NXP PCA9570 is 4-bit I2C GPO expander without interrupt functionality.
Its ports are controlled only by a data byte without register address.
As there is no other driver similar enough to be adapted for it, a new
driver is introduced here.
Signed-off-by: Sungbo Eo <[email protected]>
---
v2:
* move the direction functions below the set functions
* use devm_gpiochip_add_data() and remove the remove callback
v1:
Tested in kernel 5.4 on an ipq40xx platform.
This is my first time submitting a whole driver patch, and I'm not really familiar with this PCA expander series.
Please let me know how I can improve this patch further.
FYI there's an unmerged patch for this chip.
http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2017-May/105602.html
I don't have PCA9571 either so I didn't add support for it.
---
drivers/gpio/Kconfig | 8 ++
drivers/gpio/Makefile | 1 +
drivers/gpio/gpio-pca9570.c | 148 ++++++++++++++++++++++++++++++++++++
3 files changed, 157 insertions(+)
create mode 100644 drivers/gpio/gpio-pca9570.c
diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
index c6b5c65c8405..d10dcb81b841 100644
--- a/drivers/gpio/Kconfig
+++ b/drivers/gpio/Kconfig
@@ -962,6 +962,14 @@ config GPIO_PCA953X_IRQ
Say yes here to enable the pca953x to be used as an interrupt
controller. It requires the driver to be built in the kernel.
+config GPIO_PCA9570
+ tristate "PCA9570 4-Bit I2C GPO expander"
+ help
+ Say yes here to enable the GPO driver for the NXP PCA9570 chip.
+
+ To compile this driver as a module, choose M here: the module will
+ be called gpio-pca9570.
+
config GPIO_PCF857X
tristate "PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders"
select GPIOLIB_IRQCHIP
diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
index 1e4894e0bf0f..33cb40c28a61 100644
--- a/drivers/gpio/Makefile
+++ b/drivers/gpio/Makefile
@@ -110,6 +110,7 @@ obj-$(CONFIG_GPIO_OCTEON) += gpio-octeon.o
obj-$(CONFIG_GPIO_OMAP) += gpio-omap.o
obj-$(CONFIG_GPIO_PALMAS) += gpio-palmas.o
obj-$(CONFIG_GPIO_PCA953X) += gpio-pca953x.o
+obj-$(CONFIG_GPIO_PCA9570) += gpio-pca9570.o
obj-$(CONFIG_GPIO_PCF857X) += gpio-pcf857x.o
obj-$(CONFIG_GPIO_PCH) += gpio-pch.o
obj-$(CONFIG_GPIO_PCIE_IDIO_24) += gpio-pcie-idio-24.o
diff --git a/drivers/gpio/gpio-pca9570.c b/drivers/gpio/gpio-pca9570.c
new file mode 100644
index 000000000000..e6b6c4e791c0
--- /dev/null
+++ b/drivers/gpio/gpio-pca9570.c
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Driver for PCA9570 I2C GPO expander
+ *
+ * Copyright (C) 2020 Sungbo Eo <[email protected]>
+ *
+ * Based on gpio-tpic2810.c
+ * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
+ * Andrew F. Davis <[email protected]>
+ */
+
+#include <linux/gpio/driver.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+
+/**
+ * struct pca9570 - GPIO driver data
+ * @chip: GPIO controller chip
+ * @client: I2C device pointer
+ * @buffer: Buffer for device register
+ * @lock: Protects write sequences
+ */
+struct pca9570 {
+ struct gpio_chip chip;
+ struct i2c_client *client;
+ u8 buffer;
+ struct mutex lock;
+};
+
+static void pca9570_set_mask_bits(struct gpio_chip *chip, u8 mask, u8 bits)
+{
