I wonder if that SCSI fix (restoring a wrongly deleted mem clear) helps get rid of this oops too?
On Wednesday 08 March 2006 7:30 am, Alan Stern wrote: > > > a) How come we're only considering the zeroth slot in that array in here? > > > > We start out with the first interface setting, as we always know we have > > one of them as per the USB spec (I think, anyone from linux-usb-devel > > want to verify this?) > > In this case it wouldn't make any difference, since all the altsettings > for a particular interface are supposed to have the same bInterfaceClass, > bInterfaceSubClass, and bInterfaceProtocol. Although I don't think the > USB spec actually says this anywhere.. I'd have stopped at "wouldn't make any difference"; the kernel must make some initial choice, but userspace is free to revise it. Agreed it would be odd if altsettings had different class/subclass/protocol, but I don't see any good reason to make that illegal. > The bMaxPower value could be different for different altsettings. Erm, no; that's a per-configuration thing, not a per-altsetting thing. It's checking the config descriptor, not the interface descriptor, for that particular concern. > > > b) How do we know that there's actually anything _there_? The length of > > > that variable-sized array doesn't seem to have been stored anywhere > > > obvious by usb_parse_configuration() and choose_configuration() doesn't > > > check. What happens if the length was zero? > > > > I don't think it is allowed to be, as all USB devices have to have at > > least 1 interface. I think that's not true, and it would be worth verifying that it's not a no-interfaces device even if the USB spec required it. It's trivial to create device firmware that advertises no-interfaces, and those should never be able to make Linux hiccup (much less oops). > The code in usb_parse_configuration() guarantees that the number of > entries in the altsettings array is at least 1, because it sets nalts[n] > to 1 initially and never decreases it. The whole idea of an interface > without altsettings makes no sense... Right; there's always at least one setting. Calling them "alt" settings can be confusing; any one of them could be the "main" setting. - Dave ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ linux-usb-devel@lists.sourceforge.net To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
