[PATCH v4 11/30] drm/modes: Add a function to generate analog display modes

[Maxime Ripard]

Hi Noralf,

On Sat, Oct 01, 2022 at 02:52:06PM +0200, Noralf Trønnes wrote:
> Den 29.09.2022 18.31, skrev Maxime Ripard:
> > Multiple drivers (meson, vc4, sun4i) define analog TV 525-lines and
> > 625-lines modes in their drivers.
> > 
> > Since those modes are fairly standard, and that we'll need to use them
> > in more places in the future, it makes sense to move their definition
> > into the core framework.
> > 
> > However, analog display usually have fairly loose timings requirements,
> > the only discrete parameters being the total number of lines and pixel
> > clock frequency. Thus, we created a function that will create a display
> > mode from the standard, the pixel frequency and the active area.
> > 
> > Signed-off-by: Maxime Ripard <maxime at cerno.tech>
> > 
> > ---
> > 
> > Changes in v4:
> > - Reworded the line length check comment
> > - Switch to HZ_PER_KHZ in tests
> > - Use previous timing to fill our mode
> > - Move the number of lines check earlier
> > ---
> >  drivers/gpu/drm/drm_modes.c            | 474 +++++++++++++++++++++++++++++++++
> >  drivers/gpu/drm/tests/Makefile         |   1 +
> >  drivers/gpu/drm/tests/drm_modes_test.c | 144 ++++++++++
> >  include/drm/drm_modes.h                |  17 ++
> >  4 files changed, 636 insertions(+)
> > 
> 
> I haven't followed the discussion on this patch, but it seems rather
> excessive to add over 600 lines of code (including tests) to add 2 fixed
> modes. And it's very difficult to see from the code what the actual
> display mode timings really are, which would be useful for other
> developers down the road wanting to use them.
> 
> Why not just hardcode the modes?

Yeah, I have kind of the same feeling tbh, but it was asked back on the
v1 to ease the transition of old fbdev drivers, since they will need
such a function:
https://lore.kernel.org/dri-devel/CAMuHMdUrwzPYjA0wdR7ADj5Ov6+m03JbnY8fBYzRYyWDuNm5=g@mail.gmail.com/

Maxime
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