[PATCH 3/4] media: v4l2-core changes to use tuner token

[Shuah Khan]

Add a new field tuner_tkn to struct video_device. Drivers can
create tuner token using devm_token_create() and initialize
the tuner_tkn when frontend is registered with the dvb-core.
This change enables drivers to provide a token devres for tuner
access control.

Change v4l2-core to lock tuner token for exclusive access to
tuner function for analog TV function use. When Tuner token is
present, v4l2_open() calls devm_token_lock() to lock the token.
If token is busy, -EBUSY is returned to the user-space.

Tuner token is unlocked in error paths in v4l2_open(). This token
is held as long as the v4l2 device is open and unlocked from
v4l2_release().

Signed-off-by: Shuah Khan <shuah...@samsung.com>
---
 drivers/media/v4l2-core/v4l2-dev.c |   23 ++++++++++++++++++++++-
 include/media/v4l2-dev.h           |    1 +
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/media/v4l2-core/v4l2-dev.c 
b/drivers/media/v4l2-core/v4l2-dev.c
index 634d863..8dff809 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -26,6 +26,7 @@
 #include <linux/kmod.h>
 #include <linux/slab.h>
 #include <asm/uaccess.h>
+#include <linux/token_devres.h>
 
 #include <media/v4l2-common.h>
 #include <media/v4l2-device.h>
@@ -445,6 +446,17 @@ static int v4l2_open(struct inode *inode, struct file 
*filp)
                mutex_unlock(&videodev_lock);
                return -ENODEV;
        }
+       /* check if tuner is busy first */
+       if (vdev->tuner_tkn && vdev->dev_parent) {
+               ret = devm_token_lock(vdev->dev_parent, vdev->tuner_tkn);
+               if (ret) {
+                       mutex_unlock(&videodev_lock);
+                       dev_info(vdev->dev_parent, "v4l2: Tuner is busy\n");
+                       return ret;
+               }
+               dev_info(vdev->dev_parent, "v4l2: Tuner is locked\n");
+       }
+
        /* and increase the device refcount */
        video_get(vdev);
        mutex_unlock(&videodev_lock);
@@ -459,8 +471,13 @@ static int v4l2_open(struct inode *inode, struct file 
*filp)
                printk(KERN_DEBUG "%s: open (%d)\n",
                        video_device_node_name(vdev), ret);
        /* decrease the refcount in case of an error */
-       if (ret)
+       if (ret) {
                video_put(vdev);
+               if (vdev->tuner_tkn && vdev->dev_parent) {
+                       devm_token_unlock(vdev->dev_parent, vdev->tuner_tkn);
+                       dev_info(vdev->dev_parent, "v4l2: Tuner is unlocked\n");
+               }
+       }
        return ret;
 }
 
@@ -479,6 +496,10 @@ static int v4l2_release(struct inode *inode, struct file 
*filp)
        /* decrease the refcount unconditionally since the release()
           return value is ignored. */
        video_put(vdev);
+       if (vdev->tuner_tkn && vdev->dev_parent) {
+               devm_token_unlock(vdev->dev_parent, vdev->tuner_tkn);
+               dev_info(vdev->dev_parent, "v4l2: Tuner is unlocked\n");
+       }
        return ret;
 }
 
diff --git a/include/media/v4l2-dev.h b/include/media/v4l2-dev.h
index eec6e46..1676349 100644
--- a/include/media/v4l2-dev.h
+++ b/include/media/v4l2-dev.h
@@ -141,6 +141,7 @@ struct video_device
        /* serialization lock */
        DECLARE_BITMAP(disable_locking, BASE_VIDIOC_PRIVATE);
        struct mutex *lock;
+       char *tuner_tkn;
 };
 
 #define media_entity_to_video_device(__e) \
-- 
1.7.10.4

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