On Thu, 26 Apr 2007 14:42:39 -0400 (EDT), Alan Stern <[EMAIL PROTECTED]> wrote: > On Thu, 26 Apr 2007, Peter Korsgaard wrote: > > > Some multi-role (host/peripheral) USB controllers use a shared interrupt > > line for all parts of the chip. Export usb_hcd_irq so drivers can call it > > from their interrupt handler instead of duplicating code. > > Drivers pass an irqnum of 0 to usb_add_hcd to signal that the interrupt > > handler > > shouldn't be registerred by the core. > > There was some controversy about this sort of thing in the past, and I > don't remember what the outcome was. The difficulty is that 0 is > potentially a valid IRQ number, so it shouldn't be used to mean "don't > register the IRQ handler".
For ohci-hcd, we used -1. The problem here is, while IRQ 0 is definitely not valid for PCI devices (as Alan Cox reminded me a couple of weeks ago), USB controllers are found in odd embedded configurations often, so we cannot just use 0 as invalid everywhere. I don't know if -1 is good though. Seems like it should be. Alan Cox also cautioned against using NO_IRQ, because it's not universally defined by all platforms, and in general is an invention of old IDE. Looks like -1 is the way to go. -- Pete ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/ _______________________________________________ [email protected] To unsubscribe, use the last form field at: https://lists.sourceforge.net/lists/listinfo/linux-usb-devel
