[Intel-gfx] [v2 0/7] Add Multi Segment Gamma Support
Shankar, Uma
uma.shankar at intel.com
Wed Apr 10 13:20:44 UTC 2019
>-----Original Message-----
>From: dri-devel [mailto:dri-devel-bounces at lists.freedesktop.org] On Behalf Of Ville
>Syrjälä
>Sent: Monday, April 8, 2019 9:38 PM
>To: Shankar, Uma <uma.shankar at intel.com>
>Cc: dcastagna at chromium.org; intel-gfx at lists.freedesktop.org; dri-
>devel at lists.freedesktop.org; seanpaul at chromium.org; Syrjala, Ville
><ville.syrjala at intel.com>; Lankhorst, Maarten <maarten.lankhorst at intel.com>
>Subject: Re: [Intel-gfx] [v2 0/7] Add Multi Segment Gamma Support
>
>On Mon, Apr 08, 2019 at 03:59:51PM +0000, Shankar, Uma wrote:
>>
>>
>> >-----Original Message-----
>> >From: dri-devel [mailto:dri-devel-bounces at lists.freedesktop.org] On
>> >Behalf Of Ville Syrjälä
>> >Sent: Monday, April 8, 2019 9:15 PM
>> >To: Shankar, Uma <uma.shankar at intel.com>
>> >Cc: dcastagna at chromium.org; intel-gfx at lists.freedesktop.org; dri-
>> >devel at lists.freedesktop.org; seanpaul at chromium.org; Syrjala, Ville
>> ><ville.syrjala at intel.com>; Lankhorst, Maarten
>> ><maarten.lankhorst at intel.com>
>> >Subject: Re: [Intel-gfx] [v2 0/7] Add Multi Segment Gamma Support
>> >
>> >On Mon, Apr 08, 2019 at 03:40:39PM +0000, Shankar, Uma wrote:
>> >>
>> >>
>> >> >-----Original Message-----
>> >> >From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
>> >> >Sent: Monday, April 8, 2019 8:27 PM
>> >> >To: Shankar, Uma <uma.shankar at intel.com>
>> >> >Cc: dcastagna at chromium.org; intel-gfx at lists.freedesktop.org; dri-
>> >> >devel at lists.freedesktop.org; seanpaul at chromium.org; Syrjala, Ville
>> >> ><ville.syrjala at intel.com>; Lankhorst, Maarten
>> >> ><maarten.lankhorst at intel.com>
>> >> >Subject: Re: [Intel-gfx] [v2 0/7] Add Multi Segment Gamma Support
>> >> >
>> >> >On Mon, Apr 08, 2019 at 02:40:51PM +0000, Shankar, Uma wrote:
>> >> >>
>> >> >>
>> >> >> >-----Original Message-----
>> >> >> >From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
>> >> >> >Sent: Monday, April 8, 2019 6:01 PM
>> >> >> >To: Shankar, Uma <uma.shankar at intel.com>
>> >> >> >Cc: dcastagna at chromium.org; intel-gfx at lists.freedesktop.org;
>> >> >> >dri- devel at lists.freedesktop.org; seanpaul at chromium.org;
>> >> >> >Syrjala, Ville <ville.syrjala at intel.com>; Lankhorst, Maarten
>> >> >> ><maarten.lankhorst at intel.com>
>> >> >> >Subject: Re: [Intel-gfx] [v2 0/7] Add Multi Segment Gamma
>> >> >> >Support
>> >> >> >
>> >> >> >On Mon, Apr 08, 2019 at 12:26:23PM +0000, Shankar, Uma wrote:
>> >> >> >>
>> >> >> >>
>> >> >> >> >-----Original Message-----
>> >> >> >> >From: dri-devel
>> >> >> >> >[mailto:dri-devel-bounces at lists.freedesktop.org]
>> >> >> >> >On Behalf Of Ville Syrjälä
>> >> >> >> >Sent: Friday, April 5, 2019 9:42 PM
>> >> >> >> >To: Shankar, Uma <uma.shankar at intel.com>
>> >> >> >> >Cc: dcastagna at chromium.org; intel-gfx at lists.freedesktop.org;
>> >> >> >> >dri- devel at lists.freedesktop.org; seanpaul at chromium.org;
>> >> >> >> >Syrjala, Ville <ville.syrjala at intel.com>; Lankhorst, Maarten
>> >> >> >> ><maarten.lankhorst at intel.com>
>> >> >> >> >Subject: Re: [Intel-gfx] [v2 0/7] Add Multi Segment Gamma
>> >> >> >> >Support
>> >> >> >> >
>> >> >> >> >On Mon, Apr 01, 2019 at 11:00:04PM +0530, Uma Shankar wrote:
>> >> >> >> >> This series adds support for programmable gamma modes and
>> >> >> >> >> exposes a property interface for the same. Also added,
>> >> >> >> >> support for multi segment gamma mode introduced in ICL+
>> >> >> >> >>
>> >> >> >> >> It creates 2 property interfaces :
>> >> >> >> >> 1. GAMMA_MODE_CAPS: This is immutable property and exposes
>> >> >> >> >> the various gamma modes supported and the lut ranges. This
>> >> >> >> >> is an enum property with element as blob id. Getting the
>> >> >> >> >> blob id in userspace, user can get the mode supported and
>> >> >> >> >> also the range of gamma mode supported with number of lut
>coefficients.
