[RESEND PATCH v3 06/11] drm: add DT bindings documentation for atmel-hlcdc-dc driver

[Laurent Pinchart]

Hi Thierry,

On Monday 21 July 2014 14:12:47 Thierry Reding wrote:
> On Mon, Jul 21, 2014 at 11:57:37AM +0200, Boris BREZILLON wrote:
> > On Mon, 21 Jul 2014 11:32:55 +0200 Laurent Pinchart wrote:
> >> On Monday 21 July 2014 11:24:38 Boris BREZILLON wrote:
> >>> On Mon, 21 Jul 2014 10:59:12 +0200 Thierry Reding wrote:
> >>>> On Fri, Jul 18, 2014 at 05:43:34PM +0200, Boris BREZILLON wrote:
> >>>> [...]
> >>>> 
> >>>>>>>>>> + - atmel,panel: Should contain a phandle with 2 parameters.
> >>>>>>>>>> +   The first cell is a phandle to a DRM panel device
> >>>>>>>>>> +   The second cell encodes the RGB mode, which can take the
> >>>>>>>>>> following values:
> >>>>>>>>>> +   * 0: RGB444
> >>>>>>>>>> +   * 1: RGB565
> >>>>>>>>>> +   * 2: RGB666
> >>>>>>>>>> +   * 3: RGB888
> >>>>>>>>> 
> >>>>>>>>> These are properties of the panel and should be obtained from
> >>>>>>>>> the panel directly rather than an additional cell in this
> >>>>>>>>> specifier.
> >>>>>>>> 
> >>>>>>>> Okay.
> >>>>>>>> What's the preferred way of doing this ?
> >>>>>>>> What about defining an rgb-mode property in the panel node.
> >>>>>>> 
> >>>>>>> There's .bpc in struct drm_display_info, I suspect that it could
> >>>>>>> be used for this. Alternatively, maybe we could extend the list
> >>>>>>> of color formats that go into drm_display_info.color_formats?
> >>>>>>> RGB444 is already covered.
> >>>>> 
> >>>>> I forgot to ask about bpc meaning. If, as I think, it means "bits
> >>>>> per color" then it cannot be used to encode RGB565 where green
> >>>>> color is encoded on 6 bits and red and blue are encoded on 5 bits.
> >>>> 
> >>>> Yes, I agree that bps is not a good fit for what you need here.
> >>> 
> >>> Okay, then I think we can replace bpc and color_formats by a
> >>> bus_formats table containing all supported formats, and use an enum
> >>> (something similar to v4l2_mbus_pixelcode defined in v4l2-mediabus.h
> >>> [1]) to list the available formats.
> >>> 
> >>> As this implies quite a few changes in crtc core and some drm drivers
> >>> (nouveau, i915 and radeon), I'd like to be sure this is what both of
> >>> you had in mind.
> >> 
> >> I think it is, but just to make sure I understand you correctly, could
> >> you just show how the drm_display_info structure would look like ?
> > 
> > The new drm_display_info structure should look like this [2] (except
> > that color_formats and bpc have not be removed yet), and [1] is just
> > here to show how the video_bus_format enum would look like.
> > 
> > [1] http://code.bulix.org/rfd0yx-86557
> > [2] http://code.bulix.org/7n03b4-86556
> 
> Quoting from your paste:
> 
> 	+   const enum video_bus_format *bus_formats;
> 	+   int nbus_formats;
> 
> Do we really need more than one?

We do if we want to replace the color_formats and bpc fields.

-- 
Regards,

Laurent Pinchart
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