On Tue, 1 Dec 2009, Hans Verkuil wrote:
> On Monday 30 November 2009 15:48:24 Guennadi Liakhovetski wrote:
> > On Mon, 30 Nov 2009, Hans Verkuil wrote:
> > > On Fri, 27 Nov 2009, Guennadi Liakhovetski wrote:
> > > > On Fri, 27 Nov 2009, Hans Verkuil wrote:
> > > > > Hi Guennadi,
> > > > >
> > > > > > Convert soc-camera core and all soc-camera drivers to the new
> > > > > > mediabus API. This also takes soc-camera client drivers one step
> > > > > > closer to also be
> > > > > > usable with generic v4l2-subdev host drivers.
> > > > >
> > > > > Just a quick question:
> > > > > > @@ -323,28 +309,39 @@ static int mt9m001_s_fmt(struct v4l2_subdev
> > > > > > *sd, struct v4l2_format *f)
> > > > > > /* No support for scaling so far, just crop. TODO: use skipping
> > > > > > */ ret = mt9m001_s_crop(sd, &a);
> > > > > > if (!ret) {
> > > > > > - pix->width = mt9m001->rect.width;
> > > > > > - pix->height = mt9m001->rect.height;
> > > > > > - mt9m001->fourcc = pix->pixelformat;
> > > > > > + mf->width = mt9m001->rect.width;
> > > > > > + mf->height = mt9m001->rect.height;
> > > > > > + mt9m001->fmt = soc_mbus_find_datafmt(mf->code,
> > > > > > + mt9m001->fmts, mt9m001->num_fmts);
> > > > > > + mf->colorspace = mt9m001->fmt->colorspace;
> > > > > > }
> > > > > >
> > > > > > return ret;
> > > > > > }
> > > > > >
> > > > > > -static int mt9m001_try_fmt(struct v4l2_subdev *sd, struct
> > > > > > v4l2_format *f)
> > > > > > +static int mt9m001_try_fmt(struct v4l2_subdev *sd,
> > > > > > + struct v4l2_mbus_framefmt *mf)
> > > > > > {
> > > > > > struct i2c_client *client = sd->priv;
> > > > > > struct mt9m001 *mt9m001 = to_mt9m001(client);
> > > > > > - struct v4l2_pix_format *pix = &f->fmt.pix;
> > > > > > + const struct soc_mbus_datafmt *fmt;
> > > > > >
> > > > > > - v4l_bound_align_image(&pix->width, MT9M001_MIN_WIDTH,
> > > > > > + v4l_bound_align_image(&mf->width, MT9M001_MIN_WIDTH,
> > > > > > MT9M001_MAX_WIDTH, 1,
> > > > > > - &pix->height, MT9M001_MIN_HEIGHT + mt9m001->y_skip_top,
> > > > > > + &mf->height, MT9M001_MIN_HEIGHT + mt9m001->y_skip_top,
> > > > > > MT9M001_MAX_HEIGHT + mt9m001->y_skip_top, 0, 0);
> > > > > >
> > > > > > - if (pix->pixelformat == V4L2_PIX_FMT_SBGGR8 ||
> > > > > > - pix->pixelformat == V4L2_PIX_FMT_SBGGR16)
> > > > > > - pix->height = ALIGN(pix->height - 1, 2);
> > > > > > + if (mt9m001->fmts == mt9m001_colour_fmts)
> > > > > > + mf->height = ALIGN(mf->height - 1, 2);
> > > > > > +
> > > > > > + fmt = soc_mbus_find_datafmt(mf->code, mt9m001->fmts,
> > > > > > + mt9m001->num_fmts);
> > > > > > + if (!fmt) {
> > > > > > + fmt = mt9m001->fmt;
> > > > > > + mf->code = fmt->code;
> > > > > > + }
> > > > > > +
> > > > > > + mf->colorspace = fmt->colorspace;
> > > > > >
> > > > > > return 0;
> > > > > > }
> > > > >
> > > > > Why do the sensor drivers use soc_mbus_find_datafmt? They only seem
> > > > > to be interested in the colorspace field, but I don't see the reason
> > > > > for that. Most if not all sensors have a fixed colorspace depending
> > > > > on the pixelcode, so they can just ignore the colorspace that the
> > > > > caller requested and replace it with their own.
