Re: [RFC][PATCH 2/2] PM: Remove saved_state from dev_pm_info

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

On Sunday, 10 June 2007 16:32, Alan Stern wrote:
> On Sat, 9 Jun 2007, Rafael J. Wysocki wrote:
> 
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> > 
> > The saved_state member of struct dev_pm_info, defined in include/linux/pm.h, is
> > not used anywhere, so it can be removed.
> 
> Along the same lines, feature_removal_schedule.txt says that 
> dev->power.power_state will be removed next month.  In preparation, 
> you could consider removing the prev_state member now.  As far as I 
> know, it isn't used for anything other than avoiding resume method 
> calls to devices that were already suspended when a system sleep 
> began.

Yes, I considered that too, but I decided to leave if for now in case something
depended on it.

I'll take another look. ;-)

> I suggest that suspend and resume always be called for every device
> during a system sleep transition, regardless of the device's state.

That's reasonable, I think.

> That will have to done anyway once dev->power.power_state is gone.

Besides, that would fix the issue with the current code that if
dev->class->suspend() changes dev->power.power_state.event  to 'off',
then dev->bus->suspend() is not called, but dev->bus->resume() will be called
during the subsequent resume.

> The idea is that drivers should regard these method calls as
> notifications that the system is about to go to sleep or has just woken
> up, rather than as directives to put their device into a particular
> state.
> 
> Thus, if a driver knows that its device was already in a low-power
> state before the system sleep then it need not respond to a resume
> method call by switching the device to a high-power state.  Instead the
> driver should be free to take whatever action it thinks is appropriate.
> This is already explained in Documentation/power/devices.txt.

OK

I'll prepare a patch to remove the dev->power.power_state.event checks from the
suspend core code.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth