powerpc/pseries: Introduce api_version to migration sysfs interface

[Michael Ellerman]

On Thu, 2015-05-03 at 02:25:38 UTC, Tyrel Datwyler wrote:
> The /sys/kernel/mobility/migration interface was added all the way back
> in 2.6.37. However, the drmgr userspace tool was never augmented to use
> this interface to perfrom migrations. Instead it has continued using a
> faux rtas call coupled with performing the device tree update processing
> in userspace and communicating it back to the kernel via the ugly
> /proc/ppc64/ofdt interface.
> 
> Up until 3.12 the device tree update code in the kernel was badly broken
> and bit rotting. This code was fixed in 3.12 and is now utilized by the
> kernel suspend code as of 3.15. The kernel is now better suited to
> handle the post-mobility fixup of the device tree and drmgr should be
> transitioned to using the sysfs migration interface.
> 
> This patch introduces the api_version sysfs file to /sys/kernel/mobility
> as a means for drmgr to query the current implementation level of the
> kernel migration code. This initial versioning indicates it is capable
> of perfroming all current PAPR requirements for migration including the
> post-mobility firmware activation and device tree update.

I've put this in next.

Please send a follow-up patch that adds documentation for this and the other
sysfs files in Documentation/ABI.

cheers