[PATCH] Add support for USB Keyboard attached to UHCI
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Aaron Young wrote: >> On Mon, 26 Nov 2007 13:39:41 -0800 (PST) >> Aaron Young <ayoung at cthulhu.engr.sgi.com> wrote: >> >> >>> Konstantin, some comments: >>> >>> 3. Why can't you use the HID URB? Locking? Using the HID URB seems >>> to work fine for OHCI and EHCI. This is the reason that >>> seems to cause so much complication in your code. Back >>> in the 2.4 timeframe, Intel did a UHCI KDB implementation >>> that used the HID URB. Perhaps it would be useful to dig up that >>> old code and compare it? I can possibly pass that code on to you >>> if you want... >>> >>> Also, does enqueing two URBs for the same device cause any >>> problems (is it "legal")? >>> >>> >>> -Aaron >>> >>> >>> >> I explained it earlier: >> http://oss.sgi.com/archives/kdb/2007-11/msg00003.html >> >> KDB Poll driver should not depend on USB kernel code because (in case >> when KDB driver uses the same code with kernel USB driver) if CPU0 >> executes kernel USB driver and, in the same time, CPU1 hits breakpoint, >> CPU0 would be frozen in kernel USB driver. USB spinlocks would be >> locked by CPU0, so KDB USB code couldn't get lock and deadlock would >> occur. Or, if we don't use lock, kernel USB driver data can't be >> corrupted. >> > > Yes - you're right - it's *possible* to get into kdb while locks are > held which, if timed just perfectly, could result in kdb crashing trying > to walk lists, etc. This is also true of EHCI and OHCI (I think). > I've never seen it happen, but it could in theory... > > I'm not sure it's worth it to rewrite all this code to cover this possibility, > so what I might consider doing is just to check for the critical locks being > held out of the poll functions and if so, give an error and punt > (return -1) - i.e. the keyboard(s) for > that HC will not be useable in this case. Much easier > and probably sufficient for a debugger IMO. > > Jay, prepare for another patch for this! ;-) > > -Aaron > Aaron, I'm little bit confused . Are you going to integrate my UHCI code to KDB? --------------------------- Use http://oss.sgi.com/ecartis to modify your settings or to unsubscribe.