Re: PM interface to suspend/resume individual/specific device

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Sunday 05 July 2009, HU TAO-TGHK48 wrote:
> Below command would suspend all of devices and system
> # echo mem > /sys/power/state  
> 
> How to just suspend/resume one specific devices? E.g.
> /sys/devices/platform/serial8250
> 
> It would be useful to test the stability of PM interface of individual
> driver.
> If drivers called earlier refuse to suspend then not able to reach the
> suspend/resume function of the specific driver.
> 
> And it would be useful for automatic testing since a script can
> suspend/resume the specific device for many times without manual
> operation.
> 
> Is it possible to add "state" for each device?
> E.g. 
> # echo mem > /sys/devices/platform/serial8250/power/state

No, and you can't suspend individual devices in general.  There is such a
mechanism for USB devices.

The problem is that suspend while entering a system sleep state is generally
a different operation from a suspend done at run time and the latter wouldn't
be suitable for testing the former.

If you need to test the suspend-resume of a driver, please use the
/sys/power/pm_test interface (it works on the entire system, but it doesn't
complete the suspend, so it's suitable for testing).

Thanks,
Rafael