There is a need to access the energy model from the userspace. One such
example is the sched_ext schedulers [1]. The userspace part of the
sched_ext schedules could feed the (post-processed) energy-model
information to the BPF part of the scheduler.

Currently, debugfs is the only way to read the energy model from userspace;
however, it lacks proper notification mechanisms when a performance domain
and its associated energy model change.

This patch set introduces a generic netlink for the energy model, as
discussed in [2]. It allows a userspace program to read the performance
domain and its energy model. It notifies the userspace program when a
performance domain is created or deleted or its energy model is updated
through a multicast interface.

Specifically, it supports two commands:
  - EM_GENL_CMD_PD_GET_ID: Get the list of information for all performance domains.
  - EM_GENL_CMD_PD_GET_TBL: Get the energy model table of a performance domain.

Also, it supports three notification events:
  - EM_GENL_EVENT_PD_CREATE: When a performance domain is created.
  - EM_GENL_EVENT_PD_DELETE: When a performance domain is deleted.
  - EM_GENL_EVENT_PD_UPDATE: When the energy model table of a performance domain is updated.

The userspace code example using the EM netlink interface is at [3].

[1] https://lwn.net/Articles/922405/
[2] https://lore.kernel.org/lkml/a82423bc-8c38-4d57-93da-c4f20011cc92@arm.com/
[3] https://github.com/multics69/em-netlink/tree/patch-v1

CC: Lukasz Luba <lukasz.luba@arm.com>
CC: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
CC: Tejun Heo <tj@kernel.org>
Signed-off-by: Changwoo Min <changwoo@igalia.com>

Changwoo Min (11):
  PM: EM: Add ENERGY_MODEL_NETLINK Kconfig.
  PM: EM: Add a skeleton code for netlink notification.
  PM: EM: Initialize the netlink notification during booting.
  PM: EM: Add the infrastructure for command processing.
  PM: EM: Assign a unique ID when creating a performance domain.
  PM: EM: Expose the ID of a performance domain via debugfs.
  PM: EM: Add an iterator and accessor for the performance domain.
  PM: EM: Implement EM_GENL_CMD_PD_GET_ID.
  PM: EM: Implement EM_GENL_CMD_PD_GET_TBL.
  PM: EM: Implement event notification.
  PM: EM: Notify an event when the performance domain changes.

 include/linux/energy_model.h      |  20 +-
 include/uapi/linux/energy_model.h |  89 ++++++++
 kernel/power/Kconfig              |  10 +
 kernel/power/Makefile             |   1 +
 kernel/power/em_netlink.c         | 324 ++++++++++++++++++++++++++++++
 kernel/power/em_netlink.h         |  45 +++++
 kernel/power/energy_model.c       |  99 ++++++++-
 7 files changed, 586 insertions(+), 2 deletions(-)
 create mode 100644 include/uapi/linux/energy_model.h
 create mode 100644 kernel/power/em_netlink.c
 create mode 100644 kernel/power/em_netlink.h

-- 
2.49.0

Hi Changwoo,

On 5/29/25 01:13, Changwoo Min wrote:
> There is a need to access the energy model from the userspace. One such
> example is the sched_ext schedulers [1]. The userspace part of the
> sched_ext schedules could feed the (post-processed) energy-model
> information to the BPF part of the scheduler.
> 
> Currently, debugfs is the only way to read the energy model from userspace;
> however, it lacks proper notification mechanisms when a performance domain
> and its associated energy model change.
> 
> This patch set introduces a generic netlink for the energy model, as
> discussed in [2]. It allows a userspace program to read the performance
> domain and its energy model. It notifies the userspace program when a
> performance domain is created or deleted or its energy model is updated
> through a multicast interface.
> 
> Specifically, it supports two commands:
>    - EM_GENL_CMD_PD_GET_ID: Get the list of information for all performance domains.
>    - EM_GENL_CMD_PD_GET_TBL: Get the energy model table of a performance domain.
> 
> Also, it supports three notification events:
>    - EM_GENL_EVENT_PD_CREATE: When a performance domain is created.
>    - EM_GENL_EVENT_PD_DELETE: When a performance domain is deleted.
>    - EM_GENL_EVENT_PD_UPDATE: When the energy model table of a performance domain is updated.
> 
> The userspace code example using the EM netlink interface is at [3].
> 
> [1] https://lwn.net/Articles/922405/
> [2] https://lore.kernel.org/lkml/a82423bc-8c38-4d57-93da-c4f20011cc92@arm.com/
> [3] https://github.com/multics69/em-netlink/tree/patch-v1

Thanks for the patch set and for the reference code in user-space.
I will give it a try and then do the review.

Regards,
Lukasz