Dependency chain of new thermal driver

[Jean Delvare <khali@linux-fr.org>]

Hi Rui,

I am testing your new thermal driver and I am not very happy with the
dependencies introduced by this driver. The ACPI thermal driver selects
the generic thermal driver, which in turn selects the hwmon base
module. As the generic thermal driver's configuration option is a
boolean, this means that as soon as one selects the ACPI thermal driver
(built-in or modular), the hwmon thermal driver has to be built into
the kernel. This is a problem especially when both the ACPI_THERMAL and
THERMAL options default to y.

I fail to see why we are using select at all. The ACPI thermal driver
clearly works without the generic thermal driver (even though the
generic interface is preferred now.) Likewise, the generic thermal
interface driver doesn't need the hwmon base module to work; the hwmon
interface is only an extension, so it should be possible to build the
generic thermal driver without hwmon support. On top of that, I really
would like to be able to build the generic thermal driver as a module.

One of the reasons why I would like this to change is this bug:
https://bugzilla.redhat.com/show_bug.cgi?id=437637
http://bugzilla.kernel.org/show_bug.cgi?id=10259
(At the moment I think both reports are the exact same bug.)

We will have to fix this bug of course (not sure how...) but the fact
that the users can't temporarily remove the generic thermal driver is a
problem both for bug investigation and for working around the bug until
it's fixed. I really would like to be able to tell the user "rmmod this
module until we come up with a fix", but right now I can't.

A more modular setup would give us much more flexibility both at build
time and when bugs are reported. Please think about it.

-- 
Jean Delvare