使用dmesg打印所有日志
目录
使用修改打印级别使用dmesg打印所有日志测试小结参考文档附录(3.4内核的分析)
title: 驱动调试(一)-
date: 2019/1/9 19:35:14
toc: true
---
驱动调试(一)- 引入
uboot的启动参数中定义了我们内核启动时的信息输出
bootargs=noinitrd root=/dev/mtdblock3 init=/linuxrc console=ttySAC0如果去除=,则内核复制后没有信息输出,可以看下lcd,已经有显示了
#OpenJTAG> set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrcStarting kernel ...
Uncompressing Linux.............................................. done, booting the kernel.也可以设置为tty1,直接在LCD上输出,这个需要有lcd驱动程序了(废话 哈哈),这里我试了tty0和tty1 和tty2,tty3都是在lcd显示
set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrc console=tty1其实也可以使用多个终端输出,比如这样
set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrc console=tty1 console=ttySAC0注意 这里设置参数后不要使用save 保存到flash,直接退回到menu,输入b启动即可
那么内核的是怎么根据=xxx找到输出的硬件设备的?
框架 入口
搜索=,在有以下代码("=", );,这个宏是用来处理启动参数的
文件在\.c
/** Set up a list of consoles. Called from init/main.c*/
static int __init console_setup(char *str)
{ char name[sizeof(console_cmdline[0].name)];char *s, *options;int idx;/** Decode str into name, index, options.*/// 先复制8字节到nameif (str[0] >= '0' && str[0] <= '9') {strcpy(name, "ttyS");strncpy(name + 4, str, sizeof(name) - 5);} else {strncpy(name, str, sizeof(name) - 1);}name[sizeof(name) - 1] = 0;// 判断是否有"," 也就是是不是有选项字节if ((options = strchr(str, ',')) != NULL)*(options++) = 0;
#ifdef __sparc__if (!strcmp(str, "ttya"))strcpy(name, "ttyS0");if (!strcmp(str, "ttyb"))strcpy(name, "ttyS1");
#endif//从name中 找数字for (s = name; *s; s++)if ((*s >= '0' && *s <= '9') || *s == ',')break;idx = simple_strtoul(s, NULL, 10);*s = 0;// 这里就会添加控制台了,也就是记录下来,还没有找到硬件add_preferred_console(name, idx, options);return 1;
}
__setup("console=", console_setup);e
这里是将命令行参数解析后存入全绝的结构体变量,这里只是存起来,并没有去解析
add_preferred_console
{struct console_cmdline *c;// 这里有个全局变量 console_cmdline,保存所有的终端,这里支持8个//#define MAX_CMDLINECONSOLES 8//static struct console_cmdline console_cmdline[MAX_CMDLINECONSOLES];//step1 判断是否存在了已经for(i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)...//指向最后一个命令行的参数console_cmdlineselected_console = i; //step2 存入这个全局的数组 包括name,序号,选项c = &console_cmdline[i];memcpy(c->name, name, sizeof(c->name));c->name[sizeof(c->name) - 1] = 0;c->options = options;c->index = idx;}继续搜索这个全局变量,可以看到注册函数,匹配命令行的name和注册的驱动后加入到链表中
selected_console 在add_preferred_console 处理命令参数的时候 指向最后一个命令行的参数console_cmdlineregister_console // 如果没有注册过console,preferred_console 指向selected_console 也就是最后一个命令行参数的consoleif (preferred_console < 0 || bootconsole || !console_drivers)preferred_console = selected_console;// 如果没有注册过console,会先来一个初始化这第一个来注册的consoleif (preferred_console < 0)console->setup(console, NULL)console->index = 0; //没有注册时,强制赋值0for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];i++)...// 1. 比较命令行的名字与注册的驱动的名字,如果name匹配// 2. 执行带有option的 console->setup(console, console_cmdline[i].options)// 3. 如果成功,设置标志console->flags |= CON_ENABLED;console->index = console_cmdline[i].index;//4. 选择一个作为preferred_console,如果匹配到最后一个命令行,preferred_console就等于这个selected_console=最后一个命令行if (i == selected_console) {console->flags |= CON_CONSDEV;preferred_console = selected_console;// 5.加入到链表 console_drivers ,注册的console本身也包含了一个链表指向if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {console->next = console_drivers;console_drivers = console;if (console->next)console->next->flags &= ~CON_CONSDEV;} else {console->next = console_drivers->next;console_drivers->next = console;} 这里的链表结构应该是如下这样的:
搜索这个注册函数的调用,发现使用了这个注册函数,可以看到le的name正是""
s3c24xx_serial_initconsole// 驱动相关,先看看是不是有硬件驱动struct platform_device *dev = s3c24xx_uart_devs[0];//注册consoleregister_console(&s3c24xx_serial_console);static struct console s3c24xx_serial_console =
{.name = S3C24XX_SERIAL_NAME,.device = uart_console_device,.flags = CON_PRINTBUFFER,.index = -1,.write = s3c24xx_serial_console_write,.setup = s3c24xx_serial_console_setup
};#define S3C24XX_SERIAL_NAME "ttySAC"
#define S3C24XX_SERIAL_MAJOR 204
#define S3C24XX_SERIAL_MINOR 64write
可以在这个结构体里面发现write函数操作了实际的硬件,也就是write是是实际的写硬件函数
s3c24xx_serial_console_write>uart_console_write(cons_uart, s, count, s3c24xx_serial_console_putchar);>wr_regb(cons_uart, S3C2410_UTXH, ch);asmlinkage int printk(const char *fmt, ...)
