[PATCH 2/3] drm: rcar-du: DRM_RCAR_USE_LVDS should depend on DRM_RCAR_DU

[Geert Uytterhoeven]

Hi Laurent,

On Wed, Dec 15, 2021 at 11:12 AM Laurent Pinchart
<laurent.pinchart at ideasonboard.com> wrote:
> On Wed, Dec 15, 2021 at 10:27:46AM +0100, Geert Uytterhoeven wrote:
> > The Renesas R-Car LVDS encoder driver is a subdriver of the R-Car
> > Display Unit driver, and enabling DRM_RCAR_USE_LVDS while DRM_RCAR_DU is
> > disabled doesn't have any impact on the kernel built.  Hence add a
> > dependency on DRM_RCAR_DU, to prevent asking the user about this driver
> > when configuring a kernel without R-Car Display Unit support, like is
> > already done for DRM_RCAR_CMM.
> >
> > Fixes: 42d95d1b3a9c649b ("drm/rcar: stop using 'imply' for dependencies")
> > Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
> > ---
> > The problem pre-existed before commit 42d95d1b3a9c649b, as the
> > dependency of DRM_RCAR_LVDS on DRM_RCAR_DU was accidentally removed
> > before.
> > Fixes: c6a27fa41fabb35f ("drm: rcar-du: Convert LVDS encoder code to bridge driver")
> > ---
> >  drivers/gpu/drm/rcar-du/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/rcar-du/Kconfig b/drivers/gpu/drm/rcar-du/Kconfig
> > index 65d72be50f46f19e..a7aa556e301d1087 100644
> > --- a/drivers/gpu/drm/rcar-du/Kconfig
> > +++ b/drivers/gpu/drm/rcar-du/Kconfig
> > @@ -32,7 +32,7 @@ config DRM_RCAR_DW_HDMI
> >
> >  config DRM_RCAR_USE_LVDS
> >       bool "R-Car DU LVDS Encoder Support"
> > -     depends on DRM_BRIDGE && OF
> > +     depends on DRM_BRIDGE && OF && DRM_RCAR_DU
>
> Shouldn't the same be done for DRM_RCAR_DW_HDMI ? Even better, we could

DRM_RCAR_DW_HDMI can be enabled and built with CONFIG_COMPILE_TEST=y
and CONFIG_DRM_RCAR_DU=n (yes I've tried on RISC-V ;-)

> wrap all the entries for the subdrivers in a 'if DRM_RCAR_DU'.

That might work.  It can be tricky with bool/tristate, as sometimes m
is not properly propagated.

> >       default DRM_RCAR_DU
> >       help
> >         Enable support for the R-Car Display Unit embedded LVDS encoders.

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