Re: [PATCH 1/3] ACPI / dock: Rework the handling of notifications

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

On Friday, June 28, 2013 04:34:21 PM Yinghai Lu wrote:
> On Fri, Jun 28, 2013 at 3:53 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> >
> > The ACPI dock driver uses register_acpi_bus_notifier() which
> > installs a notifier triggered globally for all system notifications.
> > That first of all is inefficient, because the dock driver is only
> > interested in notifications associated with the devices it handles,
> > but it has to handle all system notifies for all devices.  Moreover,
> > it does that even if no docking stations are present in the system
> > (CONFIG_ACPI_DOCK set is sufficient for that to happen).  Besides,
> > that is inconvenient, because it requires the driver to do extra work
> > for each notification to find the target dock station object.
> >
> > For these reasons, rework the dock driver to install a notify
> > handler individually for each dock station in the system using
> > acpi_install_notify_handler().  This allows the dock station
> > object to be passed directly to the notify handler and makes it
> > possible to simplify the dock driver quite a bit.  It also
> > reduces the overhead related to the handling of all system
> > notifies when CONFIG_ACPI_DOCK is set.
> 
> original change to use register_acpi_bus_notifier, have two assumption
> 1.  two dock_station will have same handle.

Well, that would mean that dock_add() might be called twice for the same handle
and I don't see how that's possible.

Moreover, even if that were possible, the loop in acpi_dock_notifier_call()
would break after finding the *first* matching handle anyway, so
acpi_dock_deferred_cb() wouldn't be called for the second dock station with
the same handle, if there were two.

> 2. acpi subsystem: non root acpi device only can have one system
> notifier installed.

No, that limitation is long gone.  We removed it when we were working on ACPI
wakeup support for runtime PM.

Thanks,
Rafael


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