{va_start(args, fmt);r = vprintk(fmt, args);va_end(args);
}这个函数最后会查找这个链表来进行打印处理,通过判断是否输出到硬件
vprintk(const char *fmt, va_list args)
{// 解析数据到一个buf/* Emit the output into the temporary buffer */printed_len = vscnprintf(printk_buf, sizeof(printk_buf), fmt, args);//对buf 进行特殊处理printk_buf,填充到 log_buffor (p = printk_buf; *p; p++){//如果没有 形如 <数字> 的开头,自动补上 也就是<4>,提取这个lev//如果有,同样提取这个levemit_log_char(c)}if (cpu_online(smp_processor_id()) || have_callable_console()) {//have_callable_console 遍历 console_drivers// > for (con = console_drivers; con; con = con->next)// 这个链表就是register_console 中注册的了console_may_schedule = 0;// 打印输出release_console_sem();{....}}
} 先将数据输出到,实际的输出到硬件会去判断一个打印级别,不论是否到达打印级别,都可以使用dmesg显示这个[]
release_console_sem()
{// 静态全局变量_con_start = con_start;_log_end = log_end;call_console_drivers(_con_start, _log_end);{// 提取打印等级msg_level = LOG_BUF(cur_index + 1) - '0';_call_console_drivers(start_print, cur_index, msg_level);{// lev < 设置的log lev,则打印if ((msg_log_level < console_loglevel || ignore_loglevel) && console_drivers && start != end){//遍历console驱动链表,判断是否有write函数,如果有,执行write函数__call_console_drivers(start, end);{for (con = console_drivers; con; con = con->next){if ((con->flags & CON_ENABLED) && con->write...)con->write(con, &LOG_BUF(start), end - start);}}}}}
}打印级别
我们在里面使用的是s中判断if < ,也就是说默认的级别就是,也就是默认小于才打印
#define console_loglevel (console_printk[0]) ==7可以使用cat /proc/sys//查看是不是这个,这个值就是数组[4]
# cat /proc/sys/kernel/printk
7 4 1 7具体相关的定义在这里,可以使用\linux\.h查看
int console_printk[4] = {//=7DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel *///=4DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel *///=1MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel *///=7DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
};/* printk's without a loglevel use this.. */
#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
/* We show everything that is MORE important than this.. */
#define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
#define DEFAULT_CONSOLE_LOGLEVEL 7 /* anything MORE serious than KERN_DEBUG */#define KERN_EMERG "<0>" // 系统崩溃
#define KERN_ALERT "<1>" //必须紧急处理
#define KERN_CRIT "<2>" // 临界条件，严重的硬软件错误
#define KERN_ERR "<3>" // 报告错误
#define KERN_WARNING "<4>" //警告
#define KERN_NOTICE "<5>" //普通但还是须注意
#define KERN_INFO "<6>" // 信息
#define KERN_DEBUG "<7>" // 调试信息使用
格式可以加上打印级别,形式如下:
printk(KERN_EMERG "abc") === printk( "<0>abc");修改打印级别
临时修改/proc/sys//,重启后失效,下述命令关闭打印,也就是设置小于EVEL=1才打印
echo "1 4 1 7" > /proc/sys/kernel/printk修改初始化的数组或者是那个判断的函数
int console_printk[4] = {1,//DEFAULT_CONSOLE_LOGLEVEL, /* console_loglevel */DEFAULT_MESSAGE_LOGLEVEL, /* default_message_loglevel */MINIMUM_CONSOLE_LOGLEVEL, /* minimum_console_loglevel */DEFAULT_CONSOLE_LOGLEVEL, /* default_console_loglevel */
};或者修改 内核源代码
static void _call_console_drivers(unsigned long start,unsigned long end, int msg_log_level)
{//if ((msg_log_level < console_loglevel || ignore_loglevel) &&if ((msg_log_level < 1 || ignore_loglevel) &&console_drivers && start != end) {if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {/* wrapped write */__call_console_drivers(start & LOG_BUF_MASK,log_buf_len);__call_console_drivers(0, end & LOG_BUF_MASK);} else {__call_console_drivers(start, end);}}
}设置uboot传递的参数,我们可以看到级别定义如下,搜索文本,可以找到一些函数
更多的参考文档可以查看\-.txt,搜索
#define console_loglevel (console_printk[0])//init\main.c
static int __init debug_kernel(char *str)
{if (*str)return 0;console_loglevel = 10;return 1;
}
static int __init quiet_kernel(char *str)
{if (*str)return 0;console_loglevel = 4;return 1;
}
__setup("debug", debug_kernel);
__setup("quiet", quiet_kernel);
static int __init loglevel(char *str)
{get_option(&str, &console_loglevel);return 1;
}
__setup("loglevel=", loglevel);也就是说可以用这些参数传递打印级别
loglevel=0 console=ttySA0,115200
debug # 使用级别10
quiet # 使用级别4set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrc loglevel=0 console=ttySAC0
boot
# cat /proc/sys/kernel/printk
0 4 1 7set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrc debug console=ttySAC0
boot
# cat /proc/sys/kernel/printk
10 4 1 7set bootargs noinitrd root=/dev/mtdblock3 init=/linuxrc quiet console=ttySAC0
boot
# cat /proc/sys/kernel/printk
4 4 1 7使用dmesg打印所有日志
使用这个命令可以打印那些被屏蔽的缓冲,可以保存到文本里面去看
# dmesg
....?...................................... done, booting the kernel.
