Hi folks, I'm currently searching for all the knobs in kernel and userland to save as much power as possible on a Thinkpad X61s. Some of them are hare to find, some of them must be re-set during runtime, which makes it hard to create power saving setup. Currently, 2 settings cause some headache: 1. USB autosuspend This seems to be split into 2 settings: power/autosuspend and power/level. Some devices seem to be initialized with power/level set to "on". On my Thinkpad, this even leads to a really hot fingerprint reader. I found no way to automatically set power/level to "auto" for all new devices, I always have to set it manually for some devices. 2. Intel wireless power saving The Intel power saving needs to be turned on after the module is loaded, but sometimes I get a write error at the echo 5 > .../power_level and the kernel reports an error. Furthermore, scanning does not work anymore after setting the power_level to 5, and setting it back to 6 only gives an error. I have to reload the module to get it working again. To make it short, it's a bit frustrating. That's why I would like to enforce power saving by default for these settings, but found to way to do it. And while thinking about this, all the other knobs like SATA link power management, PCIE active state power management (in 2.6.26), the cpufreq governors, the power saving settings in the ALSA drivers, laptop mode, Ethernet link speed (on some Intel chips) and maybe more, seem to follow the same pattern: adjust the ballance between performance/latency and power consumption. So how about a global kernel policy where the user can say "I want maximum power saving per default", or "I want maximum performance", and all the currently existing settings make use of that policy to adjust their defaults? It would reduce the mess in the userspace that tries to apply such a policy, and help the user who tries to get the maximum out of the battery of his shiny new laptop. Of cause, it should be possible to exclude certain settings from that policy and leave it in a failsafe default setting, for broken hardware. I think it would be a good start to collect all the currently implemented settings that influence the power consumption in a central place, like somewhere in Documentation/laptops, with some further details what hardware is affected, what performance/latency penalties can happen and possible problems that may occur. Is this a totally new idea, or is there already some work/planning in progress? Regards, Tino -- To unsubscribe from this list: send the line "unsubscribe linux-laptop" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
