Re: [PATCH] ACPI: make acpi_bus_register_driver() return zero for success, not device count

[Karol Kozimor <sziwan-DETuoxkZsSqrDJvtcaxF/A@public.gmane.org>]

Thus wrote Bjorn Helgaas:
> pci_register_driver() used to return the number of devices claimed,
> and we made acpi_bus_register_driver() consistent with that.  But
> pci_register_driver() recently changed to return only success/failure
> (because the interface is to register the *driver*, not claim devices,
> and devices may be hot-plugged later).
> 
> So let's do the same with acpi_bus_register_driver().
> 
> Note that asus_acpi.c used to unregister itself if it didn't claim
> any devices.  Now it will remain registered, like everything else
> in drivers/acpi.

Ugh, not again... we've been there (early 2.6.x), done that and it was
absolutely confusing (I mean users reporting bogus bugs just because the
module was loaded type of confusing). Note that there's currently no easy
way to probe for a specific HID in ACPI namespace other than
acpi_bus_register_driver(), and unlike pci_register_driver() the former
has no hotplug mechanism to help. 

That's why at least some distros just plug in every ACPI module that is
kind enough to register on boot. The patch would cause asus_acpi to be
loaded on possibly every ACPI system and that's exactly the type of noise
I'd prefer to avoid (especially that there's no point in registering the
driver to wait for hotplug events in this specific case).

Therefore, while I generally agree with the idea, I'd rather ACPI used
sysfs and hot-/coldplug first so that acpi_bus_register_driver() might be
used in the same way pci_register_driver() is used now.

Of course, I might have become so out of touch with the generic code that
I'm missing something obvious, so please correct me if I'm wrong.

Best regards,

-- 
Karol 'sziwan' Kozimor
sziwan-DETuoxkZsSqrDJvtcaxF/A@public.gmane.org


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