From: Tao Ren <[email protected]>
The patch series adds hardware monitoring driver for the Maxim MAX127
chip.
Patch #1 adds the max127 hardware monitoring driver, and patch #2 adds
documentation for the driver.
Resending the patch series (v3) with XDP maintainers removed from to/cc
list to reduce noise.
Tao Ren (2):
hwmon: (max127) Add Maxim MAX127 hardware monitoring driver
docs: hwmon: Document max127 driver
Documentation/hwmon/index.rst | 1 +
Documentation/hwmon/max127.rst | 45 +++++
drivers/hwmon/Kconfig | 9 +
drivers/hwmon/Makefile | 1 +
drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++
5 files changed, 402 insertions(+)
create mode 100644 Documentation/hwmon/max127.rst
create mode 100644 drivers/hwmon/max127.c
--
2.17.1
From: Tao Ren <[email protected]>
Add hardware monitoring driver for the Maxim MAX127 chip.
MAX127 min/max range handling code is inspired by the max197 driver.
Signed-off-by: Tao Ren <[email protected]>
---
Changes in v3:
- no code change. xdp maintainers were removed from to/cc list.
Changes in v2:
- replace devm_hwmon_device_register_with_groups() with
devm_hwmon_device_register_with_info() API.
- divide min/max read and write methods to separate functions.
- fix raw-to-vin conversion logic.
- refine ctrl_byte handling so mutex is not needed to protect the
byte.
- improve i2c_transfer() error handling.
- a few other improvements (comments, variable naming, and etc.).
drivers/hwmon/Kconfig | 9 ++
drivers/hwmon/Makefile | 1 +
drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
3 files changed, 356 insertions(+)
create mode 100644 drivers/hwmon/max127.c
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 9d600e0c5584..716df51edc87 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -950,6 +950,15 @@ config SENSORS_MAX1111
This driver can also be built as a module. If so, the module
will be called max1111.
+config SENSORS_MAX127
+ tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
+ depends on I2C
+ help
+ Say y here to support Maxim's MAX127 DAS chips.
+
+ This driver can also be built as a module. If so, the module
+ will be called max127.
+
config SENSORS_MAX16065
tristate "Maxim MAX16065 System Manager and compatibles"
depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index 1083bbfac779..01ca5d3fbad4 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
+obj-$(CONFIG_SENSORS_MAX127) += max127.o
obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
new file mode 100644
index 000000000000..3df4c225a6a2
--- /dev/null
+++ b/drivers/hwmon/max127.c
@@ -0,0 +1,346 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Hardware monitoring driver for MAX127.
+ *
+ * Copyright (c) 2020 Facebook Inc.
+ */
+
+#include <linux/err.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/i2c.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/sysfs.h>
+
+/*
+ * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
+ * Format" for details.
+ */
+#define MAX127_CTRL_START BIT(7)
+#define MAX127_CTRL_SEL_SHIFT 4
+#define MAX127_CTRL_RNG BIT(3)
+#define MAX127_CTRL_BIP BIT(2)
+#define MAX127_CTRL_PD1 BIT(1)
+#define MAX127_CTRL_PD0 BIT(0)
+
+#define MAX127_NUM_CHANNELS 8
+#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
+
+/*
+ * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
+ * and Polarity Selection" for details.
+ */
+#define MAX127_FULL_RANGE 10000 /* 10V */
+#define MAX127_HALF_RANGE 5000 /* 5V */
+
+/*
+ * MAX127 returns 2 bytes at read:
+ * - the first byte contains data[11:4].
+ * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
+ * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
+ * for details.
+ */
+#define MAX127_DATA_LEN 2
+#define MAX127_DATA_SHIFT 4
+
+#define MAX127_SIGN_BIT BIT(11)
+
+struct max127_data {
+ struct mutex lock;
+ struct i2c_client *client;
+ u8 ctrl_byte[MAX127_NUM_CHANNELS];
+};
+
+static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
+{
+ int status;
+ struct i2c_msg msg = {
+ .addr = client->addr,
+ .flags = 0,
+ .len = sizeof(ctrl_byte),
+ .buf = &ctrl_byte,
+ };
+
+ status = i2c_transfer(client->adapter, &msg, 1);
+ if (status < 0)
+ return status;
+ else if (status != 1)
+ return -EIO;
+
+ return 0;
+}
+
+static int max127_read_channel(struct i2c_client *client, long *val)
+{
+ int status;
+ u8 i2c_data[MAX127_DATA_LEN];
+ struct i2c_msg msg = {
+ .addr = client->addr,
+ .flags = I2C_M_RD,
+ .len = sizeof(i2c_data),
+ .buf = i2c_data,
+ };
+
+ status = i2c_transfer(client->adapter, &msg, 1);
+ if (status < 0)
+ return status;
+ else if (status != 1)
+ return -EIO;
+
+ *val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
+ ((u16)i2c_data[0] << MAX127_DATA_SHIFT);
+ return 0;
+}
+
+static long max127_process_raw(u8 ctrl_byte, long raw)
+{
+ long scale, weight;
+
+ /*
+ * MAX127's data coding is binary in unipolar mode with 1 LSB =
+ * (Full-Scale/4096) and two’s complement binary in bipolar mode
+ * with 1 LSB = [(2 x |FS|)/4096].
+ * Refer to MAX127 datasheet, "Transfer Function" section for
+ * details.
+ */
+ scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
+ MAX127_HALF_RANGE;
+ if (ctrl_byte & MAX127_CTRL_BIP) {
+ weight = (raw & MAX127_SIGN_BIT);
+ raw &= ~MAX127_SIGN_BIT;
+ raw -= weight;
+ raw *= 2;
+ }
+
+ return raw * scale / 4096;
+}
+
+static int max127_read_input(struct max127_data *data, int channel, long *val)
+{
+ long raw;
+ int status;
+ struct i2c_client *client = data->client;
+ u8 ctrl_byte = data->ctrl_byte[channel];
+
+ mutex_lock(&data->lock);
+
+ status = max127_select_channel(client, ctrl_byte);
+ if (status)
+ goto exit;
+
+ status = max127_read_channel(client, &raw);
+ if (status)
+ goto exit;
+
+ *val = max127_process_raw(ctrl_byte, raw);
+
+exit:
+ mutex_unlock(&data->lock);
+ return status;
+}
+
+static int max127_read_min(struct max127_data *data, int channel, long *val)
+{
+ u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
+ static const int min_input_map[4] = {
+ 0, /* RNG=0, BIP=0 */
+ -MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
+ 0, /* RNG=1, BIP=0 */
+ -MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
+ };
+
+ *val = min_input_map[rng_bip];
+ return 0;
+}
+
+static int max127_read_max(struct max127_data *data, int channel, long *val)
+{
+ u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
+ static const int max_input_map[4] = {
+ MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
+ MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
+ MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
+ MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
+ };
+
+ *val = max_input_map[rng_bip];
+ return 0;
+}
+
+static int max127_write_min(struct max127_data *data, int channel, long val)
+{
+ u8 ctrl;
+
+ ctrl = data->ctrl_byte[channel];
+ if (val <= -MAX127_FULL_RANGE) {
+ ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
+ } else if (val < 0) {
+ ctrl |= MAX127_CTRL_BIP;
+ ctrl &= ~MAX127_CTRL_RNG;
+ } else {
+ ctrl &= ~MAX127_CTRL_BIP;
+ }
+ data->ctrl_byte[channel] = ctrl;
+
+ return 0;
+}
+
+static int max127_write_max(struct max127_data *data, int channel, long val)
+{
+ if (val >= MAX127_FULL_RANGE)
+ data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
+ else
+ data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
+
+ return 0;
+}
+
+static umode_t max127_is_visible(const void *_data,
+ enum hwmon_sensor_types type,
+ u32 attr, int channel)
+{
+ if (type == hwmon_in) {
+ switch (attr) {
+ case hwmon_in_input:
+ return 0444;
+
+ case hwmon_in_min:
+ case hwmon_in_max:
+ return 0644;
+
+ default:
+ break;
+ }
+ }
+
+ return 0;
+}
+
+static int max127_read(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long *val)
+{
