From a93917d39fc388c4761d2530af82513e2d3bf9f6 Mon Sep 17 00:00:00 2001 From: Andy Shevchenko Date: Thu, 22 Jul 2010 17:53:56 +0300 Subject: 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 Acked-by: Alan Stern Cc: Denis Karpov Cc: Adrian Hunter Cc: David Brownell Signed-off-by: Greg Kroah-Hartman --- .../ABI/testing/sysfs-devices-platform-_UDC_-gadget | 12 ++++++++++++ 1 file changed, 12 insertions(+) (limited to 'Documentation') diff --git a/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget b/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget index 3403402..d548eaa 100644 --- a/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget +++ b/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget @@ -7,3 +7,15 @@ Description: 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 +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 -- cgit v1.1