Re: [RFC PATCH] gpio: support for GPIO forwarding

From: Alexandre Courbot
Date: Tue Feb 24 2015 - 20:35:15 EST


On Wed, Feb 25, 2015 at 5:34 AM, David Cohen
<david.a.cohen@xxxxxxxxxxxxxxx> wrote:
> Hi,
>
>> If we decide to go ahead with the solution proposed by this patch for
>> practical reasons (which are good reasons indeed), I still have one
>> problem with its current form.
>>
>> As the discussion highlighted, this is an ACPI problem, so I'd very
>> much like it to be confined to the ACPI GPIO code, to be enabled only
>> when ACPI is, and to use function names that start with acpi_gpio. The
>> current implementation leverages platform lookup, making said lookup
>> less efficient in the process and bringing confusion about its
>> purpose. Although the two processes are indeed similar, they are
>> separate things: one is a legitimate way to map GPIOs, the other is a
>> fixup for broken firmware.
>>
>> I suppose we all agree this is a hackish fix, so let's confine it as
>> much as we can.
>
> Are we considering MFD cases hackish as well?
> i.e. if we have a driver that needs to register children devices and this
> driver needs to pass GPIO to a child.

In that case wouldn't the GPIO be best defined in the child node
itself, for the child device's driver to directly probe?
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