+ int status;
+ struct max127_data *data = dev_get_drvdata(dev);
+
+ if (type != hwmon_in)
+ return -EOPNOTSUPP;
+
+ switch (attr) {
+ case hwmon_in_input:
+ status = max127_read_input(data, channel, val);
+ break;
+
+ case hwmon_in_min:
+ status = max127_read_min(data, channel, val);
+ break;
+
+ case hwmon_in_max:
+ status = max127_read_max(data, channel, val);
+ break;
+
+ default:
+ status = -EOPNOTSUPP;
+ break;
+ }
+
+ return status;
+}
+
+static int max127_write(struct device *dev, enum hwmon_sensor_types type,
+ u32 attr, int channel, long val)
+{
+ int status;
+ struct max127_data *data = dev_get_drvdata(dev);
+
+ if (type != hwmon_in)
+ return -EOPNOTSUPP;
+
+ switch (attr) {
+ case hwmon_in_min:
+ status = max127_write_min(data, channel, val);
+ break;
+
+ case hwmon_in_max:
+ status = max127_write_max(data, channel, val);
+ break;
+
+ default:
+ status = -EOPNOTSUPP;
+ break;
+ }
+
+ return status;
+}
+
+static const struct hwmon_ops max127_hwmon_ops = {
+ .is_visible = max127_is_visible,
+ .read = max127_read,
+ .write = max127_write,
+};
+
+static const struct hwmon_channel_info *max127_info[] = {
+ HWMON_CHANNEL_INFO(in,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
+ HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
+ NULL,
+};
+
+static const struct hwmon_chip_info max127_chip_info = {
+ .ops = &max127_hwmon_ops,
+ .info = max127_info,
+};
+
+static int max127_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ int i;
+ struct device *hwmon_dev;
+ struct max127_data *data;
+ struct device *dev = &client->dev;
+
+ data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
+ if (!data)
+ return -ENOMEM;
+
+ data->client = client;
+ mutex_init(&data->lock);
+ for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
+ data->ctrl_byte[i] = (MAX127_CTRL_START |
+ MAX127_SET_CHANNEL(i));
+
+ hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
+ data,
+ &max127_chip_info,
+ NULL);
+
+ return PTR_ERR_OR_ZERO(hwmon_dev);
+}
+
+static const struct i2c_device_id max127_id[] = {
+ { "max127", 0 },
+ { }
+};
+MODULE_DEVICE_TABLE(i2c, max127_id);
+
+static struct i2c_driver max127_driver = {
+ .class = I2C_CLASS_HWMON,
+ .driver = {
+ .name = "max127",
+ },
+ .probe = max127_probe,
+ .id_table = max127_id,
+};
+
+module_i2c_driver(max127_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mike Choi <[email protected]>");
+MODULE_AUTHOR("Tao Ren <[email protected]>");
+MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
--
2.17.1
From: Tao Ren <[email protected]>
Add documentation for the max127 hardware monitoring driver.
Signed-off-by: Tao Ren <[email protected]>
---
Changes in v3:
- no code change. xdp maintainers were removed from to/cc list.
Changes in v2:
- add more description for min/max sysfs nodes.
- convert values from volt to millivolt in the document.
Documentation/hwmon/index.rst | 1 +
Documentation/hwmon/max127.rst | 45 ++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)
create mode 100644 Documentation/hwmon/max127.rst
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 408760d13813..0a07b6000c20 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
ltc4245
ltc4260
ltc4261
+ max127
max16064
max16065
max1619
diff --git a/Documentation/hwmon/max127.rst b/Documentation/hwmon/max127.rst
new file mode 100644
index 000000000000..dc192dd9c37c
--- /dev/null
+++ b/Documentation/hwmon/max127.rst
@@ -0,0 +1,45 @@
+.. SPDX-License-Identifier: GPL-2.0-or-later
+
+Kernel driver max127
+====================
+
+Author:
+
+ * Tao Ren <[email protected]>
+
+Supported chips:
+
+ * Maxim MAX127
+
+ Prefix: 'max127'
+
+ Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX127-MAX128.pdf
+
+Description
+-----------
+
+The MAX127 is a multirange, 12-bit data acquisition system (DAS) providing
+8 analog input channels that are independently software programmable for
+a variety of ranges. The available ranges are {0,5V}, {0,10V}, {-5,5V}
+and {-10,10V}.
+
+The MAX127 features a 2-wire, I2C-compatible serial interface that allows
+communication among multiple devices using SDA and SCL lines.
+
+Sysfs interface
+---------------
+
+ ============== ==============================================================
+ in[0-7]_input The input voltage (in mV) of the corresponding channel.
+ RO
+
+ in[0-7]_min The lower input limit (in mV) for the corresponding channel.
+ ADC range and LSB will be updated when the limit is changed.
+ For the MAX127, it will be adjusted to -10000, -5000, or 0.
+ RW
+
+ in[0-7]_max The higher input limit (in mV) for the corresponding channel.
+ ADC range and LSB will be updated when the limit is changed.
+ For the MAX127, it will be adjusted to 0, 5000, or 10000.
+ RW
+ ============== ==============================================================
--
2.17.1
On Thu, Nov 19, 2020 at 09:53:23AM -0800, [email protected] wrote:
> From: Tao Ren <[email protected]>
>
> Add hardware monitoring driver for the Maxim MAX127 chip.
>
> MAX127 min/max range handling code is inspired by the max197 driver.
>
> Signed-off-by: Tao Ren <[email protected]>
Nice cleanup. Couple of minor comments.
Thanks,
Guenter
> ---
> Changes in v3:
> - no code change. xdp maintainers were removed from to/cc list.
> Changes in v2:
> - replace devm_hwmon_device_register_with_groups() with
> devm_hwmon_device_register_with_info() API.
> - divide min/max read and write methods to separate functions.
> - fix raw-to-vin conversion logic.
> - refine ctrl_byte handling so mutex is not needed to protect the
> byte.
> - improve i2c_transfer() error handling.
> - a few other improvements (comments, variable naming, and etc.).
>
> drivers/hwmon/Kconfig | 9 ++
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 356 insertions(+)
> create mode 100644 drivers/hwmon/max127.c
>
> diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> index 9d600e0c5584..716df51edc87 100644
> --- a/drivers/hwmon/Kconfig
> +++ b/drivers/hwmon/Kconfig
> @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> This driver can also be built as a module. If so, the module
> will be called max1111.
>
> +config SENSORS_MAX127
> + tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> + depends on I2C
> + help
> + Say y here to support Maxim's MAX127 DAS chips.
> +
> + This driver can also be built as a module. If so, the module
> + will be called max127.
> +
> config SENSORS_MAX16065
> tristate "Maxim MAX16065 System Manager and compatibles"
> depends on I2C
> diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> index 1083bbfac779..01ca5d3fbad4 100644
> --- a/drivers/hwmon/Makefile
> +++ b/drivers/hwmon/Makefile
> @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
> obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
> obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
> +obj-$(CONFIG_SENSORS_MAX127) += max127.o
> obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
> obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
> obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
> diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> new file mode 100644
> index 000000000000..3df4c225a6a2
> --- /dev/null
> +++ b/drivers/hwmon/max127.c
> @@ -0,0 +1,346 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +/*
> + * Hardware monitoring driver for MAX127.
> + *
> + * Copyright (c) 2020 Facebook Inc.
> + */
> +
> +#include <linux/err.h>
> +#include <linux/hwmon.h>
> +#include <linux/hwmon-sysfs.h>
Not needed.
> +#include <linux/i2c.h>
> +#include <linux/init.h>
> +#include <linux/module.h>
> +#include <linux/sysfs.h>
Not needed.
> +
> +/*
> + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> + * Format" for details.
