From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

By far the most common way of looking up GPIO devices is using their
label. Provide a helpers for that to avoid every user implementing their
own matching function.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
---
 drivers/gpio/gpiolib.c      | 21 +++++++++++++++++++++
 include/linux/gpio/driver.h |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 0371d23f0a46..9f20311e4c1a 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -20,6 +20,7 @@
 #include <linux/seq_file.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/string.h>
 
 #include <linux/gpio.h>
 #include <linux/gpio/driver.h>
@@ -1081,6 +1082,26 @@ struct gpio_device *gpio_device_find(void *data,
 }
 EXPORT_SYMBOL_GPL(gpio_device_find);
 
+static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
+{
+	return gc->label && !strcmp(gc->label, label);
+}
+
+/**
+ * gpio_device_find_by_label() - wrapper around gpio_device_find() finding the
+ *                               GPIO device by its backing chip's label
+ * @label: Label to lookup
+ *
+ * Returns:
+ * Reference to the GPIO device or NULL. Reference must be released with
+ * gpio_device_put().
+ */
+struct gpio_device *gpio_device_find_by_label(const char *label)
+{
+	return gpio_device_find((void *)label, gpio_chip_match_by_label);
+}
+EXPORT_SYMBOL_GPL(gpio_device_find_by_label);
+
 static int gpiochip_match_name(struct gpio_chip *gc, void *data)
 {
 	const char *name = data;
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index bf27cc8392fb..bcf418441ef2 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -608,6 +608,7 @@ struct gpio_chip *gpiochip_find(void *data,
 
 struct gpio_device *gpio_device_find(void *data,
 				int (*match)(struct gpio_chip *gc, void *data));
+struct gpio_device *gpio_device_find_by_label(const char *label);
 
 struct gpio_device *gpio_device_get(struct gpio_device *gdev);
 void gpio_device_put(struct gpio_device *gdev);
-- 
2.39.2

On Tue, Sep 12, 2023 at 12:07:20PM +0200, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> 
> By far the most common way of looking up GPIO devices is using their
> label. Provide a helpers for that to avoid every user implementing their
> own matching function.

...

> +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> +{
> +	return gc->label && !strcmp(gc->label, label);

When gc->label can be NULL?

> +}

-- 
With Best Regards,
Andy Shevchenko

On Tue, Sep 12, 2023 at 12:57 PM Andy Shevchenko
<andriy.shevchenko@linux.intel.com> wrote:
>
> On Tue, Sep 12, 2023 at 12:07:20PM +0200, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
> >
> > By far the most common way of looking up GPIO devices is using their
> > label. Provide a helpers for that to avoid every user implementing their
> > own matching function.
>
> ...
>
> > +static int gpio_chip_match_by_label(struct gpio_chip *gc, void *label)
> > +{
> > +     return gc->label && !strcmp(gc->label, label);
>
> When gc->label can be NULL?
>

Whenever the driver doesn't assign it. The copy in gpio_device is set
to "unknown" for display in logs/user-space but not the one in
gpio_chip.

Bart

> > +}
>
> --
> With Best Regards,
> Andy Shevchenko
>
>