linux-kernel - Re: [PATCH RFC] leds: Add support for per-LED device triggers

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Date:   Wed, 15 Jul 2020 19:07:27 +0200
From:   Marek Behún <marek.behun@....cz>
To:     Pavel Machek <pavel@....cz>
Cc:     Ondrej Jirman <megous@...ous.com>, linux-kernel@...r.kernel.org,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Dan Murphy <dmurphy@...com>,
        "open list:LED SUBSYSTEM" <linux-leds@...r.kernel.org>
Subject: Re: [PATCH RFC] leds: Add support for per-LED device triggers

On Sat, 11 Jul 2020 12:04:09 +0200
Pavel Machek <pavel@....cz> wrote:

> What about this? Should address Marek's concerns about resource use...
> 
> Best regards,
>      	   	 				       		Pavel
> 

...

> @@ -280,7 +291,8 @@ int led_trigger_register(struct led_trigger *trig)
>  	down_write(&triggers_list_lock);
>  	/* Make sure the trigger's name isn't already in use */
>  	list_for_each_entry(_trig, &trigger_list, next_trig) {
> -		if (!strcmp(_trig->name, trig->name)) {
> +		if (!strcmp(_trig->name, trig->name) &&
> +		    (!_trig->private_led || _trig->private_led ==
> trig->private_led)) { up_write(&triggers_list_lock);
>  			return -EEXIST;
>  		}

Hi Pavel,

Your proposal does not add private_led member to struct led_trigger. I
think you forgot to change this from Ondrej's proposal.
This should instead check:
  the names are same and both trigger have the same type (either none
  or same). In that case return -EEXIST.

Also a couple of lines below there is code for enabling this trigger
for LEDs that have it set as default trigger. There should also be a
check whether the trigger is relevant.

In the linux/leds.h header the trigger_type in led_classdev should be
inside the CONFIG_LEDS_TRIGGERS block.

I will send new version with an example usage for a Marvell PHY driver.

Marek