लिनक्स/linux-0.01.tar/fs/char dev.c
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#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); }