Linux UART Console Driver(1)--硬件设备的注册和UART Driver的注册_linux kernel uart console

Linux UART Console Driver(1)–硬件设备的注册和UART Driver的注册

uart console 是嵌入式设备中的console，是嵌入式设备开发调试中不可缺少的部件。uart console 在系统中的设备名是/dev/console.
linux 提供的uart driver框架位于linux/drivers/tty/serial/8250目录当中。uart console driver和tty driver 是紧密相关的（linux 3.10 kernel）。
相关的文件：

1. 8250 serial相关：8250_core.c 8250_dma.c 8250_early.c
2. tty 相关： n_tty.c pty.c tty_buffer.c tty_io.c tty_ioctl.c tty_ldisc.c tty_mutex.c tty_port.c
3. console 相关：/kernel/printk.c

结构框图

图 1 uart console driver系统框图
上图为uart console的系统框架图。uart console的工作流程开始前需要建立系统框架，这包括，uart 硬件设备的注册，串口driver的注册，console信息的初始化，tty driver的注册。接下来就可以对console设备进行读写，读console和写console的执行流程是uart console driver工作的关键过程。

uart 硬件设备的注册

关键数据结构和代码片段：

struct uart_port {
	spinlock_t		lock;			/* port lock */
	unsigned long		iobase;			/* in/out[bwl] */
	unsigned char __iomem	*membase;		/* read/write[bwl] */
	unsigned int		(*serial_in)(struct uart_port *, int);
	void			(*serial_out)(struct uart_port *, int, int);
	void			(*set_termios)(struct uart_port *,
				               struct ktermios *new,
				               struct ktermios *old);
	int			(*handle_irq)(struct uart_port *);
	void			(*pm)(struct uart_port *, unsigned int state,
				      unsigned int old);
	void			(*handle_break)(struct uart_port *);
	unsigned int		irq;			/* irq number */
	unsigned long		irqflags;		/* irq flags  */
	unsigned int		uartclk;		/* base uart clock */
	unsigned int		fifosize;		/* tx fifo size */
	unsigned char		x_char;			/* xon/xoff char */
	unsigned char		regshift;		/* reg offset shift */
	unsigned char		iotype;			/* io access style */
	unsigned char		unused1;

#define UPIO_PORT		(0)
#define UPIO_HUB6		(1)
#define UPIO_MEM		(2)
#define UPIO_MEM32		(3)
#define UPIO_AU			(4)			/* Au1x00 and RT288x type IO */
#define UPIO_TSI		(5)			/* Tsi108/109 type IO */

	unsigned int		read_status_mask;	/* driver specific */
	unsigned int		ignore_status_mask;	/* driver specific */
	struct uart_state	*state;			/* pointer to parent state */
	struct uart_icount	icount;			/* statistics */

	struct console		*cons;			/* struct console, if any */
#if defined(CONFIG_SERIAL_CORE_CONSOLE) || defined(SUPPORT_SYSRQ)
	unsigned long		sysrq;			/* sysrq timeout */
#endif

	upf_t			flags;

#define UPF_FOURPORT		((__force upf_t) (1 << 1))
#define UPF_SAK			((__force upf_t) (1 << 2))
#define UPF_SPD_MASK		((__force upf_t) (0x1030))
#define UPF_SPD_HI		((__force upf_t) (0x0010))
#define UPF_SPD_VHI		((__force upf_t) (0x0020))
#define UPF_SPD_CUST		((__force upf_t) (0x0030))
#define UPF_SPD_SHI		((__force upf_t) (0x1000))
#define UPF_SPD_WARP		((__force upf_t) (0x1010))
#define UPF_SKIP_TEST		((__force upf_t) (1 << 6))
#define UPF_AUTO_IRQ		((__force upf_t) (1 << 7))
#define UPF_HARDPPS_CD		((__force upf_t) (1 << 11))
#define UPF_LOW_LATENCY		((__force upf_t) (1 << 13))
#define UPF_BUGGY_UART		((__force upf_t) (1 << 14))
#define UPF_NO_TXEN_TEST	((__force upf_t) (1 << 15))
#define UPF_MAGIC_MULTIPLIER	((__force upf_t) (1 << 16))
/* Port has hardware-assisted h/w flow control (iow, auto-RTS *not* auto-CTS) */
#define UPF_HARD_FLOW		((__force upf_t) (1 << 21))
/* Port has hardware-assisted s/w flow control */
#define UPF_SOFT_FLOW		((__force upf_t) (1 << 22))
#define UPF_CONS_FLOW		((__force upf_t) (1 << 23))
#define UPF_SHARE_IRQ		((__force upf_t) (1 << 24))
#define UPF_EXAR_EFR		((__force upf_t) (1 << 25))
#define UPF_BUG_THRE		((__force upf_t) (1 << 26))
/* The exact UART type is known and should not be probed.  */
#define UPF_FIXED_TYPE		((__force upf_t) (1 << 27))
#define UPF_BOOT_AUTOCONF	((__force upf_t) (1 << 28))
#define UPF_FIXED_PORT		((__force upf_t) (1 << 29))
#define UPF_DEAD		((__force upf_t) (1 << 30))
#define UPF_IOREMAP		((__force upf_t) (1 << 31))

