| From: Pavel Machek<pavel@xxxxxx> | | On Thu 2007-03-22 00:49:51, Dmitry Krivoschekov wrote: | > Amit Kucheria wrote: | > > On 3/21/07, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: | > >> On Wed, 2007-03-21 at 02:30 +0800, Pavel Machek wrote: | > > | > >>> No, that's not how it works; look at hda_audio, it already has | > >>> powersave. Just power down audio card 5 seconds after its control file | > >>> is closed. | > >> It's another case of doing policy in a driver. | > >> | > > | > > IMHO, this kind of policy is best handled inside the driver because it | > > is specific to the hardware. This will ensure that the driver will | > > just work on every distro without some userspace policy being present | > > and setup _correctly_. | > | > It some circumstances this policy may increase power consumption | > but not decrease it. Consider the case of repeatable operation, | | And what... that happens. Lets not break our design because you can | think of very contrieved corner case. | | > something like periodic sound beep, with period of 5s. | > In this case, a driver implementing the policy will periodically | > suspend/resume a number of devices - audio controller, codec, ADC, | > but the operation itself (suspending/resuming) will consume | > more power than power consumed by these devices in case they | > left running for a 5s. In such a case you may want to change | > the predefined value or just disable the policy. | | > Yes, we may just not close a sound device file, but phone | > applications I've seen, do close the file. | | Fix the app, then. --- I would normally call designs that expect important functions (like power on/power off) to happen as side effects of other operations (like opening and closing files) broken to begin with. It's still a bad idea to hide policy inside the driver. There's nothing contrived or corner-case-ish about cyclic operations in a world where media players, animations, etc., are utterly commonplace. And latency may be ignorable in a laptop environment, but it absolutely isn't in embedded devices, which users expect to operate immediately, as though they were gear-driven rather than computer-driven. scott -- scott preece motorola mobile devices, il67, 1800 s. oak st., champaign, il 61820 e-mail: preece@xxxxxxxxxxxx fax: +1-217-384-8550 phone: +1-217-384-8589 cell: +1-217-433-6114 pager: 2174336114@xxxxxxxxx _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
