On Wed, 30 Mar 2011, Rafael J. Wysocki wrote: > > Rafael, this does seem to be a general problem. Suppose a new device > > gets connected while the system is suspended. How is the driver's > > probe method supposed to cope if it gets called while userspace is > > still frozen but it needs to load some firmware? > > > > Is the answer that probing should always be delayed until after tasks > > are thawed? There must be lots of subsystems which would have trouble > > doing that, although we ought to be able to implement delayed probing > > from within the driver core easily enough. > > I don't know how to solve that. > > First off, the prepare routines of drivers that need to load firmware during > resume probably should preload the firmware for the devices present during the > suspend. That's okay for drivers that are bound to a device before the suspend starts. But we also need to handle new devices added while the system was asleep. > Second, I don't generally think drivers should probe for devices during resume. > I guess the delayed probing would be the cleanest appoach here. Here's the difficulty. Normally the USB subsystem does use delayed probing -- in fact, probing is done in a freezable thread. However this is a special case. Not all USB drivers support suspend/resume; those that don't get unbound during suspend and then rebound during resume. The rebinding occurs in the "complete" phase of the resume, before tasks are thawed. I suppose the rebinding could be delayed. It would be better to fix the USB DVB drivers, though, by adding PM support. But there's a bunch of them in drivers/media/dvb/dvb-usb, and AFAICS they would all need to be fixed. And I have no idea of what changes they would need. Do you have any better suggestions? Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
