Clocks

This is implemented in clocks.

Here we implement the clock functionality of the system.

This includes functionalities used in implementing:

• system time.
• timers.
• sleep (see scheduler).

We have several clock sources, and these are devices that provide us with a "time", this "time" is not bound to a specific start, but it just guarantees that:

• The time is always increasing.
  • TODO: We still haven't handled wrap around.
• Querying the time at 2 points will give you the time difference based on real time speed.
  • This depends on the granularity of the source, for example, if we implement it for RTC, then the granularity is 1 second, i.e. querying it within 1 second will mostly give you the same time.

And thus with these, we can keep track of the time.

We have 2 times in the system:

• boot time (uptime).
  • This is the time since the system booted.
  • This is calculated by periodically updating the time based on the best clock source we have.
• real time (unix time).
  • On boot, we get the current time from the RTC.
  • When we need this value, we calculate it based on the boot time and the start time we got at boot.

These times can be fetched with the get_time syscall.