[PATCH V6 2/2] video: drm: exynos: Add device tree support

[Inki Dae]

2012/9/25 Laurent Pinchart <laurent.pinchart at ideasonboard.com>:
> On Monday 24 September 2012 21:35:46 Inki Dae wrote:
>> 2012/9/22 Stephen Warren <swarren at wwwdotorg.org>:
>> > On 09/21/2012 01:22 AM, Inki Dae wrote:
>> >> 2012/9/21 Stephen Warren <swarren at wwwdotorg.org>:
>> >>> On 09/21/2012 05:22 AM, Leela Krishna Amudala wrote:
>> >>>> This patch adds device tree based discovery support for exynos DRM-FIMD
>> >>>> driver which includes driver modification to handle platform data in
>> >>>> both the cases with DT and non-DT, Also adds the documentation for
>> >>>> bindings.
>> >>>>
>> >>>> diff --git a/Documentation/devicetree/bindings/drm/exynos/fimd.txt
>> >>>> b/Documentation/devicetree/bindings/drm/exynos/fimd.txt>>>
>> >>> ...
>> >>>
>> >>>> + - samsung,fimd-display: This property should specify the phandle of
>> >>>> the
>> >>>> +   display device node which holds the video interface timing with the
>> >>>> +   below mentioned properties.
>> >>>> +
>> >>>> +   - lcd-htiming: Specifies the horizontal timing for the overlay. The
>> >>>> +     horizontal timing includes four parameters in the following
>> >>>> order.
>> >>>> +
>> >>>> +     - horizontal back porch (in number of lcd clocks)
>> >>>> +     - horizontal front porch (in number of lcd clocks)
>> >>>> +     - hsync pulse width (in number of lcd clocks)
>> >>>> +     - Display panels X resolution.
>> >>>> +
>> >>>> +   - lcd-vtiming: Specifies the vertical timing for the overlay. The
>> >>>> +     vertical timing includes four parameters in the following order.
>> >>>> +
>> >>>> +     - vertical back porch (in number of lcd lines)
>> >>>> +     - vertical front porch (in number of lcd lines)
>> >>>> +     - vsync pulse width (in number of lcd clocks)
>> >>>> +     - Display panels Y resolution.
>> >>>
>> >>> Should this not use the new videomode timings that are under discussion
>> >>> at:
>> >>>
>> >>> http://lists.freedesktop.org/archives/dri-devel/2012-July/024875.html
>> >>
>> >> ok, I agree with you. then the videomode helper is going to be merged
>> >> to mainline(3.6)? if so, this patch should be reworked based on the
>> >> videomode helper.
>> >
>> > I think the videomode helpers would be merged for 3.7 at the very
>> > earliest; 3.6 is cooked already. Given there are still some comments on
>> > the binding, perhaps it won't happen until 3.8, but it'd be best to ask
>> > on that thread so that people more directly involved with the status can
>> > answer.
>>
>> as I mentioned before, it's better to use videomode helper instead but
>> for this, we should wait for that the videomode helper are merged to
>> mainline so I think it's better to merge it as is and then modify it
>> for videomode helper to be used later.
>
> Aren't DT bindings considered as an ABI, and required to be supported more or
> less forever ? If you merge this DT binding you'll have to keep supporting it.
> That's why DT bindings should not be rushed in.
>

is ABI required for DT binding?  I know DT binding parses just lcd
timing data from device tree file so ABI isn't needed. but when it
comes to DT, I'm novice yet so there may be my missing point. could
you tell me why DT bindings are considered as an ABI? if there is my
missing point, will consider it again.

Thanks,
Inki Dae

> --
> Regards,
>
> Laurent Pinchart
>
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