Allow changing MagSafe LED behavior

[nicolasmaia]

Some MacOS tools like battery allow for customizing the MagSafe LED behavior:
https://stackoverflow.com/questions/75738532/control-magsafe-leds-on-apple-silicon-macbook/77815493#77815493

Currently on Apple silicon under Asahi Linux, if you use this extension in Max Lifespan mode, the LED never changes from orange (indicating charging) to green (indicating fully charged). It would be handy to allow for the LED to change to green when the maximum charging threshold was reached, if not by default then at least as a Settings option.

[maniacx]

I don’t think there’s a safe or supported way to directly use SMC commands from Linux in user space. Even if it were possible, I would avoid invoking SMC operations directly from a GNOME extension, since that would bypass kernel mediation and could be unsafe or lead to undefined behavior.

The correct approach would be for Asahi Linux to expose this functionality through a kernel driver, ideally via a standard sysfs interface. For example, something like:

/sys/class/leds/charging_led/

That would allow user space (including extensions) to safely read or modify the charging LED state using the existing LED subsystem.

It’s possible this is already implemented, but I don’t currently have an Asahi Linux system to verify. A quick scan into few of drivers didn’t reveal anything obvious, but it may still exist under a different name.

If it hasn’t been implemented yet, it would need to be added in the kernel. Since the SMC keys and values are already documented here:
https://asahilinux.org/docs/hw/soc/smc/#smc-keys

They could add key for charging led as described here
https://stackoverflow.com/questions/75738532/control-magsafe-leds-on-apple-silicon-macbook/77815493#77815493

this should be feasible, assuming the relevant hardware models and behavior are clearly identified.

I’d recommend opening an issue with the Asahi Linux project:
https://github.com/AsahiLinux/linux/issues

Include as much detail as possible:

• Device model(s) where this feature is supported
• Expected LED behavior (charging, full, at threshold.)
• Relevant SMC keys and values
• Any documentation or reverse-engineering references

Post this link as well
https://stackoverflow.com/questions/75738532/control-magsafe-leds-on-apple-silicon-macbook/77815493#77815493

With sufficient information, it should be straightforward for them to expose this via sysfs.

If/when Asahi Linux provides a proper sysfs interface for this, I can then add support in my GNOME extension to control the charging LED behavior.

[nicolasmaia]

@maniacx
Thank you for the detailed response.
I created an issue with the Asahi project here: AsahiLinux/linux#475
I wasn't able to give more detailed information since I'm also not very familiar with this at this point.