Re: [PATCH v8 00/13] Adds support for PHY LEDs with offload triggers

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 3/9/23 10:09, Linus Walleij wrote:
> Hi Christian,
> 
> thanks for your patch!
> 
> On Thu, Feb 16, 2023 at 2:36 AM Christian Marangi <ansuelsmth@gmail.com> wrote:
> 
>> The current idea is:
>> - LED driver implement 3 API (hw_control_status/start/stop).
>>   They are used to put the LED in hardware mode and to configure the
>>   various trigger.
>> - We have hardware triggers that are used to expose to userspace the
>>   supported hardware mode and set the hardware mode on trigger
>>   activation.
>> - We can also have triggers that both support hardware and software mode.
>> - The LED driver will declare each supported hardware blink mode and
>>   communicate with the trigger all the supported blink modes that will
>>   be available by sysfs.
>> - A trigger will use blink_set to configure the blink mode to active
>>   in hardware mode.
>> - On hardware trigger activation, only the hardware mode is enabled but
>>   the blink modes are not configured. The LED driver should reset any
>>   link mode active by default.
> 
> The series looks good as a start.
> There are some drivers and HW definitions etc for switch-controlled
> LEDs, which is great.
> 
> I am a bit reluctant on the ambition to rely on configuration from sysfs
> for the triggers, and I am also puzzled to how a certain trigger on a
> certain LED is going to associate itself with, say, a certain port.
> 
> I want to draw your attention to this recently merged patch series
> from Hans de Goede:
> https://lore.kernel.org/linux-leds/20230120114524.408368-1-hdegoede@redhat.com/
> 
> This adds the devm_led_get() API which works similar to getting
> regulators, clocks, GPIOs or any other resources.
> 
> It is not yet (I think) hooked into the device tree framework, but it
> supports software nodes so adding DT handling should be sort of
> trivial.

That series contains this (unmerged) patch to hookup DT handling:

https://lore.kernel.org/linux-leds/20230120114524.408368-6-hdegoede@redhat.com/

this was not merged because there are no current users, but adding
support is as easy as picking up that patch :)

Note there also already is a devicetree *only*:

struct led_classdev *of_led_get(struct device_node *np, int index);

Since I was working on a x86/ACPI platform I needed something more
generic though and ideally new code would use the generic approach.

Regards,

Hans





> 
> I think the ambition should be something like this (conjured example)
> for a DSA switch:
> 
>     platform {
>             switch {
>                     compatible = "foo";
> 
>                     leds {
>                             #address-cells = <1>;
>                             #size-cells = <0>;
>                             led0: led@0 {
>                                     reg = <0>;
>                                     color =...
>                                     function = ...
>                                     function-enumerator = ...
>                                     default-state = ...
>                             };
>                             led1: led@1 {
>                                     reg = <1>;
>                                     color =...
>                                     function = ...
>                                     function-enumerator = ...
>                                     default-state = ...
>                             };
>                     };
> 
>                     ports {
>                             #address-cells = <1>;
>                             #size-cells = <0>;
>                             port@0 {
>                                     reg = <0>;
>                                     label = "lan0";
>                                     phy-handle = <&phy0>;
>                                     leds = <&led0>;
>                             };
>                             port@1 {
>                                     reg = <1>;
>                                     label = "lan1";
>                                     phy-handle = <&phy1>;
>                                     leds = <&led0>;
>                             };
>                     };
> 
>                     mdio {
>                             compatible = "foo-mdio";
>                             #address-cells = <1>;
>                             #size-cells = <0>;
> 
>                             phy0: ethernet-phy@0 {
>                                     reg = <0>;
>                             };
>                             phy1: ethernet-phy@1 {
>                                     reg = <1>;
>                             };
>                     };
>             };
>     };
> 
> I am not the man to tell whether the leds = <&led0>; phandle should be on
> the port or actually on the phy, it may even vary. You guys know the answer
> to this.
> 
> But certainly something like this resource phandle will be necessary to
> assign the right LED to the right port or phy, I hope you were not going
> to rely on strings and naming conventions?
> 
> Yours,
> Linus Walleij
>