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

Rafael J. Wysocki
2012-11-24T22:03:00Z

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.
>
> 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?
>
> > Signed-off-by: Toshi Kani <toshi.kani@hp.com>
> > ---
> > drivers/acpi/bus.c | 64 ++++++++++++++++++++++++++++----------
> > drivers/acpi/scan.c | 83 +++++++++++++++++++++++++++++++++++++++++++++++++
> > include/acpi/acpi_bus.h | 6 ++++
> > 3 files changed, 137 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
> > index 07a20ee..b256bcf2 100644
> > --- a/drivers/acpi/bus.c
> > +++ b/drivers/acpi/bus.c
> > @@ -779,21 +779,16 @@ void unregister_acpi_bus_notifier(struct notifier_block *nb)
> > EXPORT_SYMBOL_GPL(unregister_acpi_bus_notifier);
> >
> > /**
> > - * acpi_bus_notify
> > - * ---------------
> > - * Callback for all 'system-level' device notifications (values 0x00-0x7F).
> > + * acpi_bus_sys_notify: Common system notify handler
> > + *
> > + * ACPI drivers may specify this common handler to its sys_notify entry.
> > + * TBD: This handler is not implemented yet.
> > */
> > -static void acpi_bus_notify(acpi_handle handle, u32 type, void *data)
> > +void acpi_bus_sys_notify(acpi_handle handle, u32 type, void *data)
>
> This isn't used anywhere. Are drivers supposed to use it? If so, what about
> the BUS_CHECK and DEVICE_CHECK notifications?
>
> > {
> > - struct acpi_device *device = NULL;
> > - struct acpi_driver *driver;
> > -
> > ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Notification %#02x to handle %p\n",
> > type, handle));
> >
> > - blocking_notifier_call_chain(&acpi_bus_notify_list,
> > - type, (void *)handle);

By the way, there is exacly one user of this chain, which is dock.c.

What about convering that to something different and dropping the chain to
start with?

Rafael

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