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:   Sun, 22 Jan 2023 23:18:19 +0100
From:   Jacek Anaszewski <jacek.anaszewski@...il.com>
To:     Lee Jones <lee@...nel.org>
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 1/20/23 14:27, Lee Jones wrote:
> 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.
> 

No problem, I still read the list and can elaborate
on various details of LED subsystem, as needed.

-- 
Best regards,
Jacek Anaszewski