[PATCH v2 3/6] gpiolib: add a second blocking notifier to struct gpio_device

[Bartosz Golaszewski <brgl@bgdev.pl>]

From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

Add a new blocking notifier to struct gpio_device and use it to notify
subscribers about the GPIO device being unregistered from the device
model.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib-cdev.c | 1 +
 drivers/gpio/gpiolib.c      | 1 +
 drivers/gpio/gpiolib.h      | 3 +++
 3 files changed, 5 insertions(+)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index df30d17f9e29..f95e1b110311 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -2749,4 +2749,5 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
 void gpiolib_cdev_unregister(struct gpio_device *gdev)
 {
 	cdev_device_del(&gdev->chrdev, &gdev->dev);
+	blocking_notifier_call_chain(&gdev->device_notifier, 0, NULL);
 }
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 769ca2333b7a..0737952882cd 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -842,6 +842,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 	spin_unlock_irqrestore(&gpio_lock, flags);
 
 	BLOCKING_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
+	BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);
 	init_rwsem(&gdev->sem);
 
 #ifdef CONFIG_PINCTRL
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index 7dd06ef45d44..54012605b4a4 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -40,6 +40,8 @@
  * @list: links gpio_device:s together for traversal
  * @line_state_notifier: used to notify subscribers about lines being
  *                       requested, released or reconfigured
+ * @device_notifier: used to notify character device wait queues about the GPIO
+ *                   device being unregistered
  * @sem: protects the structure from a NULL-pointer dereference of @chip by
  *       user-space operations when the device gets unregistered during
  *       a hot-unplug event
@@ -64,6 +66,7 @@ struct gpio_device {
 	void			*data;
 	struct list_head        list;
 	struct blocking_notifier_head line_state_notifier;
+	struct blocking_notifier_head device_notifier;
 	struct rw_semaphore	sem;
 
 #ifdef CONFIG_PINCTRL
-- 
2.39.2