On Fri, Dec 11, 2015 at 6:39 AM, Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > On Fri, Dec 4, 2015 at 6:31 PM, Martyn Welch > <martyn.welch@xxxxxxxxxxxxxxx> wrote: > >> This patch adds documentation for the gpio-switch binding. This binding >> provides a mechanism to bind named links to gpio, with the primary >> purpose of enabling standardised access to switches that might be standard >> across a group of devices but implemented differently on each device. >> >> Signed-off-by: Martyn Welch <martyn.welch@xxxxxxxxxxxxxxx> > > As mentioned in the comment to the second patch, this solves the > following generic problem: > > Expose a GPIO line to userspace using a specific name > > That means basically naming GPIO lines and marking them as > "not used by the operating system". > > This is something that has been proposed before, and postponed > because the kernel lacks the right infrastructure. That doesn't necessarily mean we can't define a binding. > Markus Pargmann also did a series that add initial values to > hogs, which is the inverse usecase of this, where you want to > *output* something by default, then maybe also make it available > to userspace. > > So what we need to see here is a patch series that does all of these > things: > > - Name lines > > - Sets them to initial values > > - Mark them as read-only > > - Mark them as "not used by the operating system" so that they > can be default-exported to userspace. No! This should not be a DT property. Whether I want to control a GPIO in the kernel or userspace is not known and can change over time. It could simply depend on kernel config. There is also the case that a GPIO has no connection or kernel driver until some time later when a DT overlay for an expansion board is applied. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
