[TIMER] k_timer_start should take 0 value for duration parameter

[zephyrbot]

Reported by Youvedeep Singh:

As per Spec :-

k_timer_start(&timer, DURATION, PERIOD);

DURATION:- "A duration specifying the time interval before the timer expires for the first time, measured in milliseconds. It must be greater than zero."
(source : http://zephyr-docs.s3-website-us-east-1.amazonaws.com/online/dev/kernel/timing/timers.html)

So minimum value programmable should be NON Zero positive value. Also Timer should be programmed with value equal to value programmed by user without any extra addition.

Also currently while programming the timer we are providing one TICK extra due to _ALIGN_TICK. So it should be removed.

(Imported from Jira ZEP-2497)

[zephyrbot]

by Johan Hedberg:

I think it makes the k_timer_start() API "worse" if we disallow K_NO_WAIT, since that value has a very intuitive meaning: "fire the timer at the earliest possible opportunity". So I think the API should allow this and deal with it appropriately (either by silent translation of 0 to 1 or in some better way that makes the first timer go off sooner than within 1ms).

[zephyrbot]

by Youvedeep Singh:

Here summerising the discussion, :-

1. Allow “K_NO_WAIT” as legal value of duration.
2. When user gives “K_NO_WAIT” as Duration then do not put it in Timeout Queue, put it directly to QUEUE WORK.
3. In TICK Based kernel currently we are add _ALIGN_TICK to duration, So adding an extra TICK to duration, That should be removed.
4. Documentation on Zephyr page need to be changed to show 0 as legal value for duration and it indicates task need to be performed ASAP.

Also a patch is under review for this - #1073

[zephyrbot]

by Youvedeep Singh:

This issue is fixed now, SO good to close this Jira.

[zephyrbot]

by Youvedeep Singh:

Patch merged.

[david-perez]

Website docs for timers still state that "a duration [...] must be greater than zero." Also, why not define duration and period as unsigned in k_timer_start, as well as in the timer struct definition?