Re: [PATCH v3 1/4] ACPI: Support system notify handler via .sys_notify

Rafael J. Wysocki
2012-11-24T22:33:27Z

On Saturday, November 24, 2012 11:01:56 PM Rafael J. Wysocki wrote:
> On Thursday, November 08, 2012 01:23:44 PM Toshi Kani wrote:
> > Added a new .sys_notify interface, which allows ACPI drivers to
> > register their system-level (ex. hotplug) notify handlers through
> > their acpi_driver table. This removes redundant ACPI namespace
> > walks from ACPI drivers for faster booting.
> >
> > The global notify handler acpi_bus_notify() is called for all
> > system-level ACPI notifications, which then calls an appropriate
> > driver's handler if any. ACPI drivers no longer need to register
> > or unregister driver's handler to each ACPI device object. It also
> > supports dynamic ACPI namespace with LoadTable & Unload opcode
> > without any modification in ACPI drivers.
> >
> > Added a common system notify handler acpi_bus_sys_notify(), which
> > allows ACPI drivers to set it to .sys_notify when this function is
> > fully implemented.
>
> I don't really understand this.
>
> > It removes functional conflict between driver's
> > notify handler and the global notify handler acpi_bus_notify().
> >
> > Note that the changes maintain backward compatibility for ACPI
> > drivers. Any drivers registered their hotplug handler through the
> > existing interfaces, such as acpi_install_notify_handler() and
> > register_acpi_bus_notifier(), will continue to work as before.
>
> I really wouldn't like to add new callbacks to struct acpi_device_ops, because
> I'd like that whole thing to go away entirely eventually, along with struct
> acpi_driver.
>
> Moreover, in this particular case, it really is not useful to have to define
> a struct acpi_driver so that one can register for receiving system
> notifications from ACPI. It would be really nice if non-ACPI drivers, such
> as PCI or platform, could do that too.

Which they do by using acpi_install_notify_handler() directly.

> Besides, acpi_os_execute_deferred() is always run on CPU0, because of some
> SMI-related peculiarity, which is not very efficient as far as the events
> handling is concerned, but we can improve the situation a bit by queing the
> execution of the registered handlers in a different workqueue. Maybe it's
> worth considering if we're going to change this code anyway?

Well, perhaps we really don't need to change it after all? Maybe we can just
switch everyone to using acpi_install_notify_handler() and then we can just
drop that code entirely?

Thanks,
Rafael

--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.