linux-kernel - Re: [PATCH v2 19/41] drm/modes: Introduce the tv

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Message-ID: <2f607c7d-6da1-c8df-1c02-8dd344a92343@gmail.com>
Date:   Fri, 2 Sep 2022 00:46:29 +0200
From:   Mateusz Kwiatkowski <kfyatek@...il.com>
To:     Maxime Ripard <maxime@...no.tech>,
        Maxime Ripard <mripard@...nel.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>, Chen-Yu Tsai <wens@...e.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Lyude Paul <lyude@...hat.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Karol Herbst <kherbst@...hat.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Emma Anholt <emma@...olt.net>, Daniel Vetter <daniel@...ll.ch>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>
Cc:     Hans de Goede <hdegoede@...hat.com>,
        linux-arm-kernel@...ts.infradead.org,
        Phil Elwell <phil@...pberrypi.com>,
        intel-gfx@...ts.freedesktop.org,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        dri-devel@...ts.freedesktop.org, Dom Cobley <dom@...pberrypi.com>,
        linux-kernel@...r.kernel.org, nouveau@...ts.freedesktop.org,
        linux-sunxi@...ts.linux.dev,
        Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v2 19/41] drm/modes: Introduce the tv_mode property as a
 command-line option

Hi Maxime,

> @@ -2212,20 +2239,22 @@ struct drm_named_mode {
>      unsigned int xres;
>      unsigned int yres;
>      unsigned int flags;
> +    unsigned int tv_mode;
>  };

Are _all_ named modes supposed to be about analog TV?

If so, then probably this structure should be renamed drm_named_analog_tv_mode
or something.

If not, then including tv_mode in all of them sounds almost dangrous. 0 is a
valid value for enum drm_connector_tv_mode, corresponding to
DRM_MODE_TV_MODE_NTSC_443. This is a very weird default (maybe it shouldn't be
the one that has a numeric value of 0?) and if there ever is a named mode that
is not related to analog TV, it looks that it will refer to NTSC-443.

Not sure where could that actually propagate, and maybe what I'm saying can't
happen, but I'm imagining weird scenarios where a GPU that has both a
VGA/HDMI/whatever output, and a composite output, switches to NTSC-443 on the
composite output by default because a named mode for the modern output is
selected.

Maybe something like DRM_MODE_TV_MODE_NONE = 0 would make sense?

Maybe not. This is not an actual suggestion, just "thinking out loud".

Best regards,
Mateusz Kwiatkowski