On Sun, 26 Sep 2004, David Brownell wrote: > > If the USB drivers are linked into the kernel, what happens when they > > start initializing devices during the resume-from-disk bootup? What about > > the early-HC-disable patch that was recently added? > > Systems that rely on that patch are systems where the BIOS (or SMM) already > screws around with the root hub state on resume. And the patch forces a > reset, which the root hub reports ... the only result of USB_SUSPEND is to > let remote wakeup trigger a resume, that patch trashes the entire device > tree (all devices got reset, it's nothing like a resume).
So the patch will have to be changed. All it really needs to do is take control from the BIOS, disable interrupts, and stop DMA activity; it doesn't need to reset the entire HC or turn off port power. But what about HCDs that are linked into the boot kernel? During the resume-from-disk bootup they won't know that they need to preserve the HC state. After all, it's their job to reset the HC. You must be suggesting that the reset be done in a way that doesn't turn off power to the root hub ports. That way the USB devices will remain suspended and won't lose their state. > > Even if we can get away without initializing and enumerating devices under > > favorable conditions, the code to do it still has to be there in order to > > handle unfavorable conditions. Since the code has to be there, why not > > use it for resume-from-power-off? > > When the power really did go off, sure. I've never said otherwise. But > you shouldn't be planning that power always goes off. So in that case, why not support selective power-off suspend? Alan Stern ------------------------------------------------------- This SF.Net email is sponsored by: YOU BE THE JUDGE. Be one of 170 Project Admins to receive an Apple iPod Mini FREE for your judgement on who ports your project to Linux PPC the best. Sponsored by IBM. Deadline: Sept. 24. Go here: http://sf.net/ppc_contest.php _______________________________________________ [EMAIL PROTECTED] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
