@@ -607,6 +607,19 @@ Buffer Flags
applications shall use this flag for output buffers if the data in
this buffer has not been created by the CPU but by some
DMA-capable unit, in which case caches have not been used.
+ * .. _`V4L2-BUF-FLAG-M2M-HOLD-CAPTURE-BUF`:
+
+ - ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF``
+ - 0x00000200
+ - Only valid if ``V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF`` is
+ set. It is typically used with stateless decoders where multiple
+ output buffers each decode to a slice of the decoded frame.
+ Applications can set this flag when queueing the output buffer
+ to prevent the driver from dequeueing the capture buffer after
+ the output buffer has been decoded (i.e. the capture buffer is
+ 'held'). If the timestamp of this output buffer differs from that
+ of the previous output buffer, then that indicates the start of a
+ new frame and the previously held capture buffer is dequeued.
* .. _`V4L2-BUF-FLAG-LAST`:
- ``V4L2_BUF_FLAG_LAST``
@@ -125,6 +125,7 @@ aborting or finishing any DMA in progress, an implicit
.. _V4L2-BUF-CAP-SUPPORTS-DMABUF:
.. _V4L2-BUF-CAP-SUPPORTS-REQUESTS:
.. _V4L2-BUF-CAP-SUPPORTS-ORPHANED-BUFS:
+.. _V4L2-BUF-CAP-SUPPORTS-M2M-HOLD-CAPTURE-BUF:
.. cssclass:: longtable
@@ -150,6 +151,11 @@ aborting or finishing any DMA in progress, an implicit
- The kernel allows calling :ref:`VIDIOC_REQBUFS` while buffers are still
mapped or exported via DMABUF. These orphaned buffers will be freed
when they are unmapped or when the exported DMABUF fds are closed.
+ * - ``V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF``
+ - 0x00000020
+ - Only valid for stateless decoders. If set, then userspace can set the
+ ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag to hold off on returning the
+ capture buffer until the OUTPUT timestamp changes.
Return Value
============
@@ -50,7 +50,8 @@ module_param(debug, int, 0644);
V4L2_BUF_FLAG_TIMESTAMP_MASK)
/* Output buffer flags that should be passed on to the driver */
#define V4L2_BUFFER_OUT_FLAGS (V4L2_BUF_FLAG_PFRAME | V4L2_BUF_FLAG_BFRAME | \
- V4L2_BUF_FLAG_KEYFRAME | V4L2_BUF_FLAG_TIMECODE)
+ V4L2_BUF_FLAG_KEYFRAME | V4L2_BUF_FLAG_TIMECODE | \
+ V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF)
/*
* __verify_planes_array() - verify that the planes array passed in struct
@@ -194,6 +195,7 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
}
vbuf->sequence = 0;
vbuf->request_fd = -1;
+ vbuf->is_held = false;
if (V4L2_TYPE_IS_MULTIPLANAR(b->type)) {
switch (b->memory) {
@@ -321,6 +323,8 @@ static int vb2_fill_vb2_v4l2_buffer(struct vb2_buffer *vb, struct v4l2_buffer *b
*/
vbuf->flags &= ~V4L2_BUF_FLAG_TIMECODE;
vbuf->field = b->field;
+ if (!(q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF))
+ vbuf->flags &= ~V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
} else {
/* Zero any output buffer flags as this is a capture buffer */
vbuf->flags &= ~V4L2_BUFFER_OUT_FLAGS;
@@ -654,6 +658,8 @@ static void fill_buf_caps(struct vb2_queue *q, u32 *caps)
*caps |= V4L2_BUF_CAP_SUPPORTS_USERPTR;
if (q->io_modes & VB2_DMABUF)
*caps |= V4L2_BUF_CAP_SUPPORTS_DMABUF;
+ if (q->subsystem_flags & VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF)
+ *caps |= V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF;
#ifdef CONFIG_MEDIA_CONTROLLER_REQUEST_API
if (q->supports_requests)
*caps |= V4L2_BUF_CAP_SUPPORTS_REQUESTS;
@@ -644,6 +644,48 @@ void v4l2_m2m_buf_copy_metadata(const struct vb2_v4l2_buffer *out_vb,
struct vb2_v4l2_buffer *cap_vb,
bool copy_frame_flags);
+/**
+ * v4l2_m2m_release_capture_buf() - check if the capture buffer should be
+ * released
+ *
+ * @out_vb: the output buffer
+ * @cap_vb: the capture buffer
+ *
+ * This helper function returns true if the current capture buffer should
+ * be released to vb2. This is the case if the output buffer specified that
+ * the capture buffer should be held (i.e. not returned to vb2) AND if the
+ * timestamp of the capture buffer differs from the output buffer timestamp.
