICENSE("GPL");
>> --
>> 2.42.0
>>
>
> Kind regards,
> Jeff LaBundy

Regards,
Anshul Dalal

2023-10-26 04:38:49

by Jeff LaBundy

[permalink] [raw]
Subject: Re: [PATCH v5 2/2] input: joystick: driver for Adafruit Seesaw Gamepad

Hi Anshul,

On Wed, Oct 25, 2023 at 03:50:04PM +0530, Anshul Dalal wrote:
> Hello Jeff,
> Thanks for the review, I plan on addressing the changes you requested in
> the next version of the patch. Though I had a few questions:

Sounds great; thank you for the informative discussion.

>
> On 10/23/23 05:12, Jeff LaBundy wrote:
> > Hi Anshul,
> >
> > On Tue, Oct 17, 2023 at 09:13:45AM +0530, Anshul Dalal wrote:
> >> Adds a driver for a mini gamepad that communicates over i2c, the gamepad
> >> has bidirectional thumb stick input and six buttons.
> >>
> >> The gamepad chip utilizes the open framework from Adafruit called 'Seesaw'
> >> to transmit the ADC data for the joystick and digital pin state for the
> >> buttons. I have only implemented the functionality required to receive the
> >> thumb stick and button state.
> >>
> >> Steps in reading the gamepad state over i2c:
> >> 1. Reset the registers
> >> 2. Set the pin mode of the pins specified by the `BUTTON_MASK` to input
> >> `BUTTON_MASK`: A bit-map for the six digital pins internally
> >> connected to the joystick buttons.
> >> 3. Enable internal pullup resistors for the `BUTTON_MASK`
> >> 4. Bulk set the pin state HIGH for `BUTTON_MASK`
> >> 5. Poll the device for button and joystick state done by:
> >> `seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)`
> >>
> >> Product page:
> >> https://www.adafruit.com/product/5743
> >> Arduino driver:
> >> https://github.com/adafruit/Adafruit_Seesaw
> >>
> >> Driver tested on RPi Zero 2W
> >>
> >> Reviewed-by: Thomas Wei?schuh <[email protected]>
> >> Signed-off-by: Anshul Dalal <[email protected]>
> >> ---
> >>
> >> Changes for v5:
> >> - Added link to the datasheet
> >> - Added debug log message when `seesaw_read_data` fails
> >>
> >> Changes for v4:
> >> - Changed `1UL << BUTTON_` to BIT(BUTTON_)
> >> - Removed `hardware_id` field from `struct seesaw_gamepad`
> >> - Removed redundant checks for the number of bytes written and received by
> >> `i2c_master_send` and `i2c_master_recv`
> >> - Used `get_unaligned_be32` to instantiate `u32 result` from `read_buf`
> >> - Changed `result & (1UL << BUTTON_)` to
> >> `test_bit(BUTTON_, (long *)&result)`
> >> - Changed `KBUILD_MODNAME` in id-tables to `SEESAW_DEVICE_NAME`
> >> - Fixed formatting issues
> >> - Changed button reporting:
> >> Since the gamepad had the action buttons in a non-standard layout:
> >> (X)
> >> (Y) (A)
> >> (B)
> >> Therefore moved to using generic directional action button event codes
> >> instead of BTN_[ABXY].
> >>
> >> Changes for v3:
> >> - no updates
> >>
> >> Changes for v2:
> >> adafruit-seesaw.c:
> >> - Renamed file from 'adafruit_seesaw.c'
> >> - Changed device name from 'seesaw_gamepad' to 'seesaw-gamepad'
> >> - Changed count parameter for receiving joystick x on line 118:
> >> `2` to `sizeof(write_buf)`
> >> - Fixed invalid buffer size on line 123 and 126:
> >> `data->y` to `sizeof(data->y)`
> >> - Added comment for the `mdelay(10)` on line 169
> >> - Changed inconsistent indentation on line 271
> >> Kconfig:
> >> - Fixed indentation for the help text
> >> - Updated module name
> >> Makefile:
> >> - Updated module object file name
> >> MAINTAINERS:
> >> - Updated file name for the driver and bindings
> >>
> >> MAINTAINERS | 7 +
> >> drivers/input/joystick/Kconfig | 9 +
> >> drivers/input/joystick/Makefile | 1 +
> >> drivers/input/joystick/adafruit-seesaw.c | 273 +++++++++++++++++++++++
> >> 4 files changed, 290 insertions(+)
