Pavel Machek wrote: ... >>In most of the cases I'm thinking of, it wouldn't be a user >>requesting a state but rather software (say, a cell phone >>progressively entering lower power states due to inactivity). I >>haven't noticed a platform with more than 3 low-power modes so far, > > > Are not your power states more like cpu power states? > These are expected to be system states, and sleeping system > does not take calls, etc... There's a great variety of behaviors and usage models out there, not sure I can draw a useful distinction between cpu power states vs. system states, but the net effect could be considered to be approximately the same in typical embedded uses: the drivers are called to place appropriate devices in a low(er)-power state, various platform thingies are slowed or powered off, and the system stops waiting for something to wake it up. In some cases the system does not wake up until an explicit user action (button press, etc.), but more commonly wake-on-device-activity (including ring from telephony unit) or time-based actions (including wake on alarm from event in user's datebook) is also wanted (rather like wake-on-LAN et al). I don't think this would correspond well to hardware-managed CPU power states like ACPI C states, for example. Thanks, -- Todd
