On Fri, Jul 30, 2010 at 1:19 PM, Marek Vasut wrote: > Dne Pá 30. července 2010 07:09:00 Eric Miao napsal(a): >> On Fri, Jul 30, 2010 at 12:44 PM, Marek Vasut 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 >> > >> > _______________________________________________ >> > linux-arm-kernel mailing list >> > linux-arm-kernel@lists.infradead.org >> > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel >