GPIO offsets used by userspace

Joel Stanley joel at
Tue Jan 31 11:25:44 AEDT 2017

On Mon, Jan 30, 2017 at 12:04 PM, Andrew Jeffery <andrew at> wrote:
> Hi all,
> Just a heads up that when the linked patch is pulled into the OpenBMC
> kernel it will break our userspace. We will need to synchronise the
> kernel bump with the fixes for the machine configs to update the magic
> GPIO offset number.
> The magic offset is essentially 512-(ngpios) (I don't know why, but
> that's the behaviour), and this now varies between AST2400 and AST2500
> systems due to the AST2500 having an extra bank, and also because the
> AST2400 has a "hole" at the end of its GPIO number space.

Can you suggest a way to detect this from userspace?

Would using the chardev api make this easier?



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