> + */
> +#define MAX127_CTRL_START BIT(7)
> +#define MAX127_CTRL_SEL_SHIFT 4
> +#define MAX127_CTRL_RNG BIT(3)
> +#define MAX127_CTRL_BIP BIT(2)
> +#define MAX127_CTRL_PD1 BIT(1)
> +#define MAX127_CTRL_PD0 BIT(0)
> +
> +#define MAX127_NUM_CHANNELS 8
> +#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> +
> +/*
> + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> + * and Polarity Selection" for details.
> + */
> +#define MAX127_FULL_RANGE 10000 /* 10V */
> +#define MAX127_HALF_RANGE 5000 /* 5V */
> +
> +/*
> + * MAX127 returns 2 bytes at read:
> + * - the first byte contains data[11:4].
> + * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> + * for details.
> + */
> +#define MAX127_DATA_LEN 2
> +#define MAX127_DATA_SHIFT 4
> +
> +#define MAX127_SIGN_BIT BIT(11)
> +
> +struct max127_data {
> + struct mutex lock;
> + struct i2c_client *client;
> + u8 ctrl_byte[MAX127_NUM_CHANNELS];
> +};
> +
> +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> +{
> + int status;
> + struct i2c_msg msg = {
> + .addr = client->addr,
> + .flags = 0,
> + .len = sizeof(ctrl_byte),
> + .buf = &ctrl_byte,
> + };
> +
> + status = i2c_transfer(client->adapter, &msg, 1);
> + if (status < 0)
> + return status;
> + else if (status != 1)
else after return is not needed.
> + return -EIO;
> +
> + return 0;
> +}
> +
> +static int max127_read_channel(struct i2c_client *client, long *val)
> +{
> + int status;
> + u8 i2c_data[MAX127_DATA_LEN];
> + struct i2c_msg msg = {
> + .addr = client->addr,
> + .flags = I2C_M_RD,
> + .len = sizeof(i2c_data),
> + .buf = i2c_data,
> + };
> +
> + status = i2c_transfer(client->adapter, &msg, 1);
> + if (status < 0)
> + return status;
> + else if (status != 1)
else after return is not needed.
> + return -EIO;
> +
> + *val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> + ((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> + return 0;
> +}
> +
> +static long max127_process_raw(u8 ctrl_byte, long raw)
> +{
> + long scale, weight;
> +
> + /*
> + * MAX127's data coding is binary in unipolar mode with 1 LSB =
> + * (Full-Scale/4096) and two’s complement binary in bipolar mode
> + * with 1 LSB = [(2 x |FS|)/4096].
> + * Refer to MAX127 datasheet, "Transfer Function" section for
> + * details.
> + */
> + scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> + MAX127_HALF_RANGE;
> + if (ctrl_byte & MAX127_CTRL_BIP) {
> + weight = (raw & MAX127_SIGN_BIT);
> + raw &= ~MAX127_SIGN_BIT;
> + raw -= weight;
> + raw *= 2;
> + }
> +
> + return raw * scale / 4096;
> +}
> +
> +static int max127_read_input(struct max127_data *data, int channel, long *val)
> +{
> + long raw;
> + int status;
> + struct i2c_client *client = data->client;
> + u8 ctrl_byte = data->ctrl_byte[channel];
> +
> + mutex_lock(&data->lock);
> +
> + status = max127_select_channel(client, ctrl_byte);
> + if (status)
> + goto exit;
> +
> + status = max127_read_channel(client, &raw);
> + if (status)
> + goto exit;
> +
> + *val = max127_process_raw(ctrl_byte, raw);
> +
> +exit:
> + mutex_unlock(&data->lock);
> + return status;
> +}
> +
> +static int max127_read_min(struct max127_data *data, int channel, long *val)
> +{
> + u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> + static const int min_input_map[4] = {
> + 0, /* RNG=0, BIP=0 */
> + -MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
> + 0, /* RNG=1, BIP=0 */
> + -MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
> + };
> +
> + *val = min_input_map[rng_bip];
> + return 0;
> +}
> +
> +static int max127_read_max(struct max127_data *data, int channel, long *val)
> +{
> + u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> + static const int max_input_map[4] = {
> + MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
> + MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
> + MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
> + MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
> + };
> +
> + *val = max_input_map[rng_bip];
> + return 0;
> +}
> +
> +static int max127_write_min(struct max127_data *data, int channel, long val)
> +{
> + u8 ctrl;
> +
> + ctrl = data->ctrl_byte[channel];
> + if (val <= -MAX127_FULL_RANGE) {
> + ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> + } else if (val < 0) {
> + ctrl |= MAX127_CTRL_BIP;
> + ctrl &= ~MAX127_CTRL_RNG;
> + } else {
> + ctrl &= ~MAX127_CTRL_BIP;
> + }
> + data->ctrl_byte[channel] = ctrl;
Needs mutex protection to avoid parallel writes (which might mess up
ctrl_byte[channel]).
> +
> + return 0;
> +}
> +
> +static int max127_write_max(struct max127_data *data, int channel, long val)
> +{
> + if (val >= MAX127_FULL_RANGE)
> + data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> + else
> + data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> +
Same here, to avoid interaction with write_min (which might otherwise
read ctrl and modify it at the same time as this function).
> + return 0;
> +}
> +
> +static umode_t max127_is_visible(const void *_data,
> + enum hwmon_sensor_types type,
> + u32 attr, int channel)
> +{
> + if (type == hwmon_in) {
> + switch (attr) {
> + case hwmon_in_input:
> + return 0444;
> +
> + case hwmon_in_min:
> + case hwmon_in_max:
> + return 0644;
> +
> + default:
> + break;
> + }
> + }
> +
> + return 0;
> +}
> +
> +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long *val)
> +{
> + int status;
> + struct max127_data *data = dev_get_drvdata(dev);
> +
> + if (type != hwmon_in)
> + return -EOPNOTSUPP;
> +
> + switch (attr) {
> + case hwmon_in_input:
> + status = max127_read_input(data, channel, val);
> + break;
> +
> + case hwmon_in_min:
> + status = max127_read_min(data, channel, val);
> + break;
> +
> + case hwmon_in_max:
> + status = max127_read_max(data, channel, val);
> + break;
> +
> + default:
> + status = -EOPNOTSUPP;
> + break;
> + }
> +
> + return status;
> +}
> +
> +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> + u32 attr, int channel, long val)
> +{
> + int status;
> + struct max127_data *data = dev_get_drvdata(dev);
> +
> + if (type != hwmon_in)
> + return -EOPNOTSUPP;
> +
> + switch (attr) {
> + case hwmon_in_min:
> + status = max127_write_min(data, channel, val);
> + break;
> +
> + case hwmon_in_max:
> + status = max127_write_max(data, channel, val);
> + break;
> +
> + default:
> + status = -EOPNOTSUPP;
> + break;
> + }
> +
> + return status;
> +}
> +
> +static const struct hwmon_ops max127_hwmon_ops = {
> + .is_visible = max127_is_visible,
> + .read = max127_read,
> + .write = max127_write,
> +};
> +
> +static const struct hwmon_channel_info *max127_info[] = {
> + HWMON_CHANNEL_INFO(in,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> + NULL,
> +};
> +
> +static const struct hwmon_chip_info max127_chip_info = {
> + .ops = &max127_hwmon_ops,
> + .info = max127_info,
> +};
> +
> +static int max127_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + int i;
> + struct device *hwmon_dev;
> + struct max127_data *data;
> + struct device *dev = &client->dev;
> +
> + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> + if (!data)
> + return -ENOMEM;
> +
> + data->client = client;
> + mutex_init(&data->lock);
> + for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> + data->ctrl_byte[i] = (MAX127_CTRL_START |
> + MAX127_SET_CHANNEL(i));
> +
> + hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> + data,
> + &max127_chip_info,
> + NULL);
> +
> + return PTR_ERR_OR_ZERO(hwmon_dev);
> +}
> +
> +static const struct i2c_device_id max127_id[] = {
> + { "max127", 0 },
> + { }
> +};
> +MODULE_DEVICE_TABLE(i2c, max127_id);
> +
> +static struct i2c_driver max127_driver = {
> + .class = I2C_CLASS_HWMON,
> + .driver = {
> + .name = "max127",
> + },
> + .probe = max127_probe,
> + .id_table = max127_id,
> +};
> +
> +module_i2c_driver(max127_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Mike Choi <[email protected]>");
> +MODULE_AUTHOR("Tao Ren <[email protected]>");
> +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
On Thu, Nov 19, 2020 at 09:53:24AM -0800, [email protected] wrote:
> From: Tao Ren <[email protected]>
>
> Add documentation for the max127 hardware monitoring driver.
