Re: [RFC][Update 2][PATCH 2/4] ACPI / PM: Expose reference count values of ACPI power resources

Greg Kroah-Hartman
2013-01-21T20:54:04Z

On Mon, Jan 21, 2013 at 02:05:47PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> Since ACPI power resources are going to be used more extensively on
> new hardware platforms, it becomes necessary for user space (powertop
> in particular) to observe some properties of those resources for
> diagnostics purposes.
>
> For this reason, export the reference counts of ACPI power resources
> to user space by adding a new reference_count attribute to the sysfs
> directory representing each power resource. The value read from
> that attribute represents the number of devices using the power
> resource at the given time. If that value is 0, it meas that the
> power resource is not used and therefore it has been turned off.

Why does userspace need to know a reference count? Is it so that if it
is not 0, it can work to try to lower it to 0? Or something else?

thanks,

greg k-h