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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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