Re: [v3 6/7] drm: Add Client Cap for advance gamma mode

Sharma, Shashank
2019-04-15T14:29:00Z

On 4/15/2019 7:42 PM, Lankhorst, Maarten wrote:
> mån 2019-04-15 klockan 19:26 +0530 skrev Sharma, Shashank:
>>> -----Original Message-----
>>> From: Lankhorst, Maarten
>>> Sent: Monday, April 15, 2019 4:28 PM
>>> To: Shankar, Uma <uma.shankar@intel.com>; intel-gfx@lists.freedeskt
>>> op.org; dri-
>>> devel@lists.freedesktop.org
>>> Cc: Syrjala, Ville <ville.syrjala@intel.com>; emil.l.velikov@gmail.
>>> com;
>>> sam@ravnborg.org; Roper, Matthew D <matthew.d.roper@intel.com>;
>>> seanpaul@chromium.org; brian.starkey@arm.com; dcastagna@chromium.or
>>> g;
>>> Sharma, Shashank <shashank.sharma@intel.com>
>>> Subject: Re: [v3 6/7] drm: Add Client Cap for advance gamma mode
>>>
>>> fre 2019-04-12 klockan 15:51 +0530 skrev Uma Shankar:
>>>> Introduced a client cap for advance cap mode
>>>> capability. Userspace should set this to get
>>>> to be able to use the new gamma_mode property.
>>>>
>>>> If this is not set, driver will work in legacy
>>>> mode.
>>>>
>>>> Suggested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>>> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
>>> Nack, this doesn't seem like a sensible idea. We already guard it
>>> behind the gamma mode property. Userspace shouldn't set the gamma
>>> mode
>>> to a value it doesn't understand.
>>>
>>> ~Maarten
>> Hey Maarten,
>> In that case, what do you suggest should be the right way to do this
>> ?
>>
>> @Ville, any comments here ?
>>
> I would say drop this patch, and just enable segmented gamma
> unconditionally, it's not the first property that can cause trouble
> when not understood.

Honestly, I kindof like this simple approach suggestion, which makes the
property focused, and easy to use. But one of the benefits I see for
this new gamma mode property was, that we can handle other advanced
gamma modes like 10/12/split and multi-segmented gamma modes too, using
this. So even though the single property is easy to use, but if we try
to cover each of the gamma modes per single property, it might get
confusing to see 4 different gamma mode properties, and how to set one
of this.

Another problem I see is, the precision and no of entries in the LUT,
for multi-segment gamma is different than traditional gamma, and we
might break some (most ?) of the old userspaces. Do you think is there
any way in which we can avoid this ?

- Shashank

> ~Maarten