Re: [Lcd4linux-devel] Dynamic loading of drivers / plugins ?

[Michael R. <re...@eu...>]

Hi Xavier, Hi list,

>>If you use a hash, you fill up the hash with all values from 
>>/proc/cpuinfo when parsing it. Subsequent calls would not parse the file 
>>again, but read the values from the hash.
> 
> Okay, I understand it ! In fact, hashes are handled by the plugins internally.

Right!

>>You have to use something like a "timeout", and remember the time when 
>>the contents of the file was last read. If the timeout is over, you have 
>>to read and parse the file again.
> What about this timeout ? Is there a helper ? Maybe a function to
>   register timeouts and see if they timed-out. It may be in yet, sorry
>  I don't have to code under my eyes :/ 

The code is that simple that I didn't write a helper for it(although 
there is a timer queue management, but this is used for widge updates).

If your timeout is 1 second or higher, and second-resolution is enough, 
use the following:

static int parse_anything(void)
{
   static time_t now=0;

   // reread every second only
   if (time(NULL)==now) return 0;
   time(&now);

   // real parsing happens here...

   return 0;
}

If you need higher resolutions (milliseconds), you need the following 
snippet:

   static struct timeval end = {0, 0};
   struct timeval now;

   // update every 10 msec
   gettimeofday(&now, NULL);
   if (now.tv_sec==end.tv_sec?
	now.tv_usec<end.tv_usec:now.tv_sec<end.tv_sec) {
     return 0;
   }
   end.tv_sec  = now.tv_sec;
   end.tv_usec = now.tv_usec + 1000*msec;
   while (end.tv_usec > 1000000) {
     end.tv_usec -= 1000000;
     end.tv_sec++;
   }

   // parse it...

> 'lcd4linux -l' can load all
> the drivers it knows, we don't matter about memory usage as it'll die
> then. Same to list plugins.
Thats what I'm thinking of, too.

> I fact, I thinked about a sort of 'callback' function : now if the eval
> doesn't know a function, it returns an error. It may call a function
> which loads the good plugin and evaluates the function, so that the
> evaluator doesn't mind and everybody's happy ;) It's not the evaluator
> that searches for plugins at startup, it 'learns' with its "errors". In
> this way, we don't need to modify much the eval.
And how should the evaluator know which .so to load?

> This .so-ing may be later, but we should keep it in mind so that we
> don't do silly things that will prevent us to make it then.
Full ACK.

bye, Michael

-- 
Michael Reinelt                                   Tel: +43 676 3079941
Geisslergasse 4                                   Fax: +43 316  692343
A-8045 Graz, Austria                          e-mail: re...@eu...