Re: [PATCH/RFC 27/48] v4l2-subdev.h: Add request field to format and selection structures

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Hans,

On Friday 18 December 2015 12:20:54 Hans Verkuil wrote:
> On 12/17/2015 09:40 AM, Laurent Pinchart wrote:
> > Let userspace specify a request ID when getting or setting formats or
> > selection rectangles.
> > 
> > From a userspace point of view the API change is minimized and doesn't
> > require any new ioctl.
> > 
> > Signed-off-by: Laurent Pinchart
> > <laurent.pinchart+renesas@ideasonboard.com>
> > ---
> > 
> >  include/uapi/linux/v4l2-subdev.h | 15 +++++++++++++--
> >  1 file changed, 13 insertions(+), 2 deletions(-)
> > 
> > diff --git a/include/uapi/linux/v4l2-subdev.h
> > b/include/uapi/linux/v4l2-subdev.h index dbce2b554e02..2f1691ce9df5
> > 100644
> > --- a/include/uapi/linux/v4l2-subdev.h
> > +++ b/include/uapi/linux/v4l2-subdev.h
> > @@ -32,10 +32,12 @@
> >   * enum v4l2_subdev_format_whence - Media bus format type
> >   * @V4L2_SUBDEV_FORMAT_TRY: try format, for negotiation only
> >   * @V4L2_SUBDEV_FORMAT_ACTIVE: active format, applied to the device
> > + * @V4L2_SUBDEV_FORMAT_REQUEST: format stored in request
> >   */
> >  enum v4l2_subdev_format_whence {
> >  	V4L2_SUBDEV_FORMAT_TRY = 0,
> >  	V4L2_SUBDEV_FORMAT_ACTIVE = 1,
> > +	V4L2_SUBDEV_FORMAT_REQUEST = 2,
> >  };
> >  
> >  /**
> > @@ -43,12 +45,17 @@ enum v4l2_subdev_format_whence {
> >   * @which: format type (from enum v4l2_subdev_format_whence)
> >   * @pad: pad number, as reported by the media API
> >   * @format: media bus format (format code and frame size)
> > + * @request: request ID (when which is set to V4L2_SUBDEV_FORMAT_REQUEST)
> > + * @reserved2: for future use, set to zero for now
> > + * @reserved: for future use, set to zero for now
> >   */
> >  struct v4l2_subdev_format {
> >  	__u32 which;
> >  	__u32 pad;
> >  	struct v4l2_mbus_framefmt format;
> > -	__u32 reserved[8];
> > +	__u16 request;
> > +	__u16 reserved2;
> > +	__u32 reserved[7];
> 
> I would prefer:
> 
> 	__u16 request;
> 	__u16 reserved[15];
> 
> >  };
> >  
> >  /**
> > @@ -139,6 +146,8 @@ struct v4l2_subdev_frame_interval_enum {
> >   *	    defined in v4l2-common.h; V4L2_SEL_TGT_* .
> >   * @flags: constraint flags, defined in v4l2-common.h; V4L2_SEL_FLAG_*.
> >   * @r: coordinates of the selection window
> > + * @request: request ID (when which is set to V4L2_SUBDEV_FORMAT_REQUEST)
> > + * @reserved2: for future use, set to zero for now
> >   * @reserved: for future use, set to zero for now
> >   *
> >   * Hardware may use multiple helper windows to process a video stream.
> > @@ -151,7 +160,9 @@ struct v4l2_subdev_selection {
> >  	__u32 target;
> >  	__u32 flags;
> >  	struct v4l2_rect r;
> > -	__u32 reserved[8];
> > +	__u16 request;
> > +	__u16 reserved2;
> > +	__u32 reserved[7];
> 
> Ditto.
> 
> Generally apps do a memset of reserved, and that will just keep working.
> But adding a reserved2 field means that they have to explicitly set
> reserved2 to 0, which won't happen.

Agreed. Consider it fixed.

> >  };
> >  
> >  /* Backwards compatibility define --- to be removed */

-- 
Regards,

Laurent Pinchart