> >> create mode 100644 drivers/input/joystick/adafruit-seesaw.c
> >>
> >> diff --git a/MAINTAINERS b/MAINTAINERS
> >> index 6c4cce45a09d..a314f9b48e21 100644
> >> --- a/MAINTAINERS
> >> +++ b/MAINTAINERS
> >> @@ -441,6 +441,13 @@ W: http://wiki.analog.com/AD7879
> >> W: https://ez.analog.com/linux-software-drivers
> >> F: drivers/input/touchscreen/ad7879.c
> >>
> >> +ADAFRUIT MINI I2C GAMEPAD
> >> +M: Anshul Dalal <[email protected]>
> >> +L: [email protected]
> >> +S: Maintained
> >> +F: Documentation/devicetree/bindings/input/adafruit,seesaw-gamepad.yaml
> >> +F: drivers/input/joystick/adafruit-seesaw.c
> >> +
> >> ADDRESS SPACE LAYOUT RANDOMIZATION (ASLR)
> >> M: Jiri Kosina <[email protected]>
> >> S: Maintained
> >> diff --git a/drivers/input/joystick/Kconfig b/drivers/input/joystick/Kconfig
> >> index ac6925ce8366..df9cd1830b29 100644
> >> --- a/drivers/input/joystick/Kconfig
> >> +++ b/drivers/input/joystick/Kconfig
> >> @@ -412,4 +412,13 @@ config JOYSTICK_SENSEHAT
> >> To compile this driver as a module, choose M here: the
> >> module will be called sensehat_joystick.
> >>
> >> +config JOYSTICK_SEESAW
> >> + tristate "Adafruit Mini I2C Gamepad with Seesaw"
> >> + depends on I2C
> >> + help
> >> + Say Y here if you want to use the Adafruit Mini I2C Gamepad.
> >> +
> >> + To compile this driver as a module, choose M here: the module will be
> >> + called adafruit-seesaw.
> >> +
> >> endif
> >> diff --git a/drivers/input/joystick/Makefile b/drivers/input/joystick/Makefile
> >> index 3937535f0098..9976f596a920 100644
> >> --- a/drivers/input/joystick/Makefile
> >> +++ b/drivers/input/joystick/Makefile
> >> @@ -28,6 +28,7 @@ obj-$(CONFIG_JOYSTICK_N64) += n64joy.o
> >> obj-$(CONFIG_JOYSTICK_PSXPAD_SPI) += psxpad-spi.o
> >> obj-$(CONFIG_JOYSTICK_PXRC) += pxrc.o
> >> obj-$(CONFIG_JOYSTICK_QWIIC) += qwiic-joystick.o
> >> +obj-$(CONFIG_JOYSTICK_SEESAW) += adafruit-seesaw.o
> >> obj-$(CONFIG_JOYSTICK_SENSEHAT) += sensehat-joystick.o
> >> obj-$(CONFIG_JOYSTICK_SIDEWINDER) += sidewinder.o
> >> obj-$(CONFIG_JOYSTICK_SPACEBALL) += spaceball.o
> >> diff --git a/drivers/input/joystick/adafruit-seesaw.c b/drivers/input/joystick/adafruit-seesaw.c
> >> new file mode 100644
> >> index 000000000000..2a1eae8d2861
> >> --- /dev/null
> >> +++ b/drivers/input/joystick/adafruit-seesaw.c
> >> @@ -0,0 +1,273 @@
> >> +// SPDX-License-Identifier: GPL-2.0-or-later
> >> +/*
> >> + * Copyright (C) 2023 Anshul Dalal <[email protected]>
> >> + *
> >> + * Driver for Adafruit Mini I2C Gamepad
> >> + *
> >> + * Based on the work of:
> >> + * Oleh Kravchenko (Sparkfun Qwiic Joystick driver)
> >> + *
> >> + * Datasheet: https://cdn-learn.adafruit.com/downloads/pdf/gamepad-qt.pdf
> >> + * Product page: https://www.adafruit.com/product/5743
> >> + * Firmware and hardware sources: https://github.com/adafruit/Adafruit_Seesaw
> >> + */
> >> +
> >> +#include <asm-generic/unaligned.h>
> >> +#include <linux/bits.h>
> >> +#include <linux/delay.h>
> >> +#include <linux/i2c.h>
> >> +#include <linux/input.h>
> >> +#include <linux/kernel.h>
> >> +#include <linux/module.h>
> >> +
> >> +/* clang-format off */
> >
> > I don't think we need this directive; at least, no other input drivers have
> > it, or really any drivers for that matter.
> >
> >> +#define SEESAW_DEVICE_NAME "seesaw-gamepad"
> >> +
> >> +#define SEESAW_STATUS_BASE 0
> >> +#define SEESAW_GPIO_BASE 1
> >> +#define SEESAW_ADC_BASE 9
> >> +
> >> +#define SEESAW_GPIO_DIRCLR_BULK 3
> >> +#define SEESAW_GPIO_BULK 4
> >> +#define SEESAW_GPIO_BULK_SET 5
> >> +#define SEESAW_GPIO_PULLENSET 11
> >> +
> >> +#define SEESAW_STATUS_HW_ID 1
> >> +#define SEESAW_STATUS_SWRST 127
> >> +
> >> +#define SEESAW_ADC_OFFSET 7
> >> +
> >> +#define BUTTON_A 5
