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

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Message-ID: <20200713011544.0adc51f1@nic.cz>
Date:   Mon, 13 Jul 2020 01:15:44 +0200
From:   Marek Behun <marek.behun@....cz>
To:     Ondřej Jirman <megous@...ous.com>
Cc:     Pavel Machek <pavel@....cz>, 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 Mon, 13 Jul 2020 00:38:21 +0200
Ondřej Jirman <megous@...ous.com> wrote:

> Hello,
> 
> On Sun, Jul 12, 2020 at 09:11:11PM +0200, Pavel Machek wrote:
> > Hi!
> >   
> 
> [....]
> 
> >  		}
> > diff --git a/include/linux/leds.h b/include/linux/leds.h
> > index 2451962d1ec5..cba52714558f 100644
> > --- a/include/linux/leds.h
> > +++ b/include/linux/leds.h
> > @@ -57,6 +57,10 @@ struct led_init_data {
> >  	bool devname_mandatory;
> >  };
> >  
> > +struct led_hw_trigger_type {
> > +	int dummy;
> > +}
> > +
> >  struct led_classdev {
> >  	const char		*name;
> >  	enum led_brightness	 brightness;
> > @@ -150,6 +154,8 @@ struct led_classdev {
> >  
> >  	/* Ensures consistent access to the LED Flash Class device */
> >  	struct mutex		led_access;
> > +
> > +	struct led_hw_trigger_type *trigger_type;
> >  };
> >  
> >  /**
> > @@ -345,6 +351,9 @@ struct led_trigger {
> >  	int		(*activate)(struct led_classdev *led_cdev);
> >  	void		(*deactivate)(struct led_classdev *led_cdev);
> >  
> > +	/* LED-private triggers have this set. */
> > +	struct led_hw_trigger_type *trigger_type;
> > +
> >  	/* LEDs under control by this trigger (for simple triggers) */
> >  	rwlock_t	  leddev_list_lock;
> >  	struct list_head  led_cdevs;  
> 
> So after trying to use this, this seems to disallow the use of multiple HW
> triggers per LED. That's fine by me, because using one HW sysfs configured
> trigger per LED that use case is my proposal, but is it desireable in general?

Why? If you register one LED and several triggers, all sharing the same
trigger_type pointer, I think it should work.

Marek