[PATCH] gpio: constify opaque pointer in gpio_device_find() match function

[PATCH] gpio: constify opaque pointer in gpio_device_find() match function

[Krzysztof Kozlowski]

The match function used in gpio_device_find() should not modify the
contents of passed opaque pointer, because such modification would not
be necessary for actual matching and it could lead to quite unreadable,
spaghetti code.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
---
 drivers/gpio/gpiolib-acpi.c | 2 +-
 drivers/gpio/gpiolib-of.c   | 7 ++++---
 drivers/gpio/gpiolib.c      | 6 +++---
 include/linux/gpio/driver.h | 2 +-
 4 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpiolib-acpi.c b/drivers/gpio/gpiolib-acpi.c
index cd3e9657cc36..899cd505073e 100644
--- a/drivers/gpio/gpiolib-acpi.c
+++ b/drivers/gpio/gpiolib-acpi.c
@@ -126,7 +126,7 @@ static DEFINE_MUTEX(acpi_gpio_deferred_req_irqs_lock);
 static LIST_HEAD(acpi_gpio_deferred_req_irqs_list);
 static bool acpi_gpio_deferred_req_irqs_done;
 
-static int acpi_gpiochip_find(struct gpio_chip *gc, void *data)
+static int acpi_gpiochip_find(struct gpio_chip *gc, const void *data)
 {
 	return device_match_acpi_handle(&gc->gpiodev->dev, data);
 }
diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 77509aa19900..35d717fd393f 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -118,9 +118,10 @@ int of_gpio_get_count(struct device *dev, const char *con_id)
 	return ret ? ret : -ENOENT;
 }
 
-static int of_gpiochip_match_node_and_xlate(struct gpio_chip *chip, void *data)
+static int of_gpiochip_match_node_and_xlate(struct gpio_chip *chip,
+					    const void *data)
 {
-	struct of_phandle_args *gpiospec = data;
+	const struct of_phandle_args *gpiospec = data;
 
 	return device_match_of_node(&chip->gpiodev->dev, gpiospec->np) &&
 				chip->of_xlate &&
@@ -852,7 +853,7 @@ static void of_gpiochip_remove_hog(struct gpio_chip *chip,
 			gpiochip_free_own_desc(desc);
 }
 
-static int of_gpiochip_match_node(struct gpio_chip *chip, void *data)
+static int of_gpiochip_match_node(struct gpio_chip *chip, const void *data)
 {
 	return device_match_of_node(&chip->gpiodev->dev, data);
 }
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 24d046268a01..0e332b24c7b8 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1114,7 +1114,7 @@ EXPORT_SYMBOL_GPL(gpiochip_remove);
  */
 struct gpio_device *gpio_device_find(void *data,
 				     int (*match)(struct gpio_chip *gc,
-						  void *data))
+						  const void *data))
 {
 	struct gpio_device *gdev;
 
@@ -1136,7 +1136,7 @@ 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)
+static int gpio_chip_match_by_label(struct gpio_chip *gc, const void *label)
 {
 	return gc->label && !strcmp(gc->label, label);
 }
@@ -1156,7 +1156,7 @@ struct gpio_device *gpio_device_find_by_label(const char *label)
 }
 EXPORT_SYMBOL_GPL(gpio_device_find_by_label);
 
-static int gpio_chip_match_by_fwnode(struct gpio_chip *gc, void *fwnode)
+static int gpio_chip_match_by_fwnode(struct gpio_chip *gc, const void *fwnode)
 {
 	return device_match_fwnode(&gc->gpiodev->dev, fwnode);
 }
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 3a37d058cfcf..51b23211794d 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -629,7 +629,7 @@ int devm_gpiochip_add_data_with_key(struct device *dev, struct gpio_chip *gc,
 				    struct lock_class_key *request_key);
 
 struct gpio_device *gpio_device_find(void *data,
-				int (*match)(struct gpio_chip *gc, void *data));
+				int (*match)(struct gpio_chip *gc, const void *data));
 struct gpio_device *gpio_device_find_by_label(const char *label);
 struct gpio_device *gpio_device_find_by_fwnode(const struct fwnode_handle *fwnode);
 
-- 
2.34.1

Re: [PATCH] gpio: constify opaque pointer in gpio_device_find() match function

[Mika Westerberg]

On Thu, Feb 08, 2024 at 09:27:04PM +0100, Krzysztof Kozlowski wrote:
> The match function used in gpio_device_find() should not modify the
> contents of passed opaque pointer, because such modification would not
> be necessary for actual matching and it could lead to quite unreadable,
> spaghetti code.
> 
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>

Re: [PATCH] gpio: constify opaque pointer in gpio_device_find() match function

[Linus Walleij]

On Thu, Feb 8, 2024 at 9:27 PM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:

> The match function used in gpio_device_find() should not modify the
> contents of passed opaque pointer, because such modification would not
> be necessary for actual matching and it could lead to quite unreadable,
> spaghetti code.
>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>

It's what we call a pure function, good const-correctness fix.
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij

Re: [PATCH] gpio: constify opaque pointer in gpio_device_find() match function

[Andy Shevchenko]

On Thu, Feb 08, 2024 at 09:27:04PM +0100, Krzysztof Kozlowski wrote:
> The match function used in gpio_device_find() should not modify the
> contents of passed opaque pointer, because such modification would not
> be necessary for actual matching and it could lead to quite unreadable,
> spaghetti code.

IIRC I also asked Bart about this in his series where something similar
was used.

Good it's not only me who sees the benefits from this.
FWIW,
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH] gpio: constify opaque pointer in gpio_device_find() match function

[Bartosz Golaszewski]

On Thu, Feb 8, 2024 at 9:27 PM Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> The match function used in gpio_device_find() should not modify the
> contents of passed opaque pointer, because such modification would not
> be necessary for actual matching and it could lead to quite unreadable,
> spaghetti code.
>
> Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
> ---

Applied, thanks!

Bart