On Mon, Aug 24, 2009 at 06:26:26PM +0100, David Vrabel wrote: > Sarah Sharp wrote: > > On Mon, Aug 24, 2009 at 03:54:16PM +0000, David Vrabel wrote: > >> The WHCI HCD will also support urbs with scatter-gather lists. Add a > >> usb_bus field to indicated how many sg list elements are supported by > >> the HCD. Use this to decide whether to pass the scatter-list to the HCD > >> or not. > >> > >> Always use scatter-gather urbs where possible, regardless of the > >> endpoint type. If the scatter-gather list doesn't have suitably sized > >> elements for a particular endpoint type then splitting it up into > >> separate urbs won't help. > > > > Does this mean control URBs may have a scatter gather list? The xHCI > > driver can't currently handle that. > > Control transfers with sg lists is not something that would work with > ehci, ohci or uhci either as the single transfer would be turned into > several independent control transfers. Ah, so usb_sg_init() should never be called for a control transfer? > >> diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c > >> index 592fe7e..bbc3934 100644 > >> --- a/drivers/usb/host/xhci-pci.c > >> +++ b/drivers/usb/host/xhci-pci.c > >> @@ -50,6 +50,8 @@ static int xhci_pci_setup(struct usb_hcd *hcd) > >> struct pci_dev *pdev = to_pci_dev(hcd->self.controller); > >> int retval; > >> > >> + hcd->self.sg_tablesize = 2048; > >> + > > > > Please set this to (TRBS_PER_SEGMENT - 1). It's not a very big number > > (currently 63). I haven't added dynamic transfer ring resizing yet, so > > there's only 63 TRBs to map to sg list entries. > > Will do. > > I've not looked at the xhci spec but rather than dynamically resizing > the transfer ring, can you reuse entries in it as they are consumed? > This would be analogous to what the whci-hcd driver does. Yes, the xHCI driver can reuse entries in the transfer ring as the hardware completes the transfers. I would only need dynamic ring resizing if pending transfers were taking up the ring, or if a driver tried to enqueue a very large sglist. Sarah -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