#define UPF_CHANGE_MASK		((__force upf_t) (0x17fff))
#define UPF_USR_MASK		((__force upf_t) (UPF_SPD_MASK|UPF_LOW_LATENCY))

	unsigned int		mctrl;			/* current modem ctrl settings */
	unsigned int		timeout;		/* character-based timeout */
	unsigned int		type;			/* port type */
	const struct uart_ops	*ops;
	unsigned int		custom_divisor;
	unsigned int		line;			/* port index */
	resource_size_t		mapbase;		/* for ioremap */
	struct device		*dev;			/* parent device */
	unsigned char		hub6;			/* this should be in the 8250 driver */
	unsigned char		suspended;
	unsigned char		irq_wake;
	unsigned char		unused[2];
	void			*private_data;		/* generic platform data pointer */
};


----------
struct uart_ops {
	unsigned int	(*tx_empty)(struct uart_port *);
	void		(*set_mctrl)(struct uart_port *, unsigned int mctrl);
	unsigned int	(*get_mctrl)(struct uart_port *);
	void		(*stop_tx)(struct uart_port *);
	void		(*start_tx)(struct uart_port *);
	void		(*throttle)(struct uart_port *);
	void		(*unthrottle)(struct uart_port *);
	void		(*send_xchar)(struct uart_port *, char ch);
	void		(*stop_rx)(struct uart_port *);
	void		(*enable_ms)(struct uart_port *);
	void		(*break_ctl)(struct uart_port *, int ctl);
	int		(*startup)(struct uart_port *);
	void		(*shutdown)(struct uart_port *);
	void		(*flush_buffer)(struct uart_port *);
	void		(*set_termios)(struct uart_port *, struct ktermios *new,
				       struct ktermios *old);
	void		(*set_ldisc)(struct uart_port *, int new);
	void		(*pm)(struct uart_port *, unsigned int state,
			      unsigned int oldstate);
	int		(*set_wake)(struct uart_port *, unsigned int state);

	/*
	 * Return a string describing the type of the port
	 */
	const char	*(*type)(struct uart_port *);

	/*
	 * Release IO and memory resources used by the port.
	 * This includes iounmap if necessary.
	 */
	void		(*release_port)(struct uart_port *);

	/*
	 * Request IO and memory resources used by the port.
	 * This includes iomapping the port if necessary.
	 */
	int		(*request_port)(struct uart_port *);
	void		(*config_port)(struct uart_port *, int);
	int		(*verify_port)(struct uart_port *, struct serial_struct *);
	int		(*ioctl)(struct uart_port *, unsigned int, unsigned long);
#ifdef CONFIG_CONSOLE_POLL
	int		(*poll_init)(struct uart_port *);
	void		(*poll_put_char)(struct uart_port *, unsigned char);
	int		(*poll_get_char)(struct uart_port *);
#endif
};
----------
struct uart_8250_port {
	struct uart_port	port;
	struct timer_list	timer;		/* "no irq" timer */
	struct list_head	list;		/* ports on this IRQ */
	unsigned short		capabilities;	/* port capabilities */
	unsigned short		bugs;		/* port bugs */
	unsigned int		tx_loadsz;	/* transmit fifo load size */
	unsigned char		acr;
	unsigned char		ier;
	unsigned char		lcr;
	unsigned char		mcr;
	unsigned char		mcr_mask;	/* mask of user bits */
	unsigned char		mcr_force;	/* mask of forced bits */
	unsigned char		cur_iotype;	/* Running I/O type */

	/*
	 * Some bits in registers are cleared on a read, so they must
	 * be saved whenever the register is read but the bits will not
	 * be immediately processed.
	 */
#define LSR_SAVE_FLAGS UART_LSR_BRK_ERROR_BITS
	unsigned char		lsr_saved_flags;
#define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA
	unsigned char		msr_saved_flags;

	struct uart_8250_dma	*dma;

	/* 8250 specific callbacks */
	int			(*dl_read)(struct uart_8250_port *);
	void			(*dl_write)(struct uart_8250_port *, int);
};


----------


----------
struct uart_8250_dma {
	dma_filter_fn		fn;
	void			*rx_param;
	void			*tx_param;

	int			rx_chan_id;
	int			tx_chan_id;

	struct dma_slave_config	rxconf;
	struct dma_slave_config	txconf;

	struct dma_chan		*rxchan;
	struct dma_chan		*txchan;

	dma_addr_t		rx_addr;
	dma_addr_t		tx_addr;

	dma_cookie_t		rx_cookie;
	dma_cookie_t		tx_cookie;

	void			*rx_buf;

	size_t			rx_size;
	size_t			tx_size;

	unsigned char		tx_running:1;
};

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在8250_core.c 中的全局数组

static struct uart_8250_port serial8250_ports[UART_NR];
//UART_NR = 3 在系统框图中可以找到这个数组
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设备注册： 在相应arch的serial.c文件中，这里属于bsp的代码。

int __init bsp_serial_port0_init(void)
{
	struct uart_port up;

