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Mon, 4 May 2026 18:21:59 +0000 Message-ID: <34992e5f-ac4b-4a0a-a8d9-8b6edd8abe0a@amd.com> Date: Mon, 4 May 2026 13:21:57 -0500 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/8] Add support for a DRM backlight capability Content-Language: en-US To: Louis Chauvet , dri-devel@lists.freedesktop.org Cc: harry.wentland@amd.com, Xaver Hugl , amd-gfx@lists.freedesktop.org, Mario Limonciello References: <20260424220953.167058-1-mario.limonciello@amd.com> <0f5cf41c-99d5-4427-86fe-18c4f1e2c95e@bootlin.com> From: Mario Limonciello In-Reply-To: <0f5cf41c-99d5-4427-86fe-18c4f1e2c95e@bootlin.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-ClientProxiedBy: SA0PR11CA0034.namprd11.prod.outlook.com (2603:10b6:806:d0::9) To SA0PR12MB4557.namprd12.prod.outlook.com (2603:10b6:806:9d::10) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: SA0PR12MB4557:EE_|SN7PR12MB7024:EE_ X-MS-Office365-Filtering-Correlation-Id: 34774b86-1a1b-40c8-8a9a-08deaa0a07f3 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; 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Learn why > this is important at https://aka.ms/LearnAboutSenderIdentification ] > > On 4/25/26 00:09, Mario Limonciello wrote: >> From: Mario Limonciello (AMD) >> >> At Display Next Hackfest 2025 we discussed the renewed need for moving >> brightness control into the DRM connector properties.  I've taken the >> previous efforts from David and Marta, rebased and adjusted for the >> current kernel. >> >> The legacy sysfs interface is synchronized with the DRM connector >> (although >> the scale may be different as DRM connector property is u16). >> >> Later after this has been adopted by enough userspace, it may make >> sense to >> configure the legacy sysfs interface to be configurable so that only >> DRM master controls backlight. >> >> I've done a first implementation with amdgpu with eDP connectors; but >> conceivably this can be extended to other connectors like DP for displays >> that can be controlled via DDC as well later. >> >> I have also used DRM review prompts to review this series and fix some >> bugs >> which were caught with two different Claude models.  The fixes are >> squashed >> into the patches. >> >> Assisted-by: Claude Opus >> Assisted-by: Claude Sonnet >> >> For ease of testing; this series is also available on this branch: >> https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/ >> log/?h=superm1/backlight-property-v3 > > Hello, > > thanks for this work, I am very interested in this progress so I can > help you to test / implement more features. Thanks! I have a few other series I'm juggling in other subsystems, but will try to get another spin this cycle. > > I think you forgot to include the revert of "backlight: Remove notifier" > in your series, it can't be applied without it. > Yes - thanks for catching this. It's on my tree at https://git.kernel.org/pub/scm/linux/kernel/git/superm1/linux.git/log/?h=superm1/backlight-property-v3 but I forgot it when I built the series to get that one. > I will take a look and see if I can create a VKMS implementation of your > work. Cool! Please take a look at the IGT patches I did too if you didn't see them. This should hopefully work once you glue it to VKMS. https://lore.kernel.org/dri-devel/20260424221021.167179-1-mario.limonciello@amd.com/ > > Thanks for this work, > >> David Rheinsberg (1): >>    backlight: add kernel-internal backlight API >> >> Mario Limonciello (6): >>    drm: link connectors to backlight devices >>    DRM: Add support for client and driver indicating support for >>      luminance >>    drm/amd/display: Pass up errors reading actual brightness >>    drm/amd: Indicate driver supports luminance >>    drm/amd/display: Allow backlight registration to fail >>    drm/amd/display: use drm backlight >> >> Marta Lofstedt (1): >>    backlight: expose the current brightness in the new kernel API >> >>   drivers/gpu/drm/Kconfig                       |   1 + >>   drivers/gpu/drm/Makefile                      |   2 + >>   drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c       |   1 + >>   .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  88 +++- >>   drivers/gpu/drm/drm_atomic_uapi.c             |  24 ++ >>   drivers/gpu/drm/drm_backlight.c               | 406 ++++++++++++++++++ >>   drivers/gpu/drm/drm_connector.c               |  12 + >>   drivers/gpu/drm/drm_drv.c                     |   8 + >>   drivers/gpu/drm/drm_ioctl.c                   |  10 + >>   drivers/gpu/drm/drm_mode_config.c             |   7 + >>   drivers/gpu/drm/drm_mode_object.c             |  66 ++- >>   drivers/gpu/drm/drm_sysfs.c                   |  54 +++ >>   drivers/video/backlight/backlight.c           |  83 ++++ >>   include/drm/drm_backlight.h                   |  45 ++ >>   include/drm/drm_connector.h                   |   8 + >>   include/drm/drm_drv.h                         |   7 + >>   include/drm/drm_file.h                        |   8 + >>   include/drm/drm_mode_config.h                 |   5 + >>   include/linux/backlight.h                     |  30 ++ >>   include/uapi/drm/drm.h                        |  10 + >>   20 files changed, 852 insertions(+), 23 deletions(-) >>   create mode 100644 drivers/gpu/drm/drm_backlight.c >>   create mode 100644 include/drm/drm_backlight.h >> >