Commit eb374f76 authored by Bartosz Golaszewski's avatar Bartosz Golaszewski
Browse files

gpio: provide gpiod_is_shared() 



Provide an interface allowing consumers to check if a GPIO descriptor
represents a GPIO that can potentially be shared by multiple consumers
at the same time. This is exposed to allow subsystems that already
work around the limitations of the current non-exclusive GPIO handling
in some ways, to gradually convert to relying on the new shared GPIO
feature of GPIOLIB.

Extend the gpiolib-shared module to mark the GPIO shared proxy
descriptors with a flag checked by the new interface.

Reviewed-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Acked-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20251112-gpio-shared-v4-6-b51f97b1abd8@linaro.org


Signed-off-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
parent 1e4f6db6

drivers/gpio/gpiolib-shared.c

+18 −0
Original line number Diff line number Diff line
@@ -314,6 +314,24 @@ int gpio_device_setup_shared(struct gpio_device *gdev) 


	guard(mutex)(&gpio_shared_lock);



	list_for_each_entry(entry, &gpio_shared_list, list) {

		list_for_each_entry(ref, &entry->refs, list) {

			if (gdev->dev.parent == &ref->adev.dev) {

				/*

				 * This is a shared GPIO proxy. Mark its

				 * descriptor as such and return here.

				 */

				__set_bit(GPIOD_FLAG_SHARED_PROXY,

					  &gdev->descs[0].flags);

				return 0;

			}

		}

	}



	/*

	 * This is not a shared GPIO proxy but it still may be the device

	 * exposing shared pins. Find them and create the proxy devices.

	 */

	list_for_each_entry(entry, &gpio_shared_list, list) {

		if (!device_match_fwnode(&gdev->dev, entry->fwnode))

			continue;

drivers/gpio/gpiolib.c

+20 −0
Original line number Diff line number Diff line
@@ -3990,6 +3990,26 @@ int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name) 
}

EXPORT_SYMBOL_GPL(gpiod_set_consumer_name);



/**

 * gpiod_is_shared() - check if this GPIO can be shared by multiple consumers

 * @desc: GPIO to inspect

 *

 * Returns:

 * True if this GPIO can be shared by multiple consumers at once. False if it's

 * a regular, exclusive GPIO.

 *

 * Note:

 * This function returning true does not mean that this GPIO is currently being

 * shared. It means the GPIO core has registered the fact that the firmware

 * configuration indicates that it can be shared by multiple consumers and is

 * in charge of arbitrating the access.

 */

bool gpiod_is_shared(const struct gpio_desc *desc)

{

	return test_bit(GPIOD_FLAG_SHARED_PROXY, &desc->flags);

}

EXPORT_SYMBOL_GPL(gpiod_is_shared);



/**

 * gpiod_to_irq() - return the IRQ corresponding to a GPIO

 * @desc: gpio whose IRQ will be returned (already requested)

drivers/gpio/gpiolib.h

+1 −0
Original line number Diff line number Diff line
@@ -205,6 +205,7 @@ struct gpio_desc { 
#define GPIOD_FLAG_EVENT_CLOCK_REALTIME	18 /* GPIO CDEV reports REALTIME timestamps in events */

#define GPIOD_FLAG_EVENT_CLOCK_HTE	19 /* GPIO CDEV reports hardware timestamps in events */

#define GPIOD_FLAG_SHARED		20 /* GPIO is shared by multiple consumers */

#define GPIOD_FLAG_SHARED_PROXY		21 /* GPIO is a virtual proxy to a physically shared pin. */



	/* Connection label */

	struct gpio_desc_label __rcu *label;

include/linux/gpio/consumer.h

+9 −0
Original line number Diff line number Diff line
@@ -167,6 +167,8 @@ int gpiod_cansleep(const struct gpio_desc *desc); 
int gpiod_to_irq(const struct gpio_desc *desc);

int gpiod_set_consumer_name(struct gpio_desc *desc, const char *name);



bool gpiod_is_shared(const struct gpio_desc *desc);



/* Convert between the old gpio_ and new gpiod_ interfaces */

struct gpio_desc *gpio_to_desc(unsigned gpio);

int desc_to_gpio(const struct gpio_desc *desc);
@@ -520,6 +522,13 @@ static inline int gpiod_set_consumer_name(struct gpio_desc *desc, 
	return -EINVAL;

}



static inline bool gpiod_is_shared(const struct gpio_desc *desc)

{

	/* GPIO can never have been requested */

	WARN_ON(desc);

	return false;

}



static inline struct gpio_desc *gpio_to_desc(unsigned gpio)

{

	return NULL;