linux-kernel - Re: [PATCH v7 15/23] drm/modes: Introduce more named modes

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Date:   Tue, 8 Nov 2022 22:27:17 +0100
From:   Mateusz Kwiatkowski <kfyatek@...il.com>
To:     Noralf Trønnes <noralf@...nnes.org>,
        Maxime Ripard <maxime@...no.tech>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Ben Skeggs <bskeggs@...hat.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Maxime Ripard <mripard@...nel.org>,
        Samuel Holland <samuel@...lland.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Emma Anholt <emma@...olt.net>,
        Karol Herbst <kherbst@...hat.com>,
        Daniel Vetter <daniel@...ll.ch>, Chen-Yu Tsai <wens@...e.org>,
        Lyude Paul <lyude@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>
Cc:     Phil Elwell <phil@...pberrypi.com>,
        Hans de Goede <hdegoede@...hat.com>,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        linux-arm-kernel@...ts.infradead.org,
        Dom Cobley <dom@...pberrypi.com>,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org
Subject: Re: [PATCH v7 15/23] drm/modes: Introduce more named modes

Hi Noralf,

W dniu 8.11.2022 o 10:38, Noralf Trønnes pisze:
>
> Den 07.11.2022 19.03, skrev Noralf Trønnes:
>>
>> Den 07.11.2022 15.16, skrev Maxime Ripard:
>>> Now that we can easily extend the named modes list, let's add a few more
>>> analog TV modes that were used in the wild, and some unit tests to make
>>> sure it works as intended.
>>>
>>> Signed-off-by: Maxime Ripard <maxime@...no.tech>
>>>
>>> ---
>>> Changes in v6:
>>> - Renamed the tests to follow DRM test naming convention
>>>
>>> Changes in v5:
>>> - Switched to KUNIT_ASSERT_NOT_NULL
>>> ---
>>>  drivers/gpu/drm/drm_modes.c                     |  2 +
>>>  drivers/gpu/drm/tests/drm_client_modeset_test.c | 54 +++++++++++++++++++++++++
>>>  2 files changed, 56 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
>>> index 49441cabdd9d..17c5b6108103 100644
>>> --- a/drivers/gpu/drm/drm_modes.c
>>> +++ b/drivers/gpu/drm/drm_modes.c
>>> @@ -2272,7 +2272,9 @@ struct drm_named_mode {
>>>  
>>>  static const struct drm_named_mode drm_named_modes[] = {
>>>  	NAMED_MODE("NTSC", 13500, 720, 480, DRM_MODE_FLAG_INTERLACE, DRM_MODE_TV_MODE_NTSC),
>>> +	NAMED_MODE("NTSC-J", 13500, 720, 480, DRM_MODE_FLAG_INTERLACE, DRM_MODE_TV_MODE_NTSC_J),
>>>  	NAMED_MODE("PAL", 13500, 720, 576, DRM_MODE_FLAG_INTERLACE, DRM_MODE_TV_MODE_PAL),
>>> +	NAMED_MODE("PAL-M", 13500, 720, 480, DRM_MODE_FLAG_INTERLACE, DRM_MODE_TV_MODE_PAL_M),
>>>  };
>> I'm now having second thoughts about the tv_mode commandline option. Can
>> we just add all the variants to this table and drop the tv_mode option?
>> IMO this will be more user friendly and less confusing.
>>
> One downside of this is that it's not possible to force connector status
> when using named modes, but I think it would be better to have a force
> option than a tv_mode option. A lot of userspace treats unknown status
> as disconnected.
>
> Anyone know if it's possible to set the connector status sysfs file
> using a udev rule?
>
> Noralf.

I think that leaving named modes only would be a bit limiting. There are use
cases for custom modes, e.g. we might want progressive 240p "NTSC" (like 80s/90s
home computers and video game consoles) or the modes with non-13.5MHz pixel
clock that Geert requested with Amiga in mind.

I'm not sure if the current cmdline-to-drm_mode conversion is flexible enough
to meaningfully facilitate those, but we're at least getting the syntax down.

Best regards,
Mateusz Kwiatkowski