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@xxxxxxxxxxxxxx>
> ---
> 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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