+ struct pca9570 *gpio = gpiochip_get_data(chip);
+ u8 buffer;
+ int err;
+
+ mutex_lock(&gpio->lock);
+
+ buffer = gpio->buffer & ~mask;
+ buffer |= (mask & bits);
+
+ err = i2c_smbus_write_byte(gpio->client, buffer);
+ if (!err)
+ gpio->buffer = buffer;
+
+ mutex_unlock(&gpio->lock);
+}
+
+static void pca9570_set(struct gpio_chip *chip, unsigned offset, int value)
+{
+ pca9570_set_mask_bits(chip, BIT(offset), value ? BIT(offset) : 0);
+}
+
+static void pca9570_set_multiple(struct gpio_chip *chip, unsigned long *mask,
+ unsigned long *bits)
+{
+ pca9570_set_mask_bits(chip, *mask, *bits);
+}
+
+static int pca9570_get_direction(struct gpio_chip *chip,
+ unsigned offset)
+{
+ /* This device always output */
+ return GPIO_LINE_DIRECTION_OUT;
+}
+
+static int pca9570_direction_input(struct gpio_chip *chip,
+ unsigned offset)
+{
+ /* This device is output only */
+ return -EINVAL;
+}
+
+static int pca9570_direction_output(struct gpio_chip *chip,
+ unsigned offset, int value)
+{
+ /* This device always output */
+ pca9570_set(chip, offset, value);
+ return 0;
+}
+
+static const struct gpio_chip template_chip = {
+ .label = "pca9570",
+ .owner = THIS_MODULE,
+ .get_direction = pca9570_get_direction,
+ .direction_input = pca9570_direction_input,
+ .direction_output = pca9570_direction_output,
+ .set = pca9570_set,
+ .set_multiple = pca9570_set_multiple,
+ .base = -1,
+ .ngpio = 4,
+ .can_sleep = true,
+};
+
+static const struct of_device_id pca9570_of_match_table[] = {
+ { .compatible = "nxp,pca9570" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, pca9570_of_match_table);
+
+static int pca9570_probe(struct i2c_client *client,
+ const struct i2c_device_id *id)
+{
+ struct pca9570 *gpio;
+ int ret;
+
+ gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
+ if (!gpio)
+ return -ENOMEM;
+
+ i2c_set_clientdata(client, gpio);
+
+ gpio->chip = template_chip;
+ gpio->chip.parent = &client->dev;
+
+ gpio->client = client;
+
+ mutex_init(&gpio->lock);
+
+ ret = devm_gpiochip_add_data(&client->dev, &gpio->chip, gpio);
+ if (ret < 0) {
+ dev_err(&client->dev, "Unable to register gpiochip\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+static const struct i2c_device_id pca9570_id_table[] = {
+ { "pca9570", },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(i2c, pca9570_id_table);
+
+static struct i2c_driver pca9570_driver = {
+ .driver = {
+ .name = "pca9570",
+ .of_match_table = pca9570_of_match_table,
+ },
+ .probe = pca9570_probe,
+ .remove = pca9570_remove,
+ .id_table = pca9570_id_table,
+};
+module_i2c_driver(pca9570_driver);
+
+MODULE_AUTHOR("Sungbo Eo <[email protected]>");
+MODULE_DESCRIPTION("GPIO expander driver for PCA9570");
+MODULE_LICENSE("GPL v2");
--
2.27.0
On Thu, Jun 25, 2020 at 10:59 AM Sungbo Eo <[email protected]> wrote:
>
> NXP PCA9570 is 4-bit I2C GPO expander without interrupt functionality.
> Its ports are controlled only by a data byte without register address.
>
> As there is no other driver similar enough to be adapted for it, a new
> driver is introduced here.
Thanks for an update. I'll look at them later, so please defer the
next version a bit (perhaps for one week).
My comments below.
...
