USB: Support for allocating USB 3.0 streams.

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@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/linux/usb/hcd.h b/include/linux/usb/hcd.h
index d268415b7a40..aca73a5c3af7 100644
--- a/include/linux/usb/hcd.h
+++ b/include/linux/usb/hcd.h
@@ -250,6 +250,16 @@ struct hc_driver {
         int     (*alloc_dev)(struct usb_hcd *, struct usb_device *);
                 /* Called by usb_disconnect to free HC device structures */
         void    (*free_dev)(struct usb_hcd *, struct usb_device *);
+        /* Change a group of bulk endpoints to support multiple stream IDs */
+        int     (*alloc_streams)(struct usb_hcd *hcd, struct usb_device *udev,
+                struct usb_host_endpoint **eps, unsigned int num_eps,
+                unsigned int num_streams, gfp_t mem_flags);
+        /* Reverts a group of bulk endpoints back to not using stream IDs.
+         * Can fail if we run out of memory.
+         */
+        int     (*free_streams)(struct usb_hcd *hcd, struct usb_device *udev,
+                struct usb_host_endpoint **eps, unsigned int num_eps,
+                gfp_t mem_flags);
 
         /* Bandwidth computation functions */
         /* Note that add_endpoint() can only be called once per endpoint before