	/* clear memory */
	memset(&up, 0, sizeof(up));

	/*
	 * UART0
	 */
	up.line = 0;
	up.type = PORT_16550A;
	up.uartclk = BSP_UART0_FREQ;
	up.fifosize = 32;
	up.irq = BSP_IRQ_OTHERS;
	up.flags = UPF_SKIP_TEST|UPF_SHARE_IRQ;
	up.mapbase = BSP_UART0_PADDR;
	up.membase = ioremap_nocache(up.mapbase, BSP_UART0_PSIZE);
	up.regshift = 2;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 2, 0)
	up.iotype = UPIO_MEM32;
	up.serial_out = dwapb_serial_out;
	up.serial_in = dwapb_serial_in;
	up.handle_irq = dwapb_serial_irq;
#else
	up.iotype = UPIO_DWAPB;
	up.private_data = (void *)BSP_UART0_USR;
#endif

	if (early_serial_setup(&up) != 0) {
		panic("Sheipa: taroko subsystem bsp_serial_init failed!");
	}

	return 0;
}

device_initcall(bsp_serial_port0_init);
//port 的注册是有三组的，因为完全一样的，这里只写一组。

----------
int __init early_serial_setup(struct uart_port *port)
{
	struct uart_port *p;

	if (port->line >= ARRAY_SIZE(serial8250_ports))
		return -ENODEV;

	serial8250_isa_init_ports();
	p = &serial8250_ports[port->line].port;
	p->iobase       = port->iobase;
	p->membase      = port->membase;
	p->irq          = port->irq;
	p->irqflags     = port->irqflags;
	p->uartclk      = port->uartclk;
	p->fifosize     = port->fifosize;
	p->regshift     = port->regshift;
	p->iotype       = port->iotype;
	p->flags        = port->flags;
	p->mapbase      = port->mapbase;
	p->private_data = port->private_data;
	p->type		= port->type;
	p->line		= port->line;

	set_io_from_upio(p);
	if (port->serial_in)
		p->serial_in = port->serial_in;
	if (port->serial_out)
		p->serial_out = port->serial_out;
	if (port->handle_irq)
		p->handle_irq = port->handle_irq;
	else
		p->handle_irq = serial8250_default_handle_irq;

	return 0;
}

static void __init serial8250_isa_init_ports(void)//初始化port数组
{
	struct uart_8250_port *up;
	static int first = 1;
	int i, irqflag = 0;

	if (!first)
		return;
	first = 0;

	if (nr_uarts > UART_NR)
		nr_uarts = UART_NR;

	for (i = 0; i < nr_uarts; i++) {
		struct uart_8250_port *up = &serial8250_ports[i];
		struct uart_port *port = &up->port;

		port->line = i;
		spin_lock_init(&port->lock);

		init_timer(&up->timer);
		up->timer.function = serial8250_timeout;
		if (!(up->port.flags & UPF_SKIP_TEST))
			up->cur_iotype = 0xFF;

		/*
		 * ALPHA_KLUDGE_MCR needs to be killed.
		 */
		up->mcr_mask = ~ALPHA_KLUDGE_MCR;
		up->mcr_force = ALPHA_KLUDGE_MCR;

		port->ops = &serial8250_pops;//
	}

	if (share_irqs)
		irqflag = IRQF_SHARED;

	for (i = 0, up = serial8250_ports;
	     i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;
	     i++, up++) {//这里不会执行old_serial_port数组的长度为0
		struct uart_port *port = &up->port;

		printk(KERN_INFO"serial board init\n");

		port->iobase   = old_serial_port[i].port;
		port->irq      = irq_canonicalize(old_serial_port[i].irq);
		port->irqflags = old_serial_port[i].irqflags;
		port->uartclk  = old_serial_port[i].baud_base * 16;
		port->flags    = old_serial_port[i].flags;
		port->hub6     = old_serial_port[i].hub6;
		port->membase  = old_serial_port[i].iomem_base;
		port->iotype   = old_serial_port[i].io_type;
		port->regshift = old_serial_port[i].iomem_reg_shift;
		set_io_from_upio(port);
		port->irqflags |= irqflag;
		if (serial8250_isa_config != NULL)
			serial8250_isa_config(i, &up->port, &up->capabilities);

	}
}
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8250_core.c 中的struct uart_ops结构：

static struct uart_ops serial8250_pops = {
	.tx_empty	= serial8250_tx_empty,
	.set_mctrl	= serial8250_set_mctrl,
	.get_mctrl	= serial8250_get_mctrl,
	.stop_tx	= serial8250_stop_tx,
	.start_tx	= serial8250_start_tx,
	.stop_rx	= serial8250_stop_rx,
	.enable_ms	= serial8250_enable_ms,
	.break_ctl	= serial8250_break_ctl,
	.startup	= serial8250_startup,
	.shutdown	= serial8250_shutdown,
	.set_termios	= serial8250_set_termios,
	.set_ldisc	= serial8250_set_ldisc,
	.pm		= serial8250_pm,
	.type		= serial8250_type,
	.release_port	= serial8250_release_port,
	.request_port	= serial8250_request_port,
	.config_port	= serial8250_config_port,
	.verify_port	= serial8250_verify_port,
#ifdef CONFIG_CONSOLE_POLL
	.poll_get_char = serial8250_get_poll_char,
	.poll_put_char = serial8250_put_poll_char,
#endif
};