> +static void pca9570_set_mask_bits(struct gpio_chip *chip, u8 mask, u8 bits)
> +{
> + struct pca9570 *gpio = gpiochip_get_data(chip);
> + u8 buffer;
> + int err;
> +
> + mutex_lock(&gpio->lock);
> + buffer = gpio->buffer & ~mask;
> + buffer |= (mask & bits);
Usual pattern is to put this on one line
buffer = (gpio->buffer & ~mask) | (bits & mask);
> + err = i2c_smbus_write_byte(gpio->client, buffer);
> + if (!err)
> + gpio->buffer = buffer;
I'm not sure I understand why this is under lock.
> +
> + mutex_unlock(&gpio->lock);
Can't you simple do it here like
if (err)
return;
... = buffer;
?
> +}
...
> +static int pca9570_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
Can't you use ->probe_new() instead?
> +{
> + struct pca9570 *gpio;
> + int ret;
> +
> + gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
> + if (!gpio)
> + return -ENOMEM;
> +
> + i2c_set_clientdata(client, gpio);
Either move this before return 0; or...
> + gpio->chip = template_chip;
> + gpio->chip.parent = &client->dev;
> +
> + gpio->client = client;
> +
> + mutex_init(&gpio->lock);
> +
> + ret = devm_gpiochip_add_data(&client->dev, &gpio->chip, gpio);
> + if (ret < 0) {
(What is the meaning of ' < 0' ?
> + dev_err(&client->dev, "Unable to register gpiochip\n");
> + return ret;
> + }
> +
> + return 0;
...simple return devm_...(...);
> +}
--
With Best Regards,
Andy Shevchenko
Hi Sungbo,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on gpio/for-next]
[also build test ERROR on v5.8-rc2 next-20200625]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Sungbo-Eo/gpio-add-GPO-driver-for-PCA9570/20200625-160356
base: https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git for-next
config: mips-allyesconfig (attached as .config)
compiler: mips-linux-gcc (GCC) 9.3.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=mips
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email protected]>
All errors (new ones prefixed by >>):
>> drivers/gpio/gpio-pca9570.c:141:12: error: 'pca9570_remove' undeclared here (not in a function); did you mean 'pca9570_probe'?
141 | .remove = pca9570_remove,
| ^~~~~~~~~~~~~~
| pca9570_probe
vim +141 drivers/gpio/gpio-pca9570.c
134
135 static struct i2c_driver pca9570_driver = {
136 .driver = {
137 .name = "pca9570",
138 .of_match_table = pca9570_of_match_table,
139 },
140 .probe = pca9570_probe,
> 141 .remove = pca9570_remove,
142 .id_table = pca9570_id_table,
143 };
144 module_i2c_driver(pca9570_driver);
145
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]
Hi Sungbo,
Thank you for the patch! Yet something to improve:
[auto build test ERROR on gpio/for-next]
[also build test ERROR on v5.8-rc2 next-20200625]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Sungbo-Eo/gpio-add-GPO-driver-for-PCA9570/20200625-160356
base: https://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-gpio.git for-next
config: x86_64-allyesconfig (attached as .config)
compiler: clang version 11.0.0 (https://github.com/llvm/llvm-project 8911a35180c6777188fefe0954a2451a2b91deaf)
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# install x86_64 cross compiling tool for clang build
# apt-get install binutils-x86-64-linux-gnu
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=x86_64
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <[email protected]>
All errors (new ones prefixed by >>):
>> drivers/gpio/gpio-pca9570.c:141:12: error: use of undeclared identifier 'pca9570_remove'; did you mean 'pca9570_probe'?
.remove = pca9570_remove,
^~~~~~~~~~~~~~
pca9570_probe
drivers/gpio/gpio-pca9570.c:101:12: note: 'pca9570_probe' declared here
static int pca9570_probe(struct i2c_client *client,
^
>> drivers/gpio/gpio-pca9570.c:141:12: error: incompatible function pointer types initializing 'int (*)(struct i2c_client *)' with an expression of type 'int (struct i2c_client *, const struct i2c_device_id *)' [-Werror,-Wincompatible-function-pointer-types]
.remove = pca9570_remove,
^~~~~~~~~~~~~~
2 errors generated.
vim +141 drivers/gpio/gpio-pca9570.c
134
135 static struct i2c_driver pca9570_driver = {
136 .driver = {
137 .name = "pca9570",
138 .of_match_table = pca9570_of_match_table,
139 },
140 .probe = pca9570_probe,
> 141 .remove = pca9570_remove,
142 .id_table = pca9570_id_table,
143 };
144 module_i2c_driver(pca9570_driver);
145
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/[email protected]
On Thu, Jun 25, 2020 at 9:58 AM Sungbo Eo <[email protected]> wrote:
>
> NXP PCA9570 is 4-bit I2C GPO expander without interrupt functionality.
> Its ports are controlled only by a data byte without register address.
>
> As there is no other driver similar enough to be adapted for it, a new
> driver is introduced here.
>
> Signed-off-by: Sungbo Eo <[email protected]>
Hi Sungbo,
on top of Andy's review, here are some more nits I spotted.
> ---
> v2:
> * move the direction functions below the set functions
> * use devm_gpiochip_add_data() and remove the remove callback
>
> v1:
> Tested in kernel 5.4 on an ipq40xx platform.
>
> This is my first time submitting a whole driver patch, and I'm not really familiar with this PCA expander series.
> Please let me know how I can improve this patch further.
>
> FYI there's an unmerged patch for this chip.
> http://driverdev.linuxdriverproject.org/pipermail/driverdev-devel/2017-May/105602.html
> I don't have PCA9571 either so I didn't add support for it.
> ---
> drivers/gpio/Kconfig | 8 ++
> drivers/gpio/Makefile | 1 +
> drivers/gpio/gpio-pca9570.c | 148 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 157 insertions(+)
> create mode 100644 drivers/gpio/gpio-pca9570.c
>
> diff --git a/drivers/gpio/Kconfig b/drivers/gpio/Kconfig
> index c6b5c65c8405..d10dcb81b841 100644
> --- a/drivers/gpio/Kconfig
> +++ b/drivers/gpio/Kconfig
> @@ -962,6 +962,14 @@ config GPIO_PCA953X_IRQ
> Say yes here to enable the pca953x to be used as an interrupt
> controller. It requires the driver to be built in the kernel.
>
> +config GPIO_PCA9570
> + tristate "PCA9570 4-Bit I2C GPO expander"
> + help
> + Say yes here to enable the GPO driver for the NXP PCA9570 chip.
> +
> + To compile this driver as a module, choose M here: the module will
> + be called gpio-pca9570.
> +
> config GPIO_PCF857X
> tristate "PCF857x, PCA{85,96}7x, and MAX732[89] I2C GPIO expanders"
> select GPIOLIB_IRQCHIP
> diff --git a/drivers/gpio/Makefile b/drivers/gpio/Makefile
> index 1e4894e0bf0f..33cb40c28a61 100644
> --- a/drivers/gpio/Makefile
> +++ b/drivers/gpio/Makefile
> @@ -110,6 +110,7 @@ obj-$(CONFIG_GPIO_OCTEON) += gpio-octeon.o
> obj-$(CONFIG_GPIO_OMAP) += gpio-omap.o
> obj-$(CONFIG_GPIO_PALMAS) += gpio-palmas.o
> obj-$(CONFIG_GPIO_PCA953X) += gpio-pca953x.o
> +obj-$(CONFIG_GPIO_PCA9570) += gpio-pca9570.o
> obj-$(CONFIG_GPIO_PCF857X) += gpio-pcf857x.o
> obj-$(CONFIG_GPIO_PCH) += gpio-pch.o
> obj-$(CONFIG_GPIO_PCIE_IDIO_24) += gpio-pcie-idio-24.o
> diff --git a/drivers/gpio/gpio-pca9570.c b/drivers/gpio/gpio-pca9570.c
> new file mode 100644
> index 000000000000..e6b6c4e791c0
> --- /dev/null
> +++ b/drivers/gpio/gpio-pca9570.c
> @@ -0,0 +1,148 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Driver for PCA9570 I2C GPO expander
> + *
> + * Copyright (C) 2020 Sungbo Eo <[email protected]>
> + *
> + * Based on gpio-tpic2810.c
> + * Copyright (C) 2015 Texas Instruments Incorporated - http://www.ti.com/
> + * Andrew F. Davis <[email protected]>
> + */
> +
> +#include <linux/gpio/driver.h>
> +#include <linux/i2c.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +
> +/**
> + * struct pca9570 - GPIO driver data
> + * @chip: GPIO controller chip
> + * @client: I2C device pointer
> + * @buffer: Buffer for device register
> + * @lock: Protects write sequences
> + */
> +struct pca9570 {
> + struct gpio_chip chip;
> + struct i2c_client *client;
> + u8 buffer;
Could you rename it to reg or something else more obvious? A buffer
can be for anything.
> + struct mutex lock;
> +};
> +
> +static void pca9570_set_mask_bits(struct gpio_chip *chip, u8 mask, u8 bits)
> +{
> + struct pca9570 *gpio = gpiochip_get_data(chip);
> + u8 buffer;
> + int err;
> +
> + mutex_lock(&gpio->lock);
> +
> + buffer = gpio->buffer & ~mask;
> + buffer |= (mask & bits);
> +
> + err = i2c_smbus_write_byte(gpio->client, buffer);
> + if (!err)
> + gpio->buffer = buffer;
> +
> + mutex_unlock(&gpio->lock);
> +}
> +
> +static void pca9570_set(struct gpio_chip *chip, unsigned offset, int value)
> +{
> + pca9570_set_mask_bits(chip, BIT(offset), value ? BIT(offset) : 0);
> +}
> +
> +static void pca9570_set_multiple(struct gpio_chip *chip, unsigned long *mask,
> + unsigned long *bits)
> +{
> + pca9570_set_mask_bits(chip, *mask, *bits);
> +}
> +
> +static int pca9570_get_direction(struct gpio_chip *chip,
> + unsigned offset)
> +{
> + /* This device always output */
> + return GPIO_LINE_DIRECTION_OUT;
> +}
> +
> +static int pca9570_direction_input(struct gpio_chip *chip,
> + unsigned offset)
> +{
> + /* This device is output only */
> + return -EINVAL;
> +}
> +
> +static int pca9570_direction_output(struct gpio_chip *chip,
> + unsigned offset, int value)
> +{
> + /* This device always output */
> + pca9570_set(chip, offset, value);
> + return 0;
> +}
> +
> +static const struct gpio_chip template_chip = {
> + .label = "pca9570",
> + .owner = THIS_MODULE,
> + .get_direction = pca9570_get_direction,
> + .direction_input = pca9570_direction_input,
> + .direction_output = pca9570_direction_output,
> + .set = pca9570_set,
> + .set_multiple = pca9570_set_multiple,
> + .base = -1,
> + .ngpio = 4,
> + .can_sleep = true,
> +};
> +
> +static const struct of_device_id pca9570_of_match_table[] = {
> + { .compatible = "nxp,pca9570" },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, pca9570_of_match_table);
If you're not using it in probe than maybe move it next to the I2C device table?
> +
> +static int pca9570_probe(struct i2c_client *client,
> + const struct i2c_device_id *id)
> +{
> + struct pca9570 *gpio;
> + int ret;
> +
> + gpio = devm_kzalloc(&client->dev, sizeof(*gpio), GFP_KERNEL);
> + if (!gpio)
> + return -ENOMEM;
> +
> + i2c_set_clientdata(client, gpio);
> +
> + gpio->chip = template_chip;
> + gpio->chip.parent = &client->dev;
> +
> + gpio->client = client;
> +
> + mutex_init(&gpio->lock);
> +
> + ret = devm_gpiochip_add_data(&client->dev, &gpio->chip, gpio);
> + if (ret < 0) {
> + dev_err(&client->dev, "Unable to register gpiochip\n");
You don't need this message, the core library will print something for
you. Just do return devm_gpiochip_add_data().
