[media] vb2: add allow_zero_bytesused flag to the vb2_queue struct

The vb2: fix bytesused == 0 handling (8a75ffb) patch changed the behavior
of __fill_vb2_buffer function, so that if bytesused is 0 it is set to the
size of the buffer. However, bytesused set to 0 is used by older codec
drivers as as indication used to mark the end of stream.

To keep backward compatibility, this patch adds a flag passed to the
vb2_queue_init function - allow_zero_bytesused. If the flag is set upon
initialization of the queue, the videobuf2 keeps the value of bytesused
intact in the OUTPUT queue and passes it to the driver.

Reported-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>

1 files changed, 33 insertions, 6 deletions

diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index 8bc2a6e8623d..1329dccfa072 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1247,6 +1247,16 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
 {
         unsigned int plane;
 
+        if (V4L2_TYPE_IS_OUTPUT(b->type)) {
+                if (WARN_ON_ONCE(b->bytesused == 0)) {
+                        pr_warn_once("use of bytesused == 0 is deprecated and will be removed in the future,\n");
+                        if (vb->vb2_queue->allow_zero_bytesused)
+                                pr_warn_once("use VIDIOC_DECODER_CMD(V4L2_DEC_CMD_STOP) instead.\n");
+                        else
+                                pr_warn_once("use the actual size instead.\n");
+                }
+        }
+
         if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
                 if (b->memory == V4L2_MEMORY_USERPTR) {
                         for (plane = 0; plane < vb->num_planes; ++plane) {
@@ -1276,13 +1286,22 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
                          * userspace clearly never bothered to set it and
                          * it's a safe assumption that they really meant to
                          * use the full plane sizes.
+                         *
+                         * Some drivers, e.g. old codec drivers, use bytesused == 0
+                         * as a way to indicate that streaming is finished.
+                         * In that case, the driver should use the
+                         * allow_zero_bytesused flag to keep old userspace
+                         * applications working.
                          */
                         for (plane = 0; plane < vb->num_planes; ++plane) {
                                 struct v4l2_plane *pdst = &v4l2_planes[plane];
                                 struct v4l2_plane *psrc = &b->m.planes[plane];
 
-                                pdst->bytesused = psrc->bytesused ?
-                                        psrc->bytesused : pdst->length;
+                                if (vb->vb2_queue->allow_zero_bytesused)
+                                        pdst->bytesused = psrc->bytesused;
+                                else
+                                        pdst->bytesused = psrc->bytesused ?
+                                                psrc->bytesused : pdst->length;
                                 pdst->data_offset = psrc->data_offset;
                         }
                 }
@@ -1295,6 +1314,11 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
                  *
                  * If bytesused == 0 for the output buffer, then fall back
                  * to the full buffer size as that's a sensible default.
+                 *
+                 * Some drivers, e.g. old codec drivers, use bytesused == 0 as
+                 * a way to indicate that streaming is finished. In that case,
+                 * the driver should use the allow_zero_bytesused flag to keep
+                 * old userspace applications working.
                  */
                 if (b->memory == V4L2_MEMORY_USERPTR) {
                         v4l2_planes[0].m.userptr = b->m.userptr;
@@ -1306,10 +1330,13 @@ static void __fill_vb2_buffer(struct vb2_buffer *vb, const struct v4l2_buffer *b
                         v4l2_planes[0].length = b->length;
                 }
 
-                if (V4L2_TYPE_IS_OUTPUT(b->type))
-                        v4l2_planes[0].bytesused = b->bytesused ?
-                                b->bytesused : v4l2_planes[0].length;
-                else
+                if (V4L2_TYPE_IS_OUTPUT(b->type)) {
+                        if (vb->vb2_queue->allow_zero_bytesused)
+                                v4l2_planes[0].bytesused = b->bytesused;
+                        else
+                                v4l2_planes[0].bytesused = b->bytesused ?
+                                        b->bytesused : v4l2_planes[0].length;
+                } else
                         v4l2_planes[0].bytesused = 0;
 
         }