Re: [PATCH/RFC 1/4] V4L: add three new ioctl()s for multi-size videobuffer management

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On Tuesday 05 April 2011 14:52:20 Guennadi Liakhovetski wrote:
> On Tue, 5 Apr 2011, Hans Verkuil wrote:
> > On Tuesday, April 05, 2011 14:21:03 Laurent Pinchart wrote:
> > > On Friday 01 April 2011 10:13:02 Guennadi Liakhovetski wrote:
> [snip]
> 
> > > >  /*
> > > >  
> > > >   *	I O C T L   C O D E S   F O R   V I D E O   D E V I C E S
> > > >   *
> > > > 
> > > > @@ -1937,6 +1957,10 @@ struct v4l2_dbg_chip_ident {
> > > > 
> > > >  #define	VIDIOC_SUBSCRIBE_EVENT	 _IOW('V', 90, struct
> > > > 
> > > > v4l2_event_subscription) #define	VIDIOC_UNSUBSCRIBE_EVENT _IOW('V',
> > > > 91, struct v4l2_event_subscription)
> > > > 
> > > > +#define VIDIOC_CREATE_BUFS	_IOWR('V', 92, struct
> > > > v4l2_create_buffers) +#define VIDIOC_DESTROY_BUFS	_IOWR('V', 93,
> > > > struct v4l2_buffer_span) +#define VIDIOC_SUBMIT_BUF	 _IOW('V', 94,
> > > > int)
> > > > +
> > > 
> > > In case we later need to pass other information (such as flags) to
> > > VIDIOC_SUBMIT_BUF, you should use a structure instead of an int.
> > 
> > I would just pass struct v4l2_buffer to this ioctl, just like QBUF/DQBUF
> > do.
> 
> Why??? You do not need all that extra information. Well, we could, of
> course, make a struct with reserved fields... but it seems nice to me to
> have the clarity here - this ioctl() _only_ gives buffer ownership to the
> kernel. No more configuration...

Right now you're correct. In the future we might need extra fields, so we need 
a structure with reserved fields.

-- 
Regards,

Laurent Pinchart
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