Re: [PATCH v10 04/15] PM / EM: Expose the Energy Model in sysfs

[Ingo Molnar]

* Quentin Perret <quentin.perret@xxxxxxx> wrote:

> Expose the Energy Model (read-only) of all performance domains in sysfs
> for convenience. To do so, add a kobject to the CPU subsystem under the
> umbrella of which a kobject for each performance domain is attached.
> 
> The resulting hierarchy is as follows for a platform with two
> performance domains for example:
> 
>    /sys/devices/system/cpu/energy_model
>    âââ pd0
>    â âââ cost
>    â âââ cpus
>    â âââ frequency
>    â âââ power
>    âââ pd4
>        âââ cost
>        âââ cpus
>        âââ frequency
>        âââ power
> 
> In this implementation, the kobject abstraction is only used as a
> convenient way of exposing data to sysfs. However, it could also be
> used in the future to allocate and release performance domains in a more
> dynamic way using reference counting.
> 
> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Signed-off-by: Quentin Perret <quentin.perret@xxxxxxx>
> ---
>  include/linux/energy_model.h |  2 +
>  kernel/power/energy_model.c  | 90 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 92 insertions(+)

Why is a read-only ABI added for 'convenience'? We really don't do that 
as ABIs are final and they come with responsibilities.

I think if this is for debug purposes it should be declared and put into 
debugfs or so.

If it's for some other purpose that purpose should be declared.

Thanks,

	Ingo