+ *
+ * This helper is to be called at the start of the device_run callback:
+ *
+ * .. code-block:: c
+ *
+ * if (v4l2_m2m_release_capture_buf(out_vb, cap_vb)) {
+ * v4l2_m2m_buf_done(cap_vb, VB2_BUF_STATE_DONE);
+ * v4l2_m2m_job_finish(...);
+ * return;
+ * }
+ * cap_vb->is_held = out_vb->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF;
+ *
+ * ...
+ *
+ * v4l2_m2m_buf_done(out_vb, VB2_BUF_STATE_DONE);
+ * if (!cap_vb->is_held) {
+ * v4l2_m2m_buf_done(cap_vb, VB2_BUF_STATE_DONE);
+ * v4l2_m2m_job_finish(...);
+ * }
+ *
+ * This allows for multiple output buffers to be used to fill in a single
+ * capture buffer. This is typically used by stateless decoders where
+ * multiple e.g. H.264 slices contribute to a single decoded frame.
+ */
+static inline bool v4l2_m2m_release_capture_buf(const struct vb2_v4l2_buffer *out_vb,
+ const struct vb2_v4l2_buffer *cap_vb)
+{
+ return cap_vb->is_held && cap_vb->vb2_buf.copied_timestamp &&
+ out_vb->vb2_buf.timestamp != cap_vb->vb2_buf.timestamp;
+}
+
/* v4l2 request helper */
void v4l2_m2m_request_queue(struct media_request *req);
@@ -505,6 +505,8 @@ struct vb2_buf_ops {
* @buf_ops: callbacks to deliver buffer information.
* between user-space and kernel-space.
* @drv_priv: driver private data.
+ * @subsystem_flags: Flags specific to the subsystem (V4L2/DVB/etc.). Not used
+ * by the vb2 core.
* @buf_struct_size: size of the driver-specific buffer structure;
* "0" indicates the driver doesn't want to use a custom buffer
* structure type. for example, ``sizeof(struct vb2_v4l2_buffer)``
@@ -571,6 +573,7 @@ struct vb2_queue {
const struct vb2_buf_ops *buf_ops;
void *drv_priv;
+ u32 subsystem_flags;
unsigned int buf_struct_size;
u32 timestamp_flags;
gfp_t gfp_flags;
@@ -33,6 +33,7 @@
* @timecode: frame timecode.
* @sequence: sequence count of this frame.
* @request_fd: the request_fd associated with this buffer
+ * @is_held: if true, then this buffer was held
* @planes: plane information (userptr/fd, length, bytesused, data_offset).