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总结下上面的操作：

1. 用bsp的硬件信息和操作函数填充uart_port.
2. 用填充过硬件信息的uart_port 初始化serial8250_ports全局数组。

UART Driver框架的建立

关键数据结构：

struct uart_driver {
	struct module		*owner;
	const char		*driver_name;
	const char		*dev_name;
	int			 major;
	int			 minor;
	int			 nr;
	struct console		*cons;

	/*
	 * these are private; the low level driver should not
	 * touch these; they should be initialised to NULL
	 */
	struct uart_state	*state;
	struct tty_driver	*tty_driver;
};

struct uart_state {
	struct tty_port		port;

	enum uart_pm_state	pm_state;
	struct circ_buf		xmit;

	struct uart_port	*uart_port;
};
struct tty_driver {
	int	magic;		/* magic number for this structure */
	struct kref kref;	/* Reference management */
	struct cdev *cdevs;
	struct module	*owner;
	const char	*driver_name;
	const char	*name;
	int	name_base;	/* offset of printed name */
	int	major;		/* major device number */
	int	minor_start;	/* start of minor device number */
	unsigned int	num;	/* number of devices allocated */
	short	type;		/* type of tty driver */
	short	subtype;	/* subtype of tty driver */
	struct ktermios init_termios; /* Initial termios */
	unsigned long	flags;		/* tty driver flags */
	struct proc_dir_entry *proc_entry; /* /proc fs entry */
	struct tty_driver *other; /* only used for the PTY driver */

	/*
	 * Pointer to the tty data structures
	 */
	struct tty_struct **ttys;
	struct tty_port **ports;
	struct ktermios **termios;
	void *driver_state;

	/*
	 * Driver methods
	 */

	const struct tty_operations *ops;
	struct list_head tty_drivers;
};


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8250_core.c 文件中

static int __init serial8250_init(void)
{
	int ret;

	serial8250_isa_init_ports();//初始化serial8250_ports数组，此函数在注册uart硬件信息时执行一次，或者在这里执行一次。

	printk(KERN_INFO "Serial: 8250/16550 driver, "
		"%d ports, IRQ sharing %sabled\n", nr_uarts,
		share_irqs ? "en" : "dis");

	serial8250_reg.nr = UART_NR;
	ret = uart_register_driver(&serial8250_reg);//注册serial8250_reg uart_driver
	if (ret)
		goto out;

	serial8250_isa_devs = platform_device_alloc("serial8250",
						    PLAT8250_DEV_LEGACY);//alloc 一个platform device
	if (!serial8250_isa_devs) {
		ret = -ENOMEM;
		goto unreg_pnp;
	}

	ret = platform_device_add(serial8250_isa_devs);
	if (ret)
		goto put_dev;

	serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);

	ret = platform_driver_register(&serial8250_isa_driver);
	if (ret == 0)
		goto out;

	platform_device_del(serial8250_isa_devs);
put_dev:
	platform_device_put(serial8250_isa_devs);
unreg_uart_drv:
	uart_unregister_driver(&serial8250_reg);
out:
	return ret;
}

上面代码中注册的uart_driver:
static struct uart_driver serial8250_reg = {
	.owner			= THIS_MODULE,
	.driver_name		= "serial",
	.dev_name		= "ttyS",
	.major			= TTY_MAJOR,
	.minor			= 64,
	.cons			= SERIAL8250_CONSOLE,
};
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注册uart_driver部分：

struct tty_driver {
	int	magic;		/* magic number for this structure */
	struct kref kref;	/* Reference management */
	struct cdev *cdevs;
	struct module	*owner;
	const char	*driver_name;
	const char	*name;
	int	name_base;	/* offset of printed name */
	int	major;		/* major device number */
	int	minor_start;	/* start of minor device number */
	unsigned int	num;	/* number of devices allocated */
	short	type;		/* type of tty driver */
	short	subtype;	/* subtype of tty driver */
	struct ktermios init_termios; /* Initial termios */
	unsigned long	flags;		/* tty driver flags */
	struct proc_dir_entry *proc_entry; /* /proc fs entry */
	struct tty_driver *other; /* only used for the PTY driver */

	/*
	 * Pointer to the tty data structures
	 */
	struct tty_struct **ttys;
	struct tty_port **ports;
	struct ktermios **termios;
	void *driver_state;

