On Tue, Mar 19, 2019 at 12:15:06PM +0100, Oliver Neukum wrote: > On Di, 2019-03-19 at 11:36 +0100, Johan Hovold wrote: > > On Mon, Feb 18, 2019 at 10:17:12AM +0100, Oliver Neukum wrote: > > > On So, 2019-02-17 at 18:59 +0100, Karoly Pados wrote: > > > > Current GPIO code in cp210x fails to take USB autosuspend into account, > > > > making it practically impossible to use GPIOs with autosuspend enabled > > > > without user configuration. Fix this like for ftdi_sio in a previous patch. > > > > Tested on a CP2102N. > > > your patch is looking good to me, but I am afraid there are issues. > > > How do the GPIO lines on the device interact with USB reset and system > > > suspend? > > > > What was your concern here, Oliver? > > If you have a device resetting or losing power (for reset_resume) the > GPIO lines will revert to the default. But that change is not reported > to user space, is it? This driver doesn't support reset_resume() so that shouldn't be an issue, right? We'd disconnect (deregister the gpiochip) and re-probe instead. > So the original patch is correct, but there are more situations rather > than suspend which could trigger the problem. This patch just added the missing auto-resume handling, but, yeah, there may be devices out there for which things may get out of sync if they lose state over suspend. I think Karoly confirmed this wasn't the case with cp210x. Johan
