Re: [virtio-comment] Re: [PATCH] Reserve device id for GPIO device

["Enrico Weigelt, metux IT consult" <lkml@metux.net>]

On 04.06.21 04:28, Jie Deng wrote:

> Has anyone ever tried to use GPIO in the guest to generate waveform ?
>
> When the frequency reaches a certain level, the waveform will become 
> inaccurate
> due to the delay and uncertainty of the communication time between 
> virtio frontend
> and backend. I'm not sure if any good solution for this case.

Wooow, that's something I didn't ever dared considering. How well that
works heavily depends on actual hardware (even on bare metal) and lots
of other factors.

Even on a bare metal Linux system, I wouldn't want userland do such
things via raw gpio devices - instead have specific (RT capable) kernel
drivers that expose themselves via some fitting hilevel subsys (eg. iio
or pwm). For those use cases, we should have specific protocols.

If it helps, we can add certain metadata, eg. timing constraints to the
line descriptions.


--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287