转自:http://blog.csdn.net/lizuobin2/article/details/52061530
上篇文章说到,再清 BSS 段之后,CPU 跳转到 sdram 里的 start_armboot() 函数,本文,分析 uboot 流程的第二阶段、第三阶段。
start_armboot函数在lib_arm/board.c中定义,是U-Boot第二阶段代码的入口。第二阶段的主要工作是进行单板级别的初始化,初始化 nandflash 、norflash 、初始化串口、设置环境变量、最终跳转到 main_loop 里,接收串口传递进来的各种命令。
第三阶段主要的工作就是设置 uboot 将要传递给内核的 tag 以及解析 uboot 头部里包含的信息,最终跳转到内核起始地址去执行,将主控权交给内核。
一、gd 结构体
-
-
gd = (gd_t*)(_armboot_start - CFG_MALLOC_LEN - sizeof(gd_t));
-
-
memset ((void*)gd, 0, sizeof (gd_t));
-
gd->bd = (bd_t*)((char*)gd - sizeof(bd_t));
-
memset (gd->bd, 0, sizeof (bd_t));
_armboot_start 是 start.S 中的汇编语言的标号
-
.globl _armboot_start
-
_armboot_start:
-
.word _start
汇编中我们可以通过不同的指令获得一个标号的地址或者标号地址处存放的数据,在 C 中,直接访问一个标号表示获取标号地址处存放的数据,一个无符号整形变量
-
extern ulong _armboot_start;
-
extern ulong _bss_start;
前边第一篇文章我们分析过堆栈的划分,为 gd 结构体 留出了128K 的空间,根据上边的代码我们可以知道这 128K 有高到低先放一个 gd_t 类型的结构体,紧挨着又放了一个它的成员 bd_t 类型的结构。
-
typedef struct global_data {
-
bd_t *bd;
-
unsigned long flags;
-
unsigned long baudrate;
-
unsigned long have_console;
-
unsigned long reloc_off;
-
unsigned long env_addr;
-
unsigned long env_valid;
-
unsigned long fb_base;
-
#ifdef CONFIG_VFD
-
unsigned char vfd_type;
-
#endif
-
#if 0
-
unsigned long cpu_clk;
-
unsigned long bus_clk;
-
unsigned long ram_size;
-
unsigned long reset_status;
-
#endif
-
void **jt;
-
} gd_t;
-
typedef struct bd_info {
-
int bi_baudrate;
-
unsigned long bi_ip_addr;
-
unsigned char bi_enetaddr[6];
-
struct environment_s *bi_env;
-
ulong bi_arch_number;
-
ulong bi_boot_params;
-
struct
-
{
-
ulong start;
-
ulong size;
-
} bi_dram[CONFIG_NR_DRAM_BANKS];
-
#ifdef CONFIG_HAS_ETH1
-
-
unsigned char bi_enet1addr[6];
-
#endif
-
} bd_t;
前边的 gd 是个全局变量:
#define DECLARE_GLOBAL_DATA_PTR register volatile gd_t *gd asm ("r8")
二、初始化工作
前边分配完了 gd 结构体之后,就开始一系列的初始化工作,初始化函数定义在 init_sequence 中
-
for (init_fnc_ptr = init_sequence; *init_fnc_ptr; ++init_fnc_ptr) {
-
if ((*init_fnc_ptr)() != 0) {
-
hang ();
-
}
-
}
-
init_fnc_t *init_sequence[] = {
-
cpu_init,
-
board_init,
-
interrupt_init,
-
env_init,
-
init_baudrate,
-
serial_init,
-
console_init_f,
-
display_banner,
-
#if defined(CONFIG_DISPLAY_CPUINFO)
-
print_cpuinfo,
-
#endif
-
#if defined(CONFIG_DISPLAY_BOARDINFO)
-
checkboard,
-
#endif
-
dram_init,
-
display_dram_config,
-
NULL,
-
};
2.1 cpu_init
-
int cpu_init (void)
-
{
-
-
-
-
#ifdef CONFIG_USE_IRQ
-
IRQ_STACK_START = _armboot_start - CFG_MALLOC_LEN - CFG_GBL_DATA_SIZE - 4;
