linux-kernel - Re: [PATCH RFC v2 05/20] drm: Introduce DRM_CAP_POST_BLEND_COLOR

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Message-ID: <52cce852-f4fb-4692-9318-1602fe878644@amd.com>
Date: Mon, 29 Sep 2025 05:40:07 -0400
From: Harry Wentland <harry.wentland@....com>
To: Louis Chauvet <louis.chauvet@...tlin.com>,
 Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Chun-Kuang Hu <chunkuang.hu@...nel.org>,
 Philipp Zabel <p.zabel@...gutronix.de>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Haneen Mohammed <hamohammed.sa@...il.com>,
 Melissa Wen <melissa.srw@...il.com>
Cc: Alex Hung <alex.hung@....com>, wayland-devel@...ts.freedesktop.org,
 leo.liu@....com, ville.syrjala@...ux.intel.com,
 pekka.paalanen@...labora.com, contact@...rsion.fr, mwen@...lia.com,
 jadahl@...hat.com, sebastian.wick@...hat.com, shashank.sharma@....com,
 agoins@...dia.com, joshua@...ggi.es, mdaenzer@...hat.com, aleixpol@....org,
 xaver.hugl@...il.com, victoria@...tem76.com, uma.shankar@...el.com,
 quic_naseer@...cinc.com, quic_cbraga@...cinc.com, quic_abhinavk@...cinc.com,
 marcan@...can.st, Liviu.Dudau@....com, sashamcintosh@...gle.com,
 chaitanya.kumar.borah@...el.com, mcanal@...lia.com, kernel@...labora.com,
 daniels@...labora.com, leandro.ribeiro@...labora.com,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
 linux-mediatek@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 Simona Vetter <simona.vetter@...ll.ch>
Subject: Re: [PATCH RFC v2 05/20] drm: Introduce
 DRM_CAP_POST_BLEND_COLOR_PIPELINE

On 2025-09-19 08:42, Louis Chauvet wrote:
> 
> 
> Le 18/09/2025 à 02:43, Nícolas F. R. A. Prado a écrit :
>> Add a new cap that drivers can set to signal they support post-blend
>> color pipelines.
>>
>> Signed-off-by: Nícolas F. R. A. Prado <nfraprado@...labora.com>
> 
> Reviewed-by: Louis Chauvet <louis.chauvet@...tlin.com>
> 
>> ---
>>   drivers/gpu/drm/drm_ioctl.c | 3 +++
>>   include/drm/drm_drv.h       | 6 ++++++
>>   include/uapi/drm/drm.h      | 6 ++++++
>>   3 files changed, 15 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
>> index 
>> ff193155129e7e863888d8958458978566b144f8..01592d10e3465ddceddef94bc417f98d3ec12087 100644
>> --- a/drivers/gpu/drm/drm_ioctl.c
>> +++ b/drivers/gpu/drm/drm_ioctl.c
>> @@ -304,6 +304,9 @@ static int drm_getcap(struct drm_device *dev, void 
>> *data, struct drm_file *file_
>>           req->value = drm_core_check_feature(dev, DRIVER_ATOMIC) &&
>>                    dev->mode_config.async_page_flip;
>>           break;
>> +    case DRM_CAP_POST_BLEND_COLOR_PIPELINE:
>> +        req->value = drm_core_check_feature(dev, 
>> DRIVER_POST_BLEND_COLOR_PIPELINE);
>> +        break;
>>       default:
>>           return -EINVAL;
>>       }
>> diff --git a/include/drm/drm_drv.h b/include/drm/drm_drv.h
>> index 
>> 42fc085f986dee9261f8b08c4fc7d93b8d6d9769..6b0f4904e69766232283d430c2540d30afef850f 100644
>> --- a/include/drm/drm_drv.h
>> +++ b/include/drm/drm_drv.h
>> @@ -122,6 +122,12 @@ enum drm_driver_feature {
>>        * the cursor planes to work correctly).
>>        */
>>       DRIVER_CURSOR_HOTSPOT           = BIT(9),
>> +    /**
>> +     * @DRIVER_POST_BLEND_COLOR_PIPELINE:
>> +     *
>> +     * Driver supports post-blend color pipeline.
>> +     */
>> +    DRIVER_POST_BLEND_COLOR_PIPELINE        = BIT(10),

Is this to let userspace know that the driver supports a
post-blending color pipeline? Why couldn't userspace simply
check whether crtc objects have "Color Pipeline" properties?

Harry

>>       /* IMPORTANT: Below are all the legacy flags, add new ones 
>> above. */
>> diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
>> index 
>> 27cc159c1d275c7a7fe057840ef792f30a582bb7..c6c53e57958e951204154ce41a69696a6876f0e8 100644
>> --- a/include/uapi/drm/drm.h
>> +++ b/include/uapi/drm/drm.h
>> @@ -812,6 +812,12 @@ struct drm_gem_change_handle {
>>    * commits.
>>    */
>>   #define DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP    0x15
>> +/**
>> + * DRM_CAP_POST_BLEND_COLOR_PIPELINE
>> + *
>> + * If set to 1, the driver supports post-blend color pipelines.
>> + */
>> +#define DRM_CAP_POST_BLEND_COLOR_PIPELINE    0x16
>>   /* DRM_IOCTL_GET_CAP ioctl argument type */
>>   struct drm_get_cap {
>>
>