USB: Add LVS Test device driver

USB: Add LVS Test device driver

OTG3 and EH Compliance Plan 1.0 talks about Super Speed OTG Verification
system (SS-OVS) which consists of an excersizer and analyzer.

USB Compliance Suite from Lecroy or Ellisys can act as such SS-OVS for
Link Layer Validation (LVS).

Some modifications are needed for an embedded Linux USB host to pass all
these tests.  Most of these tests require just Link to be in U0. They do
not work with default Linux USB stack since, default stack does port
reset and then starts sending setup packet, which is not expected by
Link Layer Validation (LVS) device of Lecroy Compliance Suit.  Then,
There are many Link Layer Tests which need host to generate specific
traffic.

This patch supports specific traffic generation cases. As of now all the
host Lecroy Link Layer-USBIF tests (except TD7.26) passes
with this patch for single run using  Lecroy USB Compliance Suite
Version 1.98 Build 239 and Lecroy USB Protocol Analyzer version 4.80
Build 1603. Therefore patch seems to be a good candidate for inclusion.
Further modification can be done on top of it.

lvstest driver will not bind to any device by default. It can bind
manually to a super speed USB host controller root hub. Therefore, regular
hub driver must be unbound before this driver is bound. For example, if
2-0:1.0 is the xhci root hub, then execute following to unbind hub driver.

 echo 2-0:1.0 > /sys/bus/usb/drivers/hub/unbind

Then write Linux Foundation's vendor ID which is used by root hubs and
SS root hub's device ID into new_id file. Writing IDs into new_id file
will also bind the lvs driver with any available SS root hub interfaces.

 echo "1D6B 3" > /sys/bus/usb/drivers/lvs/new_id

Now connect LVS device with root hub port.

Test case specific traffic can be generated as follows whenever needed:

1. To issue "Get Device descriptor" command for TD.7.06:
 echo  > /sys/bus/usb/devices/2-0\:1.0/get_dev_desc

2. To set U1 timeout to 127 for TD.7.18
 echo 127 > /sys/bus/usb/devices/2-0\:1.0/u1_timeout

3. To set U2 timeout to 0 for TD.7.18
 echo 0 > /sys/bus/usb/devices/2-0\:1.0/u2_timeout

4. To issue "Hot Reset" for TD.7.29
 echo  > /sys/bus/usb/devices/2-0\:1.0/hot_reset

5. To issue "U3 Entry" for TD.7.35
 echo  > /sys/bus/usb/devices/2-0\:1.0/u3_entry

6. To issue "U3 Exit" for TD.7.36
 echo  > /sys/bus/usb/devices/2-0\:1.0/u3_exit

Signed-off-by: Pratyush Anand <pratyush.anand@st.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>