gpiolib: add support for changing value polarity in sysfs (07697461) · Commits · 戴 / test

Documentation/gpio.txt

+15 −0

Original line number	Diff line number	Diff line
		@@ -531,6 +531,13 @@ and have the following read/write attributes:
		This file exists only if the pin can be configured as an
		interrupt generating input pin.

		"active_low" ... reads as either 0 (false) or 1 (true). Write
		any nonzero value to invert the value attribute both
		for reading and writing. Existing and subsequent
		poll(2) support configuration via the edge attribute
		for "rising" and "falling" edges will follow this
		setting.

		GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
		controller implementing GPIOs starting at #42) and have the following
		read-only attributes:
		@@ -566,6 +573,8 @@ requested using gpio_request():
		int gpio_export_link(struct device dev, const char name,
		unsigned gpio)

		/* change the polarity of a GPIO node in sysfs */
		int gpio_sysfs_set_active_low(unsigned gpio, int value);

		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
		@@ -580,3 +589,9 @@ 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.

		Drivers can use gpio_sysfs_set_active_low() to hide GPIO line polarity
		differences between boards from user space. This only affects the
		sysfs interface. Polarity change can be done both before and after
		gpio_export(), and previously enabled poll(2) support for either
		rising or falling edge will be reconfigured to follow this setting.

drivers/gpio/gpiolib.c

+149 −12

Original line number	Diff line number	Diff line
		@@ -53,6 +53,7 @@ struct gpio_desc {
		#define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */
		#define FLAG_TRIG_FALL 5 /* trigger on falling edge */
		#define FLAG_TRIG_RISE 6 /* trigger on rising edge */
		#define FLAG_ACTIVE_LOW 7 /* sysfs value has active low */

		#define PDESC_ID_SHIFT 16 /* add new flags before this one */

		@@ -210,6 +211,11 @@ static DEFINE_MUTEX(sysfs_lock);
		* * configures behavior of poll(2) on /value
		* * available only if pin can generate IRQs on input
		* * is read/write as "none", "falling", "rising", or "both"
		* /active_low
		* * configures polarity of /value
		* * is read/write as zero/nonzero
		* * also affects existing and subsequent "falling" and "rising"
		* /edge configuration
		*/

		static ssize_t gpio_direction_show(struct device *dev,
		@@ -255,7 +261,7 @@ static ssize_t gpio_direction_store(struct device *dev,
		return status ? : size;
		}

		static const DEVICE_ATTR(direction, 0644,
		static /* const */ DEVICE_ATTR(direction, 0644,
		gpio_direction_show, gpio_direction_store);

		static ssize_t gpio_value_show(struct device *dev,
		@@ -267,10 +273,17 @@ static ssize_t gpio_value_show(struct device *dev,

		mutex_lock(&sysfs_lock);

		if (!test_bit(FLAG_EXPORT, &desc->flags))
		if (!test_bit(FLAG_EXPORT, &desc->flags)) {
		status = -EIO;
		else
		status = sprintf(buf, "%d\n", !!gpio_get_value_cansleep(gpio));
		} else {
		int value;

		value = !!gpio_get_value_cansleep(gpio);
		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
		value = !value;

		status = sprintf(buf, "%d\n", value);
		}

		mutex_unlock(&sysfs_lock);
		return status;
		@@ -294,6 +307,8 @@ static ssize_t gpio_value_store(struct device *dev,

		status = strict_strtol(buf, 0, &value);
		if (status == 0) {
		if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
		value = !value;
		gpio_set_value_cansleep(gpio, value != 0);
		status = size;
		}
		@@ -303,7 +318,7 @@ static ssize_t gpio_value_store(struct device *dev,
		return status;
		}

		static /const/ DEVICE_ATTR(value, 0644,
		static const DEVICE_ATTR(value, 0644,
		gpio_value_show, gpio_value_store);

		static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
		@@ -352,9 +367,11 @@ static int gpio_setup_irq(struct gpio_desc desc, struct device dev,

		irq_flags = IRQF_SHARED;
		if (test_bit(FLAG_TRIG_FALL, &gpio_flags))
		irq_flags \|= IRQF_TRIGGER_FALLING;
		irq_flags \|= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
		IRQF_TRIGGER_RISING : IRQF_TRIGGER_FALLING;
		if (test_bit(FLAG_TRIG_RISE, &gpio_flags))
		irq_flags \|= IRQF_TRIGGER_RISING;
		irq_flags \|= test_bit(FLAG_ACTIVE_LOW, &desc->flags) ?
		IRQF_TRIGGER_FALLING : IRQF_TRIGGER_RISING;

		if (!pdesc) {
		pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
		@@ -475,9 +492,79 @@ found:

		static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);

		static int sysfs_set_active_low(struct gpio_desc desc, struct device dev,
		int value)
		{
		int status = 0;

		if (!!test_bit(FLAG_ACTIVE_LOW, &desc->flags) == !!value)
		return 0;

		if (value)
		set_bit(FLAG_ACTIVE_LOW, &desc->flags);
		else
		clear_bit(FLAG_ACTIVE_LOW, &desc->flags);