-
FIQ_STACK_START = IRQ_STACK_START - CONFIG_STACKSIZE_IRQ;
-
#endif
-
return 0;
-
}
如果使用 irq 的话,将这两个宏指向之前分配的栈空间
2.2 board_init
-
int board_init (void)
-
{
-
-
S3C24X0_CLOCK_POWER * const clk_power = S3C24X0_GetBase_CLOCK_POWER();
-
-
-
S3C24X0_GPIO * const gpio = S3C24X0_GetBase_GPIO();
-
-
-
clk_power->LOCKTIME = 0xFFFFFF;
-
-
-
-
clk_power->MPLLCON = ((M_MDIV << 12) + (M_PDIV << 4) + M_SDIV);
-
-
-
delay (4000);
-
-
-
clk_power->UPLLCON = ((U_M_MDIV << 12) + (U_M_PDIV << 4) + U_M_SDIV);
-
-
-
delay (8000);
-
-
-
gpio->GPACON = 0x007FFFFF;
-
gpio->GPBCON = 0x00044555;
-
gpio->GPBUP = 0x000007FF;
-
gpio->GPCCON = 0xAAAAAAAA;
-
gpio->GPCUP = 0x0000FFFF;
-
gpio->GPDCON = 0xAAAAAAAA;
-
gpio->GPDUP = 0x0000FFFF;
-
gpio->GPECON = 0xAAAAAAAA;
-
gpio->GPEUP = 0x0000FFFF;
-
gpio->GPFCON = 0x000055AA;
-
gpio->GPFUP = 0x000000FF;
-
gpio->GPGCON = 0xFF95FFBA;
-
gpio->GPGUP = 0x0000FFFF;
-
gpio->GPHCON = 0x002AFAAA;
-
gpio->GPHUP = 0x000007FF;
-
-
-
gd->bd->bi_arch_number = MACH_TYPE_SMDK2410;
-
-
-
-
gd->bd->bi_boot_params = 0x30000100;
-
-
-
icache_enable();
-
dcache_enable();
-
-
return 0;
-
}
重点工作,向 gd 结构体中记录了 机器ID 以及 tag 的存放地址,这俩都是要传递给内核的!!!
2.3 interrupt_init PWM的初始化,无关紧要
2.4 env_init
-
typedef struct environment_s {
-
unsigned long crc;
-
unsigned char flags;
-
unsigned char data[ENV_SIZE];
-
} env_t;
-
env_t *env_ptr = (env_t *)CFG_ENV_ADDR;
-
static env_t *flash_addr = (env_t *)CFG_ENV_ADDR;
环境变量用一个 environment_s 结构来描述,它被放置在 norflash 的 0x70000 起始的地址处,crc 是环境变量的校验和,全部的环境变量都以字符串的形式存放在 data 数组中,两个环境变量之间用 “ ” 隔开。
-
int env_init(void)
-
{
-
if (crc32(0, env_ptr->data, ENV_SIZE) == env_ptr->crc) {
-
gd->env_addr = (ulong)&(env_ptr->data);
-
gd->env_valid = 1;
-
return(0);
-
}
-
-
gd->env_addr = (ulong)&default_environment[0];
-
gd->env_valid = 0;
-
return (0);
-
}
现在env_ptr指向 Norfalsh 中的0x070000,进行校验,判断环境变量是否可用。
1、uboot 第一次启动,那么 norflash 这个地址处并没有任何东西,校验失败,则使用默认的环境变量,使全局指针 gd->env_addr 指向内存中的默认环境变量,并设置标志位 gd->env_valid 为 0 。
2、uboot 非第一次启动,那么校验成功,将全局指针 gd->env_addr 指向环境变量,并使标志位 gd->env_valid 置一。
默认环境变量的 定义 CONFIG_BOOTARGS 等宏在 Smdk2410.h (includeconfigs)
-
uchar default_environment[] = {
-
#ifdef CONFIG_BOOTARGS
-
"bootargs=" CONFIG_BOOTARGS " "
-
#endif
-
#ifdef CONFIG_BOOTCOMMAND
-
"bootcmd=" CONFIG_BOOTCOMMAND " "
-
#endif
-
#ifdef CONFIG_RAMBOOTCOMMAND
-
"ramboot=" CONFIG_RAMBOOTCOMMAND " "
-
#endif
-
#ifdef CONFIG_NFSBOOTCOMMAND
-
