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

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Message-ID: <CAMuHMdU_yfr1ybNM9Dyk6n34Cqv5WJv1wZxQ_ZGJ_T8JCOeB2g@mail.gmail.com>
Date:   Fri, 2 Sep 2022 09:35:20 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Mateusz Kwiatkowski <kfyatek@...il.com>
Cc:     Maxime Ripard <maxime@...no.tech>,
        Maxime Ripard <mripard@...nel.org>,
        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 <linux-arm-kernel@...ts.infradead.org>,
        Phil Elwell <phil@...pberrypi.com>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        Dom Cobley <dom@...pberrypi.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nouveau Dev <nouveau@...ts.freedesktop.org>,
        linux-sunxi@...ts.linux.dev
Subject: Re: [PATCH v2 09/41] drm/connector: Add TV standard property

Hi Mateusz,

On Fri, Sep 2, 2022 at 12:00 AM Mateusz Kwiatkowski <kfyatek@...il.com> 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.

Exactly. Anything outputting RGB (e.g. through a SCART or VGA connector)
doesn't care about the color subcarrier or modulator parts.  Likewise,
anything outputting CVBS doesn't care about the modulator part.

Perhaps "generic" variants of NSTC and PAL/SECAM should be added, which
would really just mean 525/60 resp. 625/50.

Alternatively, the tv_mode field could be split in two parts (either
two separate fields, or bitwise), to maintain a clear separation between
lines/fields versus color encoding and RF modulation (with zero for the
latter meaning a generic version)? That would also keep the door open
for TV_MODE_405_50, TV_MODE_819_50, TV_MODE_750_50, TV_MODE_750_60, ...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds