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    SubjectRe: [PATCH v3 1/4] ACPI: Support system notify handler via .sys_notify
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    On Mon, 2012-11-26 at 14:09 -0700, Toshi Kani wrote:
    > On Mon, 2012-11-26 at 21:44 +0100, Rafael J. Wysocki wrote:
    > > On Monday, November 26, 2012 12:06:39 PM Toshi Kani wrote:
    > > > On Sat, 2012-11-24 at 23:37 +0100, Rafael J. Wysocki wrote:
    > > > > 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.
    > > >
    > > > By using acpi_install_notify_handler(), each driver needs to walk
    > > > through the entire ACPI namespace to find its associated ACPI devices
    > > > and call it to register one by one. I think this is more work for
    > > > non-ACPI drivers than defining acpi_driver.
    > >
    > > I'm not really sure what you mean. The drivers in question already know
    > > what the relevant ACPI device nodes are (because they need them anyway
    > > for other purposes), so they don't need to look for them specifically and
    > > acpi_install_notify_handler() doesn't do any namespace walking. So what
    > > you said above simply doesn't make sense from this viewpoint.
    >
    > Yes, if drivers already know the relevant ACPI devices, then walking the
    > ACPI namespace is not necessary. I was referring the case like
    > processor_driver.c, acpi_memhotplug.c, and container.c in my statement.

    BTW, when an ACPI device is marked as non-present, which is the case
    before hot-add, we do not create an acpi_device object and therefore do
    not bind it with a driver. This is why these drivers walk the ACPI
    namespace and install their notify handlers regardless of device status.

    Thanks,
    -Toshi









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