Bug#992184: linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT be builtin?

From	Diederik de Haas <didi.debian@cknow.org>
Newsgroups	linux.debian.bugs.dist, linux.debian.kernel
Subject	Bug#992184: linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT be builtin?
Date	2021-08-15 13:10 +0200
Message-ID	<CMmbE-Q3-5@gated-at.bofh.it> (permalink)
Organization	Connecting Knowledge

Cross-posted to 2 groups.

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Source: linux
Version: 5.13.9-1~exp2
Severity: wishlist

Currently there are some LED triggers builtin and some as modules:

$ grep 'CONFIG_LEDS_TRIGGER' /boot/config-5.13.0-trunk-arm64 
CONFIG_LEDS_TRIGGERS=y
CONFIG_LEDS_TRIGGER_TIMER=m
CONFIG_LEDS_TRIGGER_ONESHOT=m
CONFIG_LEDS_TRIGGER_DISK=y
CONFIG_LEDS_TRIGGER_MTD=y
CONFIG_LEDS_TRIGGER_HEARTBEAT=m
CONFIG_LEDS_TRIGGER_BACKLIGHT=m
CONFIG_LEDS_TRIGGER_CPU=y
CONFIG_LEDS_TRIGGER_ACTIVITY=m
CONFIG_LEDS_TRIGGER_GPIO=m
CONFIG_LEDS_TRIGGER_DEFAULT_ON=m
CONFIG_LEDS_TRIGGER_TRANSIENT=m
CONFIG_LEDS_TRIGGER_CAMERA=m
CONFIG_LEDS_TRIGGER_PANIC=y
CONFIG_LEDS_TRIGGER_NETDEV=m
CONFIG_LEDS_TRIGGER_PATTERN=m
CONFIG_LEDS_TRIGGER_AUDIO=m
# CONFIG_LEDS_TRIGGER_TTY is not set

While working on
https://salsa.debian.org/kernel-team/linux/-/merge_requests/384
I noticed that after enabling the modules, the heartbeat LED on my
Rock64 didn't turn 'on', while it is defined as the default trigger in
the DeviceTree. I noticed that `/sys/devices/platform/leds/leds/led-1/trigger`
didn't even contain 'heartbeat' as trigger.
After doing `modprobe ledtrig-heartbeat`, 'heartbeat' was available and
automatically selected as the current trigger.
Doing 'modprobe' is inconvenient, but that can be worked around by
creating a file in `/etc/modprobe.d/`.

But I use it in a similar way as 'panic', which is builtin. The Rock64
has a bit of a thermal problem and f.e. compiling a kernel is out of the
question without cooling (which I do not yet have). The CPU/device gets
so hot, it freezes and the only way out is pulling the plug. So when the
'heartbeat' LED stops blinking, I know it crashed.
Like 'panic', but with a slightly different cause.

As mentioned earlier, 'heartbeat' was defined as the default trigger in
the DeviceTree of the Rock64. It turns out, there are a lot more:
diederik@bagend:~/dev/debian/salsa/kernel-team/linux$ 
grep -r 'linux,default-trigger = "heartbeat";' arch/ | wc -l
281

Most are in arch arm*, but also in arc/powerpc/microblaze/mips.

Which raises the question (of this bug): 
Should `CONFIG_LEDS_TRIGGER_HEARTBEAT=m` be changed to `=y`?

Cheers,
  Diederik

PS: kernel is tainted as I'm running 5.13.9-1~exp3 which contain
modifications from MR 384, based off of current 'master'.
PS2: I sent this bug report earlier (against src:linux-config-5.13), but there 
was a problem with bugs.d.o, so I assume it went to /dev/null

-- System Information:
Debian Release: 11.0
  APT prefers stable
  APT policy: (990, 'stable'), (500, 'stable-security'), (500, 'unstable'), 
(101, 'experimental')
Architecture: arm64 (aarch64)

Kernel: Linux 5.13.0-trunk-arm64 (SMP w/4 CPU threads)
Kernel taint flags: TAINT_UNSIGNED_MODULE
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /usr/bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

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Bug#992184: linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT be builtin? Diederik de Haas <didi.debian@cknow.org> - 2021-08-15 13:10 +0200
  Bug#992184: #992184 linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT be builtin? Diederik de Haas <didi.debian@cknow.org> - 2021-09-14 08:30 +0200
    Bug#992184: #992184 linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT be builtin? Diederik de Haas <didi.debian@cknow.org> - 2021-09-24 01:40 +0200
  Processed: Re: #992184 linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT  be builtin? "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-09-14 08:30 +0200
  Processed: Re: #992184 linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT  be builtin? "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-09-24 01:40 +0200
  Bug#992184: marked as done (linux: Should CONFIG_LEDS_TRIGGER_HEARTBEAT  be builtin?) "Debian Bug Tracking System" <owner@bugs.debian.org> - 2021-11-04 10:10 +0100

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