Hi, Rafael
Thank for the answer.
2 more things
A) The suspend/resume API assumes that all user space process/kthread
access to driver will be frozen first
This avoids race condition that processes/threads are accessing
driver while suspend()/resume() of the driver is called at the same
time.
Is my understanding correct?
B) I noticed your "Run-time PM framework" patch was submitted recently
Do you think it is fair to allow user space to trigger run-time
suspend/resume for specific device?
Sine the run-time suspend/resume would be system independent per my
understanding.
-----Original Message-----
From: Rafael J. Wysocki [mailto:rjw@xxxxxxx]
Sent: Monday, July 06, 2009 5:31 AM
To: HU TAO-TGHK48
Cc: linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx
Subject: Re: PM interface to suspend/resume
individual/specific device
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
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