*
* Should contain enough information to be able to cover all the fields
@@ -46,9 +47,13 @@ struct vb2_v4l2_buffer {
struct v4l2_timecode timecode;
__u32 sequence;
__s32 request_fd;
+ bool is_held;
struct vb2_plane planes[VB2_MAX_PLANES];
};
+/* VB2 V4L2 flags as set in vb2_queue.subsystem_flags */
+#define VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF (1 << 0)
+
/*
* to_vb2_v4l2_buffer() - cast struct vb2_buffer * to struct vb2_v4l2_buffer *
*/
@@ -915,11 +915,12 @@ struct v4l2_requestbuffers {
};
/* capabilities for struct v4l2_requestbuffers and v4l2_create_buffers */
-#define V4L2_BUF_CAP_SUPPORTS_MMAP (1 << 0)
-#define V4L2_BUF_CAP_SUPPORTS_USERPTR (1 << 1)
-#define V4L2_BUF_CAP_SUPPORTS_DMABUF (1 << 2)
-#define V4L2_BUF_CAP_SUPPORTS_REQUESTS (1 << 3)
-#define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
+#define V4L2_BUF_CAP_SUPPORTS_MMAP (1 << 0)
+#define V4L2_BUF_CAP_SUPPORTS_USERPTR (1 << 1)
+#define V4L2_BUF_CAP_SUPPORTS_DMABUF (1 << 2)
+#define V4L2_BUF_CAP_SUPPORTS_REQUESTS (1 << 3)
+#define V4L2_BUF_CAP_SUPPORTS_ORPHANED_BUFS (1 << 4)
+#define V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF (1 << 5)
/**
* struct v4l2_plane - plane info for multi-planar buffers
@@ -1041,6 +1042,8 @@ static inline __u64 v4l2_timeval_to_ns(const struct timeval *tv)
#define V4L2_BUF_FLAG_IN_REQUEST 0x00000080
/* timecode field is valid */
#define V4L2_BUF_FLAG_TIMECODE 0x00000100
+/* Don't return the capture buffer until OUTPUT timestamp changes */
+#define V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF 0x00000200
/* Buffer is prepared for queuing */
#define V4L2_BUF_FLAG_PREPARED 0x00000400
/* Cache handling flags */
This RFC patch adds support for the V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF flag. It also adds a new V4L2_BUF_CAP_SUPPORTS_M2M_HOLD_CAPTURE_BUF capability and a v4l2_m2m_release_capture_buf() helper function. Drivers should set vb2_queue->subsystem_flags to VB2_V4L2_FL_SUPPORTS_M2M_HOLD_CAPTURE_BUF to indicate support for this flag. The device_run() function should look like this: if (v4l2_m2m_release_capture_buf(out_vb, cap_vb)) { v4l2_m2m_buf_done(cap_vb, VB2_BUF_STATE_DONE); v4l2_m2m_job_finish(...); return; } cap_vb->is_held = out_vb->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF; ... v4l2_m2m_buf_done(out_vb, VB2_BUF_STATE_DONE); if (!cap_vb->is_held) { v4l2_m2m_buf_done(cap_vb, VB2_BUF_STATE_DONE); v4l2_m2m_job_finish(...); } In order to handle the corner case where V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF is always set for the output buffer, and you reached the last frame (so no new output buffer will be queued with a new timestamp), the driver must implement support for the V4L2_DEC_CMD_FLUSH command, and that should do: struct vb2_v4l2_buffer *out_vb = v4l2_m2m_last_src_buf(m2m_ctx); struct vb2_v4l2_buffer *cap_vb = v4l2_m2m_last_dst_buf(m2m_ctx); if (out_vb) { out_vb->flags &= ~V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF; } else if (cap_vb && cap_vb->is_held) { v4l2_m2m_buf_done(cap_vb, VB2_BUF_STATE_DONE); v4l2_m2m_job_finish(...); } For formats that do not support slicing (e.g. VP8), the FLUSH command just does nothing. At least, I think so. Comments on this are very welcome. We definitely need better support in v4l2-mem2mem.c for such situations (same for stateful codecs) since it's too complex for drivers to get right IMHO. Regards, Hans Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Tested-by: Boris Brezillon <boris.brezillon@collabora.com> Reviewed-by: Boris Brezillon <boris.brezillon@collabora.com> --- Documentation/media/uapi/v4l/buffer.rst | 13 ++++++ .../media/uapi/v4l/vidioc-reqbufs.rst | 6 +++ .../media/common/videobuf2/videobuf2-v4l2.c | 8 +++- include/media/v4l2-mem2mem.h | 42 +++++++++++++++++++ include/media/videobuf2-core.h | 3 ++ include/media/videobuf2-v4l2.h | 5 +++ include/uapi/linux/videodev2.h | 13 +++--- 7 files changed, 84 insertions(+), 6 deletions(-)