Hardware blink and brightness

Hardware blink and brightness

[Tony Makkiel]

Hi,
	Is there any particular reason to stipulate, (hardware) blink should be turned off, when brightness is set to 0? Following is copied from "Documentation/leds/leds-class.txt"

"Setting the brightness to zero with brightness_set() callback function
should completely turn off the LED and cancel the previously programmed
hardware blinking function, if any."

The chip driver could also use other methods for the same, keeping brightness independent of blink.

For example,  delay_on/off 
 delay_off=0 ==> blink off, led on.
 delay_on=0  ==> blink off, led off.

Or am I overlooking something?

Many Thanks,
Tony

Re: Hardware blink and brightness

[Jacek Anaszewski]

Hi Tony,

On 05/19/2016 05:57 PM, Tony Makkiel wrote:
> Hi,
> 	Is there any particular reason to stipulate, (hardware) blink should be turned off, when brightness is set to 0? Following is copied from "Documentation/leds/leds-class.txt"
>
> "Setting the brightness to zero with brightness_set() callback function
> should completely turn off the LED and cancel the previously programmed
> hardware blinking function, if any."
>
> The chip driver could also use other methods for the same, keeping brightness independent of blink.
>
> For example,  delay_on/off
>   delay_off=0 ==> blink off, led on.
>   delay_on=0  ==> blink off, led off.
>
> Or am I overlooking something?

Setting brightness to zero not only disables blinking but also
any other active trigger. Besides, would it make sense to have
blinking enabled with brightness set to 0?

Anyway, we have to keep this interface as-is so as not to break
existing users of the LED API.

-- 
Best regards,
Jacek Anaszewski

Re: Hardware blink and brightness

[Tony Makkiel]

On 20/05/16 08:25, Jacek Anaszewski wrote:
> Hi Tony,
> 
> On 05/19/2016 05:57 PM, Tony Makkiel wrote:
>> Hi,
>>     Is there any particular reason to stipulate, (hardware) blink should be turned off, when brightness is set to 0? Following is copied from "Documentation/leds/leds-class.txt"
>>
>> "Setting the brightness to zero with brightness_set() callback function
>> should completely turn off the LED and cancel the previously programmed
>> hardware blinking function, if any."
>>
>> The chip driver could also use other methods for the same, keeping brightness independent of blink.
>>
>> For example,  delay_on/off
>>   delay_off=0 ==> blink off, led on.
>>   delay_on=0  ==> blink off, led off.
>>
>> Or am I overlooking something?
> 
> Setting brightness to zero not only disables blinking but also
> any other active trigger. Besides, would it make sense to have
> blinking enabled with brightness set to 0?

I agree brightness set to 0, should turn off led. I was thinking of 
case when user turns led back ON with a brightness value. Ideally 
led comes back on blinking as was configured previously(making, 
brightness and blink independent). At present, once the brightness 
is set, blink also needs to be reconfigured. 

> 
> Anyway, we have to keep this interface as-is so as not to break
> existing users of the LED API. 

I see your point now, Thank you. I was under the wrong impression, this 
could be achieved without code change.

Initially, I thought of using delay_on/delay_off, to turn 
off blink. But with this approach, even if it will save a step 
initially (no need to reconfigure blink), will add additional 
step (re-enable trigger) to disable blink. 
>