linux-kernel - Re: [linux-pm] [RFC][PATCH 1/2] Introduce struct syscore

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Date:	Thu, 10 Mar 2011 11:42:07 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	LKML <linux-kernel@...r.kernel.org>, Greg KH <gregkh@...e.de>,
	Jesse Barnes <jbarnes@...tuousgeek.org>, mingo@...hat.com,
	"H. Peter Anvin" <hpa@...or.com>,
	Kay Sievers <kay.sievers@...e.de>,
	Linux PM mailing list <linux-pm@...ts.linux-foundation.org>,
	tglx@...utronix.de
Subject: Re: [linux-pm] [RFC][PATCH 1/2] Introduce struct syscore_ops and related functionality

On Thursday, March 10, 2011, Alan Stern wrote:
> On Thu, 10 Mar 2011, Rafael J. Wysocki wrote:
> 
> > Some subsystems need to carry out suspend/resume and shutdown
> > operations with one CPU on-line and interrupts disabled.  The only
> > way to register such operations is to define a sysdev class and
> > a sysdev specifically for this purpose which is cumbersome and
> > inefficient.  Moreover, the arguments taken by sysdev suspend,
> > resume and shutdown callbacks are practically never necessary.
> > 
> > For this reason, introduce a simpler interface allowing subsystems
> > to register operations to be executed very late during system suspend
> > and shutdown and very early during resume in the form of
> > strcut syscore_ops objects.
> 
> ...
> 
> > Index: linux-2.6/drivers/base/syscore.c
> > ===================================================================
> > --- /dev/null
> > +++ linux-2.6/drivers/base/syscore.c
> 
> It's true that the existing sys.c file lies in drivers/base; this is
> presumably because it handles a bunch of class-related registration
> stuff.  Now you're getting rid of all that, leaving just the
> power-related operations, so doesn't it make more sense to put this
> file in drivers/base/power?

I didn't, because shutdown() doesn't really belong in there (well, depending).

> > +/**
> > + * syscore_suspend - Execute all the registered system core suspend callbacks.
> > + *
> > + * This function is executed with one CPU on-line and disabled interrupts.
> > + */
> > +int syscore_suspend(void)
> > +{
> > +	struct syscore_ops *ops;
> > +
> > +	list_for_each_entry_reverse(ops, &syscore_ops_list, node)
> > +		if (ops->suspend) {
> > +			int ret = ops->suspend();
> > +			if (ret) {
> > +				pr_err("PM: System core suspend callback "
> > +					"%pF failed.\n", ops->suspend);
> > +				return ret;
> 
> If an error occurs, you need to go back and resume all the things that
> were suspended.  At least, that's what the code in sysdev_suspend does.

Right, thanks a lot!

> > +			}
> > +		}
> > +
> > +	return 0;
> > +}

Rafael
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