select on UART

[Paul Whitfield]

Thomas Dörfler wrote:
> Hi,
> 
> AFAIK select is currently limited to sockets, so there is no select
> support for serial or other devices. It would be a nice thing to add
> select support to the termios layer, but this has not yet been implemented.

FYI

The work around is to use the RTEMS specific receive call back functions 
in termios.

See http://www.rtems.com/ml/rtems-users/2001/july/msg00090.html

Here is a code snippet that uses the function

         if ( status >= 0 )
         {
             rtems_id task;
             struct ttywakeup wakeup;

             rtems_task_ident( RTEMS_SELF, RTEMS_LOCAL, &task);

             wakeup.sw_pfn = receive_callback;
             wakeup.sw_arg = (void *) task ;

             status = ioctl( fd, RTEMS_IO_RCVWAKEUP, &wakeup);
         }


And the callback is

static void passthru_receive_callback(struct termios *tty, void * arg )
{
     (void) rtems_event_send( (rtems_id) arg, EVENT_RS232_RX );
}


The sends the calling task an event when there is serial data available.

I could not find any documentation for this _non_standard_ API, so I
added a entry to the FAQ on the wiki.

Hope that helps.

Regards

Paul

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