[PATCH] drm/exynos: Get HDMI version from device tree

[Mitch Bradley]

On 1/8/2013 6:48 AM, Sean Paul wrote:
> On Tue, Jan 8, 2013 at 11:45 AM, Lucas Stach <dev at lynxeye.de> wrote:
>> Am Montag, den 07.01.2013, 16:12 -0500 schrieb Sean Paul:
>>> On Mon, Jan 7, 2013 at 3:54 PM, Mitch Bradley <wmb at firmworks.com> wrote:
>>>> On 1/7/2013 10:43 AM, Sean Paul wrote:
>>>>> Add a property to the hdmi node so we can specify the HDMI version in
>>>>> the device tree instead of just defaulting to v1.4 with the existence of
>>>>> the dt node.
>>>>>
>>>>> Signed-off-by: Sean Paul <seanpaul at chromium.org>
>>>>> ---
>>>>>  .../devicetree/bindings/drm/exynos/hdmi.txt        |    3 +++
>>>>>  drivers/gpu/drm/exynos/exynos_hdmi.c               |   19 ++++++++++---------
>>>>>  2 files changed, 13 insertions(+), 9 deletions(-)
>>>>>
>>>>> diff --git a/Documentation/devicetree/bindings/drm/exynos/hdmi.txt b/Documentation/devicetree/bindings/drm/exynos/hdmi.txt
>>>>> index 589edee..d1c7d91 100644
>>>>> --- a/Documentation/devicetree/bindings/drm/exynos/hdmi.txt
>>>>> +++ b/Documentation/devicetree/bindings/drm/exynos/hdmi.txt
>>>>> @@ -11,6 +11,8 @@ Required properties:
>>>>>       c) pin function mode.
>>>>>       d) optional flags and pull up/down.
>>>>>       e) drive strength.
>>>>> +- samsung,supports-hdmi-1.4: Define if device supports HDMI v1.4
>>>>> +- samsung,supports-hdmi-1.3: Define if device supports HDMI v1.3
>>>>
>>>> a) This seems pretty generic, not at all samsung-specific, as the HDMI
>>>> version numbering space is well-defined by the HDMI spec.
>>>>
>>>> b) It would be better to make it an integer property whose value
>>>> encodes the version number, thus eliminating the need to add new
>>>> properties as new HDMI versions appear.
>>>>
>>>
>>> Thanks for the quick review, Mitch.
>>>
>>> How about:
>>>
>>> - hdmi-version: 0=v1.3, 1=v1.4
>> Why bother obfuscating the real version number? Why not just 13=v1.3,
>> 14=v1.4?

It's hard to predict how the HDMI committee will assign version numbers
in the future, but...

In the EDID structure that HDMI devices use for identification, the major.minor
version number is encoded as two bytes, one for major and one for minor, thus
it is conceivable that the minor could exceed 9.  (reference CEA-861-D section
A.2.5 or
http://en.wikipedia.org/wiki/Extended_display_identification_data#EDID_1.3_data_format

The EDID version number is not the same as the HDMI version number, but I expect
that the committees share people and thus ways of doing things.

I think it would be safer to encode the version number as (major<<8) | minor.

>>
> 
> Sure, that sounds good to me.
> 
> Sean
> 
>> Regards,
>> Lucas
>>
>>
>