Messages in this thread | | | Date | Thu, 15 Sep 2016 09:51:50 +0200 | From | Peter Zijlstra <> | Subject | Re: lockdep: incorrect deadlock warning with two GPIO expanders |
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On Tue, Sep 13, 2016 at 02:29:24PM +0200, Linus Walleij wrote: > On Mon, Sep 12, 2016 at 5:33 PM, Peter Zijlstra <peterz@infradead.org> 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 :(
Why would this be DT or ACPI specific? Linux itself has a tree/graph of all busses and devices right? That's what all this drivers/base/ stuff is on about.
So can't you walk up that and see if you encounter the exact same driver again?
Something like:
for (nr = 0, parent = dev->parent; parent; parent = parent->parent) { if (parent->device_driver == &pca953x_driver.driver) nr++; }
Again, I have no clue how any of this works, but that seems like something that ought to work.
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