> > > >
> > > > Right, that's exactly what's done here. mt9m001 and mt9v022 drivers
> > > > support different formats, depending on the exact detected or specified
> > > > by the user model. That's why they have to search for the requested
> > > > format in supported list. and then - yes, they just put the found
> > > > format into user
> > > >
> > > > request:
> > > > > > + mf->colorspace = fmt->colorspace;
> > > > >
> > > > > I didn't have time for a full review, so I might have missed
> > > > > something.
> > >
> > > I looked at this more closely and I realized that I did indeed miss that
> > > soc_mbus_find_datafmt just searched in the pixelcode -> colorspace
> > > mapping array.
> > >
> > > I also realized that there is no need for that data structure and
> > > function to be soc-camera specific. I believe I said otherwise in an
> > > earlier review. My apologies for that, all I can say is that I had very
> > > little time to do the reviews...
> >
> > No, you did not say otherwise about _these_ struct and function - they
> > only appeared in v2 of the mediabus API, after you'd suggested to move
> > colorspace into struct v4l2_mbus_framefmt.
> >
> > > That said, there is no need for both the soc_mbus_datafmt struct and the
> > > soc_mbus_find_datafmt function. These can easily be replaced by something
> > > like this as a local function in each subdev:
> > >
> > > static enum v4l2_colorspace mt9m111_g_colorspace(enum v4l2_mbus_pixelcode
> > > code)
> > > {
> > > switch (code) {
> > > case V4L2_MBUS_FMT_YUYV:
> > > case V4L2_MBUS_FMT_YVYU:
> > > case V4L2_MBUS_FMT_UYVY:
> > > case V4L2_MBUS_FMT_VYUY:
> > > return V4L2_COLORSPACE_JPEG;
> > >
> > > case V4L2_MBUS_FMT_RGB555:
> > > case V4L2_MBUS_FMT_RGB565:
> > > case V4L2_MBUS_FMT_SBGGR8:
> > > case V4L2_MBUS_FMT_SBGGR10_2X8_PADHI_LE:
> > > return V4L2_COLORSPACE_SRGB;
> > >
> > > default:
> > > return 0;
> > > }
> > > }
> > >
> > > So if mt9m111_g_colorspace() returns 0, then the format wasn't found.
> > > (Note that the compiler might give a warning for the return 0, so that
> > > might need some editing)
> > >
> > > Much simpler and much easier to understand.
> >
> > Drivers are not forced to use that small and trivial function - everyone
> > is welcome to reinvent the wheel:-) In many cases it is indeed an
> > overkill, like mt9t031, which only supports one format. However, in some
> > other drivers this is not that trivial. First, as I said, mt9m001 and
> > mt9v022 generate that array dynamically, depending on the chip version and
> > platform configuration. So, you anyway would have to iterate over the
> > array. In other drivers, like ov772x and the recently submitted mt9t112
> > this function is also used to retrieve register configuration for a
> > specific pixel code. So, I still think that function is useful, and being
> > kept under soc-camera mediabus extensions, and being inline, it shouldn't
> > cause too many problems.
>
> It definitely shouldn't be in a soc-camera header. If this is going to be used
> as a common utility, then it should be in v4l2-mediabus.h.
Sorry, I don't understand. IMHO soc_mbus_get_fmtdesc() and
soc_mbus_bytes_per_line() are much more likely to be useful for non
soc-camera drivers, and still you wanted them to remain soc-camera
specific. Now this small and trivial function, which, as you say, only
very few need, so, I made it soc-camera specific, now you want it to be
available to all...
> But frankly the only two places where I think it is useful are mt9m001 and
> mt9v022. In all other cases is can be replaced by simpler code. For ov772x
> I would just add the pixelcode and colorspace fields to the
> ov772x_color_format struct instead and you iterate of the elements of the
> ov772x_cfmts array to find the one that matches the desired pixelcode.
>
> I think the usefulness of the datastructure and utility function depends very
> much on the sensor driver which is why I prefer to have this being just part
> of the driver source itself rather than in a generic header. That gives the
> impression that driver writers *have* to do it that way, when often it can be
> done much simpler.
Ok, how about this: I preserve the function as is in soc-camera, and leave
it as is in mt9m001, mt9v022, and ov772x (and in the forthcoming mt9t112).
In other drivers with constant format lists, where this function is only
used to find the colorspace, I'll replace it with a switch-case.
I _really_ do not understand why soc-camera internal APIs now suddenly
receive such attention.
Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/
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