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[media] v4l2-fh: add v4l2_fh_is_singular 

Several drivers need to do something when the first filehandle is opened
or the last filehandle is closed. Most implement some use count mechanism,
but if they use v4l2_fh, then you can also just check if this is the only
filehandle for the device node. A simple helper function can do this.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
This commit is contained in:
Hans Verkuil 2011-01-08 09:38:02 -03:00 committed by Mauro Carvalho Chehab
parent 73cb42068c
commit dfddb2441f
2 changed files with 27 additions and 0 deletions
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14
drivers/media/video/v4l2-fh.c
View File

@ -109,3 +109,17 @@ int v4l2_fh_release(struct file *filp)
return 0;
}
EXPORT_SYMBOL_GPL(v4l2_fh_release);
int v4l2_fh_is_singular(struct v4l2_fh *fh)
{
unsigned long flags;
int is_singular;
if (fh == NULL || fh->vdev == NULL)
return 0;
spin_lock_irqsave(&fh->vdev->fh_lock, flags);
is_singular = list_is_singular(&fh->list);
spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
return is_singular;
}
EXPORT_SYMBOL_GPL(v4l2_fh_is_singular);

13
include/media/v4l2-fh.h
View File

@ -77,5 +77,18 @@ void v4l2_fh_exit(struct v4l2_fh *fh);
* v4l2_fh struct) is NULL. This function always returns 0.
*/
int v4l2_fh_release(struct file *filp);
/*
* Returns 1 if this filehandle is the only filehandle opened for the
* associated video_device. If fh is NULL, then it returns 0.
*/
int v4l2_fh_is_singular(struct v4l2_fh *fh);
/*
* Helper function with struct file as argument. If filp->private_data is
* NULL, then it will return 0.
*/
static inline int v4l2_fh_is_singular_file(struct file *filp)
{
return v4l2_fh_is_singular(filp->private_data);
}
#endif /* V4L2_EVENT_H */