static int lp_open(struct inode * inode, struct file * file)
{
unsigned int minor = iminor(inode);
int ret = 0;
lock_kernel();
if (minor >= LP_NO) {
ret = -ENXIO;
goto out;
}
if ((LP_F(minor) & LP_EXIST) == 0) {
ret = -ENXIO;
goto out;
}
if (test_and_set_bit(LP_BUSY_BIT_POS, &LP_F(minor))) {
ret = -EBUSY;
goto out;
/* If ABORTOPEN is set and the printer is offline or out of paper,
we may still want to open it to perform ioctl()s. Therefore we
have commandeered O_NONBLOCK, even though it is being used in
a non-standard manner. This is strictly a Linux hack, and
should most likely only ever be used by the tunelp application. */
if ((LP_F(minor) & LP_ABORTOPEN) && !(file->f_flags & O_NONBLOCK)) {
int status;
lp_claim_parport_or_block (&lp_table[minor]);
status = r_str(minor);
lp_release_parport (&lp_table[minor]);
if (status & LP_POUTPA) {
printk(KERN_INFO "lp%d out of paper\n", minor);
LP_F(minor) &= ~LP_BUSY;
ret = -ENOSPC;
goto out; 作者: 墙根下的水壶 时间: 2016-05-04 11:57
函数的第一个参数是file， 应该看这个file创建的时候有没有O_NONBLOCK属性了