>
> Signed-off-by: Tao Ren <[email protected]>
For my reference:
Reviewed-by: Guenter Roeck <[email protected]>
Guenter
> ---
> Changes in v3:
> - no code change. xdp maintainers were removed from to/cc list.
> Changes in v2:
> - add more description for min/max sysfs nodes.
> - convert values from volt to millivolt in the document.
>
> Documentation/hwmon/index.rst | 1 +
> Documentation/hwmon/max127.rst | 45 ++++++++++++++++++++++++++++++++++
> 2 files changed, 46 insertions(+)
> create mode 100644 Documentation/hwmon/max127.rst
>
> diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
> index 408760d13813..0a07b6000c20 100644
> --- a/Documentation/hwmon/index.rst
> +++ b/Documentation/hwmon/index.rst
> @@ -111,6 +111,7 @@ Hardware Monitoring Kernel Drivers
> ltc4245
> ltc4260
> ltc4261
> + max127
> max16064
> max16065
> max1619
> diff --git a/Documentation/hwmon/max127.rst b/Documentation/hwmon/max127.rst
> new file mode 100644
> index 000000000000..dc192dd9c37c
> --- /dev/null
> +++ b/Documentation/hwmon/max127.rst
> @@ -0,0 +1,45 @@
> +.. SPDX-License-Identifier: GPL-2.0-or-later
> +
> +Kernel driver max127
> +====================
> +
> +Author:
> +
> + * Tao Ren <[email protected]>
> +
> +Supported chips:
> +
> + * Maxim MAX127
> +
> + Prefix: 'max127'
> +
> + Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX127-MAX128.pdf
> +
> +Description
> +-----------
> +
> +The MAX127 is a multirange, 12-bit data acquisition system (DAS) providing
> +8 analog input channels that are independently software programmable for
> +a variety of ranges. The available ranges are {0,5V}, {0,10V}, {-5,5V}
> +and {-10,10V}.
> +
> +The MAX127 features a 2-wire, I2C-compatible serial interface that allows
> +communication among multiple devices using SDA and SCL lines.
> +
> +Sysfs interface
> +---------------
> +
> + ============== ==============================================================
> + in[0-7]_input The input voltage (in mV) of the corresponding channel.
> + RO
> +
> + in[0-7]_min The lower input limit (in mV) for the corresponding channel.
> + ADC range and LSB will be updated when the limit is changed.
> + For the MAX127, it will be adjusted to -10000, -5000, or 0.
> + RW
> +
> + in[0-7]_max The higher input limit (in mV) for the corresponding channel.
> + ADC range and LSB will be updated when the limit is changed.
> + For the MAX127, it will be adjusted to 0, 5000, or 10000.
> + RW
> + ============== ==============================================================
On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> On Thu, Nov 19, 2020 at 09:53:23AM -0800, [email protected] wrote:
> > From: Tao Ren <[email protected]>
> >
> > Add hardware monitoring driver for the Maxim MAX127 chip.
> >
> > MAX127 min/max range handling code is inspired by the max197 driver.
> >
> > Signed-off-by: Tao Ren <[email protected]>
>
> Nice cleanup. Couple of minor comments.
>
> Thanks,
> Guenter
>
> > ---
> > Changes in v3:
> > - no code change. xdp maintainers were removed from to/cc list.
> > Changes in v2:
> > - replace devm_hwmon_device_register_with_groups() with
> > devm_hwmon_device_register_with_info() API.
> > - divide min/max read and write methods to separate functions.
> > - fix raw-to-vin conversion logic.
> > - refine ctrl_byte handling so mutex is not needed to protect the
> > byte.
> > - improve i2c_transfer() error handling.
> > - a few other improvements (comments, variable naming, and etc.).
> >
> > drivers/hwmon/Kconfig | 9 ++
> > drivers/hwmon/Makefile | 1 +
> > drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 356 insertions(+)
> > create mode 100644 drivers/hwmon/max127.c
> >
> > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > index 9d600e0c5584..716df51edc87 100644
> > --- a/drivers/hwmon/Kconfig
> > +++ b/drivers/hwmon/Kconfig
> > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > This driver can also be built as a module. If so, the module
> > will be called max1111.
> >
> > +config SENSORS_MAX127
> > + tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > + depends on I2C
> > + help
> > + Say y here to support Maxim's MAX127 DAS chips.
> > +
> > + This driver can also be built as a module. If so, the module
> > + will be called max127.
> > +
> > config SENSORS_MAX16065
> > tristate "Maxim MAX16065 System Manager and compatibles"
> > depends on I2C
> > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > index 1083bbfac779..01ca5d3fbad4 100644
> > --- a/drivers/hwmon/Makefile
> > +++ b/drivers/hwmon/Makefile
> > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
> > obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
> > obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
> > +obj-$(CONFIG_SENSORS_MAX127) += max127.o
> > obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
> > obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
> > obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
> > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > new file mode 100644
> > index 000000000000..3df4c225a6a2
> > --- /dev/null
> > +++ b/drivers/hwmon/max127.c
> > @@ -0,0 +1,346 @@
> > +// SPDX-License-Identifier: GPL-2.0+
> > +/*
> > + * Hardware monitoring driver for MAX127.
> > + *
> > + * Copyright (c) 2020 Facebook Inc.
> > + */
> > +
> > +#include <linux/err.h>
> > +#include <linux/hwmon.h>
> > +#include <linux/hwmon-sysfs.h>
>
> Not needed.
>
> > +#include <linux/i2c.h>
> > +#include <linux/init.h>
> > +#include <linux/module.h>
> > +#include <linux/sysfs.h>
>
> Not needed.
Thanks for pointing it out. Both includes are deleted in v4.
>
> > +
> > +/*
> > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > + * Format" for details.
> > + */
> > +#define MAX127_CTRL_START BIT(7)
> > +#define MAX127_CTRL_SEL_SHIFT 4
> > +#define MAX127_CTRL_RNG BIT(3)
> > +#define MAX127_CTRL_BIP BIT(2)
> > +#define MAX127_CTRL_PD1 BIT(1)
> > +#define MAX127_CTRL_PD0 BIT(0)
> > +
> > +#define MAX127_NUM_CHANNELS 8
> > +#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > +
> > +/*
> > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > + * and Polarity Selection" for details.
> > + */
> > +#define MAX127_FULL_RANGE 10000 /* 10V */
> > +#define MAX127_HALF_RANGE 5000 /* 5V */
> > +
> > +/*
> > + * MAX127 returns 2 bytes at read:
> > + * - the first byte contains data[11:4].
> > + * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > + * for details.
> > + */
> > +#define MAX127_DATA_LEN 2
> > +#define MAX127_DATA_SHIFT 4
> > +
> > +#define MAX127_SIGN_BIT BIT(11)
> > +
> > +struct max127_data {
> > + struct mutex lock;
> > + struct i2c_client *client;
> > + u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > +};
> > +
> > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > +{
> > + int status;
> > + struct i2c_msg msg = {
> > + .addr = client->addr,
> > + .flags = 0,
> > + .len = sizeof(ctrl_byte),
> > + .buf = &ctrl_byte,
> > + };
> > +
> > + status = i2c_transfer(client->adapter, &msg, 1);
> > + if (status < 0)
> > + return status;
> > + else if (status != 1)
>
> else after return is not needed.