	/*
	 * Driver methods
	 */

	const struct tty_operations *ops;
	struct list_head tty_drivers; //注册时 加入到tty_drivers全局链表中
};

struct tty_port {
	struct tty_bufhead	buf;		/* Locked internally */
	struct tty_struct	*tty;		/* Back pointer */
	struct tty_struct	*itty;		/* internal back ptr */
	const struct tty_port_operations *ops;	/* Port operations */
	spinlock_t		lock;		/* Lock protecting tty field */
	int			blocked_open;	/* Waiting to open */
	int			count;		/* Usage count */
	wait_queue_head_t	open_wait;	/* Open waiters */
	wait_queue_head_t	close_wait;	/* Close waiters */
	wait_queue_head_t	delta_msr_wait;	/* Modem status change */
	unsigned long		flags;		/* TTY flags ASY_*/
	unsigned long		iflags;		/* TTYP_ internal flags */
#define TTYP_FLUSHING			1  /* Flushing to ldisc in progress */
#define TTYP_FLUSHPENDING		2  /* Queued buffer flush pending */
	unsigned char		console:1,	/* port is a console */
				low_latency:1;	/* direct buffer flush */
	struct mutex		mutex;		/* Locking */
	struct mutex		buf_mutex;	/* Buffer alloc lock */
	unsigned char		*xmit_buf;	/* Optional buffer */
	unsigned int		close_delay;	/* Close port delay */
	unsigned int		closing_wait;	/* Delay for output */
	int			drain_delay;	/* Set to zero if no pure time
						   based drain is needed else
						   set to size of fifo */
	struct kref		kref;		/* Ref counter */
};


int uart_register_driver(struct uart_driver *drv)
{
	struct tty_driver *normal;
	int i, retval;

	BUG_ON(drv->state);

	/*
	 * Maybe we should be using a slab cache for this, especially if
	 * we have a large number of ports to handle.
	 */
	drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL);//创建struct uart_state 数组， 结合框架图， driver的state指向struct uart_state 数组。
	if (!drv->state)
		goto out;

	normal = alloc_tty_driver(drv->nr);//分配tty_driver
	if (!normal)
		goto out_kfree;

	drv->tty_driver = normal;
//初始化tty_driver的相关信息
	normal->driver_name	= drv->driver_name;
	normal->name		= drv->dev_name;
	normal->major		= drv->major;//4
	normal->minor_start	= drv->minor;//64
	normal->type		= TTY_DRIVER_TYPE_SERIAL;
	normal->subtype		= SERIAL_TYPE_NORMAL;
	normal->init_termios	= tty_std_termios;
	normal->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL;//终端控制属性标志
	normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;//终端波特率
	normal->flags		= TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;//设置flag，
	normal->driver_state    = drv;
	tty_set_operations(normal, &uart_ops);

	/*
	 * Initialise the UART state(s).
	 */
	for (i = 0; i < drv->nr; i++) {
		struct uart_state *state = drv->state + i;
		struct tty_port *port = &state->port;

		tty_port_init(port);//初始化uart_state内部的tty_port，同时初始化tty_port内部的tty_bufhead
		port->ops = &uart_port_ops;//设置port的ops
		port->close_delay     = HZ / 2;	/* .5 seconds */
		port->closing_wait    = 30 * HZ;/* 30 seconds */
	}

	retval = tty_register_driver(normal);//注册tty驱动
	if (retval >= 0)
		return retval;

	for (i = 0; i < drv->nr; i++)
		tty_port_destroy(&drv->state[i].port);
	put_tty_driver(normal);
out_kfree:
	kfree(drv->state);
out:
	return -ENOMEM;
}
//分配tty_driver flags = 0, lines = 3
struct tty_driver *__tty_alloc_driver(unsigned int lines, struct module *owner,
		unsigned long flags)
{
	struct tty_driver *driver;
	unsigned int cdevs = 1;
	int err;

	if (!lines || (flags & TTY_DRIVER_UNNUMBERED_NODE && lines > 1))
		return ERR_PTR(-EINVAL);

	driver = kzalloc(sizeof(struct tty_driver), GFP_KERNEL);
	if (!driver)
		return ERR_PTR(-ENOMEM);

	kref_init(&driver->kref);
	driver->magic = TTY_DRIVER_MAGIC;
	driver->num = lines;//设置tty_driver支持的设备数量
	driver->owner = owner;
	driver->flags = flags;

	if (!(flags & TTY_DRIVER_DEVPTS_MEM)) {
		driver->ttys = kcalloc(lines, sizeof(*driver->ttys),
				GFP_KERNEL);//分配长度为3的struct tty_struct *的数组
		driver->termios = kcalloc(lines, sizeof(*driver->termios),
				GFP_KERNEL);//分配终端属性结构struct ktermios *数组
		if (!driver->ttys || !driver->termios) {
			err = -ENOMEM;
			goto err_free_all;
		}
	}

	if (!(flags & TTY_DRIVER_DYNAMIC_ALLOC)) {
		driver->ports = kcalloc(lines, sizeof(*driver->ports),
				GFP_KERNEL);//分配长度为3的struct tty_port *数组
		if (!driver->ports) {
			err = -ENOMEM;
			goto err_free_all;
		}
		cdevs = lines;
	}

	driver->cdevs = kcalloc(cdevs, sizeof(*driver->cdevs), GFP_KERNEL);//分配长度为三的字符设备结构
	if (!driver->cdevs) {
		err = -ENOMEM;
		goto err_free_all;
	}