Linux version 2.6.22.6 (book@100ask) (gcc version 3.4.5) #3 Wed Jan 9 15:33:52 CST 2019
CPU: ARM920T [41129200] revision 0 (ARMv4T), cr=c0007177测试
修改级别为0,都可以实现如下效果,不打印内核启动信息
Starting kernel ...Uncompressing Linux...................................................................................................................... done, booting the kernel.
init started: BusyBox v1.7.0 (2018-11-13 23:35:45 CST)
starting pid 766, tty '': '/etc/init.d/rcS'Please press Enter to activate this console.
starting pid 771, tty '/dev/console': 'bin/sh'
也可以# cat /proc/sys// 来查看,除了那个修改函数中的if判断的,都可以打印出来如下效果
# cat /proc/sys/kernel/printk
1 4 1 7修改if判断的依然是7 4 1 7,因为这个文件本质上就是这个数组显示 哈哈
小结
内核解析uboot传递的命令行参数,来寻找实际的硬件来输出信息
console_setup>add_preferred_console注册实际的硬件驱动,加入到链表
s3c24xx_serial_initconsole>register_console>比较命令行的name 与 硬件驱动的name ,如果匹配,加入到 console_drivers链表中使用( lev "...")来输出信息,如果没有指定lev,以默认的lev=4输出,具体是在中寻找驱动找到他的write函数输出
printk>vprintk>release_console_sem>判断lev 打印使用dmesg可以打印所有日志,包括被屏蔽的
参考文档 \-.txt ,搜索查看命令行参数传递3.4内核代码分析 附录(3.4内核的分析)
这个代码讲的比较具体,先不去仔细分析了
console驱动：
一、基本概念
终端是一种字符型设备，通常使用tty简称各种类型的终端。linux的终端类型：
/dev/ttySn,串行口终端/dev/pty,伪终端/dev/tty,当前进程的控制终端，可以是介绍的其它任何一种终端/dev/ttyn,tty1~tty6是虚拟终端，tty0当前虚拟终端的别名。/dev/console，控制台终端（显示器）二、uboot传参数的处理
linux启动时uboot传递进console=ttyS2,115200n8的参数
内核中用__setup()宏声明参数处理的方法：__setup("console=", console_setup);
1.console_cmdline结构体
struct console_cmdline
{ char name[8]; //驱动名 int index; //次设备号 char *options; //选项
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE char *brl_options;
#endif
}; 2.内核调用console_setup()函数处理uboot传进的console参数
static int __init console_setup(char *str)
{ char buf[sizeof(console_cmdline[0].name) + 4]; //分配驱动名+index的缓冲区，分配12个字节 char *s, *options, *brl_options = NULL; int idx; #ifdef CONFIG_A11Y_BRAILLE_CONSOLE if (!memcmp(str, "brl,", 4)) { brl_options = ""; str += 4; } else if (!memcmp(str, "brl=", 4)) { brl_options = str + 4; str = strchr(brl_options, ','); if (!str) { printk(KERN_ERR "need port name after brl=\n"); return 1; } *(str++) = 0; }
#endif if (str[0] >= '0' && str[0] <= '9') { //第一个参数属于[0,9] strcpy(buf, "ttyS"); //则将其驱动名设为ttyS strncpy(buf + 4, str, sizeof(buf) - 5);//将次设备号放其后面 } else { strncpy(buf, str, sizeof(buf) - 1); //否则直接将驱动名+设备号拷贝到buf中} buf[sizeof(buf) - 1] = 0; if ((options = strchr(str, ',')) != NULL) //获取options，即“115200n8” *(options++) = 0; #ifdef __sparc__ if (!strcmp(str, "ttya")) strcpy(buf, "ttyS0"); if (!strcmp(str, "ttyb")) strcpy(buf, "ttyS1");
#endif for (s = buf; *s; s++) if ((*s >= '0' && *s <= '9') || *s == ',')//移动指针s到次设备号处 break; idx = simple_strtoul(s, NULL, 10); //获取次设备号，字符串转换成unsigend long long型数据，s表示字符串的开始，NULL表示字符串的结束，10表示进制 //这里返回的是次设备号=2*s = 0; __add_preferred_console(buf, idx, options, brl_options); console_set_on_cmdline = 1; return 1;
} 3.__add_preferred_console()函数
//整体的作用是根据uboot传递的参数设置全局console_cmdline数组
//该数组及全局selected_console，在register_console中会使用到
static int __add_preferred_console(char *name, int idx, char *options,char *brl_options)
{ struct console_cmdline *c; int i; for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0]; i++)//可以最多8个console if (strcmp(console_cmdline[i].name, name) == 0 && console_cmdline[i].index == idx) { //比较已注册的console_cmdline数组中的项的名字及次设备号,若console_cmdline已经存在 if (!brl_options) selected_console = i;//设置全局selected_console索引号 return 0;//则返回 } if (i == MAX_CMDLINECONSOLES)//判断console_cmdline数组是否满了 return -E2BIG; if (!brl_options) selected_console = i; //设置全局selected_console索引号 c = &console_cmdline[i];//获取全局console_cmdline数组的第i项地址 strlcpy(c->name, name, sizeof(c->name)); //填充全局console_cmdline的驱动名“ttyS2” c->options = options; //填充配置选项115200n8
#ifdef CONFIG_A11Y_BRAILLE_CONSOLE c->brl_options = brl_options;
#endif c->index = idx; //填充索引号2，即次设备号 return 0;
} 三、在console初始化之前能使用printk，使用内核提供的early printk支持。
//在调用console_init之前调用printk也能打印出信息，这是為什麼呢？在start_kernel函数中很早就调用了 parse_early_param函数，
//该函数会调用到链接脚本中.init.setup段的函数。其中就有 setup_early_serial8250_console函数。
//该函数通过 register_console(&early_serial8250_console);
//注册了一个比较简单的串口设备。可以用来打印内核启 动早期的信息。//对于early printk的console注册往往通过内核的early_param完成。
early_param(“earlycon”,setup_early_serial8250_console);
//定义一个earlycon的内核参数，内核解析这个参数时调用setup_early_serial8250_console()函数1.setup_early_serial8250_console()函数
//earlycon = uart8250,mmio,0xff5e0000,115200n8
int __init setup_early_serial8250_console(char *cmdline)