>
> > + return -EIO;
> > +
> > + return 0;
> > +}
> > +
> > +static int max127_read_channel(struct i2c_client *client, long *val)
> > +{
> > + int status;
> > + u8 i2c_data[MAX127_DATA_LEN];
> > + struct i2c_msg msg = {
> > + .addr = client->addr,
> > + .flags = I2C_M_RD,
> > + .len = sizeof(i2c_data),
> > + .buf = i2c_data,
> > + };
> > +
> > + status = i2c_transfer(client->adapter, &msg, 1);
> > + if (status < 0)
> > + return status;
> > + else if (status != 1)
>
> else after return is not needed.
I'm not sure if I understand your suggestion correctly, and I added this
branch to handle the case when i2c_transfer() returns 0, which means the
message is not transferred. Perhaps it would never happen? but anyhow, I
just simplified the check in v4; please kindly review and let me know if
you have further suggestions.
>
> > + return -EIO;
> > +
> > + *val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> > + ((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> > + return 0;
> > +}
> > +
> > +static long max127_process_raw(u8 ctrl_byte, long raw)
> > +{
> > + long scale, weight;
> > +
> > + /*
> > + * MAX127's data coding is binary in unipolar mode with 1 LSB =
> > + * (Full-Scale/4096) and two’s complement binary in bipolar mode
> > + * with 1 LSB = [(2 x |FS|)/4096].
> > + * Refer to MAX127 datasheet, "Transfer Function" section for
> > + * details.
> > + */
> > + scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> > + MAX127_HALF_RANGE;
> > + if (ctrl_byte & MAX127_CTRL_BIP) {
> > + weight = (raw & MAX127_SIGN_BIT);
> > + raw &= ~MAX127_SIGN_BIT;
> > + raw -= weight;
> > + raw *= 2;
> > + }
> > +
> > + return raw * scale / 4096;
> > +}
> > +
> > +static int max127_read_input(struct max127_data *data, int channel, long *val)
> > +{
> > + long raw;
> > + int status;
> > + struct i2c_client *client = data->client;
> > + u8 ctrl_byte = data->ctrl_byte[channel];
> > +
> > + mutex_lock(&data->lock);
> > +
> > + status = max127_select_channel(client, ctrl_byte);
> > + if (status)
> > + goto exit;
> > +
> > + status = max127_read_channel(client, &raw);
> > + if (status)
> > + goto exit;
> > +
> > + *val = max127_process_raw(ctrl_byte, raw);
> > +
> > +exit:
> > + mutex_unlock(&data->lock);
> > + return status;
> > +}
> > +
> > +static int max127_read_min(struct max127_data *data, int channel, long *val)
> > +{
> > + u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > + static const int min_input_map[4] = {
> > + 0, /* RNG=0, BIP=0 */
> > + -MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
> > + 0, /* RNG=1, BIP=0 */
> > + -MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
> > + };
> > +
> > + *val = min_input_map[rng_bip];
> > + return 0;
> > +}
> > +
> > +static int max127_read_max(struct max127_data *data, int channel, long *val)
> > +{
> > + u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > + static const int max_input_map[4] = {
> > + MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
> > + MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
> > + MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
> > + MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
> > + };
> > +
> > + *val = max_input_map[rng_bip];
> > + return 0;
> > +}
> > +
> > +static int max127_write_min(struct max127_data *data, int channel, long val)
> > +{
> > + u8 ctrl;
> > +
> > + ctrl = data->ctrl_byte[channel];
> > + if (val <= -MAX127_FULL_RANGE) {
> > + ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> > + } else if (val < 0) {
> > + ctrl |= MAX127_CTRL_BIP;
> > + ctrl &= ~MAX127_CTRL_RNG;
> > + } else {
> > + ctrl &= ~MAX127_CTRL_BIP;
> > + }
> > + data->ctrl_byte[channel] = ctrl;
>
> Needs mutex protection to avoid parallel writes (which might mess up
> ctrl_byte[channel]).
>
> > +
> > + return 0;
> > +}
> > +
> > +static int max127_write_max(struct max127_data *data, int channel, long val)
> > +{
> > + if (val >= MAX127_FULL_RANGE)
> > + data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> > + else
> > + data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> > +
> Same here, to avoid interaction with write_min (which might otherwise
> read ctrl and modify it at the same time as this function).
Thanks for pointing it out, and both functions are protected by mutex in
v4.
Cheers,
Tao
>
> > + return 0;
> > +}
> > +
> > +static umode_t max127_is_visible(const void *_data,
> > + enum hwmon_sensor_types type,
> > + u32 attr, int channel)
> > +{
> > + if (type == hwmon_in) {
> > + switch (attr) {
> > + case hwmon_in_input:
> > + return 0444;
> > +
> > + case hwmon_in_min:
> > + case hwmon_in_max:
> > + return 0644;
> > +
> > + default:
> > + break;
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> > + u32 attr, int channel, long *val)
> > +{
> > + int status;
> > + struct max127_data *data = dev_get_drvdata(dev);
> > +
> > + if (type != hwmon_in)
> > + return -EOPNOTSUPP;
> > +
> > + switch (attr) {
> > + case hwmon_in_input:
> > + status = max127_read_input(data, channel, val);
> > + break;
> > +
> > + case hwmon_in_min:
> > + status = max127_read_min(data, channel, val);
> > + break;
> > +
> > + case hwmon_in_max:
> > + status = max127_read_max(data, channel, val);
> > + break;
> > +
> > + default:
> > + status = -EOPNOTSUPP;
> > + break;
> > + }
> > +
> > + return status;
> > +}
> > +
> > +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> > + u32 attr, int channel, long val)
> > +{
> > + int status;
> > + struct max127_data *data = dev_get_drvdata(dev);
> > +
> > + if (type != hwmon_in)
> > + return -EOPNOTSUPP;
> > +
> > + switch (attr) {
> > + case hwmon_in_min:
> > + status = max127_write_min(data, channel, val);
> > + break;
> > +
> > + case hwmon_in_max:
> > + status = max127_write_max(data, channel, val);
> > + break;
> > +
> > + default:
> > + status = -EOPNOTSUPP;
> > + break;
> > + }
> > +
> > + return status;
> > +}
> > +
> > +static const struct hwmon_ops max127_hwmon_ops = {
> > + .is_visible = max127_is_visible,
> > + .read = max127_read,
> > + .write = max127_write,
> > +};
> > +
> > +static const struct hwmon_channel_info *max127_info[] = {
> > + HWMON_CHANNEL_INFO(in,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> > + NULL,
> > +};
> > +
> > +static const struct hwmon_chip_info max127_chip_info = {
> > + .ops = &max127_hwmon_ops,
> > + .info = max127_info,
> > +};
> > +
> > +static int max127_probe(struct i2c_client *client,
> > + const struct i2c_device_id *id)
> > +{
> > + int i;
> > + struct device *hwmon_dev;
> > + struct max127_data *data;
> > + struct device *dev = &client->dev;
> > +
> > + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > + if (!data)
> > + return -ENOMEM;
> > +
> > + data->client = client;
> > + mutex_init(&data->lock);
> > + for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> > + data->ctrl_byte[i] = (MAX127_CTRL_START |
> > + MAX127_SET_CHANNEL(i));
> > +
> > + hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> > + data,
> > + &max127_chip_info,
> > + NULL);
> > +
> > + return PTR_ERR_OR_ZERO(hwmon_dev);
> > +}
> > +
> > +static const struct i2c_device_id max127_id[] = {
> > + { "max127", 0 },
> > + { }
> > +};
> > +MODULE_DEVICE_TABLE(i2c, max127_id);
> > +
> > +static struct i2c_driver max127_driver = {
> > + .class = I2C_CLASS_HWMON,
> > + .driver = {
> > + .name = "max127",
> > + },
> > + .probe = max127_probe,
> > + .id_table = max127_id,
> > +};
> > +
> > +module_i2c_driver(max127_driver);
> > +
> > +MODULE_LICENSE("GPL");
> > +MODULE_AUTHOR("Mike Choi <[email protected]>");
> > +MODULE_AUTHOR("Tao Ren <[email protected]>");
> > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > On Thu, Nov 19, 2020 at 09:53:23AM -0800, [email protected] wrote:
> > > From: Tao Ren <[email protected]>
> > >
> > > Add hardware monitoring driver for the Maxim MAX127 chip.
