Commit 1e4f6db6 authored by Bartosz Golaszewski's avatar Bartosz Golaszewski
Browse files

gpiolib: support shared GPIOs in core subsystem code 



As the final step in adding official support for shared GPIOs, enable
the previously added elements in core GPIO subsystem code. Set-up shared
GPIOs when adding a GPIO chip, tear it down on removal and check if a
GPIO descriptor looked up during the firmware-node stage is shared and
fall-back to machine lookup in this case.

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-v4-5-b51f97b1abd8@linaro.org


Signed-off-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
parent e992d54c

drivers/gpio/gpiolib.c

+41 −9
Original line number Diff line number Diff line
@@ -37,6 +37,7 @@ 
#include "gpiolib-acpi.h"

#include "gpiolib-cdev.h"

#include "gpiolib-of.h"

#include "gpiolib-shared.h"

#include "gpiolib-swnode.h"

#include "gpiolib-sysfs.h"

#include "gpiolib.h"
@@ -1200,6 +1201,10 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, 
	if (ret)

		goto err_remove_irqchip_mask;



	ret = gpio_device_setup_shared(gdev);

	if (ret)

		goto err_remove_irqchip;



	/*

	 * By first adding the chardev, and then adding the device,

	 * we get a device node entry in sysfs under
@@ -1211,10 +1216,13 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data, 
	if (gpiolib_initialized) {

		ret = gpiochip_setup_dev(gdev);

		if (ret)

			goto err_remove_irqchip;

			goto err_teardown_shared;

	}



	return 0;



err_teardown_shared:

	gpio_device_teardown_shared(gdev);

err_remove_irqchip:

	gpiochip_irqchip_remove(gc);

err_remove_irqchip_mask:
@@ -1283,6 +1291,7 @@ void gpiochip_remove(struct gpio_chip *gc) 
	/* Numb the device, cancelling all outstanding operations */

	rcu_assign_pointer(gdev->chip, NULL);

	synchronize_srcu(&gdev->srcu);

	gpio_device_teardown_shared(gdev);

	gpiochip_irqchip_remove(gc);

	acpi_gpiochip_remove(gc);

	of_gpiochip_remove(gc);
@@ -4652,11 +4661,29 @@ struct gpio_desc *gpiod_find_and_request(struct device *consumer, 
	scoped_guard(srcu, &gpio_devices_srcu) {

		desc = gpiod_fwnode_lookup(fwnode, consumer, con_id, idx,

					   &flags, &lookupflags);

		if (!IS_ERR_OR_NULL(desc) &&

		    test_bit(GPIOD_FLAG_SHARED, &desc->flags)) {

			/*

			 * We're dealing with a GPIO shared by multiple

			 * consumers. This is the moment to add the machine

			 * lookup table for the proxy device as previously

			 * we only knew the consumer's fwnode.

			 */

			ret = gpio_shared_add_proxy_lookup(consumer, lookupflags);

			if (ret)

				return ERR_PTR(ret);



			/* Trigger platform lookup for shared GPIO proxy. */

			desc = ERR_PTR(-ENOENT);

			/* Trigger it even for fwnode-only gpiod_get(). */

			platform_lookup_allowed = true;

		}



		if (gpiod_not_found(desc) && platform_lookup_allowed) {

			/*

			 * Either we are not using DT or ACPI, or their lookup

			 * did not return a result. In that case, use platform

			 * lookup as a fallback.

			 * did not return a result or this is a shared GPIO. In

			 * that case, use platform lookup as a fallback.

			 */

			dev_dbg(consumer,

				"using lookup tables for GPIO lookup\n");
@@ -4679,14 +4706,19 @@ struct gpio_desc *gpiod_find_and_request(struct device *consumer, 
			return ERR_PTR(ret);



		/*

		 * This happens when there are several consumers for

		 * the same GPIO line: we just return here without

		 * further initialization. It is a bit of a hack.

		 * This is necessary to support fixed regulators.

		 *

		 * FIXME: Make this more sane and safe.

		 */

		dev_info(consumer, "nonexclusive access to GPIO for %s\n", name);

		 * This happens when there are several consumers for the same

		 * GPIO line: we just return here without further

		 * initialization. It's a hack introduced long ago to support

		 * fixed regulators. We now have a better solution with

		 * automated scanning where affected platforms just need to

		 * select the provided Kconfig option.

		 *

		 * FIXME: Remove the GPIOD_FLAGS_BIT_NONEXCLUSIVE flag after

		 * making sure all platforms use the new mechanism.

		 */

		dev_info(consumer,

			 "nonexclusive access to GPIO for %s, consider updating your code to using gpio-shared-proxy\n",

			 name);

		return desc;

	}