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

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Date:   Fri, 20 Jan 2023 13:27:50 +0000
From:   Lee Jones <lee@...nel.org>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>
Cc:     Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Qingtao Cao <qingtao.cao.au@...il.com>,
        Qingtao Cao <qingtao.cao@...i.com>,
        Pavel Machek <pavel@....cz>, linux-leds@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] leds: ledtrig-tty.c: call led_set_brightness() when
 the blocking callback is not available

On Sat, 07 Jan 2023, Jacek Anaszewski wrote:

> 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@...i.com>
> > > > ---
> > > >   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.

Thanks for helping to keep an eye on things Jacek.

Much appreciated.

-- 
Lee Jones [李琼斯]