> > >
> > > MAX127 min/max range handling code is inspired by the max197 driver.
> > >
> > > Signed-off-by: Tao Ren <[email protected]>
> >
> > Nice cleanup. Couple of minor comments.
> >
> > Thanks,
> > Guenter
> >
> > > ---
> > > Changes in v3:
> > > - no code change. xdp maintainers were removed from to/cc list.
> > > Changes in v2:
> > > - replace devm_hwmon_device_register_with_groups() with
> > > devm_hwmon_device_register_with_info() API.
> > > - divide min/max read and write methods to separate functions.
> > > - fix raw-to-vin conversion logic.
> > > - refine ctrl_byte handling so mutex is not needed to protect the
> > > byte.
> > > - improve i2c_transfer() error handling.
> > > - a few other improvements (comments, variable naming, and etc.).
> > >
> > > drivers/hwmon/Kconfig | 9 ++
> > > drivers/hwmon/Makefile | 1 +
> > > drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > > 3 files changed, 356 insertions(+)
> > > create mode 100644 drivers/hwmon/max127.c
> > >
> > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > index 9d600e0c5584..716df51edc87 100644
> > > --- a/drivers/hwmon/Kconfig
> > > +++ b/drivers/hwmon/Kconfig
> > > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > > This driver can also be built as a module. If so, the module
> > > will be called max1111.
> > >
> > > +config SENSORS_MAX127
> > > + tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > > + depends on I2C
> > > + help
> > > + Say y here to support Maxim's MAX127 DAS chips.
> > > +
> > > + This driver can also be built as a module. If so, the module
> > > + will be called max127.
> > > +
> > > config SENSORS_MAX16065
> > > tristate "Maxim MAX16065 System Manager and compatibles"
> > > depends on I2C
> > > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > > index 1083bbfac779..01ca5d3fbad4 100644
> > > --- a/drivers/hwmon/Makefile
> > > +++ b/drivers/hwmon/Makefile
> > > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
> > > obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
> > > obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > > obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
> > > +obj-$(CONFIG_SENSORS_MAX127) += max127.o
> > > obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
> > > obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
> > > obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
> > > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > > new file mode 100644
> > > index 000000000000..3df4c225a6a2
> > > --- /dev/null
> > > +++ b/drivers/hwmon/max127.c
> > > @@ -0,0 +1,346 @@
> > > +// SPDX-License-Identifier: GPL-2.0+
> > > +/*
> > > + * Hardware monitoring driver for MAX127.
> > > + *
> > > + * Copyright (c) 2020 Facebook Inc.
> > > + */
> > > +
> > > +#include <linux/err.h>
> > > +#include <linux/hwmon.h>
> > > +#include <linux/hwmon-sysfs.h>
> >
> > Not needed.
> >
> > > +#include <linux/i2c.h>
> > > +#include <linux/init.h>
> > > +#include <linux/module.h>
> > > +#include <linux/sysfs.h>
> >
> > Not needed.
>
> Thanks for pointing it out. Both includes are deleted in v4.
>
> >
> > > +
> > > +/*
> > > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > > + * Format" for details.
> > > + */
> > > +#define MAX127_CTRL_START BIT(7)
> > > +#define MAX127_CTRL_SEL_SHIFT 4
> > > +#define MAX127_CTRL_RNG BIT(3)
> > > +#define MAX127_CTRL_BIP BIT(2)
> > > +#define MAX127_CTRL_PD1 BIT(1)
> > > +#define MAX127_CTRL_PD0 BIT(0)
> > > +
> > > +#define MAX127_NUM_CHANNELS 8
> > > +#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > > +
> > > +/*
> > > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > > + * and Polarity Selection" for details.
> > > + */
> > > +#define MAX127_FULL_RANGE 10000 /* 10V */
> > > +#define MAX127_HALF_RANGE 5000 /* 5V */
> > > +
> > > +/*
> > > + * MAX127 returns 2 bytes at read:
> > > + * - the first byte contains data[11:4].
> > > + * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > > + * for details.
> > > + */
> > > +#define MAX127_DATA_LEN 2
> > > +#define MAX127_DATA_SHIFT 4
> > > +
> > > +#define MAX127_SIGN_BIT BIT(11)
> > > +
> > > +struct max127_data {
> > > + struct mutex lock;
> > > + struct i2c_client *client;
> > > + u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > > +};
> > > +
> > > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > > +{
> > > + int status;
> > > + struct i2c_msg msg = {
> > > + .addr = client->addr,
> > > + .flags = 0,
> > > + .len = sizeof(ctrl_byte),
> > > + .buf = &ctrl_byte,
> > > + };
> > > +
> > > + status = i2c_transfer(client->adapter, &msg, 1);
> > > + if (status < 0)
> > > + return status;
> > > + else if (status != 1)
> >
> > else after return is not needed.
> >
> > > + return -EIO;
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int max127_read_channel(struct i2c_client *client, long *val)
> > > +{
> > > + int status;
> > > + u8 i2c_data[MAX127_DATA_LEN];
> > > + struct i2c_msg msg = {
> > > + .addr = client->addr,
> > > + .flags = I2C_M_RD,
> > > + .len = sizeof(i2c_data),
> > > + .buf = i2c_data,
> > > + };
> > > +
> > > + status = i2c_transfer(client->adapter, &msg, 1);
> > > + if (status < 0)
> > > + return status;
> > > + else if (status != 1)
> >
> > else after return is not needed.
>
> I'm not sure if I understand your suggestion correctly, and I added this
> branch to handle the case when i2c_transfer() returns 0, which means the
> message is not transferred. Perhaps it would never happen? but anyhow, I
> just simplified the check in v4; please kindly review and let me know if
> you have further suggestions.
>
if (status < 0)
return status;
if (status != 1)
return -EIO;
Again, else after return is not needed (and static analyzers will complain
about it).
Guenter
> >
> > > + return -EIO;
> > > +
> > > + *val = (i2c_data[1] >> MAX127_DATA_SHIFT) |
> > > + ((u16)i2c_data[0] << MAX127_DATA_SHIFT);
> > > + return 0;
> > > +}
> > > +
> > > +static long max127_process_raw(u8 ctrl_byte, long raw)
> > > +{
> > > + long scale, weight;
> > > +
> > > + /*
> > > + * MAX127's data coding is binary in unipolar mode with 1 LSB =
> > > + * (Full-Scale/4096) and two’s complement binary in bipolar mode
> > > + * with 1 LSB = [(2 x |FS|)/4096].
> > > + * Refer to MAX127 datasheet, "Transfer Function" section for
> > > + * details.
