[PATCH 1/2] drm/panel: remove unnecessary dependencies

[Russell King - ARM Linux]

On Thu, Jun 12, 2014 at 06:00:07PM +0200, Arnd Bergmann wrote:
> On Thursday 12 June 2014 16:50:15 Russell King wrote:
> > DRM_PANEL_LD9040 and DRM_PANEL_S6E8AA0 both explicitly depended on
> > DRM_PANEL && DRM.  This is nonsense for two reasons:
> > 
> > (a) DRM_PANEL already depends on DRM, so DRM_PANEL can not be enabled
> > without DRM first being enabled.  Hence the && DRM is useless.
> > 
> > (b) These two configs are already beneath a menu which depends on
> > DRM_PANEL being enabled; these options will not be visible without
> > DRM_PANEL already being enabled.
> > 
> > Let's just remove this unnecessary verbosity.
> > 
> > Signed-off-by: Russell King <rmk+kernel at arm.linux.org.uk>
> 
> Unfortunately, this is wrong, because the current expression
> exploits one of the finer details of Kconfig syntax:
> 
> >  drivers/gpu/drm/panel/Kconfig | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> > index 4ec874da5668..44aea730b3aa 100644
> > --- a/drivers/gpu/drm/panel/Kconfig
> > +++ b/drivers/gpu/drm/panel/Kconfig
> > @@ -18,14 +18,12 @@ config DRM_PANEL_SIMPLE
> >  
> >  config DRM_PANEL_LD9040
> >         tristate "LD9040 RGB/SPI panel"
> > -       depends on DRM && DRM_PANEL
> >         depends on OF
> >         select SPI
> >         select VIDEOMODE_HELPERS
> >  
> >  config DRM_PANEL_S6E8AA0
> >         tristate "S6E8AA0 DSI video mode panel"
> > -       depends on DRM && DRM_PANEL
> >         depends on OF
> >         select DRM_MIPI_DSI
> >         select VIDEOMODE_HELPERS
> 
> DRM_PANEL is bool, while DRM is tristate. If DRM=m and DRM_PANEL=y,
> these two options can only be 'n' or 'm' but not 'y' with the current
> code, but they can be 'y' if you drop the explicit DRM dependency,
> which will cause a link failure.
> 
> The DRM_PANEL dependency can be removed, it is indeed unnecessary.

In which case, that's a bug for DRM_PANEL_SIMPLE which uses the same
mechanism.  Since everything is going to be in the same boat, the
menu should depend on DRM && DRM_PANEL.

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