Re: machine_is_dt() ?

On Sun, Jan 06, 2013 at 02:18:05PM +0100, Andrew Lunn wrote:

I'm moving the cpuidle code for Kirkwood into drivers/cpuidle. I'm
following the way cpuidle-calxeda.c instantiates the driver, it uses
module_init(calxeda_cpuidle_init) and calxeda_cpuidle_init() uses
of_machine_is_compatible("calxeda,highbank") so only loading the
driver in a ARCH_MULTIPLATFORM kernel when needed.

I can follow this model for when kirkwood is booted using device
tree. However, i would also like to use the driver for those boards
which are not yet converted to DT. In that situation, we have a kernel
dedicate to kirkwood and the cpuidle driver is always relevant.

Thus i need to code something like:

(of_machine_is_compatible("marvell, kirkwood") ||
 !machine_is_dt())

However, there is no macro machine_is_dt().

Is there a way to tell if a machine has been booted using a machine
number as opposed to DT?

This doesn't seem to me to be the right way to deal with this.  What
you're suggesting would mean that if you built a multiplatform kernel
which included this driver, and booted it on a non-DT platform, you'd
have this driver registered.

It looks to me like many of the CPUFREQ drivers just register themselves
if they've been built into the kernel.  No one's thought about making
them platform drivers or similar, so the current "if it's built-in, then
we use it" approach seems to have persisted.  As many of them are
initialized via a late_initcall(), I don't see any problem with them
being platform drivers, which will solve the problem in a way that's
well established.