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- UID
- 872238
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在前面提到。在对uart设备文件过程中。会将操作转换到对应的port上，这个port跟uart_driver是怎么关联起来的呢？这就是uart_add_ont_port（）的主要工作了。
顾名思义，这个函数是在uart_driver增加一个port.代码如下：
int uart_add_one_port（struct uart_driver *drv, struct uart_port *port）
{
struct uart_state *state;
int ret = 0;
struct device *tty_dev;
BUG_ON（in_interrupt（））；
if （port->line >= drv->nr）
return -EINVAL;
state = drv->state + port->line;
mutex_lock（&port_mutex）；
mutex_lock（&state->mutex）；
if （state->port） {
ret = -EINVAL;
goto out;
}
state->port = port;
state->pm_state = -1;
port->cons = drv->cons;
port->info = state->info;
/*
* If this port is a console, then the spinlock is already
* initialised.
*/
if （！（uart_console（port） && （port->cons->flags & CON_ENABLED））） {
spin_lock_init（&port->lock）；
lockdep_set_class（&port->lock, &port_lock_key）；
}
uart_configure_port（drv, state, port）；
/*
* Register the port whether it's detected or not. This allows
* setserial to be used to alter this ports parameters.
*/
tty_dev = tty_register_device（drv->tty_driver, port->line, port->dev）；
if （likely（！IS_ERR（tty_dev））） {
device_can_wakeup（tty_dev） = 1;
device_set_wakeup_enable（tty_dev, 0）；
} else
printk（KERN_ERR "Cannot register tty device on line %d\n",
port->line）；
/*
* Ensure UPF_DEAD is not set.
*/
port->flags &= ~UPF_DEAD;
out:
mutex_unlock（&state->mutex）；
mutex_unlock（&port_mutex）；
return ret;
}
首先这个函数不能在中断环境中使用。 Uart_port->line就是对uart设备文件序号。它对应的也就是uart_driver->state数组中的uart_port->line项。
它主要初始化对应uart_driver->state项。接着调用uart_configure_port（）进行port的自动配置。然后注册tty_device.如果用户空间运行了udev或者已经配置好了hotplug.就会在/dev下自动生成设备文件了。
操作流程图如下所示：
六：设备节点的open操作
在用户空间执行open操作的时候，就会执行uart_ops->open. Uart_ops的定义如下：
static const struct tty_operations uart_ops = {
.open = uart_open,
.close = uart_close,
.write = uart_write,
.put_char = uart_put_char,
.flush_chars = uart_flush_chars,
.write_room = uart_write_room,
.chars_in_buffer= uart_chars_in_buffer,
.flush_buffer = uart_flush_buffer,
.ioctl = uart_ioctl,
.throttle = uart_throttle,
.unthrottle = uart_unthrottle,
.send_xchar = uart_send_xchar,
.set_termios = uart_set_termios,
.stop = uart_stop,
.start = uart_start,
.hangup = uart_hangup,
.break_ctl = uart_break_ctl,
.wait_until_sent= uart_wait_until_sent,
#ifdef CONFIG_PROC_FS
.read_proc = uart_read_proc,
#endif
.tiocmget = uart_tiocmget,
.tiocmset = uart_tiocmset,
};
对应open的操作接口为uart_open.代码如下：
static int uart_open（struct tty_struct *tty, struct file *filp）
{
struct uart_driver *drv = （struct uart_driver *）tty->driver->driver_state;
struct uart_state *state;
int retval, line = tty->index;
BUG_ON（！kernel_locked（））；
pr_debug（"uart_open（%d） called\n", line）；
/*
* tty->driver->num won't change, so we won't fail here with
* tty->driver_data set to something non-NULL （and therefore
* we won't get caught by uart_close（））。
*/
retval = -ENODEV;
if （line >= tty->driver->num）
goto fail;
/*
* We take the semaphore inside uart_get to guarantee that we won't
* be re-entered while allocating the info structure, or while we
* request any IRQs that the driver may need. This also has the nice
* side-effect that it delays the action of uart_hangup, so we can
* guarantee that info->tty will always contain something reasonable.
*/
state = uart_get（drv, line）；
if （IS_ERR（state）） {
retval = PTR_ERR（state）；
goto fail;
}
/*
* Once we set tty->driver_data here, we are guaranteed that
* uart_close（） will decrement the driver module use count.
* Any failures from here onwards should not touch the count.
*/
tty->driver_data = state;
tty->low_latency = （state->port->flags & UPF_LOW_LATENCY） ? 1 : 0;
tty->alt_speed = 0;
state->info->tty = tty;
/*
* If the port is in the middle of closing, bail out now.
*/
if （tty_hung_up_p（filp）） {
retval = -EAGAIN;
state->count--;
mutex_unlock（&state->mutex）；
goto fail;
}
/*
* Make sure the device is in D0 state.
*/
if （state->count == 1）
uart_change_pm（state, 0）；
/*
* Start up the serial port.
*/
retval = uart_startup（state, 0）；
/*
* If we succeeded, wait until the port is ready.
*/
if （retval == 0）
retval = uart_block_til_ready（filp, state）；
mutex_unlock（&state->mutex）；
/*
* If this is the first open to succeed, adjust things to suit.
*/
if （retval == 0 && !（state->info->flags & UIF_NORMAL_ACTIVE）） {
state->info->flags |= UIF_NORMAL_ACTIVE;
uart_update_termios（state）；
}
fail:
return retval;
} |
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