> >> +#define BUTTON_B 1
> >> +#define BUTTON_X 6
> >> +#define BUTTON_Y 2
> >> +#define BUTTON_START 16
> >> +#define BUTTON_SELECT 0
> >
> > Please namespace these (e.g. SEESAW_BUTTON_A) to make it clear they refer
> > to device-specific bits and not standard keycodes (e.g. BTN_A). In fact,
> > these seem better off as part of an array of structs; more on that below.
> >
> >> +
> >> +#define ANALOG_X 14
> >> +#define ANALOG_Y 15
> >
> > Please namespace these as well.
> >
> >> +
> >> +#define SEESAW_JOYSTICK_MAX_AXIS 1023
> >> +#define SEESAW_JOYSTICK_FUZZ 2
> >> +#define SEESAW_JOYSTICK_FLAT 4
> >> +
> >> +#define SEESAW_GAMEPAD_POLL_INTERVAL 16
> >> +#define SEESAW_GAMEPAD_POLL_MIN 8
> >> +#define SEESAW_GAMEPAD_POLL_MAX 32
> >> +/* clang-format on */
> >> +
> >> +u32 BUTTON_MASK = BIT(BUTTON_A) | BIT(BUTTON_B) | BIT(BUTTON_X) |
> >> + BIT(BUTTON_Y) | BIT(BUTTON_START) | BIT(BUTTON_SELECT);
> >> +
> >> +struct seesaw_gamepad {
> >> + char physical_path[32];
> >> + struct input_dev *input_dev;
> >> + struct i2c_client *i2c_client;
> >> +};
> >> +
> >> +struct seesaw_data {
> >> + __be16 x;
> >> + __be16 y;
> >> + u8 button_a, button_b, button_x, button_y, button_start, button_select;
> >
> > Please keep these each on a separate line.
> >
> >> +};
> >
> > Please declare this struct as __packed, as that is how it appears to be used.
> >
> >> +
> >> +static int seesaw_read_data(struct i2c_client *client, struct seesaw_data *data)
> >> +{
> >> + int err;
> >
> > Please use 'ret' for return variables that can indicate a positive value on success.
> >
> >> + unsigned char write_buf[2] = { SEESAW_GPIO_BASE, SEESAW_GPIO_BULK };
> >> + unsigned char read_buf[4];
> >
> > Please use standard kernel type definitions (i.e. u8 in this case).
> >
> >> +
> >> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
> >> + if (err < 0)
> >> + return err;
> >
> > You correctly return err (or rather, ret) for negative values, but you should also
> > check that ret matches the size of the data sent. For 0 <= ret < sizeof(writebuf),
> > return -EIO.
> >
> >> + err = i2c_master_recv(client, read_buf, sizeof(read_buf));
> >> + if (err < 0)
> >> + return err;
> >
> > And here.
> >
> >> +
> >> + u32 result = get_unaligned_be32(&read_buf);
> >
> > Please do not mix declarations and code; all declarations must be at the
> > top of the function.
> >
> >> +
> >> + data->button_a = !test_bit(BUTTON_A, (long *)&result);
> >> + data->button_b = !test_bit(BUTTON_B, (long *)&result);
> >> + data->button_x = !test_bit(BUTTON_X, (long *)&result);
> >> + data->button_y = !test_bit(BUTTON_Y, (long *)&result);
> >> + data->button_start = !test_bit(BUTTON_START, (long *)&result);
> >> + data->button_select = !test_bit(BUTTON_SELECT, (long *)&result);
> >> +
> >> + write_buf[0] = SEESAW_ADC_BASE;
> >> + write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_X;
> >> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
> >> + if (err < 0)
> >> + return err;
> >> + err = i2c_master_recv(client, (char *)&data->x, sizeof(data->x));
> >> + if (err < 0)
> >> + return err;
> >
> > This is starting to look like a 16-bit register map. To that end, please
> > consider using regmap instead of open-coding each of these standard write-
> > then-read operations.
> >
> > Using regmap would also save you the trouble of managing the endianness
> > yourself, as well as having to check for incomplete transfers since its
> > functions return zero or a negative error code only.
> >
> In this driver there are only two places a 16-bit regmap could be used,
> for getting the joystick X and Y values. I see minimal utility in adding
> the boilerplate necessary to use the more sophisticated regmap API in
> this case.

