Re: [PATCH] drm/bridge: sil_sii8620: depend on INPUT instead of selecting it.

[Dmitry Torokhov]

On Wed, Jan 23, 2019 at 09:45:56AM +0100, Lukas Wunner wrote:
> On Tue, Jan 22, 2019 at 06:13:11AM -0800, Ronald Tschalär wrote:
> > commit d6abe6df706c66d803e6dd4fe98c1b6b7f125a56 (drm/bridge:
> > sil_sii8620: do not have a dependency of RC_CORE) added a dependency on
> > INPUT. However, this causes problems with other drivers, in particular
> > an input driver that depends on MFD_INTEL_LPSS_PCI (to be added in a
> > future commit):
> > 
> >   drivers/clk/Kconfig:9:error: recursive dependency detected!
> >   drivers/clk/Kconfig:9:        symbol COMMON_CLK is selected by MFD_INTEL_LPSS
> >   drivers/mfd/Kconfig:566:      symbol MFD_INTEL_LPSS is selected by MFD_INTEL_LPSS_PCI
> >   drivers/mfd/Kconfig:580:      symbol MFD_INTEL_LPSS_PCI is implied by KEYBOARD_APPLESPI
> >   drivers/input/keyboard/Kconfig:73:    symbol KEYBOARD_APPLESPI depends on INPUT
> >   drivers/input/Kconfig:8:      symbol INPUT is selected by DRM_SIL_SII8620
> >   drivers/gpu/drm/bridge/Kconfig:83:    symbol DRM_SIL_SII8620 depends on DRM_BRIDGE
> >   drivers/gpu/drm/bridge/Kconfig:1:     symbol DRM_BRIDGE is selected by DRM_PL111
> >   drivers/gpu/drm/pl111/Kconfig:1:      symbol DRM_PL111 depends on COMMON_CLK
> > 
> > According to the docs, select should only be used for non-visible
> > symbols. Furthermore almost all other references to INPUT throughout the
> > kernel config are depends, not selects. Hence this change.

I think this is not as cut and dry. We should be able to select needed
subsystems (such as INPUT, USB, etc) even if they are user visible.
User, when enabling a piece of hardware, does not need to know ultimate
details of all subsystems the driver might need ti function.

It looks like one of the drivers implies MFD_INTEL_LPSS_PCI, maybe
treating imply the same as select when detecting circular dependency is
wrong as we are allowed to deselect implied dependencies?

> > 
> > CC: Inki Dae <inki.dae@xxxxxxxxxxx>
> > CC: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> > Signed-off-by: Ronald Tschalär <ronald@xxxxxxxxxxxxx>
> 
> Reviewed-by: Lukas Wunner <lukas@xxxxxxxxx>
> 
> I think this needs to be merged through the input tree as a prerequisite
> for the applespi.c driver (keyboard + touchpad driver for 2015+ MacBook,
> MacBook Air and MacBook Pro which uses SPI instead of USB) to avoid
> breaking the build.  Adding Dmitry.

I have no idea what applespi.c is (it is definitely not in my tree), so
I think it should be merged through the same tree that the original
commit was introduced through.

> 
> Thanks,
> 
> Lukas
> 
> 
> > ---
> >  drivers/gpu/drm/bridge/Kconfig | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/Kconfig b/drivers/gpu/drm/bridge/Kconfig
> > index 2fee47b0d50b..eabedc83f25c 100644
> > --- a/drivers/gpu/drm/bridge/Kconfig
> > +++ b/drivers/gpu/drm/bridge/Kconfig
> > @@ -83,9 +83,9 @@ config DRM_PARADE_PS8622
> >  config DRM_SIL_SII8620
> >  	tristate "Silicon Image SII8620 HDMI/MHL bridge"
> >  	depends on OF
> > +	depends on INPUT
> >  	select DRM_KMS_HELPER
> >  	imply EXTCON
> > -	select INPUT
> >  	select RC_CORE

Keeping "select RC_CORE" is wrong though, as the driver appears to be
working find without RC. Maybe it should be stubbed out?

Thanks.

-- 
Dmitry