	return driver;
err_free_all:
	kfree(driver->ports);
	kfree(driver->ttys);
	kfree(driver->termios);
	kfree(driver);
	return ERR_PTR(err);
}
EXPORT_SYMBOL(__tty_alloc_driver);
//注册tty驱动函数
/*
 * Called by a tty driver to register itself.
 */
int tty_register_driver(struct tty_driver *driver)
{
	int error;
	int i;
	dev_t dev;
	struct device *d;

	if (!driver->major) {
		error = alloc_chrdev_region(&dev, driver->minor_start,
						driver->num, driver->name);
		if (!error) {
			driver->major = MAJOR(dev);
			driver->minor_start = MINOR(dev);
		}
	} else {
		dev = MKDEV(driver->major, driver->minor_start);//设备号4:64
		error = register_chrdev_region(dev, driver->num, driver->name);//注册字符设备驱动设备号空间
	}
	if (error < 0)
		goto err;

	if (driver->flags & TTY_DRIVER_DYNAMIC_ALLOC) {//没有执行
		error = tty_cdev_add(driver, dev, 0, driver->num);
		if (error)
			goto err_unreg_char;
	}

	mutex_lock(&tty_mutex);
	list_add(&driver->tty_drivers, &tty_drivers);//将新的ttydriver加入到tty_drivers全局链表中,查找driver时会根据设备号遍历这个链表。
	mutex_unlock(&tty_mutex);

	if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {//没有执行
		for (i = 0; i < driver->num; i++) {
			d = tty_register_device(driver, i, NULL);
			if (IS_ERR(d)) {
				error = PTR_ERR(d);
				goto err_unreg_devs;
			}
		}
	}
	proc_tty_register_driver(driver);//在/proc/tty/driver中创建proc entry
	driver->flags |= TTY_DRIVER_INSTALLED;
	return 0;

err_unreg_devs:
	for (i--; i >= 0; i--)
		tty_unregister_device(driver, i);

	mutex_lock(&tty_mutex);
	list_del(&driver->tty_drivers);
	mutex_unlock(&tty_mutex);

err_unreg_char:
	unregister_chrdev_region(dev, driver->num);
err:
	return error;
}
EXPORT_SYMBOL(tty_register_driver);
//注册uart_driver 完成
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添加port部分：

static void __init
serial8250_register_ports(struct uart_driver *drv, struct device *dev)
{
	int i;

	for (i = 0; i < nr_uarts; i++) {
		struct uart_8250_port *up = &serial8250_ports[i];

		if (up->port.dev)
			continue;

		up->port.dev = dev;

		if (up->port.flags & UPF_FIXED_TYPE)
			serial8250_init_fixed_type_port(up, up->port.type);

		uart_add_one_port(drv, &up->port);
	}
}

int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
{
	struct uart_state *state;
	struct tty_port *port;
	int ret = 0;
	struct device *tty_dev;

	BUG_ON(in_interrupt());

	if (uport->line >= drv->nr)
		return -EINVAL;

	state = drv->state + uport->line;
	port = &state->port;//参考系统框图tty_port 和uart_port建立的直观联系

	mutex_lock(&port_mutex);
	mutex_lock(&port->mutex);
	if (state->uart_port) {
		ret = -EINVAL;
		goto out;
	}

	state->uart_port = uport;
	state->pm_state = UART_PM_STATE_UNDEFINED;

	uport->cons = drv->cons;
	uport->state = state;

	/*
	 * If this port is a console, then the spinlock is already
	 * initialised.
	 */
	if (!(uart_console(uport) && (uport->cons->flags & CON_ENABLED))) {
		spin_lock_init(&uport->lock);
		lockdep_set_class(&uport->lock, &port_lock_key);
	}//当前没有注册console

	uart_configure_port(drv, state, uport);

	/*
	 * Register the port whether it's detected or not.  This allows
	 * setserial to be used to alter this ports parameters.
	 */
	tty_dev = tty_port_register_device_attr(port, drv->tty_driver,
			uport->line, uport->dev, port, tty_dev_attr_groups);
	if (likely(!IS_ERR(tty_dev))) {
		device_set_wakeup_capable(tty_dev, 1);
	} else {
		printk(KERN_ERR "Cannot register tty device on line %d\n",
		       uport->line);
	}

	/*
	 * Ensure UPF_DEAD is not set.
	 */
	uport->flags &= ~UPF_DEAD;

 out:
	mutex_unlock(&port->mutex);
	mutex_unlock(&port_mutex);

	return ret;
}

static void
uart_configure_port(struct uart_driver *drv, struct uart_state *state,
		    struct uart_port *port)
{
	unsigned int flags;

	/*
	 * If there isn't a port here, don't do anything further.
	 */
	if (!port->iobase && !port->mapbase && !port->membase)
		return;

	/*
	 * Now do the auto configuration stuff.  Note that config_port
	 * is expected to claim the resources and map the port for us.
	 */
	flags = 0;
	if (port->flags & UPF_AUTO_IRQ)
		flags |= UART_CONFIG_IRQ;
	if (port->flags & UPF_BOOT_AUTOCONF) {
		if (!(port->flags & UPF_FIXED_TYPE)) {
			port->type = PORT_UNKNOWN;
			flags |= UART_CONFIG_TYPE;
		}
		port->ops->config_port(port, flags);
	}

	if (port->type != PORT_UNKNOWN) {
		unsigned long flags;

		uart_report_port(drv, port); //输出注册port的打印信息

		/* Power up port for set_mctrl() */
		uart_change_pm(state, UART_PM_STATE_ON);