I counted a total of three sequences that write two bytes (i.e. a 16-bit
"address"), send a stop condition, then read back a modulo-2 number of
bytes. If the hardware can tolerate a repeated start in between the write
and read operations, which is quite common, all of these can be replaced
with a single call to regmap_read().

A fourth sequence reads back a single byte after the 16-bit "address",
while a fifth writes a single byte after the 16-bit "address." Those two
admittedly break the model.

Given those two oddballs in seesaw_probe(), maybe regmap is not the best
solution after all. You could, however, mix the two and use regmap where
it works, and roll your own where it doesn't.

>
> As for the handling of endianness, if I am not mistaken the
> `be16_to_cpu` macro should manage it.

Right, what I mean to say is that regmap calls be16_to_cpu() for you. You
do not need to do any extra operations on the values returned by regmap.

>
> If you prefer I could add the following function to reduce code duplication:
>
> int seesaw_get_analog(int pin) {
> __be16 result;
> u8 write_buf[2] = { SEESAW_ADC_BASE, SEESAW_ADC_OFFSET + pin };
> int ret;
> ret = i2c_master_send(client, write_buf, sizeof(write_buf));
> if (ret < 0)
> return ret;
> ret = i2c_master_recv(client, (char *)&result, sizeof(result));
> if (ret < 0)
> return ret;
> return result;
> }

