On Sun, Sep 30, 2012 at 5:09 PM, Roland Stigge <sti...@antcom.de> wrote: > Hi Stijn, > > On 30/09/12 16:52, Stijn Devriendt wrote: >>> One question: How did you solve the one-value-per-file in the sysfs >>> interface? >>> >> By exporting the group as a whole: >> /sys/.../gpiogroup248/value >> where value contains a decimal representing the group value. >> Again, this respects the ordering of the pins: >> >> Actual pins: 0x2D (b 0010 1101) >> Selected pins: 6 3 0 1 >> Readout: 6 (b 0 1 1 0) >> >> The export sysfs file does, however, accept multiple gpio IDs for groups. >> Not sure if this is a 'violation' per se... > > If I understand correctly, it's a violation (single-value should hold > for read and write). > > To solve it, I have the following in mind: /sys/.../gpiogroupXXX/ > contains files "bit0" ... "bit31" which contain a gpio number each, > empty if "unconnected".
Unfortunately that means you can't atomically create a group. It also creates a mess to keep ordering intact and to either keep the current pin state or override it at allocation-time. Rules are rules, but why make the interface overly complex when the multi-value file is saner, cleaner and simpler? I know I'm on the happy/corporate side of things and I can violate whatever rule I can if it gets our product shipping, but I'd still propose to have the multi-value approach, even in mainline. Regards, Stijn -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
