Re: [chrony-dev] Support for Multiple PPS Inputs on single PHC

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On 2/20/23 7:24 AM, Richard Cochran wrote:
On Mon, Feb 20, 2023 at 11:08:23AM +0100, Miroslav Lichvar wrote:
Does it need to be that way? It seems strange for the kernel to
support enabling PPS on multiple channels at the same time, but not
allow multiple applications to receive all samples from their channel.

It does not need to be that way, but nobody ever wanted multiple
readers before.

Implementing this would make the kernel side much more complex, as the
code would need per-reader tracking of the buffered time stamps, or
per-reader fifo buffers, etc.

There's two separate questions here - multiple readers receiving the same data, and multiple readers receiving data exclusively about one channel.

I'd imagine the second is (much?) easier to implement, whereas the first is a bunch of complexity.

At least personally I'm okay with the second, rather than the first, and that fixes the issue for chrony, though it doesn't allow one to, say, get raw samples in one program while having another handle them.

Matt

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