[PATCH] leds: trigger/tty: Use led_set_brightness() to support all use cases

[PATCH] leds: trigger/tty: Use led_set_brightness() to support all use cases

[Juergen Borleis]

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@pengutronix.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);
 	}
 
 out:
-- 
2.20.1

Re: [PATCH] leds: trigger/tty: Use led_set_brightness() to support all use cases

[Pavel Machek]

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On Mon 2021-05-03 11:25:42, 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.

Really? I'd need to check.

> 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.

Yeah, but that is not what we want. We are already running in the
workqueue.

We really should have a API that can be called from process context,
and just simply sets the brightness.

Best regards,
								Pavel
-- 
http://www.livejournal.com/~pavelmachek

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Re: [PATCH] leds: trigger/tty: Use led_set_brightness() to support all use cases

[Uwe Kleine-König]

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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@pengutronix.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).)

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH] leds: trigger/tty: Use led_set_brightness() to support all use cases

[Lee Jones]

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@pengutronix.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]

Re: [PATCH] leds: trigger/tty: Use led_set_brightness() to support all use cases

[Lee Jones]

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@pengutronix.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]