[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>
diff --git a/drivers/media/video/v4l2-fh.c b/drivers/media/video/v4l2-fh.c
index 27242e5..543b3fe 100644
--- a/drivers/media/video/v4l2-fh.c
+++ b/drivers/media/video/v4l2-fh.c
@@ -109,3 +109,17 @@
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);