Hi Shuah,
On 06/25/2014 01:57 AM, Shuah Khan wrote:
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.kh@xxxxxxxxxxx>
---
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;
+ }
If I understand this correctly, then this will make it impossible to open
the same video node twice since devm_token_lock will return EBUSY the
second time. Ditto for DVB as far as I could tell. That is certainly not
what you want, at least not for V4L.
In V4L2 the rules for tuner ownership are complicated, especially if the
tuner has a radio mode as well, see this presentation (the last two slides):
http://linuxtv.org/downloads/presentations/media_ws_2012_EU/ambiguities2.odp
Regards,
Hans
+ 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) \
--
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