On Fri, 6 Aug 2010, Laurent Pinchart wrote:
> Hi Guennadi,
>
> On Thursday 05 August 2010 20:03:46 Guennadi Liakhovetski wrote:
> > Many video drivers implement a discrete set of frame formats and thus face
> > a task of finding the best match for a user-requested format. Implementing
> > this in a generic function has also an advantage, that different drivers
> > with similar supported format sets will select the same format for the
> > user, which improves consistency across drivers.
> >
> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
> > ---
> >
> > I'm currently away from my hardware, so, this is only compile tested and
> > run-time tested with a test application. In any case, reviews and
> > suggestions welcome.
> >
> > drivers/media/video/v4l2-common.c | 26 ++++++++++++++++++++++++++
> > include/linux/videodev2.h | 10 ++++++++++
> > 2 files changed, 36 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/media/video/v4l2-common.c
> > b/drivers/media/video/v4l2-common.c index 4e53b0b..90727e6 100644
> > --- a/drivers/media/video/v4l2-common.c
> > +++ b/drivers/media/video/v4l2-common.c
> > @@ -1144,3 +1144,29 @@ int v4l_fill_dv_preset_info(u32 preset, struct
> > v4l2_dv_enum_preset *info) return 0;
> > }
> > EXPORT_SYMBOL_GPL(v4l_fill_dv_preset_info);
> > +
> > +struct v4l2_frmsize_discrete *v4l2_find_nearest_format(struct
> > v4l2_discrete_probe *probe, + s32 width, s32 height)
> > +{
> > + int i;
> > + u32 error, min_error = ~0;
> > + struct v4l2_frmsize_discrete *size, *best = NULL;
> > +
> > + if (!probe)
> > + return best;
> > +
> > + for (i = 0, size = probe->sizes; i < probe->num_sizes; i++, size++) {
> > + if (probe->probe && !probe->probe(probe))
>
> What's this call for ?
Well, atm, I don't think I have a specific case right now, but I think, it
can well be the case, that not all frame sizes are always usable in the
driver, depending on other circumstances. E.g., depending on the pixel /
fourcc code. So, in this case the driver just provides a probe method to
filter out inapplicable sizes.
Thanks
Guennadi
>
> > + continue;
> > + error = abs(size->width - width) + abs(size->height - height);
> > + if (error < min_error) {
> > + min_error = error;
> > + best = size;
> > + }
> > + if (!error)
> > + break;
> > + }
> > +
> > + return best;
> > +}
> > +EXPORT_SYMBOL_GPL(v4l2_find_nearest_format);
> > diff --git a/include/linux/videodev2.h b/include/linux/videodev2.h
> > index 047f7e6..f622bba 100644
> > --- a/include/linux/videodev2.h
> > +++ b/include/linux/videodev2.h
> > @@ -394,6 +394,16 @@ struct v4l2_frmsize_discrete {
> > __u32 height; /* Frame height [pixel] */
> > };
> >
> > +struct v4l2_discrete_probe {
> > + struct v4l2_frmsize_discrete *sizes;
> > + int num_sizes;
> > + void *priv;
> > + bool (*probe)(struct v4l2_discrete_probe *);
> > +};
> > +
> > +struct v4l2_frmsize_discrete *v4l2_find_nearest_format(struct
> > v4l2_discrete_probe *probe, + s32 width, s32 height);
> > +
> > struct v4l2_frmsize_stepwise {
> > __u32 min_width; /* Minimum frame width [pixel] */
> > __u32 max_width; /* Maximum frame width [pixel] */
>
> --
> Regards,
>
> Laurent Pinchart
>
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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