UART interrupt

#include <cyg/hal/system.h># include <cyg/kernel/kapi.h>
unsigned char abycin;
volatile unsigned int byrxptr = 0;
unsigned int bywrptr = 0;
cyg_uint32 uart_debug_isr(cyg_vector_t vector, cyg_addrword_t data)
{
    volatile int clr_int;
  
  // block this interrupt from occurring until this isr completes.
  cyg_interrupt_mask(vector);
  // tell the processor that we have received the interrupt.
  cyg_interrupt_acknowledge(vector);
  if (!(iord_altera_avalon_uart_status(uart_debug_base) & 0x02))    
 {
    abycin = iord_altera_avalon_uart_rxdata(uart_debug_base);
    if(byrxptr < (rxbuf_size_debug - 2)) byrxptr++;
    else byrxptr = 0;
  }
  else clr_int = iord_altera_avalon_uart_rxdata(uart_debug_base); // read udr if framing error just to clear interrupt
  // allow this interrupt to occur again.
  //cyg_interrupt_unmask (vector);
  // tell the kernel that chained interrupt processing is done. 
  //return cyg_isr_handled;
  return cyg_isr_handled | cyg_isr_call_dsr;
}
void uart_debug_dsr(cyg_vector_t vector, cyg_ucount32 count, cyg_addrword_t data)
{
  //printf("dsr\n");
  //out_str("dsr\n");
  cyg_interrupt_unmask(vector);
}
void out_str(char *s)
{
  unsigned char *c;
  
  for(c = s;; c++)
  {
  if(*c == 0)
    break;
  out_char((unsigned char)*c);
  } 
}
void out_char(unsigned char c)
{
  while(!(iord_altera_avalon_uart_status(uart_debug_base) & 0x40));
  iowr_altera_avalon_uart_txdata(uart_debug_base, c);
}
void cyg_user_start(void)
{
  int divisor = 0;
  int old = 0;
  cyg_handle_t uart_debug_handle, timer_handle;
  cyg_interrupt uart_debug_intr, timer_intr;
  cyg_interrupt_create(uart_debug_irq, 99, 0, &uart_debug_isr, &uart_debug_dsr, &uart_debug_handle, &uart_debug_intr);
  cyg_interrupt_attach(uart_debug_handle);
  cyg_interrupt_disable();
  /* other initialization tasks performed here */
  cyg_interrupt_enable();
  cyg_interrupt_unmask(uart_debug_irq);
  while(1)
  {
     while (bywrptr != byrxptr) // check to see if any data has been received by the uart
     {
        printf("bywrptr != byrxptr\n");
        processrxbuf(); // process new data received from uart
      }
      //while (rtdwrptr != rtdrxptr)
        //mdp();
  }
}