[PATCH 11/13] [ARM] pxa/balloon3: PCF857x GPIO expander and LEDs

[Eric Miao]

On Fri, Jul 30, 2010 at 1:19 PM, Marek Vasut <marek.vasut at gmail.com> wrote:
> Dne Pá 30. července 2010 07:09:00 Eric Miao napsal(a):
>> On Fri, Jul 30, 2010 at 12:44 PM, Marek Vasut <marek.vasut at gmail.com> wrote:
>> > Dne Čt 29. července 2010 12:00:41 Wookey napsal(a):
>> >> +++ Marek Vasut [2010-07-29 05:16 +0200]:
>> >> > Add supported for PCF8574A GPIO expander and LEDs attached to it.
>> >>
>> >> This IO board is an add-on used in some ballon configurations, not
>> >> part of the core board. There needs to be some way of selecting this
>> >> support when the loon is used in this configuration. We have the
>> >> balloon_has() macro which is used for dealing with the different
>> >> builds of the board itself. Perhaps it should be extended to deal with
>> >> add-on board functionality too?
>> >>
>> >> More obvious is using the CONFIG system to just enable this if
>> >> CUED_IO_BOARD is configured.
>> >
>> > You can just disable the PCF driver if you want to save space. In case
>> > you won't have the CUED board connected, the driver will just fail to
>> > probe so it's ok I believe.
>> >
>> > The macro could be extended, but do we want such a weird stuff in kernel?
>> > (especially if the driver can simply fail to probe).
>>
>> Are we able to detect this expansion board at run-time and registers
>> i2c/led-gpio if present. The thing I'm worried more on space is the
>> gpio_leds will be registered there even without the expansion board,
>> but what if someone tries to read/write to those LED controls?
>
> They won't register because the GPIOs won't be there.

Ah right, gpio_request() should fail them. If there's no way to
detect this board at run-time, I think I'm fine with the patch.

>>
>> >> Wookey
>> >
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>