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SubjectRe: [linux-pm] [RFC][PATCH 1/2] Introduce struct syscore_ops and related functionality
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?

> +/**
> + * 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.

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

Alan Stern



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