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-ci...@xs4all.nl> Tested-by: Boris Brezillon <boris.brezil...@collabora.com> Reviewed-by: Boris Brezillon <boris.brezil...@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(-) diff --git a/Documentation/media/uapi/v4l/buffer.rst b/Documentation/media/uapi/v4l/buffer.rst index 1cbd9cde57f3..afb03906ead9 100644 --- a/Documentation/media/uapi/v4l/buffer.rst +++ b/Documentation/media/uapi/v4l/buffer.rst @@ -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`` diff --git a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst index d7faef10e39b..d0c643db477a 100644 --- a/Documentation/media/uapi/v4l/vidioc-reqbufs.rst +++ b/Documentation/media/uapi/v4l/vidioc-reqbufs.rst @@ -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 ============ diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c index 5a9ba3846f0a..699787f48f46 100644 --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c @@ -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; diff --git a/include/media/v4l2-mem2mem.h b/include/media/v4l2-mem2mem.h index 0b9c3a287061..724858efded2 100644 --- a/include/media/v4l2-mem2mem.h +++ b/include/media/v4l2-mem2mem.h @@ -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); diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h index 640aabe69450..a2b2208b02da 100644 --- a/include/media/videobuf2-core.h +++ b/include/media/videobuf2-core.h @@ -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; diff --git a/include/media/videobuf2-v4l2.h b/include/media/videobuf2-v4l2.h index 8a10889dc2fd..13ab101864aa 100644 --- a/include/media/videobuf2-v4l2.h +++ b/include/media/videobuf2-v4l2.h @@ -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 * */ diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h index 530638dffd93..4fa9f543742d 100644 --- a/include/uapi/linux/videodev2.h +++ b/include/uapi/linux/videodev2.h @@ -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 */ -- 2.20.1