Hi Sakari,
Some minor comments:
On 02/15/2014 09:53 PM, Sakari Ailus wrote:
> Some devices do not produce timestamps that correspond to the end of the
> frame. The user space should be informed on the matter. This patch achieves
> that by adding buffer flags (and a mask) for timestamp sources since more
> possible timestamping points are expected than just two.
>
> A three-bit mask is defined (V4L2_BUF_FLAG_TSTAMP_SRC_MASK) and two of the
> eight possible values is are defined V4L2_BUF_FLAG_TSTAMP_SRC_EOF for end of
> frame (value zero) V4L2_BUF_FLAG_TSTAMP_SRC_SOE for start of exposure (next
> value).
>
> Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxx>
> ---
> Documentation/DocBook/media/v4l/io.xml | 31 ++++++++++++++++++++++++------
> drivers/media/v4l2-core/videobuf2-core.c | 4 +++-
> include/media/videobuf2-core.h | 2 ++
> include/uapi/linux/videodev2.h | 4 ++++
> 4 files changed, 34 insertions(+), 7 deletions(-)
>
> diff --git a/Documentation/DocBook/media/v4l/io.xml b/Documentation/DocBook/media/v4l/io.xml
> index 46d24b3..fbd0c6e 100644
> --- a/Documentation/DocBook/media/v4l/io.xml
> +++ b/Documentation/DocBook/media/v4l/io.xml
> @@ -653,12 +653,6 @@ plane, are stored in struct <structname>v4l2_plane</structname> instead.
> In that case, struct <structname>v4l2_buffer</structname> contains an array of
> plane structures.</para>
>
> - <para>For timestamp types that are sampled from the system clock
> -(V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC) it is guaranteed that the timestamp is
> -taken after the complete frame has been received (or transmitted in
> -case of video output devices). For other kinds of
> -timestamps this may vary depending on the driver.</para>
> -
> <table frame="none" pgwide="1" id="v4l2-buffer">
> <title>struct <structname>v4l2_buffer</structname></title>
> <tgroup cols="4">
> @@ -1119,6 +1113,31 @@ in which case caches have not been used.</entry>
> <entry>The CAPTURE buffer timestamp has been taken from the
> corresponding OUTPUT buffer. This flag applies only to mem2mem devices.</entry>
> </row>
> + <row>
> + <entry><constant>V4L2_BUF_FLAG_TSTAMP_SRC_MASK</constant></entry>
> + <entry>0x00070000</entry>
> + <entry>Mask for timestamp sources below. The timestamp source
> + defines the point of time the timestamp is taken in relation to
> + the frame. Logical and operation between the
> + <structfield>flags</structfield> field and
> + <constant>V4L2_BUF_FLAG_TSTAMP_SRC_MASK</constant> produces the
> + value of the timestamp source.</entry>
> + </row>
> + <row>
> + <entry><constant>V4L2_BUF_FLAG_TSTAMP_SRC_EOF</constant></entry>
> + <entry>0x00000000</entry>
> + <entry>"End of frame." The buffer timestamp has been taken
More a typographical thing than anything else: I prefer this:
"End Of Frame": the buffer...
The capitalization links back to the EOF abbreviation more directly.
> + when the last pixel of the frame has been received or the
I would say: "after the last pixel of the frame has been received or after the"
The "when" word suggests that it is exactly "when", which is not true in
practice.
> + last pixel of the frame has been transmitted.</entry>
> + </row>
> + <row>
> + <entry><constant>V4L2_BUF_FLAG_TSTAMP_SRC_SOE</constant></entry>
> + <entry>0x00010000</entry>
> + <entry>"Start of exposure." The buffer timestamp has been taken
Start Of Exposure: the buffer...
> + when the exposure of the frame has begun. This is only
Should 'when' be replaced with 'after' here as well? I think Laurent has to decide
that.
Regards,
Hans
> + valid for buffer type
> + <constant>V4L2_BUF_TYPE_VIDEO_CAPTURE</constant>.</entry>
> + </row>
> </tbody>
> </tgroup>
> </table>
> diff --git a/drivers/media/v4l2-core/videobuf2-core.c b/drivers/media/v4l2-core/videobuf2-core.c
> index 5a5fb7f..6e314b0 100644
> --- a/drivers/media/v4l2-core/videobuf2-core.c
> +++ b/drivers/media/v4l2-core/videobuf2-core.c
> @@ -2195,7 +2195,9 @@ int vb2_queue_init(struct vb2_queue *q)
> WARN_ON(!q->io_modes) ||
> WARN_ON(!q->ops->queue_setup) ||
> WARN_ON(!q->ops->buf_queue) ||
> - WARN_ON(q->timestamp_type & ~V4L2_BUF_FLAG_TIMESTAMP_MASK))
> + WARN_ON(q->timestamp_type &
> + ~(V4L2_BUF_FLAG_TIMESTAMP_MASK |
> + V4L2_BUF_FLAG_TSTAMP_SRC_MASK)))
> return -EINVAL;
>
> /* Warn that the driver should choose an appropriate timestamp type */
> diff --git a/include/media/videobuf2-core.h b/include/media/videobuf2-core.h
> index bef53ce..b6b992d 100644
> --- a/include/media/videobuf2-core.h
> +++ b/include/media/videobuf2-core.h
> @@ -312,6 +312,8 @@ struct v4l2_fh;
> * @buf_struct_size: size of the driver-specific buffer structure;
> * "0" indicates the driver doesn't want to use a custom buffer
> * structure type, so sizeof(struct vb2_buffer) will is used
> + * @timestamp_type: Timestamp flags; V4L2_BUF_FLAGS_TIMESTAMP_* and
> + * V4L2_BUF_FLAGS_TSTAMP_SRC_*
> * @gfp_flags: additional gfp flags used when allocating the buffers.
> * Typically this is 0, but it may be e.g. GFP_DMA or __GFP_DMA32
> * to force the buffer allocation to a specific memory zone.
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index e9ee444..82e8661 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -695,6 +695,10 @@ struct v4l2_buffer {
> #define V4L2_BUF_FLAG_TIMESTAMP_UNKNOWN 0x00000000
> #define V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC 0x00002000
> #define V4L2_BUF_FLAG_TIMESTAMP_COPY 0x00004000
> +/* Timestamp sources. */
> +#define V4L2_BUF_FLAG_TSTAMP_SRC_MASK 0x00070000
> +#define V4L2_BUF_FLAG_TSTAMP_SRC_EOF 0x00000000
> +#define V4L2_BUF_FLAG_TSTAMP_SRC_SOE 0x00010000
>
> /**
> * struct v4l2_exportbuffer - export of video buffer as DMABUF file descriptor
>
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