Hans de Goede e28e2f2f7c uas: Make uas work with blk-mq
With uas over usb-3 the tags inside the uas iu-s must match the usb-3 stream
ids, and those go from 1 - qdepth.

Before blk-mq calling scsi_activate_tcq(sdev, qdepth) guaranteed that we would
only get cmnd->request->tag from 0 - (qdepth - 1), and we used those as
uas-tags / stream-ids.

With blk-mq however we are guaranteed to never get more then qdepth commands
queued at the same time, but the cmnd->request->tag values may be much larger,
which breaks uas.

This commit fixes this by generating uas tags in the 1 - qdepth range ourselves
instead of using cmnd->request->tag.

While touching all involved code anyways also rename the uas_cmd_info stream
field to uas_tag, because when using uas over usb-2 streams are not used.

Cc: Christoph Hellwig <hch@infradead.org>
Reported-by: Douglas Gilbert <dgilbert@interlog.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

--
Changes in v2:
-Remove ".disable_blk_mq = true" from uas_host_template
Changes in v3:
-Rebased on top of Linus' current master branch
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2014-11-03 15:34:00 -08:00
..
2014-11-03 15:34:00 -08:00

To understand all the Linux-USB framework, you'll use these resources:

    * This source code.  This is necessarily an evolving work, and
      includes kerneldoc that should help you get a current overview.
      ("make pdfdocs", and then look at "usb.pdf" for host side and
      "gadget.pdf" for peripheral side.)  Also, Documentation/usb has
      more information.

    * The USB 2.0 specification (from www.usb.org), with supplements
      such as those for USB OTG and the various device classes.
      The USB specification has a good overview chapter, and USB
      peripherals conform to the widely known "Chapter 9".

    * Chip specifications for USB controllers.  Examples include
      host controllers (on PCs, servers, and more); peripheral
      controllers (in devices with Linux firmware, like printers or
      cell phones); and hard-wired peripherals like Ethernet adapters.

    * Specifications for other protocols implemented by USB peripheral
      functions.  Some are vendor-specific; others are vendor-neutral
      but just standardized outside of the www.usb.org team.

Here is a list of what each subdirectory here is, and what is contained in
them.

core/		- This is for the core USB host code, including the
		  usbfs files and the hub class driver ("hub_wq").

host/		- This is for USB host controller drivers.  This
		  includes UHCI, OHCI, EHCI, and others that might
		  be used with more specialized "embedded" systems.

gadget/		- This is for USB peripheral controller drivers and
		  the various gadget drivers which talk to them.


Individual USB driver directories.  A new driver should be added to the
first subdirectory in the list below that it fits into.

image/		- This is for still image drivers, like scanners or
		  digital cameras.
../input/	- This is for any driver that uses the input subsystem,
		  like keyboard, mice, touchscreens, tablets, etc.
../media/	- This is for multimedia drivers, like video cameras,
		  radios, and any other drivers that talk to the v4l
		  subsystem.
../net/		- This is for network drivers.
serial/		- This is for USB to serial drivers.
storage/	- This is for USB mass-storage drivers.
class/		- This is for all USB device drivers that do not fit
		  into any of the above categories, and work for a range
		  of USB Class specified devices. 
misc/		- This is for all USB device drivers that do not fit
		  into any of the above categories.