media: videobuf2-v4l2: Expose vb2_queue_is_busy() to drivers

vb2 queue ownership is managed by the ioctl handler helpers
(vb2_ioctl_*). There are however use cases where drivers can benefit
from checking queue ownership, for instance when open-coding an ioctl
handler that needs to perform additional checks before calling the
corresponding vb2 operation.

Expose the vb2_queue_is_busy() function in the videobuf2-v4l2.h header,
and change its first argument to a struct vb2_queue pointer as the
function name implies it operates on a queue, not a video_device.
Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/common/videobuf2/videobuf2-v4l2.c

@@ -977,12 +977,6 @@ EXPORT_SYMBOL_GPL(vb2_poll);
  * and so they simplify the driver code.
  */
 
-/* The queue is busy if there is a owner and you are not that owner. */
-static inline bool vb2_queue_is_busy(struct video_device *vdev, struct file *file)
-{
-	return vdev->queue->owner && vdev->queue->owner != file->private_data;
-}
-
 /* vb2 ioctl helpers */
 
 int vb2_ioctl_reqbufs(struct file *file, void *priv,
@@ -997,7 +991,7 @@ int vb2_ioctl_reqbufs(struct file *file, void *priv,
 	p->flags = flags;
 	if (res)
 		return res;
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	res = vb2_core_reqbufs(vdev->queue, p->memory, p->flags, &p->count);
 	/* If count == 0, then the owner has released all buffers and he
@@ -1026,7 +1020,7 @@ int vb2_ioctl_create_bufs(struct file *file, void *priv,
 		return res != -EBUSY ? res : 0;
 	if (res)
 		return res;
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 
 	res = vb2_create_bufs(vdev->queue, p);
@@ -1041,7 +1035,7 @@ int vb2_ioctl_prepare_buf(struct file *file, void *priv,
 {
 	struct video_device *vdev = video_devdata(file);
 
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	return vb2_prepare_buf(vdev->queue, vdev->v4l2_dev->mdev, p);
 }
@@ -1060,7 +1054,7 @@ int vb2_ioctl_qbuf(struct file *file, void *priv, struct v4l2_buffer *p)
 {
 	struct video_device *vdev = video_devdata(file);
 
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	return vb2_qbuf(vdev->queue, vdev->v4l2_dev->mdev, p);
 }
@@ -1070,7 +1064,7 @@ int vb2_ioctl_dqbuf(struct file *file, void *priv, struct v4l2_buffer *p)
 {
 	struct video_device *vdev = video_devdata(file);
 
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	return vb2_dqbuf(vdev->queue, p, file->f_flags & O_NONBLOCK);
 }
@@ -1080,7 +1074,7 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i)
 {
 	struct video_device *vdev = video_devdata(file);
 
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	return vb2_streamon(vdev->queue, i);
 }
@@ -1090,7 +1084,7 @@ int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i)
 {
 	struct video_device *vdev = video_devdata(file);
 
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	return vb2_streamoff(vdev->queue, i);
 }
@@ -1100,7 +1094,7 @@ int vb2_ioctl_expbuf(struct file *file, void *priv, struct v4l2_exportbuffer *p)
 {
 	struct video_device *vdev = video_devdata(file);
 
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		return -EBUSY;
 	return vb2_expbuf(vdev->queue, p);
 }
@@ -1152,7 +1146,7 @@ ssize_t vb2_fop_write(struct file *file, const char __user *buf,
 		return -EINVAL;
 	if (lock && mutex_lock_interruptible(lock))
 		return -ERESTARTSYS;
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		goto exit;
 	err = vb2_write(vdev->queue, buf, count, ppos,
 		       file->f_flags & O_NONBLOCK);
@@ -1176,7 +1170,7 @@ ssize_t vb2_fop_read(struct file *file, char __user *buf,
 		return -EINVAL;
 	if (lock && mutex_lock_interruptible(lock))
 		return -ERESTARTSYS;
-	if (vb2_queue_is_busy(vdev, file))
+	if (vb2_queue_is_busy(vdev->queue, file))
 		goto exit;
 	err = vb2_read(vdev->queue, buf, count, ppos,
 		       file->f_flags & O_NONBLOCK);

include/media/videobuf2-v4l2.h

@@ -302,10 +302,29 @@ __poll_t vb2_poll(struct vb2_queue *q, struct file *file, poll_table *wait);
  * The following functions are not part of the vb2 core API, but are simple
  * helper functions that you can use in your struct v4l2_file_operations,
  * struct v4l2_ioctl_ops and struct vb2_ops. They will serialize if vb2_queue->lock
- * or video_device->lock is set, and they will set and test vb2_queue->owner
- * to check if the calling filehandle is permitted to do the queuing operation.
+ * or video_device->lock is set, and they will set and test the queue owner
+ * (vb2_queue->owner) to check if the calling filehandle is permitted to do the
+ * queuing operation.
  */
 
+/**
+ * vb2_queue_is_busy() - check if the queue is busy
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue.
+ * @file:	file through which the vb2 queue access is performed
+ *
+ * The queue is considered busy if it has an owner and the owner is not the
+ * @file.
+ *
+ * Queue ownership is acquired and checked by some of the v4l2_ioctl_ops helpers
+ * below. Drivers can also use this function directly when they need to
+ * open-code ioctl handlers, for instance to add additional checks between the
+ * queue ownership test and the call to the corresponding vb2 operation.
+ */
+static inline bool vb2_queue_is_busy(struct vb2_queue *q, struct file *file)
+{
+	return q->owner && q->owner != file->private_data;
+}
+
 /* struct v4l2_ioctl_ops helpers */
 
 int vb2_ioctl_reqbufs(struct file *file, void *priv,