[PATCH v2] HID: Replace semaphore driver_lock with mutex

[Binoy Jayan]

The semaphore 'driver_lock' is used as a simple mutex, and
also unnecessary as suggested by Arnd. Hence removing it, as
the concurrency between the probe and remove is already
handled in the driver core.

Signed-off-by: Binoy Jayan <binoy.ja...@linaro.org>
Suggested-by: Arnd Bergmann <a...@arndb.de>
---

v1 --> v2

Removed driver_lock

 drivers/hid/hid-core.c | 15 ++++-----------
 include/linux/hid.h    |  2 +-
 2 files changed, 5 insertions(+), 12 deletions(-)

diff --git a/drivers/hid/hid-core.c b/drivers/hid/hid-core.c
index 04cee65..559533b 100644
--- a/drivers/hid/hid-core.c
+++ b/drivers/hid/hid-core.c
@@ -2225,11 +2225,9 @@ static int hid_device_probe(struct device *dev)
        const struct hid_device_id *id;
        int ret = 0;
 
-       if (down_interruptible(&hdev->driver_lock))
-               return -EINTR;
        if (down_interruptible(&hdev->driver_input_lock)) {
                ret = -EINTR;
-               goto unlock_driver_lock;
+               goto end;
        }
        hdev->io_started = false;
 
@@ -2256,8 +2254,7 @@ static int hid_device_probe(struct device *dev)
 unlock:
        if (!hdev->io_started)
                up(&hdev->driver_input_lock);
-unlock_driver_lock:
-       up(&hdev->driver_lock);
+end:
        return ret;
 }
 
@@ -2267,11 +2264,9 @@ static int hid_device_remove(struct device *dev)
        struct hid_driver *hdrv;
        int ret = 0;
 
-       if (down_interruptible(&hdev->driver_lock))
-               return -EINTR;
        if (down_interruptible(&hdev->driver_input_lock)) {
                ret = -EINTR;
-               goto unlock_driver_lock;
+               goto end;
        }
        hdev->io_started = false;
 
@@ -2287,8 +2282,7 @@ static int hid_device_remove(struct device *dev)
 
        if (!hdev->io_started)
                up(&hdev->driver_input_lock);
-unlock_driver_lock:
-       up(&hdev->driver_lock);
+end:
        return ret;
 }
 
@@ -2745,7 +2739,6 @@ struct hid_device *hid_allocate_device(void)
        init_waitqueue_head(&hdev->debug_wait);
        INIT_LIST_HEAD(&hdev->debug_list);
        spin_lock_init(&hdev->debug_list_lock);
-       sema_init(&hdev->driver_lock, 1);
        sema_init(&hdev->driver_input_lock, 1);
 
        return hdev;
diff --git a/include/linux/hid.h b/include/linux/hid.h
index 5be325d..1add2b3 100644
--- a/include/linux/hid.h
+++ b/include/linux/hid.h
@@ -516,7 +516,7 @@ struct hid_device {                                         
        /* device report descriptor */
        struct hid_report_enum report_enum[HID_REPORT_TYPES];
        struct work_struct led_work;                                    /* 
delayed LED worker */
 
-       struct semaphore driver_lock;                                   /* 
protects the current driver, except during input */
+       struct mutex driver_lock;                                       /* 
protects the current driver, except during input */
        struct semaphore driver_input_lock;                             /* 
protects the current driver */
        struct device dev;                                              /* 
device */
        struct hid_driver *driver;
-- 
Binoy Jayan