[lwip-users] Stackless, non-preemptive uSmartX RTOS and lwIP

[Marko Panger]

Hello all,

I'm about to start porting the lwIP stack on my uSmartX RTOS. It's a 
stack-less, co-operative, priority based, multitasking RTOS with some 
preemptive primitives. It supports timed pending o semaphores and 
mailboxes although is stack less. For the sake you can drop an eye on 
http://usmartx.sourceforge.net/.

I have already passed through the lwIP sources and documentation. If I 
understand well it can works in two modes. The so called raw api and 
sequential api mode. The raw api mode doesn't require an underlying 
RTOS, but the latter does. The raw API mode should be easy and straight 
forward to integrate into my os.

The sequential API looks a little bit tricky if the os is 
not-preemptive. If you look at the sample code below you can get an idea 
of how for example semaphores are used in my rtos. Basically they 
require the task to return if the resource is not available. The task 
will be than resumed by a semaphore post or a timeout event. Applying 
this to lwIP would require modification of the API calls in such a way 
that multiple calls of the same API call can be made if the semaphore is 
not available at the moment and than calling the same API function with 
"semaphore" available parameter...

Now I am kindly referring to you for some comments on this 
implementation. I'm also a little bit confused on sequential API calls - 
which file contains the available calls ? Is this api_msg.c, sockets or 
some other additional file ?

Thanks in advance four you comments !

Regards,
Marko Panger

Sample uSmartX task:
---------------------------------------------------------------------------------- 

STATUS TSK_SetLed(STATUS ucEvent) {
  static TTSK_State TskState = ACQUIRE_SEM;
  static uint32 AnchorTicks = 0;
    switch( TskState ) {
      case ACQUIRE_SEM:
          if( ucEvent == SYS_SEM_TOUT ){
              /* Handle error here */
              return SYS_ERROR;
          }
          /* Semaphore acquired within timeout */
          else if( ucEvent == SYS_SEM ) {
              AnchorTicks = TMR_GetTicks();
              TskState = DO_JOB;              }
          else {
              if( SEM_Pend(&LED_SEM, 50) == SYS_OK ) {
                  AnchorTicks = TMR_GetTicks();
                  TskState = DO_JOB;
              }
          }
          break;
                case DO_JOB:
          /* Use shared resource for 10 ms*/
          if( TMR_GetTicks() - AnchorTicks > 10 ) {
              SetLed(0);
              SEM_Post(&LED_SEM);
              TskState = ACQUIRE_SEM;
          }
          else {
              SetLed(1);              }
          break;
                default:
          break;
  }              return SYS_OK;   }
----------------------------------------------------------------------------------