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

[Stephen Boyd <sboyd@codeaurora.org>]

On 03/14, Timur Tabi wrote:
> On 03/14/2017 04:41 PM, Linus Walleij wrote:
> > On Mon, Mar 6, 2017 at 10:52 PM, Timur Tabi <timur@codeaurora.org> wrote:
> 
> >> So would it be acceptable, for example, to change msm_gpio_set() such that
> >> if the function of that pin is non-zero, just return an error?
> > 
> > I would ask the driver maintainer about his opinion, and also whoever
> > is an authority on ACPI for the TLMM-chips, I am no expert
> > in ACPI. Hell I'm not even good at device tree. Not to mention SFI.
> > Oh well...
> 
> Well, I was hoping that Stephen would respond to this question. :-)
> 
> My point is, if the driver knows that the GPIO cannot be written to (because
> it's muxed to something else), shouldn't the driver return with an error if the
> caller attempts to write?
> 

(I reply faster when my name is written!)

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.

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.

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