[PATCH v4] gpio: lib-sysfs: Add 'wakeup' attribute

[Soren Brinkmann <soren.brinkmann@xilinx.com>]

Add an attribute 'wakeup' to the GPIO sysfs interface which allows
marking/unmarking a GPIO as wake IRQ.
The file 'wakeup' is created in each exported GPIOs directory, if an IRQ
is associated with that GPIO and the irqchip implements set_wake().
Writing 'enabled' to that file will enable wake for that GPIO, while
writing 'disabled' will disable wake.
Reading that file will return either 'disabled' or 'enabled' depening on
the currently set flag for the GPIO's IRQ.

Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
---
Hi Linus, Johan,

I rebased my patch. And things look good. But the 'is_visible' things does not
behave the way I expected it to. It seems to be only triggered on an export but
not when attributes change. Hence, in my case, everything was visiible since the
inital state matches that, but even when changing the direction or things like
that, attributes don't disappear. Is that something still worked on? Expected
behavior?

	Thanks,
	Sören

v4:
 - rebased onto gpio/fixes
   - fit into the new attribute framework
   - extend is_visible to limit the wakeup attributes visibility
     according to usability
v3:
 - add documentation
v2:
 - fix error path to unlock mutex before return
---
 Documentation/ABI/testing/sysfs-gpio |  1 +
 Documentation/gpio/sysfs.txt         |  8 +++++
 drivers/gpio/gpiolib-sysfs.c         | 62 ++++++++++++++++++++++++++++++++++++
 3 files changed, 71 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-gpio b/Documentation/ABI/testing/sysfs-gpio
index 80f4c94c7bef..4cc7f4b3f724 100644
--- a/Documentation/ABI/testing/sysfs-gpio
+++ b/Documentation/ABI/testing/sysfs-gpio
@@ -20,6 +20,7 @@ Description:
 	    /value ... always readable, writes fail for input GPIOs
 	    /direction ... r/w as: in, out (default low); write: high, low
 	    /edge ... r/w as: none, falling, rising, both
+	    /wakeup ... r/w as: enabled, disabled
 	/gpiochipN ... for each gpiochip; #N is its first GPIO
 	    /base ... (r/o) same as N
 	    /label ... (r/o) descriptive, not necessarily unique
diff --git a/Documentation/gpio/sysfs.txt b/Documentation/gpio/sysfs.txt
index c2c3a97f8ff7..f703377d528f 100644
--- a/Documentation/gpio/sysfs.txt
+++ b/Documentation/gpio/sysfs.txt
@@ -97,6 +97,14 @@ and have the following read/write attributes:
 		for "rising" and "falling" edges will follow this
 		setting.
 
+	"wakeup" ... reads as either "enabled" or "disabled". Write these
+		strings to set/clear the 'wakeup' flag of the IRQ associated
+		with this GPIO. If the IRQ has the 'wakeup' flag set, it can
+		wake the system from sleep states.
+
+		This file exists only if the pin can generate interrupts and
+		the driver implements the required infrastructure.
+
 GPIO controllers have paths like /sys/class/gpio/gpiochip42/ (for the
 controller implementing GPIOs starting at #42) and have the following
 read-only attributes:
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index f62aa115d79a..14b34d15e61c 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -286,6 +286,58 @@ found:
 
 static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);
 
+static ssize_t gpio_wakeup_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	ssize_t			status;
+	const struct gpio_desc	*desc = dev_get_drvdata(dev);
+	int			irq = gpiod_to_irq(desc);
+	struct irq_desc		*irq_desc = irq_to_desc(irq);
+
+	mutex_lock(&sysfs_lock);
+
+	if (irqd_is_wakeup_set(&irq_desc->irq_data))
+		status = sprintf(buf, "enabled\n");
+	else
+		status = sprintf(buf, "disabled\n");
+
+	mutex_unlock(&sysfs_lock);
+
+	return status;
+}
+
+static ssize_t gpio_wakeup_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	int			ret;
+	unsigned int		on;
+	struct gpio_desc	*desc = dev_get_drvdata(dev);
+	int			irq = gpiod_to_irq(desc);
+
+	mutex_lock(&sysfs_lock);
+
+	if (sysfs_streq("enabled", buf)) {
+		on = true;
+	} else if (sysfs_streq("disabled", buf)) {
+		on = false;
+	} else {
+		mutex_unlock(&sysfs_lock);
+		return -EINVAL;
+	}
+
+	ret = irq_set_irq_wake(irq, on);
+
+	mutex_unlock(&sysfs_lock);
+
+	if (ret)
+		pr_warn("%s: failed to %s wake\n", __func__,
+				on ? "enable" : "disable");
+
+	return size;
+}
+
+static DEVICE_ATTR(wakeup, 0644, gpio_wakeup_show, gpio_wakeup_store);
+
 static int sysfs_set_active_low(struct gpio_desc *desc, struct device *dev,
 				int value)
 {
@@ -361,6 +413,7 @@ static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
 {
 	struct device *dev = container_of(kobj, struct device, kobj);
 	struct gpio_desc *desc = dev_get_drvdata(dev);
+	struct irq_chip *irqchip = desc->chip->irqchip;
 	umode_t mode = attr->mode;
 	bool show_direction = test_bit(FLAG_SYSFS_DIR, &desc->flags);
 
@@ -372,6 +425,14 @@ static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,
 			mode = 0;
 		if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
 			mode = 0;
+	} else if (attr == &dev_attr_wakeup.attr) {
+		if (gpiod_to_irq(desc) < 0)
+			mode = 0;
+		if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))
+			mode = 0;
+		if (!test_bit(IRQCHIP_SKIP_SET_WAKE, &irqchip->flags) &&
+				!irqchip->irq_set_wake)
+			mode = 0;
 	}
 
 	return mode;
@@ -382,6 +443,7 @@ static struct attribute *gpio_attrs[] = {
 	&dev_attr_edge.attr,
 	&dev_attr_value.attr,
 	&dev_attr_active_low.attr,
+	&dev_attr_wakeup.attr,
 	NULL,
 };
 
-- 
2.2.1.1.gb42cc81