串口驅動分兩階段初始化

第一階段 ?串口驅動沒有初始化前的準備工作，包括設備樹的解析，platform設備注冊

asmlinkage void __init start_kernel(void)
?? ?=>setup_arch
?? ??? ?=>find_legacy_serial_ports();
?? ??? ??? ??? ?=>path = of_get_property(of_chosen, "linux,stdout-path", NULL);//解析設備樹，標記默認輸出串口，uboot可以設置該節點
?? ??? ??? ??? ?if (path != NULL) //path為 /soc4080@F BE00 0000/serial@11C500
?? ??? ??? ??? ??? ?stdout = of_find_node_by_path(path);//無stdout
?? ??? ??? ??? ?=>for_each_compatible_node(np, "serial", "ns16550")//解析并遍歷設備樹，填充2個結構體 legacy_serial_infos 和 legacy_serial_ports，第二階段需要
?? ??? ??? ??? ??? ?struct device_node *parent = of_get_parent(np);//對于powerpc p4080,串口的父節點是soc, 恰好匹配{.type = "soc",}
?? ??? ??? ??? ??? ?if (of_match_node(legacy_serial_parents, parent) != NULL) {
?? ??? ??? ??? ??? ??? ?index = add_legacy_soc_port(np, np);//從設備樹解析串口基本配置參數
?? ??? ??? ??? ??? ??? ??? ?=>of_get_property(np, "clock-frequency", NULL)
?? ??? ??? ??? ??? ??? ??? ?=>of_get_property(np, "reg-shift", NULL)
?? ??? ??? ??? ??? ??? ??? ?=>of_get_property(np, "reg-offset", NULL)
?? ??? ??? ??? ??? ??? ??? ?=>of_get_property(np, "used-by-rtas", NULL)
?? ??? ??? ??? ??? ??? ??? ?=>addrp = of_get_address(soc_dev, 0, NULL, NULL);
?? ??? ??? ??? ??? ??? ??? ?=>addr = of_translate_address(soc_dev, addrp);
?? ??? ??? ??? ??? ??? ??? ?=>add_legacy_port(np, -1, UPIO_MEM, addr, addr, NO_IRQ, flags, 0);
?? ??? ??? ??? ??? ??? ??? ??? ?=>clk = of_get_property(np, "clock-frequency", NULL);
?? ??? ??? ??? ??? ??? ??? ??? ?=>spd = of_get_property(np, "current-speed", NULL);
?? ??? ??? ??? ??? ??? ??? ??? ?=>if (want_index >= 0 && want_index < MAX_LEGACY_SERIAL_PORTS)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?index = want_index;
?? ??? ??? ??? ??? ??? ??? ??? ?else
?? ??? ??? ??? ??? ??? ??? ??? ??? ?index = legacy_serial_count;
?? ??? ??? ??? ??? ??? ??? ??? ?=>if (index >= MAX_LEGACY_SERIAL_PORTS)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?return -1;
?? ??? ??? ??? ??? ??? ??? ??? ?if (index >= legacy_serial_count)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_count = index + 1;
?? ??? ??? ??? ??? ??? ??? ??? ?=>memset(&legacy_serial_ports[index], 0, ?sizeof(struct plat_serial8250_port));
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_ports[index].mapbase = base;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_ports[index].iotype = iotype;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_ports[index].uartclk = clock;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_ports[index].irq = irq;//這時中斷號為0，因為參數是NO_IRQ，后面會解析設備樹
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_ports[index].flags = flags;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_infos[index].taddr = taddr;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_infos[index].np = of_node_get(np);
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_infos[index].clock = clock;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_infos[index].speed = spd ? *spd : 0;
?? ??? ??? ??? ??? ??? ??? ??? ?legacy_serial_infos[index].irq_check_parent = irq_check_parent;
?? ??? ??? ??? ??? ??? ??? ??? ?return index;

?? ??? ??? ??? ??? ??? ?if (index >= 0 && np == stdout)
?? ??? ??? ??? ??? ??? ??? ?legacy_serial_console = index;//標記默認串口，這個分支不會走
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?of_node_put(parent);
?? ??? ??? ??? ?=>if (legacy_serial_console >= 0)//這個分支不會走
?? ??? ??? ??? ??? ?setup_legacy_serial_console(legacy_serial_console);
?? ?=>console_init();
?? ??? ?=>tty_ldisc_begin();//設置默認線路規程
?? ??? ??? ?=>tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
?? ??? ??? ??? ?=>tty_ldiscs[disc] = new_ldisc;
?? ??? ??? ??? ?new_ldisc->num = disc;
?? ??? ??? ??? ?new_ldisc->refcount = 0;
?? ??? ?=>call = __con_initcall_start;
?? ??? ?=>while (call < __con_initcall_end) {
?? ??? ??? ?==>(*call)();
?? ??? ??? ??? ?=>console_initcall(serial8250_console_init);//初始化serial8250_ports，
?? ??? ??? ??? ??? ?數組大小 #define UART_NR?? ?CONFIG_SERIAL_8250_NR_UARTS
?? ??? ??? ??? ??? ?unsigned int nr_uarts = CONFIG_SERIAL_8250_RUNTIME_UARTS;
?? ??? ??? ??? ??? ?=>serial8250_isa_init_ports();
?? ??? ??? ??? ??? ??? ?=>struct uart_8250_port *up;
?? ??? ??? ??? ??? ??? ?static int first = 1;//這個函數只會進來一次，在這邊進來了，后面再也進不來了
?? ??? ??? ??? ??? ??? ?int i, irqflag = 0;

?? ??? ??? ??? ??? ??? ?if (!first)
?? ??? ??? ??? ??? ??? ??? ?return;
?? ??? ??? ??? ??? ??? ?first = 0;
?? ??? ??? ??? ??? ??? ?=>for (i = 0; i < nr_uarts; i++) {
?? ??? ??? ??? ??? ??? ??? ?struct uart_8250_port *up = &serial8250_ports[i];

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

?? ??? ??? ??? ??? ??? ??? ?init_timer(&up->timer);
?? ??? ??? ??? ??? ??? ??? ?up->timer.function = serial8250_timeout;

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

?? ??? ??? ??? ??? ??? ??? ?up->port.ops = &serial8250_pops;
?? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ?=>后面的for循環在powerpc不會執行，因為在powerpc架構里面old_serial_port為空，而在x86則展開
?? ??? ??? ??? ??? ?=>register_console(&serial8250_console);
?? ??? ??? ??? ??? ??? ?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,//只向緩沖區打印
?? ??? ??? ??? ??? ??? ??? ?.index?? ??? ?= -1,
?? ??? ??? ??? ??? ??? ??? ?.data?? ??? ?= &serial8250_reg,
?? ??? ??? ??? ??? ??? ?};
?? ??? ??? ??? ??? ??? ?=>if (newcon->early_setup)
?? ??? ??? ??? ??? ??? ??? ?newcon->early_setup();//static int serial8250_console_early_setup(void)
?? ??? ??? ??? ??? ??? ??? ??? ?=>return serial8250_find_port_for_earlycon();
?? ??? ??? ??? ??? ??? ??? ??? ??? ?=>line = serial8250_find_port(port);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>for (line = 0; line < nr_uarts; line++) {
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?port = &serial8250_ports[line].port;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?if (uart_match_port(p, port))
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?return line;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ??? ??? ??? ?=>ret = update_console_cmdline("uart", 8250, "ttyS", line, device->options);
?? ??? ??? ??? ??? ??? ?=>if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {//將新的console加到鏈表里面, 也就是register的本質
?? ??? ??? ??? ??? ??? ??? ?newcon->next = console_drivers;
?? ??? ??? ??? ??? ??? ??? ?console_drivers = newcon;
?? ??? ??? ??? ??? ??? ??? ?if (newcon->next)
?? ??? ??? ??? ??? ??? ??? ??? ?newcon->next->flags &= ~CON_CONSDEV;
?? ??? ??? ??? ??? ??? ?} else {
?? ??? ??? ??? ??? ??? ??? ?newcon->next = console_drivers->next;
?? ??? ??? ??? ??? ??? ??? ?console_drivers->next = newcon;
?? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ?=>if (newcon->flags & CON_PRINTBUFFER) {
?? ??? ??? ??? ??? ??? ??? ?/*
?? ??? ??? ??? ??? ??? ??? ? * release_console_sem() will print out the buffered messages
?? ??? ??? ??? ??? ??? ??? ? * for us.
?? ??? ??? ??? ??? ??? ??? ? */
?? ??? ??? ??? ??? ??? ??? ?spin_lock_irqsave(&logbuf_lock, flags);
?? ??? ??? ??? ??? ??? ??? ?con_start = log_start;//打印buf的信息
?? ??? ??? ??? ??? ??? ??? ?spin_unlock_irqrestore(&logbuf_lock, flags);
?? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ?
?? ??? ??? ?==>call++;
?? ??? ?}
?? ?
int __init serial_dev_init(void)//注冊設備，根據設備樹，legacy_serial_infos 和 legacy_serial_ports 找中斷號
?? ?=>/*
?? ? * Before we register the platform serial devices, we need
?? ? * to fixup their interrupts and their IO ports.
?? ? */
?? ? for (i = 0; i < legacy_serial_count; i++) {
?? ??? ?struct plat_serial8250_port *port = &legacy_serial_ports[i];
?? ??? ?struct device_node *np = legacy_serial_infos[i].np;

?? ??? ?if (port->irq == NO_IRQ)
?? ??? ??? ?fixup_port_irq(i, np, port);
?? ??? ??? ??? ?=>virq = irq_of_parse_and_map(np, 0);//解析設備書找中斷號
?? ??? ??? ??? ?=>port->irq = virq;//找到中斷了
?? ??? ?if ((port->iotype == UPIO_MEM) || (port->iotype == UPIO_TSI))
?? ??? ??? ?fixup_port_mmio(i, np, port);
?? ??? ??? ??? ?=>port->membase = ioremap(port->mapbase, 0x100);
?? ?}
?? ?=>return platform_device_register(&serial_device);//注冊 serial_device platform設備，第二階段需要用
?? ??? ?static struct platform_device serial_device = {
?? ??? ?.name?? ?= "serial8250",
?? ??? ?.id?? ?= PLAT8250_DEV_PLATFORM,
?? ??? ?.dev?? ?= {
?? ??? ??? ?.platform_data = legacy_serial_ports,//legacy_serial_ports 在前面已經初始化
?? ??? ?},
?? ?};?? ?
?? ??? ?
第二階段 正式初始化
int __init serial8250_init(void)
?? ?=>serial8250_reg.nr = UART_NR;
?? ?ret = uart_register_driver(&serial8250_reg);//int uart_register_driver(struct uart_driver *drv)
?? ??? ?=>struct tty_driver *normal;
?? ??? ?=>drv->state = kzalloc(sizeof(struct uart_state) * drv->nr, GFP_KERNEL);
?? ??? ?=>normal = alloc_tty_driver(drv->nr);
?? ??? ?=>drv->tty_driver = normal; ?uart_driver 與 tty_driver 關聯
?? ??? ?=>normal->owner?? ??? ?= drv->owner;
?? ??? ?normal->driver_name?? ?= drv->driver_name;
?? ??? ?normal->name?? ??? ?= drv->dev_name;
?? ??? ?normal->major?? ??? ?= drv->major;
?? ??? ?normal->minor_start?? ?= drv->minor;
?? ??? ?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;
?? ??? ?normal->init_termios.c_ispeed = normal->init_termios.c_ospeed = 9600;
?? ??? ?normal->flags?? ??? ?= TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
?? ??? ?normal->driver_state ? ?= drv;tty_driver 與 uart_driver 關聯
?? ??? ?tty_set_operations(normal, &uart_ops);//void tty_set_operations(struct tty_driver *driver, const struct tty_operations *op)
?? ??? ??? ?=>driver->ops = op;
?? ??? ?=>/*
?? ??? ? * 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);
?? ??? ??? ?port->close_delay ? ? = 500;?? ?/* .5 seconds */
?? ??? ??? ?port->closing_wait ? ?= 30000;?? ?/* 30 seconds */
?? ??? ??? ?tasklet_init(&state->tlet, uart_tasklet_action,
?? ??? ??? ??? ??? ? (unsigned long)state);
?? ??? ?}
?? ??? ?=>retval = tty_register_driver(normal);
?? ??? ??? ?=>if (!(driver->flags & TTY_DRIVER_DEVPTS_MEM) && driver->num) {
?? ??? ??? ??? ?p = kzalloc(driver->num * 2 * sizeof(void *), GFP_KERNEL);
?? ??? ??? ??? ?if (!p)
?? ??? ??? ??? ??? ?return -ENOMEM;
?? ??? ??? ?}
?? ??? ??? ?=>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);
?? ??? ??? ?error = register_chrdev_region(dev, driver->num, driver->name);
?? ??? ?}
?? ??? ?=>if (p) {
?? ??? ??? ?driver->ttys = (struct tty_struct **)p;
?? ??? ??? ?driver->termios = (struct ktermios **)(p + driver->num);
?? ??? ?}
?? ??? ?=>cdev_init(&driver->cdev, &tty_fops);
?? ??? ?driver->cdev.owner = driver->owner;
?? ??? ?error = cdev_add(&driver->cdev, dev, driver->num);
?? ??? ?=>list_add(&driver->tty_drivers, &tty_drivers);
?? ??? ?=>if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {//這個流程不會進入，因為 TTY_DRIVER_DYNAMIC_DEV 被置
?? ??? ??? ?for (i = 0; i < driver->num; i++)
?? ??? ??? ??? ?tty_register_device(driver, i, NULL);
?? ??? ?}
?? ??? ?=>proc_tty_register_driver(driver);
?? ??? ?=>driver->flags |= TTY_DRIVER_INSTALLED;
?? ?=>serial8250_isa_devs = platform_device_alloc("serial8250", PLAT8250_DEV_LEGACY);
?? ?=>ret = platform_device_add(serial8250_isa_devs);//這個東東對x86有用，對于powerpc沒有太大用
?? ?=>serial8250_register_ports(&serial8250_reg, &serial8250_isa_devs->dev);
?? ?=>ret = platform_driver_register(&serial8250_isa_driver);//注冊 serial8250_isa_driver platform驅動, 與serial_device platform設備serial_device發生match, 調用probe函數
?? ??? ?static struct platform_driver serial8250_isa_driver = {
?? ??? ??? ?.probe?? ??? ?= serial8250_probe,
?? ??? ??? ?.remove?? ??? ?= __devexit_p(serial8250_remove),
?? ??? ??? ?.suspend?? ?= serial8250_suspend,
?? ??? ??? ?.resume?? ??? ?= serial8250_resume,
?? ??? ??? ?.driver?? ??? ?= {
?? ??? ??? ??? ?.name?? ?= "serial8250",
?? ??? ??? ??? ?.owner?? ?= THIS_MODULE,
?? ??? ??? ?},
?? ??? ?};

int __devinit serial8250_probe(struct platform_device *dev)
?? ?=>struct plat_serial8250_port *p = dev->dev.platform_data;
?? ?=>memset(&port, 0, sizeof(struct uart_port));
?? ?=>for (i = 0; p && p->flags != 0; p++, i++) {
?? ??? ?port.iobase?? ??? ?= p->iobase;
?? ??? ?port.membase?? ??? ?= p->membase;
?? ??? ?port.irq?? ??? ?= p->irq;
?? ??? ?port.irqflags?? ??? ?= p->irqflags;
?? ??? ?port.uartclk?? ??? ?= p->uartclk;
?? ??? ?port.regshift?? ??? ?= p->regshift;
?? ??? ?port.iotype?? ??? ?= p->iotype;
?? ??? ?port.flags?? ??? ?= p->flags;
?? ??? ?port.mapbase?? ??? ?= p->mapbase;
?? ??? ?port.hub6?? ??? ?= p->hub6;
?? ??? ?port.private_data?? ?= p->private_data;
?? ??? ?port.type?? ??? ?= p->type;
?? ??? ?port.serial_in?? ??? ?= p->serial_in;
?? ??? ?port.serial_out?? ??? ?= p->serial_out;
?? ??? ?port.dev?? ??? ?= &dev->dev;
?? ??? ?port.irqflags?? ??? ?|= irqflag;
?? ??? ?ret = serial8250_register_port(&port);
?? ??? ??? ?=>uart = serial8250_find_match_or_unused(port);
?? ??? ??? ?=>if (uart) {
?? ??? ??? ??? ?uart_remove_one_port(&serial8250_reg, &uart->port);

?? ??? ??? ??? ?uart->port.iobase ? ? ? = port->iobase;
?? ??? ??? ??? ?uart->port.membase ? ? ?= port->membase;
?? ??? ??? ??? ?uart->port.irq ? ? ? ? ?= port->irq;
?? ??? ??? ??? ?uart->port.irqflags ? ? = port->irqflags;
?? ??? ??? ??? ?uart->port.uartclk ? ? ?= port->uartclk;
?? ??? ??? ??? ?uart->port.fifosize ? ? = port->fifosize;
?? ??? ??? ??? ?uart->port.regshift ? ? = port->regshift;
?? ??? ??? ??? ?uart->port.iotype ? ? ? = port->iotype;
?? ??? ??? ??? ?uart->port.flags ? ? ? ?= port->flags | UPF_BOOT_AUTOCONF;
?? ??? ??? ??? ?uart->port.mapbase ? ? ?= port->mapbase;
?? ??? ??? ??? ?uart->port.private_data = port->private_data;
?? ??? ??? ??? ?if (port->dev)
?? ??? ??? ??? ??? ?uart->port.dev = port->dev;

?? ??? ??? ??? ?if (port->flags & UPF_FIXED_TYPE)
?? ??? ??? ??? ??? ?serial8250_init_fixed_type_port(uart, port->type);

?? ??? ??? ??? ?set_io_from_upio(&uart->port);
?? ??? ??? ??? ?/* Possibly override default I/O functions. ?*/
?? ??? ??? ??? ?if (port->serial_in)
?? ??? ??? ??? ??? ?uart->port.serial_in = port->serial_in;
?? ??? ??? ??? ?if (port->serial_out)
?? ??? ??? ??? ??? ?uart->port.serial_out = port->serial_out;

?? ??? ??? ??? ?ret = uart_add_one_port(&serial8250_reg, &uart->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;
?? ??? ??? ??? ??? ?=>state = drv->state + uport->line;line 從0開始
?? ??? ??? ??? ??? ?port = &state->port;
?? ??? ??? ??? ??? ?state->uart_port = uport; uart_port 與 uart_driver 關聯 ?( drv->state + uport->line)->uart_port = uport
?? ??? ??? ??? ??? ?state->pm_state = -1;

?? ??? ??? ??? ??? ?uport->cons = drv->cons;
?? ??? ??? ??? ??? ?uport->state = state; uart_driver 與 uart_port 關聯 uport->state = drv->state + uport->line
?? ??? ??? ??? ??? ?=>uart_configure_port(drv, state, uport);
?? ??? ??? ??? ??? ??? ?=>port->ops->config_port(port, flags);
?? ??? ??? ??? ??? ??? ?/\
?? ??? ??? ??? ??? ??? ?||
?? ??? ??? ??? ??? ??? ?V
?? ??? ??? ??? ??? ??? ?.config_port?? ?= serial8250_config_port//硬件寄存器配置都在這里面
?? ??? ??? ??? ??? ??? ??? ?=>autoconfig(up, probeflags);
?? ??? ??? ??? ??? ??? ??? ??? ?=>scratch = serial_in(up, UART_IIR) >> 6;
?? ??? ??? ??? ??? ??? ??? ??? ?=>switch (scratch)
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?case 3:
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?autoconfig_16550a(up);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ??? ?=>uart_report_port(drv, port);
?? ??? ??? ??? ??? ??? ?=>uart_change_pm(state, 0);/* Power up port for set_mctrl() */
?? ??? ??? ??? ??? ??? ?=>port->ops->set_mctrl(port, port->mctrl & TIOCM_DTR);
?? ??? ??? ??? ??? ??? ?=>register_console(port->cons);
?? ??? ??? ??? ??? ?=>tty_dev = tty_register_device(drv->tty_driver, uport->line, uport->dev);
?? ??? ??? ??? ??? ?=>if (likely(!IS_ERR(tty_dev))) {
?? ??? ??? ??? ??? ??? ?device_init_wakeup(tty_dev, 1);
?? ??? ??? ??? ??? ??? ?device_set_wakeup_enable(tty_dev, 0);
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ?if (ret == 0)
?? ??? ??? ??? ??? ?ret = uart->port.line;
?? ??? ??? ?}
?? ??? ?}
?? ?}
?? ?return 0;

內核態打印?? ??? ?
int printk(const char *fmt, ...)
?? ?=>r = vprintk(fmt, args);
?? ??? ?=>preempt_disable();//關閉搶占和關中斷
?? ??? ?raw_local_irq_save(flags);
?? ??? ?=>/* Emit the output into the temporary buffer *///準備好緩沖區
?? ??? ?printed_len += vscnprintf(printk_buf + printed_len,
?? ??? ??? ??? ??? ? ?sizeof(printk_buf) - printed_len, fmt, args);

?? ??? ?p = printk_buf;
?? ??? ?=>for ( ; *p; p++)//Copy the output into log_buf.
?? ??? ??? ??? ?emit_log_char('<');
?? ??? ??? ??? ?emit_log_char(current_log_level + '0');
?? ??? ??? ??? ?emit_log_char('>');
?? ??? ??? ??? ?if (!*p)
?? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ?emit_log_char(*p);
?? ??? ??? ??? ?if (*p == '\n')
?? ??? ??? ??? ??? ?new_text_line = 1;
?? ??? ?=>if (acquire_console_semaphore_for_printk(this_cpu))
?? ??? ??? ?release_console_sem();
?? ??? ??? ??? ?=>for ( ; ; ) {//串口打印
?? ??? ??? ??? ??? ?spin_lock_irqsave(&logbuf_lock, flags);
?? ??? ??? ??? ??? ?wake_klogd |= log_start - log_end;
?? ??? ??? ??? ??? ?if (con_start == log_end)
?? ??? ??? ??? ??? ??? ?break;?? ??? ??? ?/* Nothing to print */
?? ??? ??? ??? ??? ?_con_start = con_start;
?? ??? ??? ??? ??? ?_log_end = log_end;
?? ??? ??? ??? ??? ?con_start = log_end;?? ??? ?/* Flush */
?? ??? ??? ??? ??? ?spin_unlock(&logbuf_lock);
?? ??? ??? ??? ??? ?stop_critical_timings();?? ?/* don't trace print latency */
?? ??? ??? ??? ??? ?call_console_drivers(_con_start, _log_end);
?? ??? ??? ??? ??? ??? ?=>_call_console_drivers(start_print, cur_index, msg_level);
?? ??? ??? ??? ??? ??? ??? ?=>if ((msg_log_level < console_loglevel || ignore_loglevel) &&
?? ??? ??? ??? ??? ??? ??? ??? ??? ?console_drivers && start != end) { //根據打印級別console_loglevel決定什么信息打印到串口上
?? ??? ??? ??? ??? ??? ??? ??? ?if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {
?? ??? ??? ??? ??? ??? ??? ??? ??? ?/* wrapped write */
?? ??? ??? ??? ??? ??? ??? ??? ??? ?__call_console_drivers(start & LOG_BUF_MASK, log_buf_len);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>con->write(con, &LOG_BUF(start), end - start);//對于第一階段來說，是 serial8250_console_write
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>struct uart_8250_port *up = &serial8250_ports[co->index];
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>ier = serial_in(up, UART_IER);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>uart_console_write(&up->port, s, count, serial8250_console_putchar);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>putchar(port, *s);//serial8250_console_putchar
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>struct uart_8250_port *up = (struct uart_8250_port *)port;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>wait_for_xmitr(up, UART_LSR_THRE);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>serial_out(up, UART_TX, ch);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>wait_for_xmitr(up, BOTH_EMPTY);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>serial_out(up, UART_IER, ier);
?? ??? ??? ??? ??? ??? ??? ??? ??? ?__call_console_drivers(0, end & LOG_BUF_MASK);
?? ??? ??? ??? ??? ??? ??? ??? ?} else {
?? ??? ??? ??? ??? ??? ??? ??? ??? ?__call_console_drivers(start, end);
?? ??? ??? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?start_critical_timings();
?? ??? ??? ??? ??? ?local_irq_restore(flags);
?? ??? ??? ??? ?}
?? ??? ??? ??? ?=>if (wake_klogd)//喚醒klogd，后續可以提交給syslogd打印到syslog或者messages里面
?? ??? ??? ??? ??? ?wake_up_klogd();
?? ??? ?=>raw_local_irq_restore(flags);
?? ??? ?preempt_enable();
?? ??? ??? ?
第二階段串口初始化完畢后
打開串口的代碼調用關系如下
tty_open
chrdev_open
__dentry_open
do_last
do_filp_open
do_sys_open
ret_from_syscall

int tty_open(struct inode *inode, struct file *filp)
?? ?=>dev_t device = inode->i_rdev;
?? ?=>driver = get_tty_driver(device, &index);
?? ?=>if (!tty)
?? ??? ?tty = tty_driver_lookup_tty(driver, inode, index);
?? ?=>if (tty) {
?? ??? ?retval = tty_reopen(tty);
?? ??? ?if (retval)
?? ??? ??? ?tty = ERR_PTR(retval);
?? ?} else
?? ??? ?tty = tty_init_dev(driver, index, 0);//struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx, int first_ok)
?? ??? ??? ?=>struct tty_struct *tty
?? ??? ??? ?=>tty = alloc_tty_struct();
?? ??? ??? ?=>initialize_tty_struct(tty, driver, idx);
?? ??? ??? ??? ?=>tty->magic = TTY_MAGIC;
?? ??? ??? ??? ?tty_ldisc_init(tty);
?? ??? ??? ??? ?tty->buf.head = tty->buf.tail = NULL;
?? ??? ??? ??? ?tty_buffer_init(tty);
?? ??? ??? ??? ?tty->driver = driver;
?? ??? ??? ??? ?tty->ops = driver->ops;
?? ??? ??? ??? ?tty->index = idx;
?? ??? ??? ??? ?tty_line_name(driver, idx, tty->name);
?? ??? ??? ?=>retval = tty_driver_install_tty(driver, tty);
?? ??? ??? ?=>retval = tty_ldisc_setup(tty, tty->link);
?? ??? ??? ??? ?=>struct tty_ldisc *ld = tty->ldisc;
?? ??? ??? ??? ?=>retval = tty_ldisc_open(tty, ld);
?? ??? ??? ??? ?=>if (o_tty)?
?? ??? ??? ??? ??? ?retval = tty_ldisc_open(o_tty, o_tty->ldisc);
?? ??? ??? ??? ??? ?tty_ldisc_enable(o_tty);
?? ??? ??? ??? ?=>tty_ldisc_enable(tty);
?? ?=>filp->private_data = tty;
?? ?=>if (!retval) {
?? ??? ?if (tty->ops->open)
?? ??? ??? ?retval = tty->ops->open(tty, filp);//根據inode找到主從設備號，根據主從設備號從tty_drivers鏈表找到tty_driver
?? ??? ??? ?^
?? ??? ??? ?||
?? ??? ??? ?v
?? ??? ??? ?uart_open
?? ??? ??? ??? ?=>struct uart_driver *drv = (struct uart_driver *)tty->driver->driver_state;
?? ??? ??? ??? ?struct uart_state *state;
?? ??? ??? ??? ?struct tty_port *port;
?? ??? ??? ??? ?int retval, line = tty->index;
?? ??? ??? ??? ?=>state = uart_get(drv, line);
?? ??? ??? ??? ??? ?=>state = drv->state + line;
?? ??? ??? ??? ??? ?=>port = &state->port;
?? ??? ??? ??? ??? ?=>port->count++;
?? ??? ??? ??? ??? ?=>return state;
?? ??? ??? ??? ?=>port = &state->port;
?? ??? ??? ??? ?=>tty->driver_data = state;
?? ??? ??? ??? ?state->uart_port->state = state;
?? ??? ??? ??? ?tty->low_latency = (state->uart_port->flags & UPF_LOW_LATENCY) ? 1 : 0;
?? ??? ??? ??? ?tty->alt_speed = 0;
?? ??? ??? ??? ?tty_port_tty_set(port, tty);
?? ??? ??? ??? ?=>if (port->count == 1)
?? ??? ??? ??? ??? ?uart_change_pm(state, 0);
?? ??? ??? ??? ?=>retval = uart_startup(state, 0);
?? ??? ??? ??? ??? ?=>if (!state->xmit.buf) {
?? ??? ??? ??? ??? ??? ?/* This is protected by the per port mutex */
?? ??? ??? ??? ??? ??? ?page = get_zeroed_page(GFP_KERNEL);
?? ??? ??? ??? ??? ??? ?if (!page)
?? ??? ??? ??? ??? ??? ??? ?return -ENOMEM;

?? ??? ??? ??? ??? ??? ?state->xmit.buf = (unsigned char *) page;
?? ??? ??? ??? ??? ??? ?uart_circ_clear(&state->xmit);
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?=>retval = uport->ops->startup(uport);
?? ??? ??? ??? ??? ?^
?? ??? ??? ??? ??? ?||
?? ??? ??? ??? ??? ?v
?? ??? ??? ??? ??? ?serial8250_startup
?? ??? ??? ??? ??? ??? ?=>struct uart_port *uport = state->uart_port;
?? ??? ??? ??? ??? ??? ?struct tty_port *port = &state->port;
?? ??? ??? ??? ??? ??? ?unsigned long page;
?? ??? ??? ??? ??? ??? ?=>if (!state->xmit.buf) {
?? ??? ??? ??? ??? ??? ??? ?/* This is protected by the per port mutex */
?? ??? ??? ??? ??? ??? ??? ?page = get_zeroed_page(GFP_KERNEL);
?? ??? ??? ??? ??? ??? ??? ?if (!page)
?? ??? ??? ??? ??? ??? ??? ??? ?return -ENOMEM;

?? ??? ??? ??? ??? ??? ??? ?state->xmit.buf = (unsigned char *) page;
?? ??? ??? ??? ??? ??? ??? ?uart_circ_clear(&state->xmit);
?? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ?=>retval = uport->ops->startup(uport);
?? ??? ??? ??? ??? ??? ?^
?? ??? ??? ??? ??? ??? ?||
?? ??? ??? ??? ??? ??? ?v
?? ??? ??? ??? ??? ??? ?static int serial8250_startup(struct uart_port *port)
?? ??? ??? ??? ??? ??? ??? ?=>struct uart_8250_port *up = (struct uart_8250_port *)port;
?? ??? ??? ??? ??? ??? ??? ?=>(void) serial_inp(up, UART_LSR);//先關閉硬件中斷源
?? ??? ??? ??? ??? ??? ??? ?(void) serial_inp(up, UART_RX);
?? ??? ??? ??? ??? ??? ??? ?(void) serial_inp(up, UART_IIR);
?? ??? ??? ??? ??? ??? ??? ?(void) serial_inp(up, UART_MSR);
?? ??? ??? ??? ??? ??? ??? ?=>spin_lock_irqsave(&up->port.lock, flags);//使能中斷控制器
?? ??? ??? ??? ??? ??? ??? ?if (up->port.irqflags & IRQF_SHARED)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?enable_irq(up->port.irq);
?? ??? ??? ??? ??? ??? ??? ?spin_unlock_irqrestore(&up->port.lock, flags);
?? ??? ??? ??? ??? ??? ??? ?=>retval = serial_link_irq_chain(up);
?? ??? ??? ??? ??? ??? ??? ??? ?=>ret = request_irq(up->port.irq, serial8250_interrupt, irq_flags, "serial", i);//掛接中斷處理例程
?? ??? ??? ??? ??? ??? ??? ?=>spin_lock_irqsave(&up->port.lock, flags);//重新使能中斷源
?? ??? ??? ??? ??? ??? ??? ?/*
?? ??? ??? ??? ??? ??? ??? ? * Do a quick test to see if we receive an
?? ??? ??? ??? ??? ??? ??? ? * interrupt when we enable the TX irq.
?? ??? ??? ??? ??? ??? ??? ? */
?? ??? ??? ??? ??? ??? ??? ?serial_outp(up, UART_IER, UART_IER_THRI);
?? ??? ??? ??? ??? ??? ??? ?lsr = serial_in(up, UART_LSR);
?? ??? ??? ??? ??? ??? ??? ?iir = serial_in(up, UART_IIR);
?? ??? ??? ??? ??? ??? ??? ?serial_outp(up, UART_IER, 0);
?? ??? ??? ??? ??? ??? ??? ?spin_unlock_irqrestore(&up->port.lock, flags);
?? ??? ??? ??? ??? ??? ??? ?=>關閉再打開
?? ??? ??? ??? ??? ??? ??? ?/*
?? ??? ??? ??? ??? ??? ??? ? * Clear the interrupt registers again for luck, and clear the
?? ??? ??? ??? ??? ??? ??? ? * saved flags to avoid getting false values from polling
?? ??? ??? ??? ??? ??? ??? ? * routines or the previous session.
?? ??? ??? ??? ??? ??? ??? ? */
?? ??? ??? ??? ??? ??? ??? ?serial_inp(up, UART_LSR);
?? ??? ??? ??? ??? ??? ??? ?serial_inp(up, UART_RX);
?? ??? ??? ??? ??? ??? ??? ?serial_inp(up, UART_IIR);
?? ??? ??? ??? ??? ??? ??? ?serial_inp(up, UART_MSR);
?? ??? ??? ??? ??? ??? ??? ?up->lsr_saved_flags = 0;
?? ??? ??? ??? ??? ??? ??? ?up->msr_saved_flags = 0;

?? ??? ??? ??? ??? ??? ??? ?/*
?? ??? ??? ??? ??? ??? ??? ? * Finally, enable interrupts. ?Note: Modem status interrupts
?? ??? ??? ??? ??? ??? ??? ? * are set via set_termios(), which will be occurring imminently
?? ??? ??? ??? ??? ??? ??? ? * anyway, so we don't enable them here.
?? ??? ??? ??? ??? ??? ??? ? */
?? ??? ??? ??? ??? ??? ??? ?up->ier = UART_IER_RLSI | UART_IER_RDI;
?? ??? ??? ??? ??? ??? ??? ?serial_outp(up, UART_IER, up->ier);

?? ??? ??? ??? ??? ??? ??? ?if (up->port.flags & UPF_FOURPORT) {
?? ??? ??? ??? ??? ??? ??? ??? ?unsigned int icp;
?? ??? ??? ??? ??? ??? ??? ??? ?/*
?? ??? ??? ??? ??? ??? ??? ??? ? * Enable interrupts on the AST Fourport board
?? ??? ??? ??? ??? ??? ??? ??? ? */
?? ??? ??? ??? ??? ??? ??? ??? ?icp = (up->port.iobase & 0xfe0) | 0x01f;
?? ??? ??? ??? ??? ??? ??? ??? ?outb_p(0x80, icp);
?? ??? ??? ??? ??? ??? ??? ??? ?(void) inb_p(icp);
?? ??? ??? ??? ??? ??? ??? ?}

寫操作串口調用棧如下
uart_start
uart_write
n_tty_write
tty_write
vfs_write
sys_write
ret_from_syscall

輸出的代碼調用關系如下
ssize_t tty_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos)
?? ?=>struct tty_struct *tty;
?? ?struct inode *inode = file->f_path.dentry->d_inode;
?? ?struct tty_ldisc *ld;
?? ?=>tty = (struct tty_struct *)file->private_data;
?? ?ld = tty_ldisc_ref_wait(tty);
?? ?=>do_tty_write(ld->ops->write, tty, file, buf, count);
?? ??? ?for (;;)
?? ??? ??? ?copy_from_user(tty->write_buf, buf, size)
?? ??? ??? ?ret = write(tty, file, tty->write_buf, size)
?? ??? ??? ?^
?? ??? ??? ?||
?? ??? ??? ?v
?? ??? ??? ?ld->ops->write
?? ??? ??? ?^
?? ??? ??? ?||
?? ??? ??? ?v
?? ??? ??? ?n_tty_write
?? ??? ??? ??? ?struct tty_ldisc_ops tty_ldisc_N_TTY = {
?? ??? ??? ??? ??? ?.magic ? ? ? ? ? = TTY_LDISC_MAGIC,
?? ??? ??? ??? ??? ?.name ? ? ? ? ? ?= "n_tty",
?? ??? ??? ??? ??? ?.open ? ? ? ? ? ?= n_tty_open,
?? ??? ??? ??? ??? ?.close ? ? ? ? ? = n_tty_close,
?? ??? ??? ??? ??? ?.flush_buffer ? ?= n_tty_flush_buffer,
?? ??? ??? ??? ??? ?.chars_in_buffer = n_tty_chars_in_buffer,
?? ??? ??? ??? ??? ?.read ? ? ? ? ? ?= n_tty_read,
?? ??? ??? ??? ??? ?.write ? ? ? ? ? = n_tty_write,
?? ??? ??? ??? ??? ?.ioctl ? ? ? ? ? = n_tty_ioctl,
?? ??? ??? ??? ??? ?.set_termios ? ? = n_tty_set_termios,
?? ??? ??? ??? ??? ?.poll ? ? ? ? ? ?= n_tty_poll,
?? ??? ??? ??? ??? ?.receive_buf ? ? = n_tty_receive_buf,
?? ??? ??? ??? ??? ?.write_wakeup ? ?= n_tty_write_wakeup
?? ??? ??? ??? ?};
?? ??? ??? ??? ?=>const unsigned char *b = buf;
?? ??? ??? ??? ?DECLARE_WAITQUEUE(wait, current);
?? ??? ??? ??? ?int c;
?? ??? ??? ??? ?=>process_echoes(tty);
?? ??? ??? ??? ?=>add_wait_queue(&tty->write_wait, &wait);
?? ??? ??? ??? ?=>while (1)?
?? ??? ??? ??? ??? ?==>set_current_state(TASK_INTERRUPTIBLE);
?? ??? ??? ??? ??? ?if (signal_pending(current)) {
?? ??? ??? ??? ??? ??? ?retval = -ERESTARTSYS;
?? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?==>while (nr > 0) {
?? ??? ??? ??? ??? ??? ?===>c = tty->ops->write(tty, b, nr);
?? ??? ??? ??? ??? ??? ?^
?? ??? ??? ??? ??? ??? ?||
?? ??? ??? ??? ??? ??? ?v
?? ??? ??? ??? ??? ??? ?uart_write
?? ??? ??? ??? ??? ??? ??? ?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,
?? ??? ??? ??? ??? ??? ??? ??? ?.set_ldisc?? ?= uart_set_ldisc,
?? ??? ??? ??? ??? ??? ??? ??? ?.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
?? ??? ??? ??? ??? ??? ??? ??? ?.proc_fops?? ?= &uart_proc_fops,
?? ??? ??? ??? ??? ??? ??? ?#endif
?? ??? ??? ??? ??? ??? ??? ??? ?.tiocmget?? ?= uart_tiocmget,
?? ??? ??? ??? ??? ??? ??? ??? ?.tiocmset?? ?= uart_tiocmset,
?? ??? ??? ??? ??? ??? ??? ?#ifdef CONFIG_CONSOLE_POLL
?? ??? ??? ??? ??? ??? ??? ??? ?.poll_init?? ?= uart_poll_init,
?? ??? ??? ??? ??? ??? ??? ??? ?.poll_get_char?? ?= uart_poll_get_char,
?? ??? ??? ??? ??? ??? ??? ??? ?.poll_put_char?? ?= uart_poll_put_char,
?? ??? ??? ??? ??? ??? ??? ?#endif
?? ??? ??? ??? ??? ??? ??? ?};
?? ??? ??? ??? ??? ??? ??? ?=>struct uart_state *state = tty->driver_data;
?? ??? ??? ??? ??? ??? ??? ?struct uart_port *port;
?? ??? ??? ??? ??? ??? ??? ?struct circ_buf *circ;
?? ??? ??? ??? ??? ??? ??? ?unsigned long flags;
?? ??? ??? ??? ??? ??? ??? ?=>port = state->uart_port;
?? ??? ??? ??? ??? ??? ??? ?circ = &state->xmit;
?? ??? ??? ??? ??? ??? ??? ?=>while (1) {
?? ??? ??? ??? ??? ??? ??? ??? ?c = CIRC_SPACE_TO_END(circ->head, circ->tail, UART_XMIT_SIZE);
?? ??? ??? ??? ??? ??? ??? ??? ?if (count < c)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?c = count;
?? ??? ??? ??? ??? ??? ??? ??? ?if (c <= 0)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ??? ??? ??? ?memcpy(circ->buf + circ->head, buf, c);
?? ??? ??? ??? ??? ??? ??? ??? ?circ->head = (circ->head + c) & (UART_XMIT_SIZE - 1);
?? ??? ??? ??? ??? ??? ??? ??? ?buf += c;
?? ??? ??? ??? ??? ??? ??? ??? ?count -= c;
?? ??? ??? ??? ??? ??? ??? ??? ?ret += c;
?? ??? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ??? ?=>uart_start(tty);
?? ??? ??? ??? ??? ??? ??? ??? ?=>struct uart_state *state = tty->driver_data;
?? ??? ??? ??? ??? ??? ??? ??? ?struct uart_port *port = state->uart_port;
?? ??? ??? ??? ??? ??? ??? ??? ?=>__uart_start(tty);
?? ??? ??? ??? ??? ??? ??? ??? ??? ?=>struct uart_state *state = tty->driver_data;
?? ??? ??? ??? ??? ??? ??? ??? ??? ?struct uart_port *port = state->uart_port;
?? ??? ??? ??? ??? ??? ??? ??? ??? ?=>if (!uart_circ_empty(&state->xmit) && state->xmit.buf && !tty->stopped && !tty->hw_stopped)
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?port->ops->start_tx(port);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?^
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?||
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?v
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?serial8250_start_tx
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?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
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?};
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>struct uart_8250_port *up = (struct uart_8250_port *)port;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>serial_out
?? ??? ??? ??? ??? ??? ?===>if (c < 0) {
?? ??? ??? ??? ??? ??? ??? ?retval = c;
?? ??? ??? ??? ??? ??? ??? ?goto break_out;
?? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ?if (!c)
?? ??? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ??? ?b += c;
?? ??? ??? ??? ??? ??? ?nr -= c;
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?==>if (!nr)
?? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ?if (file->f_flags & O_NONBLOCK) {
?? ??? ??? ??? ??? ??? ?retval = -EAGAIN;
?? ??? ??? ??? ??? ??? ?break;
?? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ?schedule();
?? ??? ??? ??? ?=>__set_current_state(TASK_RUNNING);
?? ??? ??? ??? ?remove_wait_queue(&tty->write_wait, &wait);
?? ??? ??? ??? ?if (b - buf != nr && tty->fasync)
?? ??? ??? ??? ??? ?set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
?? ??? ??? ??? ?return (b - buf) ? b - buf : retval;
?? ?=>tty_ldisc_deref(ld);
?? ?
?? ?