> > > + */
> > > + scale = (ctrl_byte & MAX127_CTRL_RNG) ? MAX127_FULL_RANGE :
> > > + MAX127_HALF_RANGE;
> > > + if (ctrl_byte & MAX127_CTRL_BIP) {
> > > + weight = (raw & MAX127_SIGN_BIT);
> > > + raw &= ~MAX127_SIGN_BIT;
> > > + raw -= weight;
> > > + raw *= 2;
> > > + }
> > > +
> > > + return raw * scale / 4096;
> > > +}
> > > +
> > > +static int max127_read_input(struct max127_data *data, int channel, long *val)
> > > +{
> > > + long raw;
> > > + int status;
> > > + struct i2c_client *client = data->client;
> > > + u8 ctrl_byte = data->ctrl_byte[channel];
> > > +
> > > + mutex_lock(&data->lock);
> > > +
> > > + status = max127_select_channel(client, ctrl_byte);
> > > + if (status)
> > > + goto exit;
> > > +
> > > + status = max127_read_channel(client, &raw);
> > > + if (status)
> > > + goto exit;
> > > +
> > > + *val = max127_process_raw(ctrl_byte, raw);
> > > +
> > > +exit:
> > > + mutex_unlock(&data->lock);
> > > + return status;
> > > +}
> > > +
> > > +static int max127_read_min(struct max127_data *data, int channel, long *val)
> > > +{
> > > + u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > > + static const int min_input_map[4] = {
> > > + 0, /* RNG=0, BIP=0 */
> > > + -MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
> > > + 0, /* RNG=1, BIP=0 */
> > > + -MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
> > > + };
> > > +
> > > + *val = min_input_map[rng_bip];
> > > + return 0;
> > > +}
> > > +
> > > +static int max127_read_max(struct max127_data *data, int channel, long *val)
> > > +{
> > > + u8 rng_bip = (data->ctrl_byte[channel] >> 2) & 3;
> > > + static const int max_input_map[4] = {
> > > + MAX127_HALF_RANGE, /* RNG=0, BIP=0 */
> > > + MAX127_HALF_RANGE, /* RNG=0, BIP=1 */
> > > + MAX127_FULL_RANGE, /* RNG=1, BIP=0 */
> > > + MAX127_FULL_RANGE, /* RNG=1, BIP=1 */
> > > + };
> > > +
> > > + *val = max_input_map[rng_bip];
> > > + return 0;
> > > +}
> > > +
> > > +static int max127_write_min(struct max127_data *data, int channel, long val)
> > > +{
> > > + u8 ctrl;
> > > +
> > > + ctrl = data->ctrl_byte[channel];
> > > + if (val <= -MAX127_FULL_RANGE) {
> > > + ctrl |= (MAX127_CTRL_RNG | MAX127_CTRL_BIP);
> > > + } else if (val < 0) {
> > > + ctrl |= MAX127_CTRL_BIP;
> > > + ctrl &= ~MAX127_CTRL_RNG;
> > > + } else {
> > > + ctrl &= ~MAX127_CTRL_BIP;
> > > + }
> > > + data->ctrl_byte[channel] = ctrl;
> >
> > Needs mutex protection to avoid parallel writes (which might mess up
> > ctrl_byte[channel]).
> >
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int max127_write_max(struct max127_data *data, int channel, long val)
> > > +{
> > > + if (val >= MAX127_FULL_RANGE)
> > > + data->ctrl_byte[channel] |= MAX127_CTRL_RNG;
> > > + else
> > > + data->ctrl_byte[channel] &= ~MAX127_CTRL_RNG;
> > > +
> > Same here, to avoid interaction with write_min (which might otherwise
> > read ctrl and modify it at the same time as this function).
>
> Thanks for pointing it out, and both functions are protected by mutex in
> v4.
>
>
> Cheers,
>
> Tao
>
> >
> > > + return 0;
> > > +}
> > > +
> > > +static umode_t max127_is_visible(const void *_data,
> > > + enum hwmon_sensor_types type,
> > > + u32 attr, int channel)
> > > +{
> > > + if (type == hwmon_in) {
> > > + switch (attr) {
> > > + case hwmon_in_input:
> > > + return 0444;
> > > +
> > > + case hwmon_in_min:
> > > + case hwmon_in_max:
> > > + return 0644;
> > > +
> > > + default:
> > > + break;
> > > + }
> > > + }
> > > +
> > > + return 0;
> > > +}
> > > +
> > > +static int max127_read(struct device *dev, enum hwmon_sensor_types type,
> > > + u32 attr, int channel, long *val)
> > > +{
> > > + int status;
> > > + struct max127_data *data = dev_get_drvdata(dev);
> > > +
> > > + if (type != hwmon_in)
> > > + return -EOPNOTSUPP;
> > > +
> > > + switch (attr) {
> > > + case hwmon_in_input:
> > > + status = max127_read_input(data, channel, val);
> > > + break;
> > > +
> > > + case hwmon_in_min:
> > > + status = max127_read_min(data, channel, val);
> > > + break;
> > > +
> > > + case hwmon_in_max:
> > > + status = max127_read_max(data, channel, val);
> > > + break;
> > > +
> > > + default:
> > > + status = -EOPNOTSUPP;
> > > + break;
> > > + }
> > > +
> > > + return status;
> > > +}
> > > +
> > > +static int max127_write(struct device *dev, enum hwmon_sensor_types type,
> > > + u32 attr, int channel, long val)
> > > +{
> > > + int status;
> > > + struct max127_data *data = dev_get_drvdata(dev);
> > > +
> > > + if (type != hwmon_in)
> > > + return -EOPNOTSUPP;
> > > +
> > > + switch (attr) {
> > > + case hwmon_in_min:
> > > + status = max127_write_min(data, channel, val);
> > > + break;
> > > +
> > > + case hwmon_in_max:
> > > + status = max127_write_max(data, channel, val);
> > > + break;
> > > +
> > > + default:
> > > + status = -EOPNOTSUPP;
> > > + break;
> > > + }
> > > +
> > > + return status;
> > > +}
> > > +
> > > +static const struct hwmon_ops max127_hwmon_ops = {
> > > + .is_visible = max127_is_visible,
> > > + .read = max127_read,
> > > + .write = max127_write,
> > > +};
> > > +
> > > +static const struct hwmon_channel_info *max127_info[] = {
> > > + HWMON_CHANNEL_INFO(in,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX,
> > > + HWMON_I_INPUT | HWMON_I_MIN | HWMON_I_MAX),
> > > + NULL,
> > > +};
> > > +
> > > +static const struct hwmon_chip_info max127_chip_info = {
> > > + .ops = &max127_hwmon_ops,
> > > + .info = max127_info,
> > > +};
> > > +
> > > +static int max127_probe(struct i2c_client *client,
> > > + const struct i2c_device_id *id)
> > > +{
> > > + int i;
> > > + struct device *hwmon_dev;
> > > + struct max127_data *data;
> > > + struct device *dev = &client->dev;
> > > +
> > > + data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
> > > + if (!data)
> > > + return -ENOMEM;
> > > +
> > > + data->client = client;
> > > + mutex_init(&data->lock);
> > > + for (i = 0; i < ARRAY_SIZE(data->ctrl_byte); i++)
> > > + data->ctrl_byte[i] = (MAX127_CTRL_START |
> > > + MAX127_SET_CHANNEL(i));
> > > +
> > > + hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
> > > + data,
> > > + &max127_chip_info,
> > > + NULL);
> > > +
> > > + return PTR_ERR_OR_ZERO(hwmon_dev);
> > > +}
> > > +
> > > +static const struct i2c_device_id max127_id[] = {
> > > + { "max127", 0 },
> > > + { }
> > > +};
> > > +MODULE_DEVICE_TABLE(i2c, max127_id);
> > > +
> > > +static struct i2c_driver max127_driver = {
> > > + .class = I2C_CLASS_HWMON,
> > > + .driver = {
> > > + .name = "max127",
> > > + },
> > > + .probe = max127_probe,
> > > + .id_table = max127_id,
> > > +};
> > > +
> > > +module_i2c_driver(max127_driver);
> > > +
> > > +MODULE_LICENSE("GPL");
> > > +MODULE_AUTHOR("Mike Choi <[email protected]>");
> > > +MODULE_AUTHOR("Tao Ren <[email protected]>");
> > > +MODULE_DESCRIPTION("MAX127 Hardware Monitoring driver");
On Mon, Nov 23, 2020 at 05:16:41AM -0800, Guenter Roeck wrote:
> On Sun, Nov 22, 2020 at 11:54:49PM -0800, Tao Ren wrote:
> > On Sun, Nov 22, 2020 at 10:33:42AM -0800, Guenter Roeck wrote:
> > > On Thu, Nov 19, 2020 at 09:53:23AM -0800, [email protected] wrote:
> > > > From: Tao Ren <[email protected]>
> > > >
> > > > Add hardware monitoring driver for the Maxim MAX127 chip.
