Knowledge Base Nr: 00079 stxetx.c - http://www.swe-kaiser.de

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linux: treiber für serielle schnittstelle mit STX/ETX protokoll als module (incl. testprogramm).

  
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/tty.h>
#include <linux/sched.h>
#include <asm/uaccess.h>

#include "direct.h"

static int direct_proc_pid=0;
static int direct_buf_pos=0;
static char direct_buffer[2000];
static int direct_mode=IDLE;

int direct_open(struct tty_struct * tty)
{
  //printk("<1> opening .xx..pid:%d\n",current->pid);
  direct_proc_pid=current->pid;
  direct_buf_pos=0;
  direct_mode=IDLE;
  return 0;
}

int direct_write(struct tty_struct *tty, struct file *filp,const unsigned char * data, unsigned int count)
{
  int i;

  tty->driver.put_char(tty,STX);
  for (i=0;i<count;i++)
    tty->driver.put_char(tty,data[i]);
  tty->driver.put_char(tty,ETX);
  tty->driver.flush_chars(tty);
  return count;
}

int direct_read(struct tty_struct *tty, struct file *filp, unsigned char *buf, unsigned int count)
{
  int helper;

  //printk("<1> reading ...\n");

  copy_to_user(buf,direct_buffer,direct_buf_pos);

  helper=direct_buf_pos;

  direct_buf_pos=0;

  return helper;
}

void direct_receive(struct tty_struct *tty,const unsigned char *cp, char *fp, int count)
{
  int action=0;
  int i;

   //printk ("<1> receiving data...\n");
   for (i=0;i<count;i++)
   {
     if (cp[i]==STX)
     {
       //if (direct_buf_pos > 0)
       //    direct_buffer[direct_buf_pos++]=STX;
       direct_buf_pos = 0;

       //direct_buf_pos=0;
       direct_mode=READING;
     }
     else if(cp[i]==ETX)
     {
       direct_mode=IDLE;
       action=1;
     }
     else if (direct_mode==READING)
       direct_buffer[direct_buf_pos++]=cp[i];

   }
  if (action)
    kill_proc(direct_proc_pid,SIGIO,1);

}

int direct_room(struct tty_struct *tty)
{
  return -1;
}

struct tty_ldisc direct_ldisc={
          TTY_LDISC_MAGIC,
          "DIRECT",
          0,
          0,
          direct_open,
          0,//close
          0,
          0,
          direct_read,
          direct_write,
          0,//ioctl
          0,//set_termios
          0,//poll
          direct_receive,
          direct_room,
          0
};


int init_module(void)
{
  int status=tty_register_ldisc(N_DIRECT,&direct_ldisc);
  if (status!=0)
    printk("<1> konnte nicht ld registrieren ...\n");
  else
    printk("<1> ld registriert ok ...\n");
  return status;
}

void cleanup_module(void)
{
  int status=tty_register_ldisc(N_DIRECT,NULL);

   if (status!=0)
    printk("<1> konnte nicht ld deregistrieren ...\n");
  else
    printk("<1> ld deregistriert ok ...\n");
}