Re: [PATCH v2] leds: ledtrig-morse: send out morse code

From: Jacek Anaszewski
Date: Wed Jul 04 2018 - 16:37:04 EST

Hi All,

On 07/04/2018 08:19 PM, Pavel Machek wrote:

On Wed, Jul 04, 2018 at 08:53:05AM +0200, Pavel Machek wrote:
As I stated before, I don't think morse encoder belongs in kernel.

On the opposite, I think that the kernel needs to be a bit more autonomous
when it comes to reporting its own issues. Being able to report a panic
when userland cannot be accessed for example is the reason why we've seen
various features such as blinking keyboard LEDs for this.

Being able to report panics by blinking would be nice... but proposed
patch does NOT do that.

Actually we do have already drivers/leds/trigger/ledtrig-panic.c.

LED pattern trigger should be merged, instead.

Well, just like we have LED and LED triggers in the kernel, I think having
a generic way to use patterns could be nice and in this case Morse could be
one such pattern, but if that means it's limited to userland to configure
it then it sadly voids all of its benefits.

Proposed patch is already limited to configuration from userland... so
it does not have any benefits.

We could turn this piece of code into a lib and make it usable by
both kernel/panic.c (similar to panic_blink) as well by
the ledtrig-morse.c.

If special "panic blinking" mode is wanted -- I guess that would make


a) trigger may not be right infrastructure for that; triggers need
quite a lot kernel to be working, as they run in separate threads --
panic blinking probably should be mdelay / brightness set / mdelay,
and probably limited to LEDs that can be accessed without sleeping.

b) we may want trigger to be used for something else (Caps lock? HDD
activity?) when not panicked. Thus, again, trigger is not exactly
suitable. (It might make sense to blink many/all LEDs simultaneously
to make it super obvious to the user).


Best regards,
Jacek Anaszewski