Hi, On Tuesday 25 April 2006 00:31, Nigel Cunningham wrote: > On Tuesday 25 April 2006 07:29, David Brownell wrote: > > I've noticed a bunch of problem reports that go like this: > > > > - boot system with some USB devices attached > > - echo disk > /sys/power/state > > - ... later resume ... > > - now those USB devices don't work right > > - unplug them/replug them, all is OK > > > > I recently observed this myself and tracked down one problem. The solution > > involves what kexec() does in much the same situation: before starting a > > new kernel, most hardware needs to be reset. Today, swsusp will suspend it > > instead, which is the root cause of the problem. > > I'm not sure that it is. If we switched to not freezing devices, we'd then > cause issues with hardware such as hard drives. They need to know that we > just want things quiesced, mainly because we don't want to spin down drives. That's right. And kernel_restart_prepare(NULL) will make them spin down? If so, they have to be treated in a special way. OTOH I think at least some device driver writers assume that .resume() will always be called after .suspend() which only is true for non-modular drivers (or for modular drivers loaded from an initrd before resume). The David's change makes this assumptions explicitly invalid and that's why I said I agreed with it. However you're absolutely right about hard disks. Greetings, Rafael