Assuming regmap is out of the picture, I'd like to see something even more
generic like the following:

static int seesaw_register_read(struct i2c_client *client,
u16 reg, void *val, u16 len)
{
__be16 reg_buf = cpu_to_be16(reg);
int ret;

ret = i2c_master_send(client, (char *)&reg_buf, sizeof(reg_buf));
if (ret < 0)
return ret;

ret = i2c_master_recv(client, (char *)&val, len);
if (ret < 0)
return ret;

return 0;
}

A call to seesaw_register_read() might look like the following:

int error;
__be16 val;

error = seesaw_register_read(client,
SEESAW_ADC_BASE + SEESAW_ADC_OFFSET + ANALOG_X,
&val, sizeof(val);
if (error)
return error;

input_report_abs(input, ABS_X, be16_to_cpu(val));

Last but not least:

static int seesaw_register_write(struct i2c_client *client, u16 reg, u8 val)
{
u8 buf[sizeof(reg) + sizeof(val)];
int ret;

put_unaligned_be16(reg, buf);
*(buf + sizeof(reg)) = val;

ret = i2c_master_send(client, (char *)&buf, sizeof(buf));
if (ret < 0)
return ret;

return 0;
}

And to reset the device:

error = seesaw_register_write(client,
SEESAW_STATUS_BASE + SEESAW_STATUS_SWRST, 0xFF);
if (error)
return error;

You can extend this as necessary to support the pin configuration registers
discussed below. Does this seem like a reasonable compromise?

