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authorAndy Shevchenko <andy.shevchenko@gmail.com>2010-07-22 17:53:56 +0300
committerGreg Kroah-Hartman <gregkh@suse.de>2010-08-10 14:35:42 -0700
commita93917d39fc388c4761d2530af82513e2d3bf9f6 (patch)
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parent8156d158efa6370a8183f47327f122edbb4f2cb6 (diff)
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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>
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget b/Documentation/ABI/testing/sysfs-devices-platform-_UDC_-gadget
index 34034027b13..d548eaac230 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 <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