Re: [PATCH 1/1] leds: ledtrig-tty.c: call led_set_brightness() when the blocking callback is not available

[Jacek Anaszewski]

Hi all,

On 1/4/23 17:20, Lee Jones wrote:
> On Fri, 09 Dec 2022, Uwe Kleine-König wrote:
>
> > On Fri, Dec 09, 2022 at 10:10:38AM +1000, Qingtao Cao wrote:
> > > The Marvell GPIO controller's driver will setup its struct gpio_chip's can_sleep
> > > false, making create_gpio_led() setting up the brightness_set function pointer
> > > instead of the brightness_set_blocking function pointer. In this case the
> > > nonblocking version led_set_brightness() should be fallen back on by ledtrig_tty_work()
> > >
> > > Signed-off-by: Qingtao Cao <qingtao.cao@xxxxxxxx>
> > > ---
> > >   drivers/leds/trigger/ledtrig-tty.c | 10 ++++++++--
> > >   1 file changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
> > > index f62db7e520b5..e43d285b5d06 100644
> > > --- a/drivers/leds/trigger/ledtrig-tty.c
> > > +++ b/drivers/leds/trigger/ledtrig-tty.c
> > > @@ -122,12 +122,18 @@ 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);
> > > +		if (trigger_data->led_cdev->brightness_set_blocking)
> > > +			led_set_brightness_sync(trigger_data->led_cdev, LED_ON);
> > > +		else if (trigger_data->led_cdev->brightness_set)
> > > +			led_set_brightness(trigger_data->led_cdev, LED_ON);
> >
> > I had similar issues in the past where a function call worked for
> > sleeping LEDs but not atomic ones (or the other way around? Don't
> > remember the details.)
> >
> > I wonder if there isn't a function that does the right thing no matter
> > what type the LED is. The other triggers should have the same issue, and
> > doing the above check in all of them just looks wrong.
>
> Anyone fancy taking a deeper dive into this?
>
> I'd usually have a go myself, but I'm presently swamped.
>
> Pavel already has an idea?

There is led_set_brightness_nosleep() and it should be used here
from the beginning. Generally it should be used always in triggers.

--
Best regards,
Jacek Anaszewski