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 - VB2_FILEIO_ALLOW_ZERO_BYTESUSED. If the flag is
set upon initialization of the queue, the videobuf2 keeps the value of
bytesused intact and passes it to the driver.
Reported-by: Nicolas Dufresne <nicolas.dufresne@xxxxxxxxxxxxx>
Signed-off-by: Kamil Debski <k.debski@xxxxxxxxxxx>
---
drivers/media/v4l2-core/videobuf2-core.c | 33 ++++++++++++++++++++++++------
include/media/videobuf2-core.h | 3 +++
2 files changed, 30 insertions(+), 6 deletions(-)
diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
index d09a891..1068dbb 100644
--- a/drivers/media/v4l2-core/videobuf2-core.c
+++ b/drivers/media/v4l2-core/videobuf2-core.c
@@ -1276,13 +1276,23 @@ 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 following
+ * io_flag VB2_FILEIO_ALLOW_ZERO_BYTESUSED 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->io_flags &
+ VB2_FILEIO_ALLOW_ZERO_BYTESUSED)
+ pdst->bytesused = psrc->bytesused;
+ else
+ pdst->bytesused = psrc->bytesused ?
+ psrc->bytesused : pdst->length;
pdst->data_offset = psrc->data_offset;
}
}
@@ -1295,6 +1305,12 @@ 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 following io_flag
+ * VB2_FILEIO_ALLOW_ZERO_BYTESUSED to keep old userspace
+ * applications working.
*/
if (b->memory == V4L2_MEMORY_USERPTR) {
v4l2_planes[0].m.userptr = b->m.userptr;
@@ -1306,11 +1322,16 @@ 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->io_flags &
+ VB2_FILEIO_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;
+ }
}
diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
index bd2cec2..0540bc3 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -138,10 +138,13 @@ enum vb2_io_modes {
* by default the 'streaming' style is used by the file io emulator
* @VB2_FILEIO_READ_ONCE: report EOF after reading the first buffer
* @VB2_FILEIO_WRITE_IMMEDIATELY: queue buffer after each write() call
+ * @VB2_FILEIO_ALLOW_ZERO_BYTESUSED: the driver setting this flag will handle
+ * bytesused == 0 as a special case
*/
enum vb2_fileio_flags {
VB2_FILEIO_READ_ONCE = (1 << 0),
VB2_FILEIO_WRITE_IMMEDIATELY = (1 << 1),
+ VB2_FILEIO_ALLOW_ZERO_BYTESUSED = (1 << 2),
};
/**
--
1.7.9.5
--
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