gpiolib: allow exported GPIO nodes to be named using sysfs links (a4177ee7) · Commits · 戴 / test

Documentation/gpio.txt

+10 −0

Original line number	Diff line number	Diff line
		@@ -555,6 +555,11 @@ requested using gpio_request():
		/* reverse gpio_export() */
		void gpio_unexport();

		/* create a sysfs link to an exported GPIO node */
		int gpio_export_link(struct device dev, const char name,
		unsigned gpio)


		After a kernel driver requests a GPIO, it may only be made available in
		the sysfs interface by gpio_export(). The driver can control whether the
		signal direction may change. This helps drivers prevent userspace code
		@@ -563,3 +568,8 @@ from accidentally clobbering important system state.
		This explicit exporting can help with debugging (by making some kinds
		of experiments easier), or can provide an always-there interface that's
		suitable for documenting as part of a board support package.

		After the GPIO has been exported, gpio_export_link() allows creating
		symlinks from elsewhere in sysfs to the GPIO sysfs node. Drivers can
		use this to provide the interface under their own device in sysfs with
		a descriptive name.

+45 −0

Original line number	Diff line number	Diff line
		@@ -504,6 +504,51 @@ static int match_export(struct device dev, void data)
		return dev_get_drvdata(dev) == data;
		}

		/**
		* gpio_export_link - create a sysfs link to an exported GPIO node
		* @dev: device under which to create symlink
		* @name: name of the symlink
		* @gpio: gpio to create symlink to, already exported
		*
		* Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
		* node. Caller is responsible for unlinking.
		*
		* Returns zero on success, else an error.
		*/
		int gpio_export_link(struct device dev, const char name, unsigned gpio)
		{
		struct gpio_desc *desc;
		int status = -EINVAL;

		if (!gpio_is_valid(gpio))
		goto done;

		mutex_lock(&sysfs_lock);

		desc = &gpio_desc[gpio];

		if (test_bit(FLAG_EXPORT, &desc->flags)) {
		struct device *tdev;

		tdev = class_find_device(&gpio_class, NULL, desc, match_export);
		if (tdev != NULL) {
		status = sysfs_create_link(&dev->kobj, &tdev->kobj,
		name);
		} else {
		status = -ENODEV;
		}
		}

		mutex_unlock(&sysfs_lock);

		done:
		if (status)
		pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);

		return status;
		}
		EXPORT_SYMBOL_GPL(gpio_export_link);

		/**
		* gpio_unexport - reverse effect of gpio_export()
		* @gpio: gpio to make unavailable

+8 −0

Original line number	Diff line number	Diff line
		@@ -141,6 +141,8 @@ extern int __gpio_to_irq(unsigned gpio);
		* but more typically is configured entirely from userspace.
		*/
		extern int gpio_export(unsigned gpio, bool direction_may_change);
		extern int gpio_export_link(struct device dev, const char name,
		unsigned gpio);
		extern void gpio_unexport(unsigned gpio);

		#endif /* CONFIG_GPIO_SYSFS */
		@@ -185,6 +187,12 @@ static inline int gpio_export(unsigned gpio, bool direction_may_change)
		return -ENOSYS;
		}

		static inline int gpio_export_link(struct device dev, const char name,
		unsigned gpio)
		{
		return -ENOSYS;
		}

		static inline void gpio_unexport(unsigned gpio)
		{
		}

+11 −0

Original line number	Diff line number	Diff line
		@@ -12,6 +12,8 @@
		#include <linux/types.h>
		#include <linux/errno.h>

		struct device;

		/*
		* Some platforms don't support the GPIO programming interface.
		*
		@@ -89,6 +91,15 @@ static inline int gpio_export(unsigned gpio, bool direction_may_change)
		return -EINVAL;
		}

		static inline int gpio_export_link(struct device dev, const char name,
		unsigned gpio)
		{
		/* GPIO can never have been exported */
		WARN_ON(1);
		return -EINVAL;
		}


		static inline void gpio_unexport(unsigned gpio)
		{
		/* GPIO can never have been exported */