Nokia N900: u-SD card in v4.2+

[Tony Lindgren]

* Pavel Machek <pavel at ucw.cz> [160113 11:13]:
> On Mon 2016-01-11 14:10:23, Kishon Vijay Abraham I wrote:
> > 
> > 'select' is generally not recommended since it selects a config without
> > caring for the dependency. With adding 'depends on', MMC won't be enabled and
> > will end up in the same problem.
> 
> Well... it really should "depend on". Not ideal, but you'll likely
> realize what went on.
> 
> Silently compiling known-bad kernel is ... well.. bad.

Force selects will lead into build errors sooner or later.

> > Tony has already added a Documentation noting that CONFIG_REGULATOR_PBIAS
> > should be enabled for MMCs to work.
> > commit d8e1f5ed11a39a68da00f05000466c4f6db4456e
> > Author: Tony Lindgren <tony at atomide.com>
> > Date:   Mon Oct 12 16:19:54 2015 -0700
> > 
> >     Documentation: ARM: List new omap MMC requirements
> > 
> > Maybe we should also make the error message a little more verbose to tell the
> > user that CONFIG_REGULATOR_PBIAS be selected?
> 
> That would help.
> 
> As would #error if we recognize broken config.

Can't we just add a check to the omap_hsmmc.c? In cases where
MMC1 has the PBIAS regulator configured but not available, print
an error about missing CONFIG_REGULATOR_PBIAS error and return
-EPROBE_DEFER?

Regards,

Tony