RFC: new design of phosphor-time-manager on sdbusplus

[Patrick Williams]

On Thu, Jan 19, 2017 at 03:37:34PM +0800, Mine wrote:
> Currently the time_mode/owner has 8 combinations, some of them are not valid.
> Could you help to verify what's the expected behavior in each combinations?
> 
> Mode      | Owner | Set BMC Time  | Set Host Time
> ------------- | --------- | ----------------------- |
> -------------------------------------
> NTP        | BMC   | Not allowed      | Not allowed
> NTP        | HOST | Invalid case     | Invalid case
> NTP        | SPLIT | Not allowed      | OK, and just save offset
> NTP        | BOTH | Not allowed     | OK, and set time to BMC
> MANUAL | BMC   | OK                  | Not allowed
> MANUAL | HOST | Not allowed      | OK, and set time to BMC
> MANUAL | SPLIT | OK                  | OK, and just save offset
> MANUAL | BOTH | OK                  | OK, and set time to BMC

Why is 'Set BMC Time' not allowed in any NTP mode in your table?  There
is no reason to stop 'Set BMC Time' except in the NTP/HOST case.

> If my understanding is correct, then we can see:
> * NTP/HOST is invalid case, such case shall not exist, the current
> implementation
>   either hacks settingsd to change the mode to MANUAL, or just behaves
> like MANUAL;

When the 'host' owns the clock, 'ntp' vs 'manual' is irrelevant.

> * NTP/BOTH has the same behavior as MANULA/HOST, they can be merged.

No, these are significantly different.  NTP/BOTH means that we run the
NTP client on the BMC but allow either side to set the time.
MANUAL/HOST means we do not run the NTP client and the BMC is prohibited
from setting the time in any way.

> That's why I propose to combine the settings to:
> * NTP-BMC
> * NTP-SPLIT
> * NTP-BOTH (or MANUAL-HOST)
> * MANUAL-BMC
> * MANUAL-SPLIT
> * MANUAL-BOTH
> 
> Then we don't have to "hack" or "disagree" with settingsd, and the
> logic could be
> a little simpler.

1. NTP vs Manual controls if the NTP-client is running.
2. Owner controls who is allowed to set the time.

-- 
Patrick Williams
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