On Thu, 30 Dec 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.
>
> One usb_hcd structure is designated to be the "primary HCD", and a pointer
> is added to the usb_hcd structure to keep track of that. A new function
> call, usb_hcd_is_primary_hcd() is added to check whether the USB hcd is
> marked as the primary HCD (or if it is not part of a roothub pair). To
> allow the USB core and xHCI driver to access either roothub in a pair, a
> "shared_hcd" pointer is added to the usb_hcd structure.
I'm not sure this "shared_hcd" pointer is needed. Does it ever get
used in a non-trivial way?
> 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
> primary_hcd pointer argument is NULL. If it is passed a non-NULL
> primary_hcd pointer, it sets usb_hcd->shared_hcd and usb_hcd->primary_hcd
> fields. It will also skip the bandwidth_mutex allocation, and set the
> secondary hcd's bandwidth_mutex pointer to the primary HCD's mutex.
>
> IRQs are only allocated once for the primary roothub.
>
> Introduce a new usb_hcd driver flag that indicates the host controller
> driver wants to create two roothubs. If the HCD_SHARED flag is set, then
> the USB core PCI probe methods will allocate a second roothub, and make
> sure that second roothub gets freed during rmmod and in initialization
> error paths.
This doesn't seem like the right approach. The creation of a secondary
usb_hcd should be handled by the driver that needs it; it isn't such a
common activity that we need to implement it in the USB core. In
particular, hcd-pci.c shouldn't be changed.
> If the driver that wants to create two roothubs is an xHCI driver, the
> roothub that is allocated last is marked as the USB 2.0 roothub.
Didn't we agree earlier that xhci-hcd needs to register its USB-2 root
hub first?
> diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
> index 79bad2c..a061c31 100644
> --- a/drivers/usb/core/hcd.c
> +++ b/drivers/usb/core/hcd.c
> @@ -2184,13 +2195,49 @@ struct usb_hcd *usb_create_hcd (const struct hc_driver *driver,
> "USB Host Controller";
> return hcd;
> }
> +EXPORT_SYMBOL_GPL(usb_create_shared_hcd);
> +
> +/**
> + * usb_create_hcd - create and initialize an HCD structure
> + * @driver: HC driver that will use this hcd
> + * @dev: device for this HC, stored in hcd->self.controller
> + * @bus_name: value to store in hcd->self.bus_name
> + * @shared_hcd: a pointer to the usb_hcd structure that is sharing the
> + * PCI device. Used for allocating two usb_hcd structures
> + * under one xHCI host controller PCI device (a USB 2.0 bus
> + * and a USB 3.0 bus).
This last argument doesn't really exist, as you can see below.
> + * Context: !in_interrupt()
> + *
> + * Allocate a struct usb_hcd, with extra space at the end for the
> + * HC driver's private data. Initialize the generic members of the
> + * hcd structure.
> + *
> + * If memory is unavailable, returns NULL.
> + */
> +struct usb_hcd *usb_create_hcd(const struct hc_driver *driver,
> + struct device *dev, const char *bus_name)
> +{
> + return usb_create_shared_hcd(driver, dev, bus_name, NULL);
> +}
> EXPORT_SYMBOL_GPL(usb_create_hcd);
> @@ -2209,6 +2256,14 @@ void usb_put_hcd (struct usb_hcd *hcd)
> }
> EXPORT_SYMBOL_GPL(usb_put_hcd);
>
> +inline int usb_hcd_is_primary_hcd(struct usb_hcd *hcd)
> +{
> + if (!hcd->primary_hcd)
> + return 1;
> + return hcd == hcd->primary_hcd;
Do you really need to set hcd->primary_hcd to point to hcd itself? My
inclination would be to leave it unset.
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