{char *options;int err;options = strstr(cmdline, "uart8250,");//找到“uart8250,”字符串，返回此字符串的起始位置if (!options) {options = strstr(cmdline, "uart,");if (!options)return 0;}options = strchr(cmdline, ',') + 1;//options指针指向第一个逗号后边的字符串地址err = early_serial8250_setup(options);//进行配置if (err < 0)return err;/*static struct console early_serial8250_console __initdata = {.name = "uart",.write = early_serial8250_write,.flags = CON_PRINTBUFFER | CON_BOOT,//所用具有CON_BOOT属性的console都会在内核初始化到late initcall阶段被注销，相互消他们的函数是.index = -1,};*///注册一个早期的console,到真正的console_init时，此console会被注销，因为设置了CON_BOOT标志register_console(&early_serial8250_console);return 0;
}static int __init early_serial8250_setup(char *options)
{struct early_serial8250_device *device = &early_device;int err;if (device->port.membase || device->port.iobase)//early_device设备的端口地址若配置过则返回return 0;err = parse_options(device, options);//解析参数并配置early_device设备对应的uart_port结构if (err < 0)return err;init_port(device);//early_device设备对应的初始化uart_port结构return 0;
}static int __init parse_options(struct early_serial8250_device *device,char *options)
{struct uart_port *port = &device->port;//找到early_device设备对应的uart_port结构int mmio, mmio32, length;if (!options)return -ENODEV;port->uartclk = BASE_BAUD * 16;//串口时钟mmio = !strncmp(options, "mmio,", 5);//查找"mmio,"字符串，找到mmio=1mmio32 = !strncmp(options, "mmio32,", 7);//mmio32=0if (mmio || mmio32) {port->iotype = (mmio ? UPIO_MEM : UPIO_MEM32);//串口类型设为UPIO_MEM=2port->mapbase = simple_strtoul(options + (mmio ? 5 : 7),&options, 0);//获得串口的配置寄存器基础地址（物理地址），这里是得到0xff5e0000if (mmio32)port->regshift = 2;
#ifdef CONFIG_FIX_EARLYCON_MEMset_fixmap_nocache(FIX_EARLYCON_MEM_BASE,port->mapbase & PAGE_MASK);port->membase =(void __iomem *)__fix_to_virt(FIX_EARLYCON_MEM_BASE);port->membase += port->mapbase & ~PAGE_MASK;
#elseport->membase = ioremap_nocache(port->mapbase, 64);//映射到内存的配置寄存器基础地址if (!port->membase) {printk(KERN_ERR "%s: Couldn't ioremap 0x%llx\n", __func__,(unsigned long long) port->mapbase);return -ENOMEM;}
#endif} else if (!strncmp(options, "io,", 3)) {port->iotype = UPIO_PORT;port->iobase = simple_strtoul(options + 3, &options, 0);mmio = 0;} elsereturn -EINVAL;options = strchr(options, ',');//指针移到“115200n8”字符串处if (options) {//存在options++;device->baud = simple_strtoul(options, NULL, 0);//取得波特率115200length = min(strcspn(options, " "), sizeof(device->options));strncpy(device->options, options, length);//将字符串115200n8拷贝到设备的device->options字段中} else {device->baud = probe_baud(port);snprintf(device->options, sizeof(device->options), "%u",device->baud);}if (mmio || mmio32)printk(KERN_INFO "Early serial console at MMIO%s 0x%llx (options '%s')\n",mmio32 ? "32" : "",(unsigned long long)port->mapbase,device->options);elseprintk(KERN_INFO"Early serial console at I/O port 0x%lx (options '%s')\n",port->iobase,device->options);return 0;
}static void __init init_port(struct early_serial8250_device *device)
{struct uart_port *port = &device->port;unsigned int divisor;unsigned char c;serial_out(port, UART_LCR, 0x3); /* 8n1 */serial_out(port, UART_IER, 0); /* no interrupt */serial_out(port, UART_FCR, 0); /* no fifo */serial_out(port, UART_MCR, 0x3); /* DTR + RTS */divisor = port->uartclk / (16 * device->baud);//根据波特率设置分频c = serial_in(port, UART_LCR);serial_out(port, UART_LCR, c | UART_LCR_DLAB);serial_out(port, UART_DLL, divisor & 0xff);serial_out(port, UART_DLM, (divisor >> 8) & 0xff);serial_out(port, UART_LCR, c & ~UART_LCR_DLAB);
}void register_console(struct console *newcon)
{int i;unsigned long flags;struct console *bcon = NULL;/*现在是注册一个early console，即static struct console early_serial8250_console __initdata = {.name = "uart",.write = early_serial8250_write,.flags = CON_PRINTBUFFER | CON_BOOT,//所用具有CON_BOOT属性的console都会在内核初始化到late initcall阶段被注销，相互消他们的函数是.index = -1,};*/if (console_drivers && newcon->flags & CON_BOOT) {//注册的是否是引导控制台。early console的CON_BOOT置位，表示只是一个引导控制台，以后会被注销for_each_console(bcon) {遍历全局console_drivers数组 if (!(bcon->flags & CON_BOOT)) {//判断是否已经有引导控制台了,有了的话就直接退出printk(KERN_INFO "Too late to register bootconsole %s%d\n",newcon->name, newcon->index);return;}}}if (console_drivers && console_drivers->flags & CON_BOOT)//如果注册的是引导控制台 bcon = console_drivers;//让bcon指向全局console_drivers if (preferred_console < 0 || bcon || !console_drivers)preferred_console = selected_console;//设置preferred_console为uboot命令选择的selected_console(即索引) if (newcon->early_setup)//early console没有初始化early_setup字段，以下这个函数不执行newcon->early_setup();//调用serial8250_console_early_setup()if (preferred_console < 0) {if (newcon->index < 0)newcon->index = 0;if (newcon->setup == NULL ||newcon->setup(newcon, NULL) == 0) {newcon->flags |= CON_ENABLED;if (newcon->device) {newcon->flags |= CON_CONSDEV;preferred_console = 0;}}}//传给内核参数://Kernel command line: console=ttyS2,115200n8 rw root=/dev/ram0 initrd=0xc2000000,20M mem=128M ip=192.168.1.220::192.168.1.1:255.255.255.0::eth0:off//所以这里将根据传参console=ttyS2,115200来配置作为console的ttyS2串口for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];i++) {//遍历全局console_cmdline找到匹配的 if (strcmp(console_cmdline[i].name, newcon->name) != 0)//比较终端名称“ttyS”continue;if (newcon->index >= 0 &&newcon->index != console_cmdline[i].index)//console_cmdline[i].index=2。