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, > CLOCK_MONOTONIC_RAW, CLOCK_REALTIME_COARSE, > CLOCK_MONOTONIC_COARSE, CLOCK_BOOTTIME and CLOCK_TAI. > 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. -- To unsubscribe from this list: send the line "unsubscribe linux-iio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
