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Date:   Mon, 7 Nov 2022 11:21:26 +0100
From:   Maxime Ripard <maxime@cerno.tech>
To:     Noralf =?utf-8?Q?Tr=C3=B8nnes?= <noralf@tronnes.org>
Cc:     Karol Herbst <kherbst@redhat.com>, Emma Anholt <emma@anholt.net>,
        Ben Skeggs <bskeggs@redhat.com>, Chen-Yu Tsai <wens@csie.org>,
        Rodrigo Vivi <rodrigo.vivi@intel.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Jani Nikula <jani.nikula@linux.intel.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
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        Lyude Paul <lyude@redhat.com>, linux-sunxi@lists.linux.dev,
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        Phil Elwell <phil@raspberrypi.com>,
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        nouveau@lists.freedesktop.org, Hans de Goede <hdegoede@redhat.com>,
        Dom Cobley <dom@raspberrypi.com>,
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        dri-devel@lists.freedesktop.org,
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        Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [PATCH v6 16/23] drm/probe-helper: Provide a TV get_modes helper
Message-ID: <20221107102126.klxrvfe34e6uriyx@houat>
References: <20220728-rpi-analog-tv-properties-v6-0-e7792734108f@cerno.tech>
 <20220728-rpi-analog-tv-properties-v6-16-e7792734108f@cerno.tech>
 <842076aa-8d7c-96d6-ba46-d0e66dacd2df@tronnes.org>
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Hi Noralf,

I'll leave aside your comments on the code, since we'll use your implementa=
tion.

On Sun, Nov 06, 2022 at 05:33:48PM +0100, Noralf Tr=F8nnes wrote:
> Den 26.10.2022 17.33, skrev maxime@cerno.tech:
> > +
> > +	if (cmdline->tv_mode_specified)
> > +		default_mode =3D cmdline->tv_mode;
>=20
> I realised that we don't verify tv_mode coming from the command line,
> not here and not in the reset helper. Should we do that? A driver should
> be programmed defensively to handle an illegal/unsupported value, but it
> doesn't feel right to allow an illegal enum value coming through the
> core/helpers.

I don't think we can end up with an invalid value here if it's been
specified.

We parse the command line through drm_mode_parse_tv_mode() (introduced
in patch 13 "drm/modes: Introduce the tv_mode property as a command-line
option") that will pick the tv mode part of the command line, and call
drm_get_tv_mode_from_name() using it.

drm_get_tv_mode_from_name() will return a EINVAL if it's not a value we
expect, and mode->tv_mode is only set on success. And AFAIK, there's no
other path that will set tv_mode.

Maxime

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