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References: <20240109181104.1670304-1-andri@yngvason.is> <20240109181104.1670304-3-andri@yngvason.is>
In-Reply-To: <20240109181104.1670304-3-andri@yngvason.is>
From: Daniel Stone <daniel@fooishbar.org>
Date: Tue, 9 Jan 2024 22:32:18 +0000
Message-ID: <CAPj87rNan8B5urDFkmD_Vti4to6p3NmvXYsTFQTNg-Ue2ieDug@mail.gmail.com>
Subject: Re: [PATCH 2/7] drm/uAPI: Add "active color format" drm property as
 feedback for userspace
To: Andri Yngvason <andri@yngvason.is>
Cc: Harry Wentland <harry.wentland@amd.com>, Leo Li <sunpeng.li@amd.com>, 
	Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>, Alex Deucher <alexander.deucher@amd.com>, 
	=?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>, 
	"Pan, Xinhui" <Xinhui.Pan@amd.com>, David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>, Maxime Ripard <mripard@kernel.org>, 
	Thomas Zimmermann <tzimmermann@suse.de>, Jani Nikula <jani.nikula@linux.intel.com>, 
	Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, 
	Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>, amd-gfx@lists.freedesktop.org, 
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, 
	intel-gfx@lists.freedesktop.org, Simon Ser <contact@emersion.fr>, 
	Werner Sembach <wse@tuxedocomputers.com>
Content-Type: text/plain; charset="UTF-8"

Hi,

On Tue, 9 Jan 2024 at 18:12, Andri Yngvason <andri@yngvason.is> wrote:
> + * active color format:
> + *     This read-only property tells userspace the color format actually used
> + *     by the hardware display engine "on the cable" on a connector. The chosen
> + *     value depends on hardware capabilities, both display engine and
> + *     connected monitor. Drivers shall use
> + *     drm_connector_attach_active_color_format_property() to install this
> + *     property. Possible values are "not applicable", "rgb", "ycbcr444",
> + *     "ycbcr422", and "ycbcr420".

How does userspace determine what's happened without polling? Will it
only change after an `ALLOW_MODESET` commit, and be guaranteed to be
updated after the commit has completed and the event being sent?
Should it send a HOTPLUG event? Other?

Cheers,
Daniel