Nouveau - Sep 2022 - [PATCH v2 10/41] drm/modes: Add a function to generate analog display modes

Hi Mateusz,

On Wed, Aug 31, 2022 at 3:44 AM Mateusz Kwiatkowski <kfyatek at gmail.com>
wrote:
> Wow. That's an enormous amount of effort put into this patch.
>
> But I'm tempted to say that this is actually overengineered quite a bit
:D
> Considering that there's no way to access all these calculations from
user
> space, and I can't imagine anybody using anything else than those
standard
> 480i/576i (and maybe 240p/288p) modes at 13.5 MHz any time soon... I'm
not
> sure if we actually need all this.
We'll need it when we get an Amiga DRM driver, which will use
7/14/28 MHz pixel clocks.
> But anyway, I'm not the maintainer of this subsystem, so I'm not
the one to
> decide.
>
> > +enum drm_mode_analog {
> > +    DRM_MODE_ANALOG_NTSC,
> > +    DRM_MODE_ANALOG_PAL,
> > +};
>
> Using "NTSC" and "PAL" to describe the 50Hz and 60Hz
analog TV modes is common,
> but strictly speaking a misnomer. Those are color encoding systems, and
your
> patchset fully supports lesser used, but standard encodings for those (e.g.
> PAL-M for 60Hz and SECAM for 50Hz). I'd propose switching to some more
neutral
> naming scheme. Some ideas:
>
> - DRM_MODE_ANALOG_60_HZ / DRM_MODE_ANALOG_50_HZ (after standard refresh
rate)
> - DRM_MODE_ANALOG_525_LINES / DRM_MODE_ANALOG_625_LINES (after standard
line
>   count)
IMHO these are bad names, as e.g. VGA640x480 at 60 is also analog, using
60 Hz and 525 lines.  Add "TV" to the name?
> - DRM_MODE_ANALOG_JM / DRM_MODE_ANALOG_BDGHIKLN (after corresponding ITU
System
>   Letter Designations)
Or DRM_MODE_ITU_*?
But given the long list of letters, this looks fragile to me.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at
linux-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

Hi,

On Wed, Aug 31, 2022 at 10:14:28AM +0200, Geert Uytterhoeven
wrote:
> > > +enum drm_mode_analog {
> > > +    DRM_MODE_ANALOG_NTSC,
> > > +    DRM_MODE_ANALOG_PAL,
> > > +};
> >
> > Using "NTSC" and "PAL" to describe the 50Hz and
60Hz analog TV modes is common,
> > but strictly speaking a misnomer. Those are color encoding systems,
and your
> > patchset fully supports lesser used, but standard encodings for those
(e.g.
> > PAL-M for 60Hz and SECAM for 50Hz). I'd propose switching to some
more neutral
> > naming scheme. Some ideas:
> >
> > - DRM_MODE_ANALOG_60_HZ / DRM_MODE_ANALOG_50_HZ (after standard
refresh rate)
> > - DRM_MODE_ANALOG_525_LINES / DRM_MODE_ANALOG_625_LINES (after
standard line
> >   count)
> 
> IMHO these are bad names, as e.g. VGA640x480 at 60 is also analog, using
> 60 Hz and 525 lines.  Add "TV" to the name?
> 
> > - DRM_MODE_ANALOG_JM / DRM_MODE_ANALOG_BDGHIKLN (after corresponding
ITU System
> >   Letter Designations)
> 
> Or DRM_MODE_ITU_*?
> But given the long list of letters, this looks fragile to me.
Does it matter at all? It's an internal API that isn't exposed at all.
I'd rather have a common name that everyone can understand in this case
rather than a *perfect* name where most will scratch their head
wondering what it's about.

Maxime
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