?? ??? ??? ??? ?

irqreturn_t serial8250_interrupt(int irq, void *dev_id)
?? ?=>struct irq_info *i = dev_id;
?? ?struct list_head *l, *end = NULL;
?? ?=>l = i->head;
?? ?=>do {
?? ??? ?struct uart_8250_port *up = list_entry(l, struct uart_8250_port, list);
?? ??? ?unsigned intiir = serial_in(up, UART_IIR);
?? ??? ?if (!(iir & UART_IIR_NO_INT)) {
?? ??? ??? ?serial8250_handle_port(up);
?? ??? ??? ??? ?=>status = serial_inp(up, UART_LSR);
?? ??? ??? ??? ?=>if (status & (UART_LSR_DR | UART_LSR_BI))
?? ??? ??? ??? ??? ?receive_chars(up, &status);
?? ??? ??? ??? ??? ??? ?=>struct tty_struct *tty = up->port.state->port.tty;
?? ??? ??? ??? ??? ??? ?unsigned char ch, lsr = *status;
?? ??? ??? ??? ??? ??? ?int max_count = 256;
?? ??? ??? ??? ??? ??? ?=>do {
?? ??? ??? ??? ??? ??? ??? ?if (likely(lsr & UART_LSR_DR))
?? ??? ??? ??? ??? ??? ??? ??? ?ch = serial_inp(up, UART_RX);
?? ??? ??? ??? ??? ??? ??? ?uart_insert_char(&up->port, lsr, UART_LSR_OE, ch, flag);
?? ??? ??? ??? ??? ??? ??? ??? ?=>struct tty_struct *tty = port->state->port.tty;
?? ??? ??? ??? ??? ??? ??? ??? ?=>if ((status & port->ignore_status_mask & ~overrun) == 0)
?? ??? ??? ??? ??? ??? ??? ??? ??? ?tty_insert_flip_char(tty, ch, flag);
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>struct tty_buffer *tb = tty->buf.tail;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?if (tb && tb->used < tb->size) {
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?tb->flag_buf_ptr[tb->used] = flag;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?tb->char_buf_ptr[tb->used++] = ch;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?return 1;
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?}
?? ??? ??? ??? ??? ??? ??? ??? ??? ??? ?=>return tty_insert_flip_string_flags(tty, &ch, &flag, 1);
?? ??? ??? ??? ??? ??? ?} while ((lsr & (UART_LSR_DR | UART_LSR_BI)) && (max_count-- > 0));
?? ??? ??? ??? ??? ??? ?=>tty_flip_buffer_push(tty);
?? ??? ??? ??? ??? ??? ?=>*status = lsr;
?? ??? ??? ??? ?=>check_modem_status(up);
?? ??? ??? ??? ?=>if (status & UART_LSR_THRE)
?? ??? ??? ??? ??? ?transmit_chars(up);
?? ??? ??? ?handled = 1;

?? ??? ??? ?end = NULL;
?? ??? ?}
?? ??? ?} while (l != end);
?? ?=>return IRQ_RETVAL(handled);
?? ??? ?
?? ?
?? ?
?? ?
linux下串口（serial）和串口驅動
https://blog.csdn.net/wangzhen209/article/details/76685756

linux 串口驅動詳細分析
https://blog.csdn.net/dai_xiangjun/article/details/41241881

tty初探—uart驅動框架分析
https://blog.csdn.net/lizuobin2/article/details/51773305

serival(串口驅動)分析
https://wenku.baidu.com/view/49bc74c3b7360b4c2f3f6420.html

LINUX 日志級別(LOGLEVEL)詳解
http://smilejay.com/2011/12/linux_loglevel/

Linux中tty框架與uart框架之間的調用關系剖析
http://blog.chinaunix.net/uid-29025972-id-4738659.html

linux關于串口的配置和多線程收發
http://www.360doc.com/content/17/0831/23/44391309_683701497.shtml

Linux下的串口編程及非阻塞模式
https://www.cnblogs.com/ynxf/p/6105072.html

Linux open系統調用流程淺析
https://www.jianshu.com/p/f3f5a33f2c59

淺析linux中open系統調用
http://www.360doc.com/content/12/0507/15/9171956_209262761.shtml

ttyUSB串口設備節點生成過程
https://blog.csdn.net/mingtianwoyueni/article/details/63709861

Linux串口驅動分析read
https://blog.csdn.net/longwang155069/article/details/42776059

tty初探—uart驅動框架分析
https://blog.csdn.net/lizuobin2/article/details/51773305

串口驅動分析
https://blog.csdn.net/weed_hz/article/details/8946391

linux設備驅動之8250串口驅動
https://blog.csdn.net/zjy900507/article/details/78678783

總結

以上是生活随笔為你收集整理的慢慢欣赏linux之串口驱动代码分析 - 基于powerpc 2.6.x版本的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。