On Wed, 11 May 2005, David Brownell wrote: > > I haven't tried it out yet, but it looks good. One thing stuck out > > though: Why did you remove the test that prevents new drivers from trying > > to bind to suspended devices? > > It was superfluous; they'd get errors later, probe would still > fail cleanly. And it seemed as if any fixes to that should sit > a few layers up.
It probably would fail, although not quite as cleanly. But I agree that fixes should go higher up (i.e., the driver core). > > Also, I think that deadlock on dpm_sem in the PM core is now gone, so > > there shouldn't be any problem about unbinding drivers with no suspend > > method. > > I thought so too, but then I looked at the code and I see that > device_release_driver() calls device_detach_shutdown() which > normally calls dpm_runtime_suspend() which grabs dpm_sem; which > is the deadlock, given it's called from a context which already > holds that lock. (And it all seems rather counterproductive, > since we want to unbind the driver specifically because there > is no suspend method!!) I'll have to look into this more thoroughly. > There might be a way out though: adding a NOP shutdown method > to the driver that usb_register() creates. (And maybe adding > such an entry to struct usb_driver ... so the usbcore NOP method > only gets used for drivers that don't provide their own.) I don't see what adding a shutdown method has to do with drivers that don't support suspend/resume. Anyway, the dpm_sem problem still needs to be fixed in the PM core. > I understand wanting to make storage handle suspend/resume; > and it should be pretty straightforward, too. > > On the other hand, having a way around that dpm_sem deadlock > would make all drivers handle suspend "sanely" without needing > such new code ... and it'd be a huge step towards letting us > get rid of CONFIG_USB_SUSPEND as an option (having its updated > guts be the default). Agreed. Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by Oracle Space Sweepstakes Want to be the first software developer in space? Enter now for the Oracle Space Sweepstakes! http://ads.osdn.com/?ad_id=7393&alloc_id=16281&op=click _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
