> What drivers/devices don't work with persist? We need to know that now, > otherwise all other distros and users have problems, right? We have seen a problem with the LTE modem in the Chromebook Pixel using the usb/serial/option.c driver, but we are not quite sure of the root cause yet. It occasionally seems to loose its power session due to autosuspend and then hit core/hub.c:check_port_resume_type(), where it gets the reset_resume flag if persist is enabled. However, since the option driver does not implement the (optional) reset_resume method, this eventually ends up leaving the device in a state where it is neither working nor getting cleanly reenumerated. We are still actively investigating that issue to figure out the underlying bug (not sure whether it is a general problem with drivers that do not implement reset_resume... also, we are still only on 3.4 and have not tried to confirm it on 3.8 yet). However, as we generally hadn't intended persist to be active and this had slipped through our (admittedly very crude) userspace implementation, I proposed this patch so that going forward our devices could always have the persist setting we intend for them at all times. -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
