On Mon, 29 Nov 2010, Sarah Sharp wrote: > Introduce the notion of a PCI device that may be associated with more than > one USB host controller driver (struct usb_hcd). This patch is the start > of the work to separate the xHCI host controller into two roothubs: a USB > 3.0 roothub with SuperSpeed-only ports, and a USB 2.0 roothub with > HS/FS/LS ports. > > Only one pointer can be stored in the PCI device's private pointer, so > designate one roothub as the "main" hcd. For xHCI, this will always be > the USB 3.0 roothub. Introduce usb_hcd_is_main_hcd(), a way to check > whether a usb_hcd structure pointer matches the one stored in the > hcd->self.controller device's private pointer. > > Make sure that only one interrupt is requested for the whole PCI device, > by using usb_hcd_is_main_hcd(). > > Add a new function, usb_create_shared_hcd(), that does roothub allocation > for paired roothubs. It will act just like usb_create_hcd() did if the > shared_hcd pointer argument is NULL. If it is passed a non-NULL > shared_hcd pointer, it sets usb_hcd->shared_hcd, so each roothub can > access the other partner in the pair. > > The bandwidth_mutex needs to be shared across both xHCI roothubs, so make > usb_create_shared_hcd() only allocate the mutex once. When it is passed a > valid shared_hcd pointer, it stores the mutex pointer from the partner in > the new roothub. The bandwidth mutex is only deallocated when the > shared_hcd pointer is NULL. The first shared roothub that is released > will set shared_hcd to NULL. The second shared roothub that is released > (or a USB host controller driver that doesn't set up shared roothubs) will > deallocate the bandwidth mutex. This seems like a lot of extra effort for something used by only one driver. Why not just add a little extra code into usb_hcd_pci_probe() to make it avoid allocating resources twice? Alan Stern -- 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
