[net-next,v2,00/13] leds: introduce new LED hw control APIs

Since this series is cross subsystem between LED and netdev,
a stable branch was created to facilitate merging process.

This is based on top of branch ib-leds-netdev-v6.5 present here [1].

This is a continue of [2]. It was decided to take a more gradual
approach to implement LEDs support for switch and phy starting with
basic support and then implementing the hw control part when we have all
the prereq done.

This is the main part of the series, the one that actually implement the
hw control API.

Some history about this feature and why
=======================================

This proposal is highly requested by the entire net community but the API
is not strictly designed for net usage but for a more generic usage.

Initial version were very flexible and designed to try to support every
aspect of the LED driver with many complex function that served multiple
purpose. There was an idea to have sw only and hw only LEDs and sw only
and hw only LEDs.

With some heads up from Andrew from the net mailing list, it was suggested
to implement a more basic yet easy to implement system.

These API strictly work with a designated trigger to offload their
function.
This may be confused with hw blink offload but LED may have an even more
advanced configuration where the entire aspect of the trigger is
offloaded and completely handled by the hardware.

An example of this usage are PHY or switch port LEDs. Almost every of
these kind of device have multiple LED attached and provide info of the
current port state.

Currently we lack any support of them but these device always provide a
way to configure them, from basic feature like turning the LED off or no
(implemented in previous series related to this feature) or even entirely
driven by the hw and power on/off/blink based on some events, like tx/rx
traffic, ethernet cable attached, link speed of 10mbps, 100mbps, 1000mbps
or more. They can also support multiple logic like blink with traffic only
if a particular link speed is attached. (an example of this is when a LED
is designated to be turned on only with 100mbps link speed and configured
to blink on traffic and a secondary LED of a different color is present to
serve the same function but only when the link speed is 1000mbps)

These case are very common for a PHY or a switch but they were never
standardized so OEM support all kind of variant and configuration.

Again with Andrew we compared some feature and we reached a common set
of modes that are for sure present in every kind of devices.

And this concludes history and why.

What is present in this series
==============================

This patch contain the required API to support this feature, I decided on
the name of hw control to quickly describe this feature.

I documented each require API in the related Documentation for leds-class
so I think it might me redundant to expose them here. Feel free to tell me
how to improve it if anything is not clear.

On an abstract idea, this feature require this:

    - The trigger needs to make use of it, this is currently implemented
      for the netdev trigger but other trigger can be expanded if the
      device expose these function. An idea might be a anything that
      handle a storage disk and have the LED configurable to blink when
      there is any activity to the disk.

    - The LED driver needs to expose and implement these new API.

Currently a LED driver supports only a trigger. The trigger should use
the related helper to check if the LED can be driven hy hardware.

The different modes a trigger support are exposed in the kernel include
leds.h header and are used by the LED driver to understand what to do.

On Thu, 25 May 2023 16:53:48 +0200 Christian Marangi wrote:
> This is based on top of branch ib-leds-netdev-v6.5 present here [1].

I merged that PR now, but you'll need to repost.
Build bots don't read English (yet?) so posting patches which can't 
be immediately applied is basically an RFC (and should be marked as
such).

On Thu, May 25, 2023 at 08:43:38PM -0700, Jakub Kicinski wrote:
> On Thu, 25 May 2023 16:53:48 +0200 Christian Marangi wrote:
> > This is based on top of branch ib-leds-netdev-v6.5 present here [1].
> 
> I merged that PR now, but you'll need to repost.
> Build bots don't read English (yet?) so posting patches which can't 
> be immediately applied is basically an RFC (and should be marked as
> such).

Hi, thanks for helping in this! The series already applied directly on
net-next but I sent v3 anyway rebased on latest commit from net-next
just to be sure.