Re: lockdep: incorrect deadlock warning with two GPIO expanders

From: Linus Walleij
Date: Tue Sep 13 2016 - 08:29:33 EST

On Mon, Sep 12, 2016 at 5:33 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Mon, Sep 12, 2016 at 05:16:14PM +0200, Bartosz Golaszewski wrote:

>> AFAIK there is no clean way to tell that a GPIO is used by an I2C
>> multiplexer at probe time. Linus, Alexandre could you confirm?

Nominally, the GPIO descriptors are just abstract resources such
as regulators or clocks, they can be used for a lot but just like
a clock, regulator, dma channel etc does not know who is using
it and for what, it does not know this, no.

> You cannot inspect the device tree while probing?

Of course it *can* but we would end up encoding a special
case every time something like this happens, tied to just
device tree, then another bolt-on for ACPI etc.

I have a hard time following the problem really, I'm
afraid I'm simply just not smart enough :(

Linus Walleij