"The following patches implement a more generalized infrastructure (than latency.c) for connecting drivers and subsystem's that could implement power performance optimizations with the data needed to implement such policies," began Mark Gross, describing his Quality of Service power management patchset. He added, "these patches are following up on the discussions and presentations at the power management summit last summer." Mark continued:

"The idea is that from an abstract point of view how much to throttle hardware can be expressed as a function of QoS types of parameters; Latency, throughput, and idle time outs.

"The qos_parameter patch is intended to put into place the registration and notification infrastructure for enabling QoS based policy choices by drivers, where constraints on throttling are communicated through the qos_params module."

"Intel's Open Source Technology Center is pleased to announce the LessWatts.org project, an open source project for saving power on Linux," began an email posted to the lkml by Arjan van de Ven. The announcement continued:

"LessWatts.org is a place to bring users, developers and distribution makers together around power reduction for linux machines, from mobile to desktop to server to datacenter. LessWatts.org is about a system-level approach to power savings, from the lowest level device drivers in the kernel to the most advanced desktop applications. LessWatts.org is about things you can do to reduce power usage. LessWatts.org is about longer battery life, a lower airconditioning bill, about reducing the impact of computers on the environment."

The announcement went on to note, "at this time of launching the LessWatts.org project, the technology development projects are those that Intel has started, is involved in or has just started working on, such as PowerTOP, Tickless Idle, Graphics and various link power management techniques. We'd like to invite all developers and projects that focus on power saving to join the LessWatts.org effort and community."

"It turns out that USB devices suck when it comes to powermanagement issues :(" lamented Greg KH in posting some patches to handle USB autosuspend problems. He noted that the patches were intended for inclusion in the upcoming 2.6.23 kernel, "a number of patches have been submitted near the end of this kernel release cycle that add new device ids to the quirk table in the kernel to disable autosuspend for specific devices. However, a number of developers are very worried that even with the testing that has been done, once 2.6.23 is released, we are going to get a whole raft of angry users when their devices break in nasty ways." He proved an example, "it seems that almost 2/3 of all USB printers just can not handle autosuspend. And there's a _lot_ of USB printers out there..."

Later in the discussion, Linux creator Linus Torvalds commented, "in general, I think the USB blacklist/whitelists are generally a sign of some deeper bug." He continued on to point out a number of quirks in the USB layer that need to be addressed and added:

"We used to have a lot of those things due to simply incorrect SCSI probing, causing devices to lock up because Linux probed them with bad or unexpected modepages etc. I suspect we still have old blacklist entries from those days that just never got cleaned up, because nobody ever dared remove the blacklist entry.

"We should strive to make the default behaviour be so safe that we never need a black-list (or a whitelist), and basically consider blacklists to be not a way to 'fix up a device', but a way to avoid some really serious AND *RARE* error."

"With all the tickless [story] and other goodies going into the kernel in the last few months, there is a lot of hope that this helps Linux reduce power consumption," Arjan van de Ven began on the lkml, "and the good news is that it does... once you fix some bugs and fix a bunch of userspace applications." He referred to a promising graph generated utilizing the recently introduced PowerTOP utility [story], measuring power consumption before and after applying a series of related bug fixes.

The tests began with a Lenovo T61 laptop running the stock 32-bit Fedora 7 kernel which includes the tickless kernel. This was compared against the stock 2.6.22-rc4 kernel with a series of improvements including a fix for the Ondemand CPUFREQ governor, the new CPUIDLE infrastructure, the Active Link Power Management patch, disabling the laptop's TV-out capability, and using a cli utility to properly reduce the laptop's backlight. Arjan summarizes, "with kernel fixes and features, the power consumption of this laptop went from 21.06 Watts to 18.25 Watts; with 2 additional userspace fixes the power consumption ended up at 15.5 Watts."