Re: [PATCH 00/10] fujitsu-laptop: use device-specific data instead of module-wide globals

From: MichaÅ KÄpieÅ
Date: Sat May 06 2017 - 08:56:59 EST

> Just to make sure we are all on the same page here, choosing the "two
> separate modules, each with one driver for one ACPI device" approach
> would mean ending up with two modules:
> - fujitsu-laptop, binding to the FUJ02E3 ACPI device, handling
> everything _except_ backlight,
> - fujitsu-backlight, binding to the FUJ02B1 ACPI device, handling
> backlight and depending on fujitsu-laptop.
> We would need to export one function from fujitsu-laptop, namely
> fext_backlight(). I understand this would require creating a separate
> header file which would then be included in fujitsu-backlight.
> fext_backlight() causes the FUNC method of the FUJ02E3 ACPI device to be
> called. This method is marked as Serialized, which AFAIU means we do
> not need a separate lock in kernel code because all calls to this method
> are implicitly serialized by firmware itself.
> I do not see anything "unnatural" in this approach, but I would love to
> be corrected if I am wrong.

To be fair, one thing that may be "unnatural" with this approach is that
even though fujitsu-backlight would depend on fujitsu-laptop, it would
still have to get a handle to FUJ02E3 using:

acpi_get_handle(NULL, "\\_SB.FEXT", ...)

because call_fext_func() - and thus fext_backlight() - needs to be
passed a handle to FUJ02E3 and the two ACPI devices (FUJ02B1 handled by
fujitsu-backlight and FUJ02E3 handled by fujitsu-laptop) are not related
from the perspective of the ACPI device hierarchy. Unless there is a
better way of implementing this, in which case I am open to suggestions.

Best regards,
MichaÅ KÄpieÅ