[Intel-gfx] [v3 6/7] drm: Add Client Cap for advance gamma mode

[Sharma, Shashank]

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 at intel.com>; intel-gfx at lists.freedeskt
>>> op.org; dri-
>>> devel at lists.freedesktop.org
>>> Cc: Syrjala, Ville <ville.syrjala at intel.com>; emil.l.velikov at gmail.
>>> com;
>>> sam at ravnborg.org; Roper, Matthew D <matthew.d.roper at intel.com>;
>>> seanpaul at chromium.org; brian.starkey at arm.com; dcastagna at chromium.or
>>> g;
>>> Sharma, Shashank <shashank.sharma at 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 at linux.intel.com>
>>>> Signed-off-by: Uma Shankar <uma.shankar at 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