On 8/6/2012 5:58 PM, Johannes Stezenbach wrote: > On Mon, Aug 06, 2012 at 08:35:51AM +0200, Linus Walleij wrote: >> On Mon, Aug 6, 2012 at 4:18 AM, Stephen Warren <swar...@wwwdotorg.org> wrote: >> >>> I can't comment on the sysfs-vs-dev interface location, but I don't >>> think it addresses Johannes' issue; finding out which GPIO IDs are >>> provided by which devices. >>> >>> Perhaps in each device's sysfs node, there should be some information >>> re: which GPIO range it provides. Right now, perhaps a text file with >>> the GPIO base it it. >> >> Yes that could work ... > > The method used by the gpio-mxs.c driver (of_alias_get_id) > would also work. The question is which method is preferable. > > Ideally I would like to use DT attributes to identify my GPIOs > in the same way as they appear in the schematics. E.g. > one device may have GPIOs called PORT_A.0 to PORT_A.7, > another one may be EXT.0 to EXT.15. But a single integer ID > is good enough since GPIO usage is platform specific anyway. > However, the mapping must be static and not depend e.g. on > module load order like now if you use pl061 and some i2c GPIO. > Software must be able to rely on that e.g. GPIO ID 11 > always refers to EXT.3.
There is precedence for a "slot-names" property that correlates specific hardware entities with physical labels. It has been applied to PCI plug-in slots and to other devices. See, for example, http://www.openfirmware.org/1275/proposals/Closed/Accepted/381-it.txt > > >>> With the new /dev interface you mention above, >>> perhaps a symlink to the /dev file, or a file containing the /dev file's >>> major/minor number. Or, is there such a thing already (other than >>> debugfs's gpio file). >> >> Nothing I know of, but yes the day we come up with something, >> it needs to be backward-compatible some way. >> >> The problem is that there is really no reference userspace >> like "lsgpio" or so. Maybe the first step could be to create that. > > I don't know much about OpenWrt, but I've seen they have > something: > https://dev.openwrt.org/browser/trunk/target/linux/generic/files/drivers/char/gpio_dev.c > https://dev.openwrt.org/browser/trunk/target/linux/generic/files/include/linux/gpio_dev.h > https://dev.openwrt.org/browser/trunk/package/gpioctl/src/main.c > > > Johannes > _______________________________________________ > devicetree-discuss mailing list > devicetree-disc...@lists.ozlabs.org > https://lists.ozlabs.org/listinfo/devicetree-discuss > -- 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/
