137 lines
3.0 KiB
C
137 lines
3.0 KiB
C
/*
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* linux/fs/char_dev.c
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*
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* (C) 1991 Linus Torvalds
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*/
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#include <errno.h>
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#include <sys/types.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <asm/segment.h>
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#include <asm/io.h>
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extern int tty_read(unsigned minor,char * buf,int count,unsigned short flags);
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extern int tty_write(unsigned minor,char * buf,int count);
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typedef (*crw_ptr)(int,unsigned,char *,int,off_t *,unsigned short);
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static int rw_ttyx(int rw,unsigned minor,char * buf,int count,off_t * pos, unsigned short flags)
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{
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return ((rw==READ)?tty_read(minor,buf,count,flags):
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tty_write(minor,buf,count));
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}
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static int rw_tty(int rw,unsigned minor,char * buf,int count, off_t * pos, unsigned short flags)
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{
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if (current->tty<0)
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return -EPERM;
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return rw_ttyx(rw,current->tty,buf,count,pos,flags);
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}
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static int rw_ram(int rw,char * buf, int count, off_t *pos)
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{
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return -EIO;
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}
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static int rw_mem(int rw,char * buf, int count, off_t * pos)
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{
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return -EIO;
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}
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static int rw_kmem(int rw,char * buf, int count, off_t * pos)
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{
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/* kmem by Damiano */
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int i = *pos; /* Current position where to read */
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/* i can go from 0 to LOW_MEM (See include/linux/mm.h */
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/* I am not shure about it but it doesn't mem fault :-) */
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while ( (count-- > 0) && (i <LOW_MEM) ) {
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if (rw==READ)
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put_fs_byte( *(char *)i ,buf++);
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else
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return (-EIO);
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i++;
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}
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i -= *pos; /* Count how many read or write */
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*pos += i; /* Update position */
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return (i); /* Return number read */
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}
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static int rw_port(int rw,char * buf, int count, off_t * pos)
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{
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int i=*pos;
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while (count-->0 && i<65536) {
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if (rw==READ)
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put_fs_byte(inb(i),buf++);
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else
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outb(get_fs_byte(buf++),i);
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i++;
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}
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i -= *pos;
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*pos += i;
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return i;
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}
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static int rw_memory(int rw, unsigned minor, char * buf, int count,
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off_t * pos, unsigned short flags)
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{
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switch(minor) {
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case 0:
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return rw_ram(rw,buf,count,pos);
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case 1:
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return rw_mem(rw,buf,count,pos);
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case 2:
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return rw_kmem(rw,buf,count,pos);
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case 3:
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return (rw==READ)?0:count; /* rw_null */
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case 4:
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return rw_port(rw,buf,count,pos);
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default:
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return -EIO;
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}
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}
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#define NRDEVS ((sizeof (crw_table))/(sizeof (crw_ptr)))
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static crw_ptr crw_table[]={
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NULL, /* nodev */
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rw_memory, /* /dev/mem etc */
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NULL, /* /dev/fd */
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NULL, /* /dev/hd */
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rw_ttyx, /* /dev/ttyx */
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rw_tty, /* /dev/tty */
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NULL, /* /dev/lp */
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NULL}; /* unnamed pipes */
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int char_read(struct inode * inode, struct file * filp, char * buf, int count)
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{
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unsigned int major,minor;
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crw_ptr call_addr;
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major = MAJOR(inode->i_rdev);
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minor = MINOR(inode->i_rdev);
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if (major >= NRDEVS)
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return -ENODEV;
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if (!(call_addr = crw_table[major]))
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return -ENODEV;
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return call_addr(READ,minor,buf,count,&filp->f_pos,filp->f_flags);
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}
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int char_write(struct inode * inode, struct file * filp, char * buf, int count)
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{
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unsigned int major,minor;
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crw_ptr call_addr;
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major = MAJOR(inode->i_rdev);
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minor = MINOR(inode->i_rdev);
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if (major >= NRDEVS)
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return -ENODEV;
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if (!(call_addr=crw_table[major]))
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return -ENODEV;
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return call_addr(WRITE,minor,buf,count,&filp->f_pos,filp->f_flags);
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}
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