Re: [PATCH v11 1/3] rust: add basic serial device bus abstractions

[Markus Probst <markus.probst@posteo.de>]

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On Sun, 2026-05-31 at 23:49 +0200, Danilo Krummrich wrote:
> On Sun May 31, 2026 at 9:42 PM CEST, Markus Probst wrote:
> > I just noticed, is it even possible to use SRCU here? Currently the mutex not
> > only ensures that no drvdata access happens after drvdata drop, but also that
> > the receive_buf waits for the probe to complete, as the drvdata hasn't been
> > initialized yet.
> 
> Yeah, if you drop the completion, you need the mutex.
Is the performance impact on an mutex or on srcu + completion higher?

> 
> (In case it wasn't discussed in previous versions already, there is also the
> option to just attach separate private data to the receive callback, which would
> avoid this synchonization problem in the first place.
> 
> You could have serdev::Device<Core>::open(), which takes its own private data
> and a corresponding close(), this way you'd allow drivers to control whether
> they want the serial line "open" or not. You just need to make sure it is closed
> eventually.)
This would add complexity with types, as we need to ensure that write,
set_baudrate, set_parity etc. does not run when closed.
> 
> That said, I don't know what turns out to be the better approach. And maybe it
> simply isn't something this initial series has to tackle? I think your driver
> does not implement the receive callback?
The initial driver with only leds: no.

That changes once the driver also takes care of hwmon (ADC sensor and
fan failure) and input (power button and possibly other buttons).

Thanks
- Markus Probst

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