Concept of meta

Intro

With meta information in each module the main program is set up depending on the configuration. At the end there will be a short example of such meta information.

If you continue to read, you should understand this concept: M4 - very short intro (Deutsch)#divert

Also have a look at the files explained while reading - that will help.

meta.c / meta_magic.m4

The creation of this file is mainly controlled by the file "meta_magic.m4".

What is in the file meta_magic.m4?

framework for the file meta.c

The framework consists of several divert sections, in which code of the used modules is injected.

Only the idea of the injection is explained with the first injection point.

The second section starts with "divert(initearly_divert)dnl" and contains the function "ethersex_meta_init", but the final closing brace of the function is missing. So if you define further divert sections with the index "initearly_divert", then it will be in the output before the closing brace and so part of "ethersex_meta_init".

Therefore later in in the file some macros are defined - in this case it is named "initearly".

This macros and some others are all defined the same way:

define(`initearly',`dnl
divert(inetearly_divert) $1 ();
divert(-1)')

So if the meta macro initearly(<module-initearly-functionname>) is used, the module initearly function will be called from the function ethersex_meta_init, because the function call will be in the output directly after the section.

The closing brace of the function is part of the next section "divert(net_init_divert)".

structure of meta.c

meta.c itself contains several functions, which are called at important points in the firmware:

• ethersex_meta_init

  is called in the startup before the pins are initialized

• ethersex_meta_startup

  is called before the main loop starts

• ethersex_meta_mainloop

  is called in the main loop - injected functions should do only short processings or reset the watchdog by thereselfs ...

• periodic_process

  is the last function called in ethersex_meta_mainloop - after all the injected modules function

  does some network and console reading (ECMD support and other) - at the momenet I don't know the backgrounds of this operations.

  further operations can be injected here - a counter incremented on each call can be used to delay the injected code ...

Closing

After all this explained I want to mention that some modules are not only in that structured way integrated into the project. There are also direct compiler directives for them in the framework itself ... this looks like needed "hacks".