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.
At the start of the device_run function drivers should first check if the
current capture buffer should be released:
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;
}
And at the end they should check (out_vb->flags &
V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF)
and, if set, skip returning the capture buffer to vb2.
This has only been compile tested, and this is missing the documentation. I
would
like to know if this works in a real driver first before turning this into a
proper
patch series.
Regards,
Hans
Signed-off-by: Hans Verkuil <hverkuil-ci...@xs4all.nl>
---
diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c
b/drivers/media/common/videobuf2/videobuf2-v4l2.c
index fb9ac7696fc6..83372de9b815 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
@@ -321,6 +322,8 @@ 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;
@@ -659,6 +662,8 @@ 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 bb3e63d6bd1a..6af1d519938f 100644
--- a/include/media/v4l2-mem2mem.h
+++ b/include/media/v4l2-mem2mem.h
@@ -648,6 +648,38 @@ 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:
+ *
+ * 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;
+ * }
+ *
+ * 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 (out_vb->flags & V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF) &&
+ 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 22f3ff76a8b5..e9d99023c637 100644
--- a/include/media/videobuf2-core.h
+++ b/include/media/videobuf2-core.h
@@ -504,6 +504,8 @@ 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)``
@@ -570,6 +572,7 @@ 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..4e52427a4114 100644
--- a/include/media/videobuf2-v4l2.h
+++ b/include/media/videobuf2-v4l2.h
@@ -49,6 +49,9 @@ struct vb2_v4l2_buffer {
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 1050a75fb7ef..26925d63ea05 100644
--- a/include/uapi/linux/videodev2.h
+++ b/include/uapi/linux/videodev2.h
@@ -907,11 +907,12 @@ 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
@@ -1033,6 +1034,8 @@ 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 */
