On 11/13/2018 10:42 AM, Hans Verkuil wrote:
> From: Hans Verkuil
>
> Add support for 'tags' to struct v4l2_buffer. These can be used
> by m2m devices so userspace can set a tag for an output buffer and
> this value will then be copied to the capture buffer(s).
>
> This tag can be used to refer to capture buffers, something that
> is needed by stateless HW codecs.
>
> The new V4L2_BUF_CAP_SUPPORTS_TAGS capability indicates whether
> or not tags are supported.
>
> Signed-off-by: Hans Verkuil
> ---
> include/uapi/linux/videodev2.h | 38 +-
> 1 file changed, 37 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index c8e8ff810190..ec1fef2a9445 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -879,6 +879,7 @@ struct v4l2_requestbuffers {
> #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_TAGS (1 << 4)
>
> /**
> * struct v4l2_plane - plane info for multi-planar buffers
> @@ -912,6 +913,11 @@ struct v4l2_plane {
> __u32 reserved[11];
> };
>
> +struct v4l2_buffer_tag {
> + __u32 low;
> + __u32 high;
> +};
> +
> /**
> * struct v4l2_buffer - video buffer info
> * @index: id number of the buffer
> @@ -950,7 +956,10 @@ struct v4l2_buffer {
> __u32 flags;
> __u32 field;
> struct timeval timestamp;
> - struct v4l2_timecodetimecode;
> + union {
> + struct v4l2_timecodetimecode;
> + struct v4l2_buffer_tag tag;
> + };
> __u32 sequence;
>
> /* memory location */
> @@ -988,6 +997,8 @@ struct v4l2_buffer {
> #define V4L2_BUF_FLAG_IN_REQUEST 0x0080
> /* timecode field is valid */
> #define V4L2_BUF_FLAG_TIMECODE 0x0100
> +/* tag field is valid */
> +#define V4L2_BUF_FLAG_TAG0x0200
> /* Buffer is prepared for queuing */
> #define V4L2_BUF_FLAG_PREPARED 0x0400
> /* Cache handling flags */
> @@ -1007,6 +1018,31 @@ struct v4l2_buffer {
> /* request_fd is valid */
> #define V4L2_BUF_FLAG_REQUEST_FD 0x0080
>
> +static inline void v4l2_buffer_set_tag(struct v4l2_buffer *buf, __u64 tag)
> +{
> + buf->tag.high = tag >> 32;
> + buf->tag.low = tag & 0xULL;
> + buf->flags |= V4L2_BUF_FLAG_TAG;
> +}
> +
> +static inline void v4l2_buffer_set_tag_ptr(struct v4l2_buffer *buf,
> +const void *tag)
> +{
> + v4l2_buffer_set_tag(buf, (uintptr_t)tag);
> +}
> +
> +static inline __u64 v4l2_buffer_get_tag(const struct v4l2_buffer *buf)
> +{
> + if (!(buf->flags & V4L2_BUF_FLAG_TAG))
> + return 0;
> + return (((__u64)buf->tag.high) << 32) | (__u64)buf->tag.low;
> +}
> +
> +static inline void *v4l2_buffer_get_tag_ptr(const struct v4l2_buffer *buf)
> +{
> + return (void *)(uintptr_t)v4l2_buffer_get_tag(buf);
> +}
> +
I'm reconsidering my decision to use a u64 for the tag. It is too fiddly due
to the fact that I have to use a struct v4l2_buffer_tag. I think I'll just
use a u32.
I'll post a new version where I make this change.
Regards,
Hans
> /**
> * struct v4l2_exportbuffer - export of video buffer as DMABUF file
> descriptor
> *
>
