Hi Laurent,
thank you for the comments.
Am Dienstag, den 26.08.2014, 12:01 +0200 schrieb Laurent Pinchart:
[...]
> > +};
> > +
> > +const struct v4l2_pixfmt *v4l2_pixfmt_by_fourcc(u32 fourcc)
> > +{
> > + int i;
>
> The loop counter is always positive, it can be an unsigned int.
I'll change that.
> > + for (i = 0; i < ARRAY_SIZE(v4l2_pixfmts); i++) {
> > + if (v4l2_pixfmts[i].pixelformat == fourcc)
> > + return v4l2_pixfmts + i;
> > + }
>
> We currently have 123 pixel formats defined, and that number will keep
> increasing. I wonder if something more efficient than an O(n) array lookup
> would be worth it.
How about a function similar to soc_mbus_find_fmtdesc that uses an array
provided by the driver:
const struct v4l2_pixfmt_info *v4l2_find_pixfmt(u32 pixelformat,
const struct v4l2_pixfmt_info *array, unsigned int len)
{
unsigned int i;
for (i = 0; i < len; i++) {
if (pixelformat == array[i].pixelformat)
return array + i;
}
return NULL;
}
And a function to fill this driver specific array from the global array
once:
void v4l2_init_pixfmt_array(struct v4l2_pixfmt_info *array, int len)
{
unsigned int i;
for (i = 0; i < len; i++)
array[i] = *v4l2_pixfmt_by_fourcc(array[i].pixelformat);
}
A driver could then do the following:
static struct v4l2_pixfmt_info driver_formats[] = {
{ .pixelformat = V4L2_PIX_FMT_YUYV },
{ .pixelformat = V4L2_PIX_FMT_YUV420 },
};
int driver_probe(...)
{
...
v4l2_init_pixfmt_array(driver_formats,
ARRAY_SIZE(driver_formats));
...
}
[...]
> > +unsigned int v4l2_sizeimage(const struct v4l2_pixfmt *fmt, unsigned int
> > width,
> > + unsigned int height)
> > +{
>
> A small comment would be useful here to explain why we don't round up in the
> second case.
Agreed, I think the YUV410 case is a good example for this.
[...]
> > +/**
> > + * struct v4l2_pixfmt - internal V4L2 pixel format description
>
> Maybe struct v4l2_pixfmt_info ?
That's fine with me.
regards
Philipp
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