		/*
		 * Ensure that the modem control lines are de-activated.
		 * keep the DTR setting that is set in uart_set_options()
		 * We probably don't need a spinlock around this, but
		 */
		spin_lock_irqsave(&port->lock, flags);
		port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
		spin_unlock_irqrestore(&port->lock, flags);

		/*
		 * If this driver supports console, and it hasn't been
		 * successfully registered yet, try to re-register it.
		 * It may be that the port was not available.
		 */
		if (port->cons && !(port->cons->flags & CON_ENABLED))
			register_console(port->cons);//注册console

		/*
		 * Power down all ports by default, except the
		 * console if we have one.
		 */
		if (!uart_console(port))
			uart_change_pm(state, UART_PM_STATE_OFF);
	}
}

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console 相关：

struct console {
	char	name[16];
	void	(*write)(struct console *, const char *, unsigned);
	int	(*read)(struct console *, char *, unsigned);
	struct tty_driver *(*device)(struct console *, int *);
	void	(*unblank)(void);
	int	(*setup)(struct console *, char *);
	int	(*early_setup)(void);
	short	flags;
	short	index;
	int	cflag;
	void	*data;
	struct	 console *next;
};

static struct console serial8250_console = {
	.name		= "ttyS",
	.write		= serial8250_console_write,
	.device		= uart_console_device,
	.setup		= serial8250_console_setup,
	.early_setup	= serial8250_console_early_setup,
	.flags		= CON_PRINTBUFFER | CON_ANYTIME,
	.index		= -1,
	.data		= &serial8250_reg,
};
//注册console
void register_console(struct console *newcon)
{
	int i;
	unsigned long flags;
	struct console *bcon = NULL;

	/*
	 * before we register a new CON_BOOT console, make sure we don't
	 * already have a valid console
	 */
	if (console_drivers && newcon->flags & CON_BOOT) { //此时console_driver有值， 此时注册的console不是boot console， console_driver是指向console的指针，管理console链表
		/* find the last or real console */
		for_each_console(bcon) {
			if (!(bcon->flags & CON_BOOT)) {
				printk(KERN_INFO "Too late to register bootconsole %s%d\n",
					newcon->name, newcon->index);
				return;
			}
		}
	}

	if (console_drivers && console_drivers->flags & CON_BOOT)//此时console是boot console
		bcon = console_drivers; 

	if (preferred_console < 0 || bcon || !console_drivers)
		preferred_console = selected_console;

	if (newcon->early_setup)//无任何功能的函数
		newcon->early_setup();

	/*
	 *	See if we want to use this console driver. If we
	 *	didn't select a console we take the first one
	 *	that registers here.
	 */
	if (preferred_console < 0) { //会执行
		if (newcon->index < 0)
			newcon->index = 0;
		if (newcon->setup == NULL ||
		    newcon->setup(newcon, NULL) == 0) { 
			newcon->flags |= CON_ENABLED;//设置为使能
			if (newcon->device) {
				newcon->flags |= CON_CONSDEV; //此console确为console
				preferred_console = 0; //设置找到标志
			}
		}
	}

	/*
	 *	See if this console matches one we selected on
	 *	the command line.
	 */
	for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
			i++) { //console_cmdline 从传递给kernel的参数中获得信息
		if (strcmp(console_cmdline[i].name, newcon->name) != 0)
			continue;
		if (newcon->index >= 0 &&
		    newcon->index != console_cmdline[i].index) //参数为ttys1 此时newcon index =-1
			continue;
		if (newcon->index < 0)
			newcon->index = console_cmdline[i].index; //设置index = 1
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE
		if (console_cmdline[i].brl_options) {
			newcon->flags |= CON_BRL;
			braille_register_console(newcon,
					console_cmdline[i].index,
					console_cmdline[i].options,
					console_cmdline[i].brl_options);
			return;
		}
#endif
		if (newcon->setup &&
		    newcon->setup(newcon, console_cmdline[i].options) != 0) //重新设置波特率等信息
			break;
		newcon->flags |= CON_ENABLED;
		newcon->index = console_cmdline[i].index;
		if (i == selected_console) {
			newcon->flags |= CON_CONSDEV;
			preferred_console = selected_console;
		}
		break;
	}

	if (!(newcon->flags & CON_ENABLED))
		return;

	/*
	 * If we have a bootconsole, and are switching to a real console,
	 * don't print everything out again, since when the boot console, and
	 * the real console are the same physical device, it's annoying to
	 * see the beginning boot messages twice
	 */
	if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
		newcon->flags &= ~CON_PRINTBUFFER;

