On So 07-01-06 03:36:02, Adam Belay wrote: > On Wed, Jan 04, 2006 at 10:34:05PM +0100, Pavel Machek wrote: > > On Út 27-12-05 20:22:04, Patrick Mochel wrote: > > We want _common_ values, anyway. So, we do not want "D0", "D1", "D2", > > "D3hot" in PCI cases. We probably want "on", "D1", "D2", "suspend", > > and I'm not sure about those "D1" and "D2" parts. Userspace should not > > have to know about details, it will mostly use "on"/"suspend" anyway. > > > > > > One day, when we find device that needs it, we may want to add more > > > > states. I don't know about such device currently. > > > > > > There are many devices already do - there are PCI, PCI-X, PCI Express, > > > ACPI devices, etc that do. But, you simply cannot create a single > > > decent > > > > I asked for an example. > > Look at the ACPI spec, it has several examples... > > 1.) most sound cards have more than two states. (once again latency over > power savings trade offs) What is the latency in typical "most sound card" case? > 2.) many PCI devices with wake support use different D-levels depending > on wake settings ...can be done internally in driver. > 4.) IDE hard drives and other storage media have "sleep", "suspend", > etc. Yep; but spindown takes 5 seconds, so if you need to reset ide bus or not to get it back is driver detail. Plus notice how power consuption in sleep and suspend is almost same; motor not running is big deal there. Ouch and hdparm already handles these. > 5.) SATA controllers have more states than just "on" and "off". Also > these states are independent of the PCI d-states. ...so "bus provides list of states" ideas do not really work. > 6.) many video cards implement D1 and D2 as you've already seen. This > is often more a matter of "we only know how to restore from such and such > states" Excatly, so "on"/"off" is enough for them. > 7.) Many processors support of wealth of different power states Processors are handled specially, anyway. Pavel -- Thanks, Sharp!