		/* reconfigure poll(2) support if enabled on one edge only */
		if (dev != NULL && (!!test_bit(FLAG_TRIG_RISE, &desc->flags) ^
		!!test_bit(FLAG_TRIG_FALL, &desc->flags))) {
		unsigned long trigger_flags = desc->flags & GPIO_TRIGGER_MASK;

		gpio_setup_irq(desc, dev, 0);
		status = gpio_setup_irq(desc, dev, trigger_flags);
		}

		return status;
		}

		static ssize_t gpio_active_low_show(struct device *dev,
		struct device_attribute attr, char buf)
		{
		const struct gpio_desc *desc = dev_get_drvdata(dev);
		ssize_t status;

		mutex_lock(&sysfs_lock);

		if (!test_bit(FLAG_EXPORT, &desc->flags))
		status = -EIO;
		else
		status = sprintf(buf, "%d\n",
		!!test_bit(FLAG_ACTIVE_LOW, &desc->flags));

		mutex_unlock(&sysfs_lock);

		return status;
		}

		static ssize_t gpio_active_low_store(struct device *dev,
		struct device_attribute attr, const char buf, size_t size)
		{
		struct gpio_desc *desc = dev_get_drvdata(dev);
		ssize_t status;

		mutex_lock(&sysfs_lock);

		if (!test_bit(FLAG_EXPORT, &desc->flags)) {
		status = -EIO;
		} else {
		long value;

		status = strict_strtol(buf, 0, &value);
		if (status == 0)
		status = sysfs_set_active_low(desc, dev, value != 0);
		}

		mutex_unlock(&sysfs_lock);

		return status ? : size;
		}

		static const DEVICE_ATTR(active_low, 0644,
		gpio_active_low_show, gpio_active_low_store);

		static const struct attribute *gpio_attrs[] = {
		&dev_attr_direction.attr,
		&dev_attr_value.attr,
		&dev_attr_active_low.attr,
		NULL,
		};

		@@ -662,12 +749,12 @@ int gpio_export(unsigned gpio, bool direction_may_change)
		dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
		desc, ioname ? ioname : "gpio%d", gpio);
		if (!IS_ERR(dev)) {
		if (direction_may_change)
		status = sysfs_create_group(&dev->kobj,
		&gpio_attr_group);
		else

		if (!status && direction_may_change)
		status = device_create_file(dev,
		&dev_attr_value);
		&dev_attr_direction);

		if (!status && gpio_to_irq(gpio) >= 0
		&& (direction_may_change
		@@ -744,6 +831,55 @@ done:
		}
		EXPORT_SYMBOL_GPL(gpio_export_link);


		/**
		* gpio_sysfs_set_active_low - set the polarity of gpio sysfs value
		* @gpio: gpio to change
		* @value: non-zero to use active low, i.e. inverted values
		*
		* Set the polarity of /sys/class/gpio/gpioN/value sysfs attribute.
		* The GPIO does not have to be exported yet. If poll(2) support has
		* been enabled for either rising or falling edge, it will be
		* reconfigured to follow the new polarity.
		*
		* Returns zero on success, else an error.
		*/
		int gpio_sysfs_set_active_low(unsigned gpio, int value)
		{
		struct gpio_desc *desc;
		struct device *dev = NULL;
		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 *dev;

		dev = class_find_device(&gpio_class, NULL, desc, match_export);
		if (dev == NULL) {
		status = -ENODEV;
		goto unlock;
		}
		}

		status = sysfs_set_active_low(desc, dev, value);

		unlock:
		mutex_unlock(&sysfs_lock);

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

		return status;
		}
		EXPORT_SYMBOL_GPL(gpio_sysfs_set_active_low);

		/**
		* gpio_unexport - reverse effect of gpio_export()
		* @gpio: gpio to make unavailable
		@@ -1094,6 +1230,7 @@ void gpio_free(unsigned gpio)
		}
		desc_set_label(desc, NULL);
		module_put(desc->chip->owner);
		clear_bit(FLAG_ACTIVE_LOW, &desc->flags);
		clear_bit(FLAG_REQUESTED, &desc->flags);
		} else
		WARN_ON(extra_checks);

include/asm-generic/gpio.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -145,6 +145,7 @@ extern int __gpio_to_irq(unsigned gpio);
		extern int gpio_export(unsigned gpio, bool direction_may_change);
		extern int gpio_export_link(struct device dev, const char name,
		unsigned gpio);
		extern int gpio_sysfs_set_active_low(unsigned gpio, int value);
		extern void gpio_unexport(unsigned gpio);

		#endif /* CONFIG_GPIO_SYSFS */
		@@ -197,6 +198,11 @@ static inline int gpio_export_link(struct device dev, const char name,
		return -ENOSYS;
		}

		static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
		{
		return -ENOSYS;
		}

		static inline void gpio_unexport(unsigned gpio)
		{
		}

include/linux/gpio.h

+6 −0

Original line number	Diff line number	Diff line
		@@ -99,6 +99,12 @@ static inline int gpio_export_link(struct device dev, const char name,
		return -EINVAL;
		}

		static inline int gpio_sysfs_set_active_low(unsigned gpio, int value)
		{
		/* GPIO can never have been requested */
		WARN_ON(1);
		return -EINVAL;
		}

		static inline void gpio_unexport(unsigned gpio)
		{

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