Re: [PATCH v2] gpio: mcp23s08: convert driver to DT

From: Linus Walleij
Date: Wed Feb 13 2013 - 07:51:18 EST

On Wed, Feb 13, 2013 at 12:13 PM, Lars Poeschel <poeschel@xxxxxxxxxxx> wrote:
> On Monday 11 February 2013 at 22:25:51, Grant Likely wrote:
>> However, is the pullup selection per-gpio line? If so, then why not
>> encode it into the flags field of the gpio specifier?
> Yes, the pullup is per-gpio line. I am working on that. It turns out, that
> this is a bit difficult for me, as there is no real documentation and no
> other driver is doing it or something similar yet. Exception are very few
> gpio soc drivers where situation is a bit different. They seem to rely an
> fixed global gpio numbers and they are always memory mapped.
> But as I said I am working on it...

Part of your problem is that pull-up is pin control territory.

We invented that subsystem for a reason, and that reason
was that the GPIO subsystem had a hard time accomodating
things like this.

If you look in drivers/pinctrl/pinctrl-abx500.c which is my
latest submitted pinctrl driver you can see that this is basically
a quite simple GPIO chip, we just model it as a pin controller
with a GPIO front-end too exactly because it can do things
like multiplexing, pull-up and pull-down.

Have you considered this approach?

Linus Walleij
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at