[asterisk-dev] M9645: provide zaptel master timing to spans

[Paul Cadach]

Tzafrir Cohen wrote:
> I'd like to get your input regarding
> http://bugs.digium.com/view.php?id=9645
>
> The patch adds an extra span method:
>
>  int (*sync_tick)(struct zt_span *span, int is_master);
>
> The zaptel sync master span will call it to any span (in which it is not
> NULL) at each of its ticks.

Is it better to have a call to such API every N (1000, 10000) ticks? At 
least it will offload CPU processing, but still make channel driver to be 
able to adapt its slave clocks according to zaptel's master clocks.

To be clear, when zaptel detects master clock change, it will immediately 
call such callback to notify channel drivers about master change event. Of 
course, it should pass its own tick counter to allow channel drivers to 
adapt their clocks independedly on callback call frequency. IMHO this should 
offload CPU/etc. but provide the same behavior as Tzafrir suggests.

Also, to perform card's clock source manipulation, you should collect 
relatively high number of ticks to be accurate as possible, so I think 
calling the callback often than one time per second is overkill.


WBR,
Paul.