	/*
	 *	Put this console in the list - keep the
	 *	preferred driver at the head of the list.
	 */
	console_lock();
	if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
		newcon->next = console_drivers; //加入console_driver 链表
		console_drivers = newcon;
		if (newcon->next)
			newcon->next->flags &= ~CON_CONSDEV; //取消boot console的系统console标志
	} else {
		newcon->next = console_drivers->next;
		console_drivers->next = newcon;
	}
	if (newcon->flags & CON_PRINTBUFFER) {
		/*
		 * console_unlock(); will print out the buffered messages
		 * for us.
		 */
		raw_spin_lock_irqsave(&logbuf_lock, flags);
		console_seq = syslog_seq;
		console_idx = syslog_idx;
		console_prev = syslog_prev;
		raw_spin_unlock_irqrestore(&logbuf_lock, flags);
		/*
		 * We're about to replay the log buffer.  Only do this to the
		 * just-registered console to avoid excessive message spam to
		 * the already-registered consoles.
		 */
		exclusive_console = newcon;
	}
	console_unlock();
	console_sysfs_notify();

	/*
	 * By unregistering the bootconsoles after we enable the real console
	 * we get the "console xxx enabled" message on all the consoles -
	 * boot consoles, real consoles, etc - this is to ensure that end
	 * users know there might be something in the kernel's log buffer that
	 * went to the bootconsole (that they do not see on the real console)
	 */
	if (bcon &&
	    ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
	    !keep_bootcon) {
		/* we need to iterate through twice, to make sure we print
		 * everything out, before we unregister the console(s)
		 */
		printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
			newcon->name, newcon->index); //打印注册新console成功
		for_each_console(bcon)
			if (bcon->flags & CON_BOOT)
				unregister_console(bcon);
	} else {
		printk(KERN_INFO "%sconsole [%s%d] enabled\n",
			(newcon->flags & CON_BOOT) ? "boot" : "" ,
			newcon->name, newcon->index);
	}
}
EXPORT_SYMBOL(register_console);

struct device *tty_port_register_device_attr(struct tty_port *port,
		struct tty_driver *driver, unsigned index,
		struct device *device, void *drvdata,
		const struct attribute_group **attr_grp)
{
	tty_port_link_device(port, driver, index);
	return tty_register_device_attr(driver, index, device, drvdata,
			attr_grp);
}
EXPORT_SYMBOL_GPL(tty_port_register_device_attr);

void tty_port_link_device(struct tty_port *port,
		struct tty_driver *driver, unsigned index)
{
	if (WARN_ON(index >= driver->num))
		return;
	driver->ports[index] = port;//将tty_port保存到tty_driver的指针数组中
}

struct device *tty_register_device_attr(struct tty_driver *driver,
				   unsigned index, struct device *device,
				   void *drvdata,
				   const struct attribute_group **attr_grp)
{
	char name[64];
	dev_t devt = MKDEV(driver->major, driver->minor_start) + index;
	struct device *dev = NULL;
	int retval = -ENODEV;
	bool cdev = false;

	if (index >= driver->num) {
		printk(KERN_ERR "Attempt to register invalid tty line number "
		       " (%d).\n", index);
		return ERR_PTR(-EINVAL);
	}

	if (driver->type == TTY_DRIVER_TYPE_PTY)
		pty_line_name(driver, index, name);
	else
		tty_line_name(driver, index, name);//按设备号,根据tty_driver名ttyS设置名称

	if (!(driver->flags & TTY_DRIVER_DYNAMIC_ALLOC)) {//将之前创建的三个字符设备驱动加入到设备驱动框架中
		retval = tty_cdev_add(driver, devt, index, 1);
		if (retval)
			goto error;
		cdev = true;
	}

	dev = kzalloc(sizeof(*dev), GFP_KERNEL);
	if (!dev) {
		retval = -ENOMEM;
		goto error;
	}

	dev->devt = devt; //设置设备号
	dev->class = tty_class; //将会出现在tty class目录下
	dev->parent = device; //父设备是serial8250 platform device
	dev->release = tty_device_create_release;
	dev_set_name(dev, "%s", name); //设置设备名称
	dev->groups = attr_grp;// 属性文件组
	dev_set_drvdata(dev, drvdata);

	retval = device_register(dev); //添加到sys设备框架中， 之后通过mdev将会在/dev创建ttySn设备
	if (retval)
		goto error;

	return dev;

error:
	put_device(dev);
	if (cdev)
		cdev_del(&driver->cdevs[index]);
	return ERR_PTR(retval);
}
EXPORT_SYMBOL_GPL(tty_register_device_attr);
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到此为止，三个串口设备注册完成。系统启动后，在dev目录下会生成ttyS0， ttyS1, ttyS2,代表三个串口的三个设备节点。
总结下uart driver框架建立的全过程：
1.注册uart driver， 创建关联的tty driver和tty driver相关的字符设备驱动， 以及uart_state. uart_state 内部有tty_port.
2. 注册所有的uart port， 将uart port与tty port关联起来，同时注册系统参数指定的console， 最后将三个字符设备驱动和表示三个port的device注册到驱动模型中。
完成uart硬件设备注册和uart driver 框架建立后，就可以通过打开，读写ttySn节点来操作串口。（必要的serial_in, serial_out等硬件相关函数已经填好）。

ttySn设备的操作在下一节整理介绍。