On 8/31/22 10:13 PM, Tomi Valkeinen wrote:
> V4L2_FRAME_DESC_ENTRY_MAX is currently set to 4. In theory it's possible
> to have an arbitrary amount of streams in a single pad, so preferably
> there should be no hardcoded maximum number.
>
> However, I believe a reasonable max is 8, which would cover a CSI-2 pad
> with 4 streams of pixel data and 4 streams of metadata.
>
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> Reviewed-by: Hans Verkuil <hverkuil-cisco@xxxxxxxxx>
> Reviewed-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> ---
> include/media/v4l2-subdev.h | 6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
> index 9689f38a0af1..3797b99bb408 100644
> --- a/include/media/v4l2-subdev.h
> +++ b/include/media/v4l2-subdev.h
> @@ -358,7 +358,11 @@ struct v4l2_mbus_frame_desc_entry {
> } bus;
> };
>
> -#define V4L2_FRAME_DESC_ENTRY_MAX 4
> + /*
> + * If this number is too small, it should be dropped altogether and the
> + * API switched to a dynamic number of frame descriptor entries.
> + */
> +#define V4L2_FRAME_DESC_ENTRY_MAX 8
The number 8 here is still not enough I think, CSI2 specification already
extended the VC identifier to be at most 5 bits, which support a max of
32 VCs.
Considering the metadata, the number should be larger, it looks like that
we have to switch using dynamic number?
BTW, does this change break the uAPI?
>
> /**
> * enum v4l2_mbus_frame_desc_type - media bus frame description type
>
--
Best regards,
Bingbu Cao