>
> >> + /*
> >> + * ADC reads left as max and right as 0, must be reversed since kernel
> >> + * expects reports in opposite order.
> >> + */
> >> + data->x = SEESAW_JOYSTICK_MAX_AXIS - be16_to_cpu(data->x);
> >> +
> >> + write_buf[1] = SEESAW_ADC_OFFSET + ANALOG_Y;
> >> + err = i2c_master_send(client, write_buf, sizeof(write_buf));
> >> + if (err < 0)
> >> + return err;
> >> + err = i2c_master_recv(client, (char *)&data->y, sizeof(data->y));
> >> + if (err < 0)
> >> + return err;
> >> + data->y = be16_to_cpu(data->y);
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +static void seesaw_poll(struct input_dev *input)
> >> +{
> >> + struct seesaw_gamepad *private = input_get_drvdata(input);
> >> + struct seesaw_data data;
> >> + int err;
> >> +
> >> + err = seesaw_read_data(private->i2c_client, &data);
> >> + if (err != 0) {
> >> + dev_dbg(&input->dev, "failed to read joystick state: %d\n",
> >> + err);
> >
> > This should be dev_err_ratelimited().
> >
> >> + return;
> >> + }
> >> +
> >> + input_report_abs(input, ABS_X, data.x);
> >> + input_report_abs(input, ABS_Y, data.y);
> >> + input_report_key(input, BTN_EAST, data.button_a);
> >> + input_report_key(input, BTN_SOUTH, data.button_b);
> >> + input_report_key(input, BTN_NORTH, data.button_x);
> >> + input_report_key(input, BTN_WEST, data.button_y);
> >> + input_report_key(input, BTN_START, data.button_start);
> >> + input_report_key(input, BTN_SELECT, data.button_select);
> >
> > I think you can make this much cleaner and smaller by defining an array
> > of structs, each with a key code and bit position. You can then simply
> > iterate over the array and call input_report_key() once per element as
> > in the following:
> >
> > struct seesaw_btn_desc {
> > unsigned int code;
> > unsigned int shift;
> > };
> >
> > static const struct seesaw_btn_desc seesaw_btns[] = {
> > {
> > .code = BTN_EAST,
> > .mask = 5,
> > },
> > [...]
> > };
> >
> > And then:
> >
> > btn_status = ...;
> >
> > for (i = 0; i < ARRAY_SIZE(seesaw_btns); i++)
> > input_report_key(input, seesaw_btns[i].code,
> > btn_status & seesaw_btns[i].mask);
> >
> > This would also make it easier to quickly discern what keycodes are mapped
> > to which bits in the register.
> >
> >> + input_sync(input);
> >> +}
> >> +
> >> +static int seesaw_probe(struct i2c_client *client)
> >> +{
> >> + int err;
> >> + struct seesaw_gamepad *private;
> >
> > I'd rather this be called something like 'seesaw' rather than private.
> >
> >> + unsigned char register_reset[] = { SEESAW_STATUS_BASE,
> >> + SEESAW_STATUS_SWRST, 0xFF };
> >> + unsigned char get_hw_id[] = { SEESAW_STATUS_BASE, SEESAW_STATUS_HW_ID };
> >> +
> >> + err = i2c_master_send(client, register_reset, sizeof(register_reset));
> >> + if (err < 0)
> >> + return err;
> >> +
> >> + /* Wait for the registers to reset before proceeding */
> >> + mdelay(10);
> >> +
> >> + private = devm_kzalloc(&client->dev, sizeof(*private), GFP_KERNEL);
> >> + if (!private)
> >> + return -ENOMEM;
> >> +
> >> + err = i2c_master_send(client, get_hw_id, sizeof(get_hw_id));
> >> + if (err < 0)
> >> + return err;
> >> +
> >> + unsigned char hardware_id;
> >
> > Same comment as earlier with regard to mixed declarations.
> >
> >> +
> >> + err = i2c_master_recv(client, &hardware_id, 1);
> >> + if (err < 0)
> >> + return err;
> >> +
> >> + dev_dbg(&client->dev, "Adafruit Seesaw Gamepad, Hardware ID: %02x\n",
> >> + hardware_id);
> >> +
> >> + private->i2c_client = client;
> >> + scnprintf(private->physical_path, sizeof(private->physical_path),
> >> + "i2c/%s", dev_name(&client->dev));
> >
> > This seems overly complex; can we not simply set input_dev->phys to the
> > literal "i2c/seesaw-gamepad"? Why to copy at runtime and incur the cost
> > of carrying 'physical_path' throughout the life of the module?
> >
> >> + i2c_set_clientdata(client, private);
> >> +
> >> + private->input_dev = devm_input_allocate_device(&client->dev);
> >> + if (!private->input_dev)
> >> + return -ENOMEM;
> >> +
> >> + private->input_dev->id.bustype = BUS_I2C;
> >> + private->input_dev->name = "Adafruit Seesaw Gamepad";
> >> + private->input_dev->phys = private->physical_path;
> >> + input_set_drvdata(private->input_dev, private);
> >> + input_set_abs_params(private->input_dev, ABS_X, 0,
> >> + SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
> >> + SEESAW_JOYSTICK_FLAT);
> >> + input_set_abs_params(private->input_dev, ABS_Y, 0,
> >> + SEESAW_JOYSTICK_MAX_AXIS, SEESAW_JOYSTICK_FUZZ,
> >> + SEESAW_JOYSTICK_FLAT);
> >> + input_set_capability(private->input_dev, EV_KEY, BTN_EAST);
> >> + input_set_capability(private->input_dev, EV_KEY, BTN_SOUTH);
> >> + input_set_capability(private->input_dev, EV_KEY, BTN_NORTH);
> >> + input_set_capability(private->input_dev, EV_KEY, BTN_WEST);
> >> + input_set_capability(private->input_dev, EV_KEY, BTN_START);
> >> + input_set_capability(private->input_dev, EV_KEY, BTN_SELECT);
> >
> > Same comment with regard to creating an array of structs, and hence only
> > having to call input_set_capability() from within a small loop.
> >
> >> +
> >> + err = input_setup_polling(private->input_dev, seesaw_poll);
> >> + if (err) {
> >> + dev_err(&client->dev, "failed to set up polling: %d\n", err);
> >> + return err;
> >> + }
> >> +
> >> + input_set_poll_interval(private->input_dev,
> >> + SEESAW_GAMEPAD_POLL_INTERVAL);
> >> + input_set_max_poll_interval(private->input_dev,
> >> + SEESAW_GAMEPAD_POLL_MAX);
> >> + input_set_min_poll_interval(private->input_dev,
> >> + SEESAW_GAMEPAD_POLL_MIN);
> >> +
> >> + err = input_register_device(private->input_dev);
> >> + if (err) {
> >> + dev_err(&client->dev, "failed to register joystick: %d\n", err);
> >> + return err;
> >> + }
> >> +
> >> + /* Set Pin Mode to input and enable pull-up resistors */
> >> + unsigned char pin_mode[] = { SEESAW_GPIO_BASE, SEESAW_GPIO_DIRCLR_BULK,
> >> + BUTTON_MASK >> 24, BUTTON_MASK >> 16,
> >> + BUTTON_MASK >> 8, BUTTON_MASK };
> >> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
> >> + if (err < 0)
> >> + return err;
> >> + pin_mode[1] = SEESAW_GPIO_PULLENSET;
> >> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
> >> + if (err < 0)
> >> + return err;
> >> + pin_mode[1] = SEESAW_GPIO_BULK_SET;
> >> + err = i2c_master_send(client, pin_mode, sizeof(pin_mode));
> >> + if (err < 0)
> >> + return err;
> >
> > Please configure the HW before the input device is live and being polled.
> >
>
> Could you elaborate on what you meant by this. To my knowledge, the
> device is ready to be polled right after the pin state for the
> `BUTTON_MASK` is configured. That is also how it's done in the Arduino
> driver provided by the manufacturer. Please clarify if I'm missing
> something here.

