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

Rafael J. Wysocki
2012-11-28T18:23:49Z

On Wednesday, November 28, 2012 09:54:43 AM Toshi Kani wrote:
> > > > > > 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.
> >
> > So maybe we should create struct acpi_device objects in that case too?
>
> I think it has some challenge as well. We bind an ACPI driver with
> device_register(), which calls device_add()-> kobject_add(). So, all
> non-present ACPI device objects will show up in sysfs, unless we can
> change the core. This will change user interface. There can be quite
> many non-present devices in ACPI namespace depending on FW
> implementation.

If additional devices appear in sysfs, that's not a problem. If there
were fewer of them, that would be a real one. :-)

Thanks,
Rafael

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