netdev - Expose ltr/obff interface by sysfs

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Message-ID: <403610A45A2B5242BD291EDAE8B37D300FD0A434@SHSMSX102.ccr.corp.intel.com>
Date:	Fri, 6 Apr 2012 02:43:59 +0000
From:	"Hao, Xudong" <xudong.hao@...el.com>
To:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>
CC:	Jesse Barnes <jbarnes@...tuousgeek.org>
Subject: Expose ltr/obff interface by sysfs

Hi, 

I'm working on virtualization Xen/KVM. I saw there are ltr/obff enabling/disabling function in pci.c, but no called till now. I want to know if anybody(driver developer) are working for using it? Can driver change the LTR latency value dynamically?

/*
LTR(Latency tolerance reporting) allows devices to send messages to the root complex indicating their latency tolerance for snooped & unsnooped memory transactions.
OBFF (optimized buffer flush/fill), where supported, can help improve energy efficiency by giving devices information about when interrupts and other activity will have a reduced power impact.
*/

One way to control ltr/obff is used by driver, however, I'm considering that in virtualization, how guest OS driver control them. I have an idea that expose an inode interface by sysfs, like "reset" inode implemented in pci-sysfs.c, so that system user/administrator can enable/disable ltr/obff or set latency value on userspace, but not limited on driver. Comments?

< pls CC me when reply this mail, thanks >

Best Regards,
Xudong Hao

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