//比较次设备号 continue;if (newcon->index < 0)newcon->index = console_cmdline[i].index;//将终端号赋值给serial8250_console->index#ifdef CONFIG_A11Y_BRAILLE_CONSOLE//没有定义，下边不执行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//console_cmdline[i].options = "115200n8"，对于early console而言setup字段未被初始化，故下边的函数不执行if (newcon->setup &&newcon->setup(newcon, console_cmdline[i].options) != 0)//调用serial8250_console_setup()对终端进行配置break;newcon->flags |= CON_ENABLED; //设置标志为CON_ENABLE(这个在printk调用中使用到) newcon->index = console_cmdline[i].index;//设置索引号 if (i == selected_console) { //索引号和uboot指定的console的一样 newcon->flags |= CON_CONSDEV;//设置标志CON_CONSDEV(全局console_drivers链表中靠前) preferred_console = selected_console;}break;}//for循环作用大致是查看注册的console是否是uboot知道的引导console，是则设置相关标志和preferred_consoleif (!(newcon->flags & CON_ENABLED))return;if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))//防止重复打印 newcon->flags &= ~CON_PRINTBUFFER;acquire_console_sem();if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {//如果是preferred控制台newcon->next = console_drivers;console_drivers = newcon;//添加进全局console_drivers链表前面位置（printk中会遍历该表调用合适的console的write方法打印信息）if (newcon->next)newcon->next->flags &= ~CON_CONSDEV;} else {//如果不是preferred控制台 newcon->next = console_drivers->next;console_drivers->next = newcon; //添加进全局console_drivers链表后面位置}//主册console主要是刷选preferred_console放置在全局console_drivers链表前面,剩下的console放置链表靠后的位置,并设置相应的flags,//console_drivers最终会在printk函数的层层调用中遍历到,并调用console的write方法将信息打印出来if (newcon->flags & CON_PRINTBUFFER) {spin_lock_irqsave(&logbuf_lock, flags);con_start = log_start;spin_unlock_irqrestore(&logbuf_lock, flags);}release_console_sem();if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",newcon->name, newcon->index);for_each_console(bcon)if (bcon->flags & CON_BOOT)unregister_console(bcon);} else {//调用这里printk(KERN_INFO "%sconsole [%s%d] enabled\n",(newcon->flags & CON_BOOT) ? "boot" : "" ,newcon->name, newcon->index);}
}四、在未对console进行初始化之前，内核使用early console进行打印。之后内核进行真正的console初始化
//console_init()在start_kernel()中调用，用来对控制台初始化，这个函数执行完成后，串口可以看到内核用printk()函数打印的信息
void __init console_init(void)
{initcall_t *call;/* Setup the default TTY line discipline. *///此函数调用tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY)//#define N_TTY 0/*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};内核定义一个tty_ldiscs数组，然后根据数组下标来存放对应的线路规程的操作集，而这里的数组下标表示的就是具体的协议，在头文件中已经通过宏定义好了。例如N_TTY 0。 所以可以发现:ldisc[0] 存放的是N_TTY对应的线路规程操作集ldisc[1]存放的是N_SLIP对应的线路规程操作集ldisc[2]存放的就是N_MOUSE对应的线路规程操作集依次类推。此处就是ldisc[N_TTY] = tty_ldisc_N_TTY。int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc){unsigned long flags;int ret = 0;if (disc < N_TTY || disc >= NR_LDISCS)return -EINVAL;spin_lock_irqsave(&tty_ldisc_lock, flags);tty_ldiscs[disc] = new_ldisc;//tty_ldiscs[0]存放的是N_TTY对应的线路规程操作集new_ldisc->num = disc;//0new_ldisc->refcount = 0;spin_unlock_irqrestore(&tty_ldisc_lock, flags);return ret;}
*/tty_ldisc_begin();//这段代码前面是注册了第0个(逻辑上1)线路规程//依次调用从__con_initcall_start到__con_initcall_end之间的函数指针//会调用两个函数就是con_init()和serial8250_console_init()call = __con_initcall_start;while (call < __con_initcall_end) {(*call)();call++;}
}static int __init serial8250_console_init(void)
{if (nr_uarts > UART_NR)//串口数量不能大于3个nr_uarts = UART_NR;serial8250_isa_init_ports();//对三个串口的uart_8250_port结构静态常量serial8250_ports结构进行初始化,主要是将up->port.ops = &serial8250_pops/*static struct console serial8250_console = {.name = "ttyS",.write = serial8250_console_write,//写方法.device = uart_console_device,//tty驱动.setup = serial8250_console_setup,//设置串口波特率，也就是设置串口。很重要，里面涉及到平台特性，波特率相关。.early_setup = serial8250_console_early_setup,.flags = CON_PRINTBUFFER | CON_ANYTIME,.index = -1,.data = &serial8250_reg,};*/register_console(&serial8250_console);//在这里注册serial8250_console真正的console终端return 0;
}
console_initcall(serial8250_console_init);
/*
serial8250_console_init()函数会比serial8250_probe()先调用,所以调用register_console的时候,port还没有初始化,所以当
register_console调用serial8250_console_setup()设置buad,parity bits的时候,
serial8250_console_setup()会检测port->iobase和port->membase是否是有效值,如果不是就返回,
放弃初始化console,所以实际上,console不是在serial8250_console_init()里边初始化,
如果要在serial8250_console_init初始化,需要将port静态初始化.当serial8250_probe()调用uart_add_one_port->uart_configure_port:
if (port->cons && !(port->cons->flags & CON_ENABLED)){printk("%s retister console\n", __FUNCTION__);register_console(port->cons);
}
该函数会检查console有没有初始化,如果没有初始化,则调用register_console来初始化.
所以console放在这里初始化也是比较好一些,可以将console_initcall(serial8250_console_init) comment.
*///对三个串口的uart_8250_port结构静态常量serial8250_ports结构进行初始化,主要是将up->port.ops = &serial8250_pops
static void __init serial8250_isa_init_ports(void)
{struct uart_8250_port *up;static int first = 1;int i, irqflag = 0;if (!first)//静态变量，serial8250_console_init()第一次进入这个函数，之后serial8250_init()再进入这个函数就会直接返回return;first = 0;//对三个串口的uart_8250_port结构serial8250_ports结构体进行初始化for (i = 0; i < nr_uarts; i++) {struct uart_8250_port *up = &serial8250_ports[i];up->port.line = i;//0代表串口0,1代表串口1spin_lock_init(&up->port.lock);init_timer(&up->timer);//初始化定时器up->timer.function = serial8250_timeout;//初始化定时器的超时函数//ALPHA_KLUDGE_MCR needs to be killed.up->mcr_mask = ~ALPHA_KLUDGE_MCR;up->mcr_force = ALPHA_KLUDGE_MCR;//初始化uart_8250_port指向的uart_port字段port的操作up->port.ops = &serial8250_pops;/*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};*/}if (share_irqs)//中断是否共享（这里设置成不共享）irqflag = IRQF_SHARED;//条件不满足，不会进来初始化for (i = 0, up = serial8250_ports;i < ARRAY_SIZE(old_serial_port) && i < nr_uarts;i++, up++) {
/* up->port.iobase = old_serial_port[i].port;up->port.irq = irq_canonicalize(old_serial_port[i].irq);up->port.irqflags = old_serial_port[i].irqflags;up->port.uartclk = old_serial_port[i].baud_base * 16;up->port.flags = old_serial_port[i].flags;up->port.hub6 = old_serial_port[i].hub6;up->port.membase = old_serial_port[i].iomem_base;up->port.iotype = old_serial_port[i].io_type;up->port.regshift = old_serial_port[i].iomem_reg_shift;set_io_from_upio(&up->port);up->port.irqflags |= irqflag;if (serial8250_isa_config != NULL)serial8250_isa_config(i, &up->port, &up->capabilities);
*/}
}//下边再次调用register_console()注册serial8250_console真正的console终端
void register_console(struct console *newcon)
{int i;unsigned long flags;struct console *bcon = NULL;/*现在是注册一个serial8250_console，即static struct console serial8250_console = {.name = "ttyS",.write = serial8250_console_write,//写方法.device = uart_console_device,//tty驱动.setup = serial8250_console_setup,//设置串口波特率，也就是设置串口。很重要，里面涉及到平台特性，波特率相关。.early_setup = serial8250_console_early_setup,.flags = CON_PRINTBUFFER | CON_ANYTIME,.index = -1,.data = &serial8250_reg,};*/if (console_drivers && newcon->flags & CON_BOOT) {//注册的是serial8250_console，CON_BOOT没有置位，不是引导控制台。下边不会进去遍历for_each_console(bcon) {遍历全局console_drivers数组 if (!(bcon->flags & CON_BOOT)) {//判断是否已经有引导控制台了,有了的话就直接退出printk(KERN_INFO "Too late to register bootconsole %s%d\n",newcon->name, newcon->index);return;}}}if (console_drivers && console_drivers->flags & CON_BOOT)//如果注册的是引导控制台，serial8250_console不是引导控制台bcon = console_drivers;//这里不执行 if (preferred_console < 0 || bcon || !console_drivers)preferred_console = selected_console;//设置preferred_console为uboot命令选择的selected_console(即在Uboot传入的参数“console=ttyS2,115200n8”在console_cmdline[]数组中的索引) //这里preferred_console =0if (newcon->early_setup)//serial8250_console初始化early_setup字段newcon->early_setup();//调用serial8250_console_early_setup()if (preferred_console < 0) {//由于preferred_console =0，不会进入下边if (newcon->index < 0)newcon->index = 0;if (newcon->setup == NULL ||newcon->setup(newcon, NULL) == 0) {newcon->flags |= CON_ENABLED;if (newcon->device) {newcon->flags |= CON_CONSDEV;preferred_console = 0;}}}//传给内核参数://Kernel command line: console=ttyS2,115200n8 rw root=/dev/ram0 initrd=0xc2000000,20M mem=128M ip=192.168.1.220::192.168.1.1:255.255.255.0::eth0:off//所以这里将根据传参console=ttyS2,115200来配置作为console的ttyS2串口for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];i++) {//遍历全局console_cmdline找到匹配的，i=0就是匹配的“ttyS2”if (strcmp(console_cmdline[i].name, newcon->name) != 0)//比较终端名称“ttyS”continue;if (newcon->index >= 0 &&newcon->index != console_cmdline[i].index)//console_cmdline[i].index=2。//比较次设备号 continue;if (newcon->index < 0)newcon->index = console_cmdline[i].index;//将终端号赋值给serial8250_console->index，这里是2//console_cmdline[i].options = "115200n8"，对于serial8250_console而言setup字段已初始化if (newcon->setup && newcon->setup(newcon, console_cmdline[i].options) != 0)//调用serial8250_console_setup()对终端进行配置，调用不成功break;//在这里注册serial8250_console时，调用serial8250_console_setup()由于port->iobase和port->membase不是有效值，//故返回错误，这样下边的操作不会执行，直接break跳出，从flag1出跳出函数。即在这里serial8250_console没有注册成功//由于内核在下边的操作队串口进行初始化时，还会调用register_console（）来注册serial8250_console，在那时注册就会成功newcon->flags |= CON_ENABLED; //设置标志为CON_ENABLE,表示console使能(这个在printk调用中使用到) newcon->index = console_cmdline[i].index;//设置索引号 if (i == selected_console) { //索引号和uboot指定的console的一样 newcon->flags |= CON_CONSDEV;//设置标志CON_CONSDEV(全局console_drivers链表中靠前) preferred_console = selected_console;}break;}//for循环作用大致是查看注册的console是否是uboot知道的引导console，是则设置相关标志和preferred_console//flag1：if (!(newcon->flags & CON_ENABLED))//若前边没有设置CON_ENABLED标志，就退出return;if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))//防止重复打印 newcon->flags &= ~CON_PRINTBUFFER;acquire_console_sem();if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {//如果是preferred控制台newcon->next = console_drivers;console_drivers = newcon;//添加进全局console_drivers链表前面位置（printk中会遍历该表调用合适的console的write方法打印信息）if (newcon->next)newcon->next->flags &= ~CON_CONSDEV;} else {//如果不是preferred控制台 newcon->next = console_drivers->next;console_drivers->next = newcon; //添加进全局console_drivers链表后面位置}//主册console主要是刷选preferred_console放置在全局console_drivers链表前面,剩下的console放置链表靠后的位置,并设置相应的flags,//console_drivers最终会在printk函数的层层调用中遍历到,并调用console的write方法将信息打印出来if (newcon->flags & CON_PRINTBUFFER) {spin_lock_irqsave(&logbuf_lock, flags);con_start = log_start;spin_unlock_irqrestore(&logbuf_lock, flags);}release_console_sem();if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",newcon->name, newcon->index);for_each_console(bcon)if (bcon->flags & CON_BOOT)unregister_console(bcon);} else {//调用这里printk(KERN_INFO "%sconsole [%s%d] enabled\n",(newcon->flags & CON_BOOT) ? "boot" : "" ,newcon->name, newcon->index);}
}//serial8250_console_early_setup()-->serial8250_find_port_for_earlycon()
int serial8250_find_port_for_earlycon(void)
{struct early_serial8250_device *device = &early_device;//early console初始化时对early_device结构的初始化struct uart_port *port = &device->port;int line;int ret;if (!device->port.membase && !device->port.iobase)//early_device结构初始化时已经配置好return -ENODEV;//early console注册时不会调用此函数。//当真正的console初始化时，会调用此函数。//真正的console初始化时，会查找early console注册时用的是哪一个串口号，从serial8250_ports[]中根据uart_port->mapbase地址来比对line = serial8250_find_port(port);//根据uart_port结构找到串口号，比对没有找到串口号，line返回负值if (line < 0)return -ENODEV;//从这里返回，下边的不再执行//若找到early console用的串口号，更新当初传入内核参数使用的console_cmdline[i]，名称改成ttyS。。。。ret = update_console_cmdline("uart", 8250, "ttyS", line, device->options);if (ret < 0)ret = update_console_cmdline("uart", 0,"ttyS", line, device->options);return ret;
}static int __init serial8250_console_setup(struct console *co, char *options)
{struct uart_port *port;int baud = 9600;int bits = 8;int parity = 'n';int flow = 'n';if (co->index >= nr_uarts)//console的索引，这里是2，即ttyS2co->index = 0;port = &serial8250_ports[co->index].port;//找到对应的ttyS2的uart_port结构//由于console_init在注册serial8250_console时调用的register_console()函数调用serial8250_console_setup()//进入这个函数时，由于ttyS2的uart_port结构没有初始化，port->iobase 和port->membase值都未设置，所以直接从下边返回//当进行串口初始化时，还会回来注册serial8250_console，再调用到这里，由于设置了ttyS2的uart_port结构，所以下边的配置就会成功if (!port->iobase && !port->membase)//第一次注册时，由于未设置，从这里直接返回return -ENODEV;if (options)//如果options不为空，就将options里的数值写给baud, &parity, &bits, &flowuart_parse_options(options, &baud, &parity, &bits, &flow);//没有配置options，则使用缺省值，否则使用传下来的的参数options里的串口配置return uart_set_options(port, co, baud, parity, bits, flow);
}五、通过四知道，在对console注册时，没有成功，由于串口还没有配置。当对串口配置时再对console注册就能成功。
serial8250_console就能注册到内核全局变量console_drivers中。这样终端打印时就通过注册的serial8250_console就能将信息打印到终端上。//内核的打印函数
asmlinkage int printk(const char *fmt, ...)
