On Sun, Apr 26, 2020 at 03:08:38PM -0400, Dave Mielke wrote: > We're working on getting brltty to run as an unprivileged user with just a few > required capabilities. We don't want one of those required capabilities to be > CAP_DAC_OVERRIDE (bypass file permission checks). > > Some USB-connected braille devices don't respond very well to being > autosuspended. We get around this, when running as root, by writing to the > SYSFS power/autosuspend file associated with the device. Our problem is that > only the root user can write to it. > > Other than using CAP_DAC_OVERRIDE (which we don't want to do), what other > way(s) might we be able to use to overcome this restriction? For example, is > there some kind of safe (enough) udev rule? Have a udev rule that turns autosuspend off for each specific USB device that you know does not work with autosuspend. Do you have such a list? If so, we can add it to the USB core with the USB_QUIRK_DISCONNECT_SUSPEND flag. Or is it the USB_QUIRK_NO_LPM that they need? I can't remember, but you can test it out from userspace by reading about those in the Documentation/admin-guide/kernel-parameters.txt file. Hope this helps, greg k-h
