linux-kernel - Re: [PATCH v2 09/41] drm/connector: Add TV standard property

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Message-ID: <20220907121009.toizfolruuazcrns@houat>
Date:   Wed, 7 Sep 2022 14:10:09 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Mateusz Kwiatkowski <kfyatek@...il.com>
Cc:     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>,
        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 09/41] drm/connector: Add TV standard property

Hi,

On Fri, Sep 02, 2022 at 12:00:33AM +0200, Mateusz Kwiatkowski wrote:
> W dniu 29.08.2022 o 15:11, Maxime Ripard pisze:
> > The TV mode property has been around for a while now to select and get the
> > current TV mode output on an analog TV connector.
> >
> > Despite that property name being generic, its content isn't and has been
> > driver-specific which makes it hard to build any generic behaviour on top
> > of it, both in kernel and user-space.
> >
> > Let's create a new bitmask tv norm property, that can contain any of the
> > analog TV standards currently supported by kernel drivers. Each driver can
> > then pass in a bitmask of the modes it supports.
> 
> This is not a bitmask property anymore, you've just changed it to an enum.
> The commit message is now misleading.
> 
> > +static const struct drm_prop_enum_list drm_tv_mode_enum_list[] = {
> > +    { DRM_MODE_TV_MODE_NTSC_443, "NTSC-443" },
> > +    { DRM_MODE_TV_MODE_NTSC_J, "NTSC-J" },
> > +    { DRM_MODE_TV_MODE_NTSC_M, "NTSC-M" },
> > +    { DRM_MODE_TV_MODE_PAL_60, "PAL-60" },
> > +    { DRM_MODE_TV_MODE_PAL_B, "PAL-B" },
> > +    { DRM_MODE_TV_MODE_PAL_D, "PAL-D" },
> > +    { DRM_MODE_TV_MODE_PAL_G, "PAL-G" },
> > +    { DRM_MODE_TV_MODE_PAL_H, "PAL-H" },
> > +    { DRM_MODE_TV_MODE_PAL_I, "PAL-I" },
> > +    { DRM_MODE_TV_MODE_PAL_M, "PAL-M" },
> > +    { DRM_MODE_TV_MODE_PAL_N, "PAL-N" },
> > +    { DRM_MODE_TV_MODE_PAL_NC, "PAL-Nc" },
> > +    { DRM_MODE_TV_MODE_SECAM_60, "SECAM-60" },
> > +    { DRM_MODE_TV_MODE_SECAM_B, "SECAM-B" },
> > +    { DRM_MODE_TV_MODE_SECAM_D, "SECAM-D" },
> > +    { DRM_MODE_TV_MODE_SECAM_G, "SECAM-G" },
> > +    { DRM_MODE_TV_MODE_SECAM_K, "SECAM-K" },
> > +    { DRM_MODE_TV_MODE_SECAM_K1, "SECAM-K1" },
> > +    { DRM_MODE_TV_MODE_SECAM_L, "SECAM-L" },
> > +};
> 
> I did not comment on it the last time, but this list looks a little bit random.
> 
> Compared to the standards defined by V4L2, you also define SECAM-60 (a good
> thing to define, because why not), but don't define PAL-B1, PAL-D1, PAL-K,
> SECAM-H, SECAM-LC (whatever that is - probably just another name for SECAM-L,
> see my comment about PAL-Nc below), or NTSC-M-KR (a Korean variant of NTSC).
> 
> Like I mentioned previously, I'm personally not a fan of including all those
> CCIR/ITU system variants, as they don't mean any difference to the output unless
> there is an RF modulator involved. But I get it that they have already been used
> and regressing probably wouldn't be a very good idea. But in that case keeping
> it consistent with the set of values used by V4L2 would be wise, I think.

Ack. What would be the list of standards we'd absolutely need? NSTC-M,
NTSC-J, PAL-60, PAL-B, PAL-M, SECAM-60 and SECAM-B?

> > +/**
> > + * drm_mode_create_tv_properties - create TV specific connector properties
> > + * @dev: DRM device
> > + * @supported_tv_modes: Bitmask of TV modes supported (See DRM_MODE_TV_MODE_*)
> > +
> > + * Called by a driver's TV initialization routine, this function creates
> > + * the TV specific connector properties for a given device.  Caller is
> > + * responsible for allocating a list of format names and passing them to
> > + * this routine.
> > + *
> > + * Returns:
> > + * 0 on success or a negative error code on failure.
> > + */
> > +int drm_mode_create_tv_properties(struct drm_device *dev,
> > +                  unsigned int supported_tv_modes)
> 
> supported_tv_modes is supposed to be a bitmask of BIT(DRM_MODE_TV_MODE_*)
> (or (1<<DRM_MODE_TV_MODE_*)) rather than DRM_MODE_TV_MODE_* directly, but this
> is not said explicitly anywhere in this doc comment.

The argument doc mentions that it's a "Bitmask of TV modes supported
(See DRM_MODE_TV_MODE_*)", how would you improve it?

Thanks!
Maxime

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