linux/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget
Andy Shevchenko a93917d39f USB: gadget: storage: optional SCSI WRITE FUA bit
MS Windows mounts removable storage in "Removal optimized mode" by
default. All the writes to the media are synchronous which is achieved
by setting FUA (Force Unit Access) bit in SCSI WRITE(10,12) commands.
This prevents I/O requests aggregation in block layer dramatically
decreasing performance.

This patch brings an option to accept or ignore mentioned bit
 a) via specifying module parameter "nofua", or
 b) through sysfs entry
	/sys/devices/platform/_UDC_/gadget/gadget-lunX/nofua
	(_UDC_ is the name of the USB Device Controller driver)

Patch is based on the work that was done by Denis Karpov for Maemo 5
platform.

Signed-off-by: Andy Shevchenko <ext-andriy.shevchenko@nokia.com>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Denis Karpov <ext-denis.2.karpov@nokia.com>
Cc: Adrian Hunter <adrian.hunter@nokia.com>
Cc: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-08-10 14:35:42 -07:00

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What: /sys/devices/platform/_UDC_/gadget/suspended
Date: April 2010
Contact: Fabien Chouteau <fabien.chouteau@barco.com>
Description:
Show the suspend state of an USB composite gadget.
1 -> suspended
0 -> resumed
(_UDC_ is the name of the USB Device Controller driver)
What: /sys/devices/platform/_UDC_/gadget/gadget-lunX/nofua
Date: July 2010
Contact: Andy Shevchenko <andy.shevchenko@gmail.com>
Description:
Show or set the reaction on the FUA (Force Unit Access) bit in
the SCSI WRITE(10,12) commands when a gadget in USB Mass
Storage mode.
Possible values are:
1 -> ignore the FUA flag
0 -> obey the FUA flag