Normally, we want to do the following:

1. Configure the hardware.
2. Register the input device.
3. Request an interrupt line or enable polling.

Here, we have placed step (1) at the end of the sequence, which is dangerous
for two reasons:

1. For a brief moment, the device is availing button status to the input core
while the pull-up resistors are not yet enabled, and the buttons are in an
undefined state. Any kind of electrical noise or disturbance may trigger a
false button event.

2. The input poller is reading registers and changing the device's internal
address pointer at the same time probe() is still writing some registers.
This is a concurrency problem.

If what is shown is how the Arduino reference design operates, then I would
argue the reference design is mistaken, or not subject to the same constraints
and behaviors as a Linux input driver. Therefore, please set the pin mode much
earlier in probe().

>
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +#ifdef CONFIG_OF
> >> +static const struct of_device_id of_seesaw_match[] = {
> >> + {
> >> + .compatible = "adafruit,seesaw-gamepad",
> >> + },
> >> + { /* Sentinel */ }
> >> +};
> >> +MODULE_DEVICE_TABLE(of, of_seesaw_match);
> >> +#endif /* CONFIG_OF */
> >
> > Please correct me if I am wrong, but it does not seem that OF support is
> > required by this driver. There are no properties beyond the standard ones
> > understood by the I2C core, which can match based on the ID table below.
> >
> >> +
> >> +/* clang-format off */
> >> +static const struct i2c_device_id seesaw_id_table[] = {
> >> + { SEESAW_DEVICE_NAME, 0 },
> >> + { /* Sentinel */ }
> >> +};
> >> +/* clang-format on */
> >
> > Again, I don't see any need for these directives.
> >
> >> +
> >
> > Nit: unnecessary NL.
> >
> >> +MODULE_DEVICE_TABLE(i2c, seesaw_id_table);
> >> +
> >> +static struct i2c_driver seesaw_driver = {
> >> + .driver = {
> >> + .name = SEESAW_DEVICE_NAME,
> >> + .of_match_table = of_match_ptr(of_seesaw_match),
> >> + },
> >> + .id_table = seesaw_id_table,
> >> + .probe = seesaw_probe,
> >> +};
> >> +module_i2c_driver(seesaw_driver);
> >> +
> >> +MODULE_AUTHOR("Anshul Dalal <[email protected]>");
> >> +MODULE_DESCRIPTION("Adafruit Mini I2C Gamepad driver");
> >> +MODULE_LICENSE("GPL");
> >> --
> >> 2.42.0
> >>
> >
> > Kind regards,
> > Jeff LaBundy
>
> Regards,
> Anshul Dalal

Kind regards,
Jeff LaBundy