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https://github.com/ivabus/speakersafetyd
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43 lines
1.9 KiB
Markdown
43 lines
1.9 KiB
Markdown
## Asahi Linux speaker safety daemon
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This is still very much a work in progress, is probably not "proper" Rust,
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and almost definitely makes competent developers extremely sad.
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We currently rely on a local version of the `alsa` crate, pending the merge of
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bindings to `snd_ctl_elem_value_{read,write}` and `snd_ctl_elem_set_id`.
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## What works
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* Parsing config file
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* All borrows seem to work fine
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* Volume getting/setting
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## Needs improvement
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* Probably everything
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## Need to implement
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* Daemonise and loop
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* Threading (should probably make sure it works as intended first)
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* Getting V/ISENSE (pending changes to the codec drivers, we have mock implementations)
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* Actually fail safe (see below)
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## On failing safe
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We need a way to guarantee safety on _any_ fail condition. The TAS codecs have a safe
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mode which cuts all outputs down by 18 dB. This works out to being about half their
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full output capabiltiy. It might be worth having the `macaudio` driver start them
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explicitly in this mode, and only unlock full output capability with an IOCTL that
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can be sent by `speakersafetyd` when it's sure it has started correctly. We would
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then of course also need an IOCTL to do the opposite if we encounter a runtime error.
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It was suggested by someone on IRC that this would be conducive to some sort of
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keepalive IOCTL, where the driver would automatically put the codecs into safe mode
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if it didn't hear from us for a while. This seems like it would suck to implement.
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Like any SLA, it is likely that we will never be able to guarantee 100% safety for all
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nonstandard setups. The reference PipeWire DSP graph plus this should be enough for 99% of
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users, but I feel at some point those who insist on using Pulse or raw ALSA are just going
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to have to put up with a best effort service and accept the (small) risk of this failing.
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## Sundry
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The `alsa` crate is Copyright (c) 2015-2021 David Henningsson, and other
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contributors. Redistributed under the MIT license.
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