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

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Date: Fri, 23 Feb 2024 14:24:42 +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 Fri, 23 Feb 2024, Lee Jones wrote:

> 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.

Starting to think I've gone too far back in the LEDs ML's history? =;-)

-- 
Lee Jones [李琼斯]