This patch limits the amount of data that will be transferred in a single command/data/status exchange to 240 sectors (about 120KB on most devices).
This is to increase compatibility with existing devices. Apparently, many
of them don't like large transfers. Those devices are broken, but there
are enough of them (and they are otherwise impossible to detect) to make
this patch valuable.
Future versions of the kernel may allow runtime tuning of this parameter
for higher performance.
Greg, please apply.
Matt
# This is a BitKeeper generated patch for the following project:
# Project Name: greg k-h's linux 2.5 USB kernel tree
# This patch format is intended for GNU patch command version 2.5 or higher.
# This patch includes the following deltas:
# ChangeSet 1.1841 -> 1.1842
# drivers/usb/storage/scsiglue.c 1.61 -> 1.62
#
# The following is the BitKeeper ChangeSet Log
# --------------------------------------------
# 03/11/02 [EMAIL PROTECTED] 1.1842
# Limit transfer size to (what appears to be) what all devices can handle.
# Future kernels may make this more adjustable by userspace after init.
# --------------------------------------------
#
diff -Nru a/drivers/usb/storage/scsiglue.c b/drivers/usb/storage/scsiglue.c
--- a/drivers/usb/storage/scsiglue.c Sun Nov 2 10:56:55 2003
+++ b/drivers/usb/storage/scsiglue.c Sun Nov 2 10:56:55 2003
@@ -312,6 +312,9 @@
/* lots of sg segments can be handled */
.sg_tablesize = SG_ALL,
+ /* limit the total size of a transfer to 120 KB */
+ .max_sectors = 240,
+
/* merge commands... this seems to help performance, but
* periodically someone should test to see which setting is more
* optimal.
--
Matthew Dharm Home: [EMAIL PROTECTED]
Maintainer, Linux USB Mass Storage Driver
G: Let me guess, you started on the 'net with AOL, right?
C: WOW! d00d! U r leet!
-- Greg and Customer
User Friendly, 2/12/1999
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