linux-kernel - Re: [PATCH] leds: trigger/tty: Use led_set

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Message-ID: <20240223142218.GA1666215@google.com>
Date: Fri, 23 Feb 2024 14:22:18 +0000
From: Lee Jones <lee@...nel.org>
To: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc: Juergen Borleis <jbe@...gutronix.de>, linux-leds@...r.kernel.org,
	Pavel Machek <pavel@....cz>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: [PATCH] leds: trigger/tty: Use led_set_brightness() to support
 all use cases

On Mon, 09 Jan 2023, Uwe Kleine-König wrote:

> Hello Jürgen,
> 
> On Mon, May 03, 2021 at 11:25:42AM +0200, Juergen Borleis wrote:
> > Using led_set_brightness_sync() only works for LEDs which are connected
> > via some kind of external bus like I²C or SPI. But it doesn't work for
> > the simple use case of directly connected LEDs via GPIOs.
> > Because this function only honors the led_classdev::brightness_set_blocking
> > callback. But the LED-GPIO driver registers the
> > led_classdev::brightness_set member if the GPIO can be modified directly
> > and thus, TTY triggers fail silently with -ENOTSUPP.
> > 
> > With the previously used led_set_brightness() it works for both use cases.
> > This function first checks for the simple case where the GPIO can be changed
> > without additional overhead, and if it fails, does the modification via a
> > workqueue.
> > 
> > Signed-off-by: Juergen Borleis <jbe@...gutronix.de>
> > ---
> >  drivers/leds/trigger/ledtrig-tty.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
> > index f62db7e..af61281 100644
> > --- a/drivers/leds/trigger/ledtrig-tty.c
> > +++ b/drivers/leds/trigger/ledtrig-tty.c
> > @@ -122,12 +122,12 @@ static void ledtrig_tty_work(struct work_struct *work)
> >  
> >  	if (icount.rx != trigger_data->rx ||
> >  	    icount.tx != trigger_data->tx) {
> > -		led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
> > +		led_set_brightness(trigger_data->led_cdev, LED_ON);
> >  
> >  		trigger_data->rx = icount.rx;
> >  		trigger_data->tx = icount.tx;
> >  	} else {
> > -		led_set_brightness_sync(trigger_data->led_cdev, LED_OFF);
> > +		led_set_brightness(trigger_data->led_cdev, LED_OFF);
> >  	}
> 
> This problem still exists, right?
> 
> I think the right thing here is to call led_set_brightness_nosleep()
> however.
> 
> Having said that, I think there are too many variants of
> led_set_brightness which makes it difficult to pick the right one.
> 
> (I'm aware of
>  - led_set_brightness_nosleep
>  - led_set_brightness_nopm
>  - led_set_brightness_sync
>  - led_set_brightness
> 
> and there are a few more static variants in led-core.c
> (__led_set_brightness, __led_set_brightness_blocking,
> set_brightness_delayed).)

This patch (and this response) was never sent to me.

Not a great deal I can do if I'm not aware of it.

-- 
Lee Jones [李琼斯]