लिनक्स/linux-0.01.tar/fs/char dev.c
< लिनक्स | linux-0.01.tar
#include <errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
extern int tty_read(unsigned minor,char * buf,int count);
extern int tty_write(unsigned minor,char * buf,int count);
static int rw_ttyx(int rw,unsigned minor,char * buf,int count);
static int rw_tty(int rw,unsigned minor,char * buf,int count);
typedef (*crw_ptr)(int rw,unsigned minor,char * buf,int count);
#define NRDEVS ((sizeof (crw_table))/(sizeof (crw_ptr)))
static crw_ptr crw_table[]={
NULL, /* nodev */
NULL, /* /dev/mem */
NULL, /* /dev/fd */
NULL, /* /dev/hd */
rw_ttyx, /* /dev/ttyx */
rw_tty, /* /dev/tty */
NULL, /* /dev/lp */
NULL}; /* unnamed pipes */
static int rw_ttyx(int rw,unsigned minor,char * buf,int count)
{
return ((rw==READ)?tty_read(minor,buf,count):
tty_write(minor,buf,count));
}
static int rw_tty(int rw,unsigned minor,char * buf,int count)
{
if (current->tty<0)
return -EPERM;
return rw_ttyx(rw,current->tty,buf,count);
}
int rw_char(int rw,int dev, char * buf, int count)
{
crw_ptr call_addr;
if (MAJOR(dev)>=NRDEVS)
panic("rw_char: dev>NRDEV");
if (!(call_addr=crw_table[MAJOR(dev)])) {
printk("dev: %04x\n",dev);
panic("Trying to r/w from/to nonexistent character device");
}
return call_addr(rw,MINOR(dev),buf,count);
}