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From: Lars-Peter Clausen <>
To: Gregor Boirie <>,
	Jonathan Cameron <>,
	Jonathan Cameron <>,
Subject: Re: using monotonic clok for timstamping
Date: Tue, 9 Feb 2016 21:52:06 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On 02/09/2016 12:06 PM, Gregor Boirie wrote:
> To sump up, implementing timestamping clock selection support in IIO
> should be based on the following principles.
> Selected timestamping clock is a per-device attribute which the userspace
> may access through a sysfs file.
> It must be applicable to both buffered samples and events.

Just playing out ideas here to make sure we have everything covered, but
could be there be a setup where you'd want different timestamps for events
and buffers?

> Userspace may choose amongst a subset of available POSIX clocks. A good
> starting point would be: CLOCK_REALTIME, CLOCK_MONOTONIC,
> Please delete as appropriate if needed and see clock_gettime(2).
> One remaining question is : how do we ensure sample and event timestamps
> consistency with respect to clock changes ? 2 suggestions:
> * reject the ability to select a new clock as long as an events chardev is
> opened
>   or a buffered samples channel is enabled ;
> * clock may be changed at any time since it could be implemented in an atomic
>   way (a simple atomic_t can hold an int / clockid_t if I'm no wrong).

Not sure if we need to prevent it. If somebody changes it during an active
measurement it is their problem I'd say.

  parent reply	other threads:[~2016-02-09 20:52 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-03 10:55 Gregor Boirie
2016-02-03 11:22 ` Lars-Peter Clausen
2016-02-06 18:33   ` Jonathan Cameron
2016-02-08  9:55     ` Lars-Peter Clausen
2016-02-08 17:15       ` Jonathan Cameron
2016-02-09 11:06         ` Gregor Boirie
2016-02-09 14:19           ` Gregor Boirie
2016-02-09 20:49             ` Jonathan Cameron
2016-02-09 20:52           ` Lars-Peter Clausen [this message]
2016-02-09 21:02             ` Jonathan Cameron
2016-02-10  9:46             ` Gregor Boirie

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