> > > >
> > > > MAX127 min/max range handling code is inspired by the max197 driver.
> > > >
> > > > Signed-off-by: Tao Ren <[email protected]>
> > >
> > > Nice cleanup. Couple of minor comments.
> > >
> > > Thanks,
> > > Guenter
> > >
> > > > ---
> > > > Changes in v3:
> > > > - no code change. xdp maintainers were removed from to/cc list.
> > > > Changes in v2:
> > > > - replace devm_hwmon_device_register_with_groups() with
> > > > devm_hwmon_device_register_with_info() API.
> > > > - divide min/max read and write methods to separate functions.
> > > > - fix raw-to-vin conversion logic.
> > > > - refine ctrl_byte handling so mutex is not needed to protect the
> > > > byte.
> > > > - improve i2c_transfer() error handling.
> > > > - a few other improvements (comments, variable naming, and etc.).
> > > >
> > > > drivers/hwmon/Kconfig | 9 ++
> > > > drivers/hwmon/Makefile | 1 +
> > > > drivers/hwmon/max127.c | 346 +++++++++++++++++++++++++++++++++++++++++
> > > > 3 files changed, 356 insertions(+)
> > > > create mode 100644 drivers/hwmon/max127.c
> > > >
> > > > diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
> > > > index 9d600e0c5584..716df51edc87 100644
> > > > --- a/drivers/hwmon/Kconfig
> > > > +++ b/drivers/hwmon/Kconfig
> > > > @@ -950,6 +950,15 @@ config SENSORS_MAX1111
> > > > This driver can also be built as a module. If so, the module
> > > > will be called max1111.
> > > >
> > > > +config SENSORS_MAX127
> > > > + tristate "Maxim MAX127 12-bit 8-channel Data Acquisition System"
> > > > + depends on I2C
> > > > + help
> > > > + Say y here to support Maxim's MAX127 DAS chips.
> > > > +
> > > > + This driver can also be built as a module. If so, the module
> > > > + will be called max127.
> > > > +
> > > > config SENSORS_MAX16065
> > > > tristate "Maxim MAX16065 System Manager and compatibles"
> > > > depends on I2C
> > > > diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
> > > > index 1083bbfac779..01ca5d3fbad4 100644
> > > > --- a/drivers/hwmon/Makefile
> > > > +++ b/drivers/hwmon/Makefile
> > > > @@ -127,6 +127,7 @@ obj-$(CONFIG_SENSORS_LTC4260) += ltc4260.o
> > > > obj-$(CONFIG_SENSORS_LTC4261) += ltc4261.o
> > > > obj-$(CONFIG_SENSORS_LTQ_CPUTEMP) += ltq-cputemp.o
> > > > obj-$(CONFIG_SENSORS_MAX1111) += max1111.o
> > > > +obj-$(CONFIG_SENSORS_MAX127) += max127.o
> > > > obj-$(CONFIG_SENSORS_MAX16065) += max16065.o
> > > > obj-$(CONFIG_SENSORS_MAX1619) += max1619.o
> > > > obj-$(CONFIG_SENSORS_MAX1668) += max1668.o
> > > > diff --git a/drivers/hwmon/max127.c b/drivers/hwmon/max127.c
> > > > new file mode 100644
> > > > index 000000000000..3df4c225a6a2
> > > > --- /dev/null
> > > > +++ b/drivers/hwmon/max127.c
> > > > @@ -0,0 +1,346 @@
> > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > +/*
> > > > + * Hardware monitoring driver for MAX127.
> > > > + *
> > > > + * Copyright (c) 2020 Facebook Inc.
> > > > + */
> > > > +
> > > > +#include <linux/err.h>
> > > > +#include <linux/hwmon.h>
> > > > +#include <linux/hwmon-sysfs.h>
> > >
> > > Not needed.
> > >
> > > > +#include <linux/i2c.h>
> > > > +#include <linux/init.h>
> > > > +#include <linux/module.h>
> > > > +#include <linux/sysfs.h>
> > >
> > > Not needed.
> >
> > Thanks for pointing it out. Both includes are deleted in v4.
> >
> > >
> > > > +
> > > > +/*
> > > > + * MAX127 Control Byte. Refer to MAX127 datasheet, Table 1 "Control-Byte
> > > > + * Format" for details.
> > > > + */
> > > > +#define MAX127_CTRL_START BIT(7)
> > > > +#define MAX127_CTRL_SEL_SHIFT 4
> > > > +#define MAX127_CTRL_RNG BIT(3)
> > > > +#define MAX127_CTRL_BIP BIT(2)
> > > > +#define MAX127_CTRL_PD1 BIT(1)
> > > > +#define MAX127_CTRL_PD0 BIT(0)
> > > > +
> > > > +#define MAX127_NUM_CHANNELS 8
> > > > +#define MAX127_SET_CHANNEL(ch) (((ch) & 7) << MAX127_CTRL_SEL_SHIFT)
> > > > +
> > > > +/*
> > > > + * MAX127 channel input ranges. Refer to MAX127 datasheet, Table 3 "Range
> > > > + * and Polarity Selection" for details.
> > > > + */
> > > > +#define MAX127_FULL_RANGE 10000 /* 10V */
> > > > +#define MAX127_HALF_RANGE 5000 /* 5V */
> > > > +
> > > > +/*
> > > > + * MAX127 returns 2 bytes at read:
> > > > + * - the first byte contains data[11:4].
> > > > + * - the second byte contains data[3:0] (MSB) and 4 dummy 0s (LSB).
> > > > + * Refer to MAX127 datasheet, "Read a Conversion (Read Cycle)" section
> > > > + * for details.
> > > > + */
> > > > +#define MAX127_DATA_LEN 2
> > > > +#define MAX127_DATA_SHIFT 4
> > > > +
> > > > +#define MAX127_SIGN_BIT BIT(11)
> > > > +
> > > > +struct max127_data {
> > > > + struct mutex lock;
> > > > + struct i2c_client *client;
> > > > + u8 ctrl_byte[MAX127_NUM_CHANNELS];
> > > > +};
> > > > +
> > > > +static int max127_select_channel(struct i2c_client *client, u8 ctrl_byte)
> > > > +{
> > > > + int status;
> > > > + struct i2c_msg msg = {
> > > > + .addr = client->addr,
> > > > + .flags = 0,
> > > > + .len = sizeof(ctrl_byte),
> > > > + .buf = &ctrl_byte,
> > > > + };
> > > > +
> > > > + status = i2c_transfer(client->adapter, &msg, 1);
> > > > + if (status < 0)
> > > > + return status;
> > > > + else if (status != 1)
> > >
> > > else after return is not needed.
> > >
> > > > + return -EIO;
> > > > +
> > > > + return 0;
> > > > +}
> > > > +
> > > > +static int max127_read_channel(struct i2c_client *client, long *val)
> > > > +{
> > > > + int status;
> > > > + u8 i2c_data[MAX127_DATA_LEN];
> > > > + struct i2c_msg msg = {
> > > > + .addr = client->addr,
> > > > + .flags = I2C_M_RD,
> > > > + .len = sizeof(i2c_data),
> > > > + .buf = i2c_data,
> > > > + };
> > > > +
> > > > + status = i2c_transfer(client->adapter, &msg, 1);
> > > > + if (status < 0)
> > > > + return status;
> > > > + else if (status != 1)
> > >
> > > else after return is not needed.
> >
> > I'm not sure if I understand your suggestion correctly, and I added this
> > branch to handle the case when i2c_transfer() returns 0, which means the
> > message is not transferred. Perhaps it would never happen? but anyhow, I
> > just simplified the check in v4; please kindly review and let me know if
> > you have further suggestions.
> >
>
> if (status < 0)
> return status;
> if (status != 1)
> return -EIO;
>
> Again, else after return is not needed (and static analyzers will complain
> about it).
>
> Guenter
Ahh, I get it now (I didn't know static analyzers would complain about
it). Thanks for the sharing, and it's fixed in v5.
Cheers,
Tao