[PATCH 21/22] gpio: remove the RW semaphore from the GPIO device

[Bartosz Golaszewski <brgl@bgdev.pl>]

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

With all accesses to gdev->chip being protected with SRCU, we can now
remove the RW-semaphore specific to the character device which
fullfilled the same role up to this point.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
 drivers/gpio/gpiolib-cdev.c | 1 -
 drivers/gpio/gpiolib.c      | 4 ----
 drivers/gpio/gpiolib.h      | 5 -----
 3 files changed, 10 deletions(-)

diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 9aaddcc08e29..be0a3f591af4 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -24,7 +24,6 @@
 #include <linux/pinctrl/consumer.h>
 #include <linux/poll.h>
 #include <linux/rbtree.h>
-#include <linux/rwsem.h>
 #include <linux/seq_file.h>
 #include <linux/spinlock.h>
 #include <linux/timekeeping.h>
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9990d87e32fe..5741bbfdc178 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -955,7 +955,6 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
 
 	BLOCKING_INIT_NOTIFIER_HEAD(&gdev->line_state_notifier);
 	BLOCKING_INIT_NOTIFIER_HEAD(&gdev->device_notifier);
-	init_rwsem(&gdev->sem);
 
 	ret = init_srcu_struct(&gdev->srcu);
 	if (ret)
@@ -1094,8 +1093,6 @@ void gpiochip_remove(struct gpio_chip *gc)
 	struct gpio_device *gdev = gc->gpiodev;
 	unsigned int i;
 
-	down_write(&gdev->sem);
-
 	/* FIXME: should the legacy sysfs handling be moved to gpio_device? */
 	gpiochip_sysfs_unregister(gdev);
 	gpiochip_free_hogs(gc);
@@ -1133,7 +1130,6 @@ void gpiochip_remove(struct gpio_chip *gc)
 	 * gone.
 	 */
 	gcdev_unregister(gdev);
-	up_write(&gdev->sem);
 	gpio_device_put(gdev);
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);
diff --git a/drivers/gpio/gpiolib.h b/drivers/gpio/gpiolib.h
index c96afc800bea..c76acb8f95c6 100644
--- a/drivers/gpio/gpiolib.h
+++ b/drivers/gpio/gpiolib.h
@@ -16,7 +16,6 @@
 #include <linux/gpio/driver.h>
 #include <linux/module.h>
 #include <linux/notifier.h>
-#include <linux/rwsem.h>
 #include <linux/srcu.h>
 
 #define GPIOCHIP_NAME	"gpiochip"
@@ -46,9 +45,6 @@
  *                       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
  * @srcu: protects the pointer to the underlying GPIO chip
  * @pin_ranges: range of pins served by the GPIO driver
  *
@@ -73,7 +69,6 @@ struct gpio_device {
 	struct list_head        list;
 	struct blocking_notifier_head line_state_notifier;
 	struct blocking_notifier_head device_notifier;
-	struct rw_semaphore	sem;
 	struct srcu_struct	srcu;
 
 #ifdef CONFIG_PINCTRL
-- 
2.40.1