linux-kernel - Re: [PATCH v7 14/23] drm/modes: Properly generate a drm_display

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Date:   Thu, 10 Nov 2022 10:31:20 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Noralf Trønnes <noralf@...nnes.org>
Cc:     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>,
        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>,
        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>,
        Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
        dri-devel@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org
Subject: Re: [PATCH v7 14/23] drm/modes: Properly generate a drm_display_mode
 from a named mode

Hi,

On Mon, Nov 07, 2022 at 06:49:57PM +0100, Noralf Trønnes wrote:
> Den 07.11.2022 15.16, skrev Maxime Ripard:
> > The framework will get the drm_display_mode from the drm_cmdline_mode it
> > got by parsing the video command line argument by calling
> > drm_connector_pick_cmdline_mode().
> > 
> > The heavy lifting will then be done by the drm_mode_create_from_cmdline_mode()
> > function.
> > 
> > In the case of the named modes though, there's no real code to make that
> > translation and we rely on the drivers to guess which actual display mode
> > we meant.
> > 
> > Let's modify drm_mode_create_from_cmdline_mode() to properly generate the
> > drm_display_mode we mean when passing a named mode.
> > 
> > Signed-off-by: Maxime Ripard <maxime@...no.tech>
> > 
> > ---
> > Changes in v7:
> > - Use tv_mode_specified in drm_mode_parse_command_line_for_connector
> > 
> > Changes in v6:
> > - Fix get_modes to return 0 instead of an error code
> > - Rename the tests to follow the DRM test naming convention
> > 
> > Changes in v5:
> > - Switched to KUNIT_ASSERT_NOT_NULL
> > ---
> >  drivers/gpu/drm/drm_modes.c                     | 34 ++++++++++-
> >  drivers/gpu/drm/tests/drm_client_modeset_test.c | 77 ++++++++++++++++++++++++-
> >  2 files changed, 109 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> > index dc037f7ceb37..49441cabdd9d 100644
> > --- a/drivers/gpu/drm/drm_modes.c
> > +++ b/drivers/gpu/drm/drm_modes.c
> > @@ -2497,6 +2497,36 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
> >  }
> >  EXPORT_SYMBOL(drm_mode_parse_command_line_for_connector);
> >  
> > +static struct drm_display_mode *drm_named_mode(struct drm_device *dev,
> > +					       struct drm_cmdline_mode *cmd)
> > +{
> > +	struct drm_display_mode *mode;
> > +	unsigned int i;
> > +
> > +	for (i = 0; i < ARRAY_SIZE(drm_named_modes); i++) {
> > +		const struct drm_named_mode *named_mode = &drm_named_modes[i];
> > +
> > +		if (strcmp(cmd->name, named_mode->name))
> > +			continue;
> > +
> > +		if (!cmd->tv_mode_specified)
> > +			continue;
> 
> Only a named mode will set cmd->name, so is this check necessary?

Yeah, but (and even though it's not the case at the moment) there's no
implication that a named mode will be about TV. We could use it for
VGA/XGA/etc just as well, in which case we wouldn't have
tv_mode_specified.

Maxime

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