From mboxrd@z Thu Jan 1 00:00:00 1970 From: marek.vasut@gmail.com (Marek Vasut) Date: Fri, 30 Jul 2010 21:34:29 +0200 Subject: [Balloon] [PATCH 11/13] [ARM] pxa/balloon3: PCF857x =?utf-8?q?GPIO=09expander?= =?utf-8?q?_and=09LEDs?= In-Reply-To: References: <1280373389-32475-1-git-send-email-marek.vasut@gmail.com> <20100730093939.GJ6845@dream.aleph1.co.uk> Message-ID: <201007302134.29333.marek.vasut@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Dne P? 30. ?ervence 2010 20:54:29 Paul Fidler napsal(a): > On Jul 30 2010, Wookey wrote: > >+++ Marek Vasut [2010-07-30 06:44 +0200]: > >> Dne ?t 29. ?ervence 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? > > > > That was how this list suggested we deal with the unprobe-able build > > variation, I beleive. > > > >> (especially if the driver can simply fail to probe). > > I'd strongly recommend not adding anything at all in the kernel > to specifically support the CUED IO Board. The LEDs attached to > the PCF8574 on the board can be driven from user space quite easily > using programs such as as i2cset from the i2ctools package. > > We've been using these boards at CUED for a number of years now > without any kernel support beyond i2c-pxa.ko and i2c-dev.ko. > > If support is added for these LEDs in the kernel, it would be nice > if we could still write their PCF8574 device using the i2c-dev ioctls. > It would be inconvenient (for us) if the only way to set these LEDs > was by writing a 1 or 0 to /sys/devices/system/leds-gpio/balloon3:gpio:ledN > (or similar). And also _please_ keep the CC correct. Cheers > > Best wishes, > > Paul. > > > Paul Fidler