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Change-Id: I7a544d2d43b83135def296674f777e48fe5fd80a
Closes: CID#190866
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libosmo{core,gsm,vty} code is GPLv2+. The tdef code originated in
osmo-msc.git and was moved here without changing the license. That
was a mistake, it always was meant to be under GPLv2-or-later after
moving to libosmocore.git.
Copyright is with sysmocom, so I as the managing director can
approve the license change.
Change-Id: Ie483ff6f6ea0a56c477649677b4b163c49df11d7
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During FSM design for osmo-msc, I noticed that the current behavior that
keep_timer=true doesn't guarantee a running timer can make FSM design a bit
complex, especially when using osmo_tdef for timeout definitions.
A desirable keep_timer=true behavior is one that keeps the previous timer
running, but starts a timer if no timer is running yet.
The simplest example is: a given state repeatedly transitions back to itself,
but wants to set a timeout only on first entering, avoiding to restart the
timeout on re-entering.
Another example is a repeated transition between two or more states, where the
first time we enter this group a timeout should start, but it should not
restart from scratch on every transition.
When using osmo_tdef timeout definitions for this, so far separate meaningless
states have to be introduced that merely set a fixed timeout.
To simplify, add osmo_fsm_inst_state_chg_keep_or_start_timer(), and use this in
osmo_tdef_fsm_inst_state_chg() when both keep_timer == true *and* T != 0.
In tdef_test.ok, the changes show that on first entering state L, the previous
T=1 is now kept with a large remaining timeout. When entering state L from O,
where no timer was running, this time L's T123 is started.
Change-Id: Id647511a4b18e0c4de0e66fb1f35dc9adb9177db
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Move T_def from osmo-bsc to libosmocore as osmo_tdef. Adjust naming to be more
consistent. Upgrade to first class API:
- add timer grouping
- add generic vty support
- add mising API doc
- add C test
- add VTY transcript tests, also as examples for using the API
From osmo_fsm_inst_state_chg() API doc, cross reference to osmo_tdef API.
The root reason for moving to libosmocore is that I want to use the
mgw_endpoint_fsm in osmo-msc for inter-MSC handover, and hence want to move the
FSM to libosmo-mgcp-client. This FSM uses the T_def from osmo-bsc. Though the
mgw_endpoint_fsm's use of T_def is minimal, I intend to use the osmo_tdef API
in osmo-msc (and probably elsewhere) as well. libosmocore is the most sensible
place for this.
osmo_tdef provides:
- a list of Tnnnn (GSM) timers with description, unit and default value.
- vty UI to allow users to configure non-default timeouts.
- API to tie T timers to osmo_fsm states and set them on state transitions.
- a few standard units (minute, second, millisecond) as well as a custom unit
(which relies on the timer's human readable description to indicate the
meaning of the value).
- conversion for standard units: for example, some GSM timers are defined in
minutes, while our FSM definitions need timeouts in seconds. Conversion is
for convenience only and can be easily avoided via the custom unit.
By keeping separate osmo_tdef arrays, several groups of timers can be kept
separately. The VTY tests in tests/tdef/ showcase different schemes:
- tests/vty/tdef_vty_test_config_root.c:
Keep several timer definitions in separately named groups: showcase the
osmo_tdef_vty_groups*() API. Each timer group exists exactly once.
- tests/vty/tdef_vty_test_config_subnode.c:
Keep a single list of timers without separate grouping.
Put this list on a specific subnode below the CONFIG_NODE.
There could be several separate subnodes with timers like this, i.e.
continuing from this example, sets timers could be separated by placing
timers in specific config subnodes instead of using the global group name.
- tests/vty/tdef_vty_test_dynamic.c:
Dynamically allocate timer definitions per each new created object.
Thus there can be an arbitrary number of independent timer definitions, one
per allocated object.
T_def was introduced during the recent osmo-bsc refactoring for inter-BSC
handover, and has proven useful:
- without osmo_tdef, each invocation of osmo_fsm_inst_state_chg() needs to be
programmed with the right timeout value, for all code paths that invoke this
state change. It is a likely source of errors to get one of them wrong. By
defining a T timer exactly for an FSM state, the caller can merely invoke the
state change and trust on the original state definition to apply the correct
timeout.
- it is helpful to have a standardized config file UI to provide user
configurable timeouts, instead of inventing new VTY commands for each
separate application of T timer numbers.
Change-Id: Ibd6b1ed7f1bd6e1f2e0fde53352055a4468f23e5
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