5 files changed, 169 insertions, 0 deletions

diff --git a/Documentation/usb/bulk-streams.txt b/Documentation/usb/bulk-streams.txt
new file mode 100644
index 000000000000..ffc02021863e
--- /dev/null
+++ b/Documentation/usb/bulk-streams.txt
@@ -0,0 +1,78 @@
+Background
+==========
+
+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.
+
+Streams are defined in sections 4.4.6.4 and 8.12.1.4 of the Universal Serial Bus
+3.0 specification at http://www.usb.org/developers/docs/  The USB Attached SCSI
+Protocol, which uses streams to queue multiple SCSI commands, can be found on
+the T10 website (http://t10.org/).
+
+
+Device-side implications
+========================
+
+Once a buffer has been queued to a stream ring, the device is notified (through
+an out-of-band mechanism on another endpoint) that data is ready for that stream
+ID.  The device then tells the host which "stream" it wants to start.  The host
+can also initiate a transfer on a stream without the device asking, but the
+device can refuse that transfer.  Devices can switch between streams at any
+time.
+
+
+Driver implications
+===================
+
+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);
+
+Device drivers will call this API to request that the host controller driver
+allocate memory so the driver can use up to num_streams stream IDs.  They must
+pass an array of usb_host_endpoints that need to be setup with similar stream
+IDs.  This is to ensure that a UASP driver will be able to use the same stream
+ID for the bulk IN and OUT endpoints used in a Bi-directional command sequence.
+
+The return value is an error condition (if one of the endpoints doesn't support
+streams, or the xHCI driver ran out of memory), or the number of streams the
+host controller allocated for this endpoint.  The xHCI host controller hardware
+declares how many stream IDs it can support, and each bulk endpoint on a
+SuperSpeed device will say how many stream IDs it can handle.  Therefore,
+drivers should be able to deal with being allocated less stream IDs than they
+requested.
+
+Do NOT call this function if you have URBs enqueued for any of the endpoints
+passed in as arguments.  Do not call this function to request less than two
+streams.
+
+Drivers will only be allowed to call this API once for the same endpoint
+without calling usb_free_streams().  This is a simplification for the xHCI host
+controller driver, and may change in the future.
+
+
+Picking new Stream IDs to use
+============================
+
+Stream ID 0 is reserved, and should not be used to communicate with devices.  If
+usb_alloc_streams() returns with a value of N, you may use streams 1 though N.
+To queue an URB for a specific stream, set the urb->stream_id value.  If the
+endpoint does not support streams, an error will be returned.
+
+Note that new API to choose the next stream ID will have to be added if the xHCI
+driver supports secondary stream IDs.
+
+
+Clean up
+========
+
+If a driver wishes to stop using streams to communicate with the device, it
+should call
+
+void usb_free_streams(struct usb_interface *interface,
+                struct usb_host_endpoint **eps, unsigned int num_eps,
+                gfp_t mem_flags);
+
+All stream IDs will be deallocated when the driver releases the interface, to
+ensure that drivers that don't support streams will be able to use the endpoint.
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index 6a05e6934455..3aaee2811f01 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -1814,6 +1814,75 @@ void usb_hcd_reset_endpoint(struct usb_device *udev,
         }
 }
 
+/**
+ * usb_alloc_streams - allocate bulk endpoint stream IDs.
+ * @interface:          alternate setting that includes all endpoints.
+ * @eps:                array of endpoints that need streams.
+ * @num_eps:            number of endpoints in the array.
+ * @num_streams:        number of streams to allocate.
+ * @mem_flags:          flags hcd should use to allocate memory.
+ *
+ * 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);
+
+/**
+ * usb_free_streams - free bulk endpoint stream IDs.
+ * @interface:  alternate setting that includes all endpoints.
+ * @eps:        array of endpoints to remove streams from.
+ * @num_eps:    number of endpoints in the array.
+ * @mem_flags:  flags hcd should use to allocate memory.
+ *
+ * Reverts a group of bulk endpoints back to not using stream IDs.
+ * Can fail if we are given bad arguments, or HCD is broken.
+ */
+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);
+
 /* Protect against drivers that try to unlink URBs after the device
  * is gone, by waiting until all unlinks for @udev are finished.
  * Since we don't currently track URBs by device, simply wait until
diff --git a/drivers/usb/host/xhci-pci.c b/drivers/usb/host/xhci-pci.c
index 98a73cd20cc6..d295bbc15eb7 100644
--- a/drivers/usb/host/xhci-pci.c
+++ b/drivers/usb/host/xhci-pci.c
@@ -132,6 +132,8 @@ static const struct hc_driver xhci_pci_hc_driver = {
         .urb_dequeue =          xhci_urb_dequeue,
         .alloc_dev =            xhci_alloc_dev,
         .free_dev =             xhci_free_dev,
+        .alloc_streams =        xhci_alloc_streams,
+        .free_streams =         xhci_free_streams,
         .add_endpoint =         xhci_add_endpoint,
         .drop_endpoint =        xhci_drop_endpoint,
         .endpoint_reset =       xhci_endpoint_reset,
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 191af498c4f5..1ea25377ca0d 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -570,6 +570,16 @@ static inline void usb_mark_last_busy(struct usb_device *udev)
 /* for drivers using iso endpoints */
 extern int usb_get_current_frame_number(struct usb_device *usb_dev);
 
+/* Sets up a group of bulk endpoints to support multiple stream IDs. */
+extern 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);
+
+/* Reverts a group of bulk endpoints back to not using stream IDs. */
+extern void usb_free_streams(struct usb_interface *interface,
+                struct usb_host_endpoint **eps, unsigned int num_eps,
+                gfp_t mem_flags);
+
 /* used these for multi-interface device registration */
 extern int usb_driver_claim_interface(struct usb_driver *driver,
                         struct usb_interface *iface, void *priv);
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