Re: [PATCH 6/8] leds: tps68470: Support the WLED driver

[Pavel Machek <pavel@ucw.cz>]

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On Wed 2023-03-22 16:09:24, Daniel Scally wrote:
> The TPS68470 PMIC provides a third LED driver in addition to the two
> indicator LEDs. Add support for the WLED. To ensure the LED is active
> for as long as the kernel instructs it to be we need to re-trigger it
> periodically to avoid the IC's internal timeouts.

Wow. No!

If hardware does not wart you to burn the LED, it is not okay to just
work around that. These are not designed for continuous operation.

> diff --git a/drivers/leds/leds-tps68470.c b/drivers/leds/leds-tps68470.c
> index 44df175d25de..abcd3494b1a8 100644

Fun sha1 hash ;-).

> @@ -52,11 +61,33 @@ enum ctrlb_current {
>  	CTRLB_16MA	= 3,
>  };
>  
> +/*
> + * The WLED can operate in different modes, including a Flash and Torch mode. In
> + * each mode there's a timeout which ranges from a matter of milliseconds to up
> + * to 13 seconds. We don't want that timeout to apply though because the LED
> + * should be lit until we say that it should no longer be lit, re-trigger the
> + * LED periodically to keep it alive.
> + */

We don't want the LED to overheat. That takes precedence.

Find out what are the maximum limits for on time at various current
levels. LED framework should be used for torch mode, with current set
such that unlimited operation is safe. V4L2 should be used for flash
mode.

BR,
										Pavel
-- 
People of Russia, stop Putin before his war on Ukraine escalates.

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