>> >> >> >> >>
>> >> >> >> >> 2. GAMMA_MODE: This is for user to set the gamma mode and
>> >> >> >> >> send the lut values for that particular mode.
>> >> >> >> >
>> >> >> >> >I think we should just go for the BLOB_ENUM prop type instead.
>> >> >> >> >Then the possible values and the current value are all part of the same
>prop.
>> >> >> >>
>> >> >> >> Hi Ville,
>> >> >> >> With the current approach, we have enum property with values
>> >> >> >> as blob_ids (representing platform capabilities). This should
>> >> >> >> not get modified and needs to be immutable.
>> >> >> >
>> >> >> >That's not quite what we want. We want to let the user modify
>> >> >> >the current value so that they can actually select the gamma mode.
>> >> >> >Otherwise we need yet another prop for it, or we have to deduce
>> >> >> >it from the LUT size (that apporach would actually work for
>> >> >> >i915 but may not work for other drivers/hardware).
>> >> >> >
>> >> >> >>
>> >> >> >> Userspace can query the property and get the blob using the blob_ids.
>> >> >> >> Thereby getting all the platform capabilities.
>> >> >> >>
>> >> >> >> Now to set the LUT values, he can use another blob property
>> >> >> >> and pass the luts. This is inline to how gamma/degamma is
>> >> >> >> implemented where we have one immutable LUT_SIZE property
>> >> >> >> (indicating number of
>> >> >> >> luts) and another blob property for actual lut values..
>> >> >>
>> >> >> Hi Ville,
>> >> >> Just to clarify and clear some doubts :)
>> >> >>
>> >> >> We should be able to set the gamma mode using the blob enum value.
>> >> >> Userspace will get the list enum vals (blob ids with mode name
>> >> >> embedded) and
>> >> >select one and do a setprop to set a mode.
>> >> >> Driver will get the blob_id and will be able to get the mode to
>> >> >> be set. So exposing capabilities and setting the mode should be
>> >> >> possible with this one
>> >> >property. I hope my understanding is correct.
>> >> >>
>> >> >> Now to send the actual blob values to be set, we need to use
>> >> >> some other property interface. Should we use the currently
>> >> >> available "gamma blob
>> >> >(gamma_lut_property)" property to send the lut values.
>> >> >> The challenge there is that it currently uses 16 bit lut values
>> >> >> struct drm_color_lut {
>> >> >> __u16 red;
>> >> >> __u16 green;
>> >> >> __u16 blue;
>> >> >> __u16 reserved;
>> >> >> };
>> >> >> which is not sufficient for HDR usecases. Or should we need a
>> >> >> new property for
>> >> >advance lut/extended lut like below:
>> >> >> https://patchwork.freedesktop.org/patch/294732/?series=30875&rev
>> >> >> =7
>> >> >>
>> >> >> What do you suggest ?
>> >> >
>> >> >I was thinking that we might get away with reusing the current
>> >> >props and just change the interpretation of the data when
>> >> >gamma_mode is set. But I'm not sure that's going to work out so
>> >> >well if one client sets this up and then another client comes
>> >> >along that doesn't understand the new props at all. But even with
>> >> >separate props I think we might still end up in a mess because the
>> >> >new client wouldn't know how to unset the higher precision LUT
>> >> >before setting up the old style prop and the
>> >kernel would then refuse the operation with with both props being set.
>> >> >
>> >> >So I think we might need a client cap for this which simply
>> >> >changes how the data in the existing props is represented. So
>> >> >internally we could always store things in the new high precision
>> >> >format, but we'd convert to/from the old format when dealing with an older
>client.
>> >>
>> >> We could also say that if a legacy gamma_mode_property is set
>> >> (which will be used by legacy apps or apps not aware of new
>> >> interface), in driver we will simply unset the earlier gamma_mode
>> >> and fallback to legacy mode (whatever it was for a particular
>> >> platform). This way we should be able to deal with this situation and an explicit
>unset may not be needed.
>> >What do you think ?
>> >
>> >I don't want (non-immutable) properties that magically change values.
>> >That way lies madness.
>>
>> Oh ok. So do you suggest that we add some kind of flag to be set by
>> user, based on which we take either legacy or advance_gamma path. Is my
>understanding correct ?
>
>Yeah, just another client cap. I can't immediately think of a nicer way to extend the
>precision.
Sure Ville, I am implementing based on this suggestion. Basically will expose a new
advance_gamma_mode flag as a client cap. Something like:
#define DRM_CLIENT_CAP_ADVANCE_GAMMA_MODES 6
The new users will set this and we will assume that advance gamma mode paths is active.
If the flag is not set, driver will take the legacy path and enable default gamma_mode for
that particular platform.
In both cases, we will use the existing GAMMA_LUT blob property to send the lut values
from userspace.
Will send out the next version soon. Thanks for your valuable feedback and suggestions.
Regards,
Uma Shankar
>
>--
>Ville Syrjälä
>Intel
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