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, 9 Dec 2022 13:40:58 +0100
From:   Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
To:     Qingtao Cao <qingtao.cao.au@...il.com>
Cc:     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 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.

Best regards
Uwe

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

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