> + return ret;
> + }
> +
> + return 0;
> +}
> +
> +static const struct i2c_device_id pca9570_id_table[] = {
> + { "pca9570", },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(i2c, pca9570_id_table);
> +
> +static struct i2c_driver pca9570_driver = {
> + .driver = {
> + .name = "pca9570",
> + .of_match_table = pca9570_of_match_table,
> + },
> + .probe = pca9570_probe,
> + .remove = pca9570_remove,
> + .id_table = pca9570_id_table,
> +};
> +module_i2c_driver(pca9570_driver);
> +
> +MODULE_AUTHOR("Sungbo Eo <[email protected]>");
> +MODULE_DESCRIPTION("GPIO expander driver for PCA9570");
> +MODULE_LICENSE("GPL v2");
> --
Bart
On Tue, Jun 30, 2020 at 12:28 PM Bartosz Golaszewski
<[email protected]> wrote:
> On Thu, Jun 25, 2020 at 9:58 AM Sungbo Eo <[email protected]> wrote:
> > +static const struct of_device_id pca9570_of_match_table[] = {
> > + { .compatible = "nxp,pca9570" },
> > + { /* sentinel */ }
> > +};
> > +MODULE_DEVICE_TABLE(of, pca9570_of_match_table);
>
> If you're not using it in probe than maybe move it next to the I2C device table?
(Side note)
...and even if so it can be assessed via a struct device pointer:
dev->driver->id_table (don't remember by heart, but you have an idea).
--
With Best Regards,
Andy Shevchenko
Thanks for all the reviews! I've updated the patch, please have a look.
And I have something to ask.
# echo 1 > gpio408/value
# cat gpio408/value
cat: read error: I/O error
# cat gpio408/direction
out
# echo out > gpio408/direction
# echo in > gpio408/direction
[ 91.006691] gpio-408 (sysfs): gpiod_direction_input: missing get()
but have direction_input()
ash: write error: I/O error
I've never dealt with GPO expander before, so this seems a bit odd to me.
Is it perfectly okay to leave get() and direction_input() unimplemented?
Thanks.
On 2020-06-30 18:53, Andy Shevchenko wrote:
> On Tue, Jun 30, 2020 at 12:28 PM Bartosz Golaszewski
> <[email protected]> wrote:
>> On Thu, Jun 25, 2020 at 9:58 AM Sungbo Eo <[email protected]> wrote:
>
>>> +static const struct of_device_id pca9570_of_match_table[] = {
>>> + { .compatible = "nxp,pca9570" },
>>> + { /* sentinel */ }
>>> +};
>>> +MODULE_DEVICE_TABLE(of, pca9570_of_match_table);
>>
>> If you're not using it in probe than maybe move it next to the I2C device table?
>
> (Side note)
> ...and even if so it can be assessed via a struct device pointer:
> dev->driver->id_table (don't remember by heart, but you have an idea).
>
On Tue, Jun 30, 2020 at 7:11 PM Sungbo Eo <[email protected]> wrote:
>
> Thanks for all the reviews! I've updated the patch, please have a look.
>
> And I have something to ask.
>
> # echo 1 > gpio408/value
> # cat gpio408/value
> cat: read error: I/O error
> # cat gpio408/direction
> out
> # echo out > gpio408/direction
> # echo in > gpio408/direction
> [ 91.006691] gpio-408 (sysfs): gpiod_direction_input: missing get()
> but have direction_input()
> ash: write error: I/O error
>
> I've never dealt with GPO expander before, so this seems a bit odd to me.
> Is it perfectly okay to leave get() and direction_input() unimplemented?
Actually it would be better to return the value you set for output in ->get().
--
With Best Regards,
Andy Shevchenko