Re: [PATCH] pinctrl: qcom: add get_direction function

[Stephen Boyd <sboyd@xxxxxxxxxxxxxx>]

On 03/14, Timur Tabi wrote:
> Stephen Boyd wrote:
> >I don't see any problem with failing msm_gpio_set() when the
> >function is "not gpio", but I also wonder why it matters. Drivers
> >shouldn't be doing that, because if the gpio is muxed to some
> >other functionality they shouldn't be treating it as a gpio in
> >the first place.
> 
> The idea is to notify drivers with an error code when they make a
> mistake. Perhaps the device tree or the ACPI table has an error?

In general the kernel isn't a firmware validator. At least that's
the way I view it. Others may have different opinions here.

> 
> >Perhaps we can have some sort of gpio validation debug option
> >that the check goes under. Then we could fail and print a big
> >warning if this happens, but if we aren't debugging then we don't
> >do any checking and rely on drivers to do the right thing.
> 
> I could add that, but I still think returning an error code is
> appropriate.  On the TLMM, we know for sure that the pin must be set
> to function 0 in order for the read/write routines to operate
> correctly.

On ACPI we could make the gpio_get() path fail if the pin isn't
in GPIO mode? That would work assuming ACPI can't change the pin
muxing at runtime. On DT we might have runtime muxing though so I
don't see how it would work there.

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