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Message-ID: <20221107102126.klxrvfe34e6uriyx@houat>
Date: Mon, 7 Nov 2022 11:21:26 +0100
From: Maxime Ripard <maxime@...no.tech>
To: Noralf Trønnes <noralf@...nnes.org>
Cc: Karol Herbst <kherbst@...hat.com>, Emma Anholt <emma@...olt.net>,
Ben Skeggs <bskeggs@...hat.com>, Chen-Yu Tsai <wens@...e.org>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Daniel Vetter <daniel@...ll.ch>,
Thomas Zimmermann <tzimmermann@...e.de>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Samuel Holland <samuel@...lland.org>,
Jernej Skrabec <jernej.skrabec@...il.com>,
David Airlie <airlied@...ux.ie>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Lyude Paul <lyude@...hat.com>, linux-sunxi@...ts.linux.dev,
intel-gfx@...ts.freedesktop.org,
Phil Elwell <phil@...pberrypi.com>,
linux-arm-kernel@...ts.infradead.org,
nouveau@...ts.freedesktop.org, Hans de Goede <hdegoede@...hat.com>,
Dom Cobley <dom@...pberrypi.com>,
Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
dri-devel@...ts.freedesktop.org,
Dave Stevenson <dave.stevenson@...pberrypi.com>,
linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH v6 16/23] drm/probe-helper: Provide a TV get_modes helper
Hi Noralf,
I'll leave aside your comments on the code, since we'll use your implementation.
On Sun, Nov 06, 2022 at 05:33:48PM +0100, Noralf Trønnes wrote:
> Den 26.10.2022 17.33, skrev maxime@...no.tech:
> > +
> > + if (cmdline->tv_mode_specified)
> > + default_mode = cmdline->tv_mode;
>
> 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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