media: v4l2: Add REMOVE_BUFS ioctl

VIDIOC_REMOVE_BUFS ioctl allows to remove buffers from a queue.
The number of buffers to remove in given by count field of
struct v4l2_remove_buffers and the range start at the index
specified in the same structure.

Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Reviewed-by: Mauro Carvalho Chehab <mchehab@kernel.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
[hverkuil: vidioc-remove-bufs.rst: mention no bufs are freed on error]

include/media/v4l2-ioctl.h

@@ -163,6 +163,8 @@ struct v4l2_fh;
  *	:ref:`VIDIOC_CREATE_BUFS <vidioc_create_bufs>` ioctl
  * @vidioc_prepare_buf: pointer to the function that implements
  *	:ref:`VIDIOC_PREPARE_BUF <vidioc_prepare_buf>` ioctl
+ * @vidioc_remove_bufs: pointer to the function that implements
+ *	:ref:`VIDIOC_REMOVE_BUFS <vidioc_remove_bufs>` ioctl
  * @vidioc_overlay: pointer to the function that implements
  *	:ref:`VIDIOC_OVERLAY <vidioc_overlay>` ioctl
  * @vidioc_g_fbuf: pointer to the function that implements
@@ -422,6 +424,8 @@ struct v4l2_ioctl_ops {
 				  struct v4l2_create_buffers *b);
 	int (*vidioc_prepare_buf)(struct file *file, void *fh,
 				  struct v4l2_buffer *b);
+	int (*vidioc_remove_bufs)(struct file *file, void *fh,
+				  struct v4l2_remove_buffers *d);
 
 	int (*vidioc_overlay)(struct file *file, void *fh, unsigned int i);
 	int (*vidioc_g_fbuf)(struct file *file, void *fh,

include/media/videobuf2-core.h

@@ -870,6 +870,16 @@ int vb2_core_create_bufs(struct vb2_queue *q, enum vb2_memory memory,
  */
 int vb2_core_prepare_buf(struct vb2_queue *q, struct vb2_buffer *vb, void *pb);
 
+/**
+ * vb2_core_remove_bufs() -
+ * @q:		pointer to &struct vb2_queue with videobuf2 queue.
+ * @start:	first index of the range of buffers to remove.
+ * @count:	number of buffers to remove.
+ *
+ *  Return: returns zero on success; an error code otherwise.
+ */
+int vb2_core_remove_bufs(struct vb2_queue *q, unsigned int start, unsigned int count);
+
 /**
  * vb2_core_qbuf() - Queue a buffer from userspace
  *

include/media/videobuf2-v4l2.h

@@ -334,6 +334,8 @@ int vb2_ioctl_streamon(struct file *file, void *priv, enum v4l2_buf_type i);
 int vb2_ioctl_streamoff(struct file *file, void *priv, enum v4l2_buf_type i);
 int vb2_ioctl_expbuf(struct file *file, void *priv,
 	struct v4l2_exportbuffer *p);
+int vb2_ioctl_remove_bufs(struct file *file, void *priv,
+			  struct v4l2_remove_buffers *p);
 
 /* struct v4l2_file_operations helpers */