{va_list args; //可变参数链表int r;#ifdef CONFIG_KGDB_KDBif (unlikely(kdb_trap_printk)) {va_start(args, fmt);r = vkdb_printf(fmt, args);va_end(args);return r;}
#endifva_start(args, fmt); //获取第一个可变参数r = vprintk(fmt, args); //调用vprintk函数va_end(args); //释放可变参数链表指针return r;
}//vprintk函数
asmlinkage int vprintk(const char *fmt, va_list args)
{int printed_len = 0;int current_log_level = default_message_loglevel;unsigned long flags;int this_cpu;char *p;boot_delay_msec();printk_delay();preempt_disable();raw_local_irq_save(flags);this_cpu = smp_processor_id();if (unlikely(printk_cpu == this_cpu)) {if (!oops_in_progress) {recursion_bug = 1;goto out_restore_irqs;}zap_locks();}lockdep_off();spin_lock(&logbuf_lock);printk_cpu = this_cpu;if (recursion_bug) {recursion_bug = 0;strcpy(printk_buf, recursion_bug_msg);printed_len = strlen(recursion_bug_msg);}printed_len += vscnprintf(printk_buf + printed_len,sizeof(printk_buf) - printed_len, fmt, args);p = printk_buf;if (p[0] == '<') {//处理打印级别字段unsigned char c = p[1];if (c && p[2] == '>') {switch (c) {case '0' ... '7': /* loglevel */current_log_level = c - '0';case 'd': /* KERN_DEFAULT */if (!new_text_line) {emit_log_char('\n');new_text_line = 1;}case 'c': /* KERN_CONT */p += 3;break;}}}for ( ; *p; p++) {if (new_text_line) {/* Always output the token */emit_log_char('<');emit_log_char(current_log_level + '0');emit_log_char('>');printed_len += 3;new_text_line = 0;if (printk_time) { //打印时间信息/* Follow the token with the time */char tbuf[50], *tp;unsigned tlen;unsigned long long t;unsigned long nanosec_rem;t = cpu_clock(printk_cpu);nanosec_rem = do_div(t, 1000000000);tlen = sprintf(tbuf, "[%5lu.lu] ",(unsigned long) t,nanosec_rem / 1000);for (tp = tbuf; tp < tbuf + tlen; tp++)emit_log_char(*tp);printed_len += tlen;}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();lockdep_on();
out_restore_irqs:raw_local_irq_restore(flags);preempt_enable();return printed_len;
}//接着调用release_console_sem函数
void release_console_sem(void)
{unsigned long flags;unsigned _con_start, _log_end;unsigned wake_klogd = 0;if (console_suspended) {up(&console_sem);return;}console_may_schedule = 0;for ( ; ; ) {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);start_critical_timings();local_irq_restore(flags);}console_locked = 0;up(&console_sem);spin_unlock_irqrestore(&logbuf_lock, flags);if (wake_klogd)wake_up_klogd();
}
EXPORT_SYMBOL(release_console_sem);//调用call_console_drivers函数
static void call_console_drivers(unsigned start, unsigned end)
{unsigned cur_index, start_print;static int msg_level = -1;BUG_ON(((int)(start - end)) > 0);cur_index = start;start_print = start;while (cur_index != end) {if (msg_level < 0 && ((end - cur_index) > 2) &&LOG_BUF(cur_index + 0) == '<' &&LOG_BUF(cur_index + 1) >= '0' &&LOG_BUF(cur_index + 1) <= '7' &&LOG_BUF(cur_index + 2) == '>') {msg_level = LOG_BUF(cur_index + 1) - '0';cur_index += 3;start_print = cur_index;}while (cur_index != end) {char c = LOG_BUF(cur_index);cur_index++;if (c == '\n') {if (msg_level < 0) {msg_level = default_message_loglevel;}_call_console_drivers(start_print, cur_index, msg_level);msg_level = -1;start_print = cur_index;break;}}}_call_console_drivers(start_print, end, msg_level);
}_call_console_drivers函数//调用console的写方法
static void __call_console_drivers(unsigned start, unsigned end)
{ struct console *con; for_each_console(con) {//遍历console_drivers数组 #define for_each_console(con) for (con = console_drivers; con != NULL; con = con->next) if ((con->flags & CON_ENABLED) && con->write &&(cpu_online(smp_processor_id()) ||(con->flags & CON_ANYTIME))) con->write(con, &LOG_BUF(start), end - start); //调用console的写方法 }
} //由于已经注册的终端是serial8250_console，这个终端的写方法是调用serial8250_console_write()函数--->uart_console_write()--->serial8250_console_putchar()
//--->serial_out()最终打印在串口2终端上
/*static struct console serial8250_console = {.name = "ttyS",.write = serial8250_console_write,//写方法.device = uart_console_device,//tty驱动.setup = serial8250_console_setup,//设置串口波特率，也就是设置串口。很重要，里面涉及到平台特性，波特率相关。.early_setup = serial8250_console_early_setup,.flags = CON_PRINTBUFFER | CON_ANYTIME,.index = -1,.data = &serial8250_reg,};*/
console_drivers链表在register_console中会设置
