On Fri, 2 Apr 2010, Sarah Sharp wrote:
> Bulk endpoint streams were added in the USB 3.0 specification. Streams
> allow a device driver to overload a bulk endpoint so that multiple
> transfers can be queued at once.
>
> The device then decides which transfer it wants to work on first, and can
> queue part of a transfer before it switches to a new stream. All this
> switching is invisible to the device driver, which just gets a completion
> for the URB. Drivers that use streams must be able to handle URBs
> completing in a different order than they were submitted to the endpoint.
>
> This requires adding new API to set up xHCI data structures to support
> multiple queues ("stream rings") per endpoint. Drivers will allocate a
> number of stream IDs before enqueueing URBs to the bulk endpoints of the
> device, and free the stream IDs in their disconnect function. See
> Documentation/usb/bulk-streams.txt for details.
>
> The new mass storage device class, USB Attached SCSI Protocol (UASP), uses
> these streams API.
>
> Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx>
> ---
> drivers/usb/core/driver.c | 54 +++++++++++++++++++++++++++++++++++++++++++
> drivers/usb/core/hcd.h | 10 ++++++++
> drivers/usb/host/xhci-pci.c | 2 +
> include/linux/usb.h | 10 ++++++++
> 4 files changed, 76 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/usb/core/driver.c b/drivers/usb/core/driver.c
> index f3c2338..cc599da 100644
> --- a/drivers/usb/core/driver.c
> +++ b/drivers/usb/core/driver.c
> @@ -497,6 +497,60 @@ void usb_driver_release_interface(struct usb_driver *driver,
> }
> EXPORT_SYMBOL_GPL(usb_driver_release_interface);
>
> +/* Sets up a group of bulk endpoints to have num_streams stream IDs available.
> + * Drivers may queue multiple transfers to different stream IDs, which may
> + * complete in a different order than they were queued.
> + */
> +int usb_alloc_streams(struct usb_interface *interface,
> + struct usb_host_endpoint **eps, unsigned int num_eps,
> + unsigned int num_streams, gfp_t mem_flags)
> +{
> + struct usb_hcd *hcd;
> + struct usb_device *dev;
> + int i;
> +
> + dev = interface_to_usbdev(interface);
> + hcd = bus_to_hcd(dev->bus);
> + if (!hcd->driver->alloc_streams || !hcd->driver->free_streams)
> + return -EINVAL;
> + if (dev->speed != USB_SPEED_SUPER)
> + return -EINVAL;
> +
> + /* Streams only apply to bulk endpoints. */
> + for (i = 0; i < num_eps; i++)
> + if (!usb_endpoint_xfer_bulk(&eps[i]->desc))
> + return -EINVAL;
> +
> + return hcd->driver->alloc_streams(hcd, dev, eps, num_eps,
> + num_streams, mem_flags);
> +}
> +EXPORT_SYMBOL_GPL(usb_alloc_streams);
> +
> +/* Reverts a group of bulk endpoints back to not using stream IDs.
> + * Can fail if we are given bad arguments.
> + */
> +void usb_free_streams(struct usb_interface *interface,
> + struct usb_host_endpoint **eps, unsigned int num_eps,
> + gfp_t mem_flags)
> +{
> + struct usb_hcd *hcd;
> + struct usb_device *dev;
> + int i;
> +
> + dev = interface_to_usbdev(interface);
> + hcd = bus_to_hcd(dev->bus);
> + if (dev->speed != USB_SPEED_SUPER)
> + return;
> +
> + /* Streams only apply to bulk endpoints. */
> + for (i = 0; i < num_eps; i++)
> + if (!usb_endpoint_xfer_bulk(&eps[i]->desc))
> + return;
> +
> + hcd->driver->free_streams(hcd, dev, eps, num_eps, mem_flags);
> +}
> +EXPORT_SYMBOL_GPL(usb_free_streams);
Don't these routines belong in hcd.c rather than driver.c? They are
basically glue between the core and the HCDs, after all.
Alan Stern
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