usb/bulk-streams.txt: convert to ReST and add to driver-api book

This document describe some USB core functions. Add it to the
driver-api book.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/driver-api/usb/bulk-streams.rst b/Documentation/driver-api/usb/bulk-streams.rst
new file mode 100644 (file)
index 0000000..99b515b
--- /dev/null
+++ b/Documentation/driver-api/usb/bulk-streams.rst
@@ -0,0 +1,83 @@
+USB bulk streams
+~~~~~~~~~~~~~~~~
+
+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/Documentation/driver-api/usb/index.rst b/Documentation/driver-api/usb/index.rst
index 5dfb04b2d7304ee939d9b424bfa4f9d992f641a4..6fe7611f733296e0be95fd886bbc4580aa425fc1 100644 (file)
--- a/Documentation/driver-api/usb/index.rst
+++ b/Documentation/driver-api/usb/index.rst
@@ -7,6 +7,7 @@ Linux USB API
    usb
    gadget
    anchors
+   bulk-streams
    writing_usb_driver
    writing_musb_glue_layer
 

diff --git a/Documentation/usb/bulk-streams.txt b/Documentation/usb/bulk-streams.txt
deleted file mode 100644 (file)
index ffc0202..0000000
--- a/Documentation/usb/bulk-streams.txt
+++ /dev/null
@@ -1,78 +0,0 @@
-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.