1.7 Der Systemruf ioctl
- vor allem für Gerätetreiber
- für Operationen, die nicht mit read/write usw.
funktionieren
/* Ausschnitte aus /usr/src/linux/fs/ioctl.c (Kernel 2.2.5) */
asmlinkage int sys_ioctl(unsigned int fd, unsigned int cmd, unsigned long
arg)
{
struct file * filp;
unsigned int flag;
int on, error = -EBADF;
lock_kernel();
filp = fget(fd);
if (!filp)
goto out;
error = 0;
switch (cmd) {
case FIOCLEX:
FD_SET(fd, ¤t->files->close_on_exec);
break;
case FIONCLEX:
FD_CLR(fd, ¤t->files->close_on_exec);
break;
case FIONBIO:
if ((error = get_user(on, (int *)arg)) != 0)
break;
flag = O_NONBLOCK;
#ifdef __sparc__
/* SunOS compatibility item. */
if(O_NONBLOCK != O_NDELAY)
flag |= O_NDELAY;
#endif
if (on)
filp->f_flags |= flag;
else
filp->f_flags &= ~flag;
break;
case FIOASYNC:
if ((error = get_user(on, (int *)arg)) != 0)
break;
flag = on ? FASYNC : 0;
/* Did FASYNC state change ? */
if ((flag ^ filp->f_flags) & FASYNC) {
if (filp->f_op && filp->f_op->fasync)
filp->f_op->fasync(fd, filp, on);
}
if (on)
filp->f_flags |= FASYNC;
else
filp->f_flags &= ~FASYNC;
break;
default:
error = -ENOTTY;
if (!filp->f_dentry || !filp->f_dentry->d_inode)
error = -ENOENT;
else if (S_ISREG(filp->f_dentry->d_inode->i_mode))
/*file*/ error = file_ioctl(filp, cmd, arg); /*file*/
else if (filp->f_op && filp->f_op->ioctl)
error =
filp->f_op->ioctl(filp->f_dentry->d_inod }
fput(filp);
out:
unlock_kernel();
return error;
}
static int file_ioctl(struct file *filp,unsigned int cmd,unsigned long arg)
{
int error;
int block;
struct inode * inode = filp->f_dentry->d_inode;
switch (cmd) {
case FIBMAP: /*Nummer des i-ten Blocks der Datei*/
if (inode->i_op == NULL)
return -EBADF;
if (inode->i_op->bmap == NULL)
return -EINVAL;
if ((error = get_user(block, (int *) arg)) != 0)
return error;
block = inode->i_op->bmap(inode,block);
return put_user(block, (int *) arg);
case FIGETBSZ: /*Blockgröße des FS*/
if (inode->i_sb == NULL)
return -EBADF;
return put_user(inode->i_sb->s_blocksize,
(int *) arg);
case FIONREAD: /* Anzahl noch nicht gelesener Bytes*/
return put_user(inode->i_size - filp->f_pos,
(int *) arg);
}
if (filp->f_op && filp->f_op->ioctl)
return filp->f_op->ioctl(inode, filp, cmd, arg);
/*ioctl von spez. FS*/
return -ENOTTY;
}
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