Re: [PATCH/RFC 26/48] videodev2.h: Add request field to v4l2_pix_format_mplane

[Hans Verkuil <hverkuil@xs4all.nl>]

Hi Laurent,

On 12/17/2015 09:40 AM, Laurent Pinchart wrote:
> Let userspace specify a request ID when getting or setting formats. The
> support is limited to the multi-planar API at the moment, extending it
> to the single-planar API is possible if needed.
> 
> From a userspace point of view the API change is also minimized and
> doesn't require any new ioctl.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
> ---
>  include/uapi/linux/videodev2.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index 5af1d2d87558..5b2a8bc80eb2 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -1973,6 +1973,7 @@ struct v4l2_plane_pix_format {
>   * @ycbcr_enc:		enum v4l2_ycbcr_encoding, Y'CbCr encoding
>   * @quantization:	enum v4l2_quantization, colorspace quantization
>   * @xfer_func:		enum v4l2_xfer_func, colorspace transfer function
> + * @request:		request ID
>   */
>  struct v4l2_pix_format_mplane {
>  	__u32				width;
> @@ -1987,7 +1988,8 @@ struct v4l2_pix_format_mplane {
>  	__u8				ycbcr_enc;
>  	__u8				quantization;
>  	__u8				xfer_func;
> -	__u8				reserved[7];
> +	__u8				reserved[3];
> +	__u32				request;

I think I mentioned this before: I feel uncomfortable using 4 bytes of the reserved
fields when the request ID is limited to 16 bits anyway.

I would prefer a __u16 here. Also put the request field *before* the reserved
array, not after.

Regards,

	Hans

>  } __attribute__ ((packed));
>  
>  /**
>