"nfsboot=" CONFIG_NFSBOOTCOMMAND " "
-
#endif
-
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
-
"bootdelay=" MK_STR(CONFIG_BOOTDELAY) " "
-
#endif
-
#if defined(CONFIG_BAUDRATE) && (CONFIG_BAUDRATE >= 0)
-
"baudrate=" MK_STR(CONFIG_BAUDRATE) " "
-
#endif
-
#ifdef CONFIG_LOADS_ECHO
-
"loads_echo=" MK_STR(CONFIG_LOADS_ECHO) " "
-
#endif
-
#ifdef CONFIG_ETHADDR
-
"ethaddr=" MK_STR(CONFIG_ETHADDR) " "
-
#endif
-
#ifdef CONFIG_ETH1ADDR
-
"eth1addr=" MK_STR(CONFIG_ETH1ADDR) " "
-
#endif
-
#ifdef CONFIG_ETH2ADDR
-
"eth2addr=" MK_STR(CONFIG_ETH2ADDR) " "
-
#endif
-
#ifdef CONFIG_ETH3ADDR
-
"eth3addr=" MK_STR(CONFIG_ETH3ADDR) " "
-
#endif
-
#ifdef CONFIG_IPADDR
-
"ipaddr=" MK_STR(CONFIG_IPADDR) " "
-
#endif
-
#ifdef CONFIG_SERVERIP
-
"serverip=" MK_STR(CONFIG_SERVERIP) " "
-
#endif
-
#ifdef CFG_AUTOLOAD
-
"autoload=" CFG_AUTOLOAD " "
-
#endif
-
#ifdef CONFIG_PREBOOT
-
"preboot=" CONFIG_PREBOOT " "
-
#endif
-
#ifdef CONFIG_ROOTPATH
-
"rootpath=" MK_STR(CONFIG_ROOTPATH) " "
-
#endif
-
#ifdef CONFIG_GATEWAYIP
-
"gatewayip=" MK_STR(CONFIG_GATEWAYIP) " "
-
#endif
-
#ifdef CONFIG_NETMASK
-
"netmask=" MK_STR(CONFIG_NETMASK) " "
-
#endif
-
#ifdef CONFIG_HOSTNAME
-
"hostname=" MK_STR(CONFIG_HOSTNAME) " "
-
#endif
-
#ifdef CONFIG_BOOTFILE
-
"bootfile=" MK_STR(CONFIG_BOOTFILE) " "
-
#endif
-
#ifdef CONFIG_LOADADDR
-
"loadaddr=" MK_STR(CONFIG_LOADADDR) " "
-
#endif
-
#ifdef CONFIG_CLOCKS_IN_MHZ
-
"clocks_in_mhz=1 "
-
#endif
-
#if defined(CONFIG_PCI_BOOTDELAY) && (CONFIG_PCI_BOOTDELAY > 0)
-
"pcidelay=" MK_STR(CONFIG_PCI_BOOTDELAY) " "
-
#endif
-
#ifdef CONFIG_EXTRA_ENV_SETTINGS
-
CONFIG_EXTRA_ENV_SETTINGS
-
#endif
-
" "
-
};
以 "bootargs=" CONFIG_BOOTARGS " " 为例:
#define CONFIG_BOOTARGS "root=ramfs devfs=mount console=ttySA0,9600"
确实如同前边说所,data 里边放置的都是一个个字符串,两个环境变量之间 通过 “ ”隔开。
2.5 init_baudrate 设置波特率 首先从环境变量中读取,如果没有则设置为 115200
2.6 serial_init 串口初始化
-
int serial_init (void)
-
{
-
serial_setbrg ();
-
-
return (0);
-
}
-
void serial_setbrg (void)
-
{
-
S3C24X0_UART * const uart = S3C24X0_GetBase_UART(UART_NR);
-
int i;
-
unsigned int reg = 0;
-
-
-
reg = get_PCLK() / (16 * gd->baudrate) - 1;
-
-
-
uart->UFCON = 0x07;
-
uart->UMCON = 0x0;
-
-
uart->ULCON = 0x3;
-
-
-
-
-
uart->UCON = 0x245;
-
uart->UBRDIV = reg;
-
-
#ifdef CONFIG_HWFLOW
-
uart->UMCON = 0x1;
-
#endif
-
for (i = 0; i < 100; i++);
-
}
串口控制寄存器的设置.....以前移植的时候遇到一个问题,get_PCLK() 这个函数需要修改,2410 和 2440 不一样。
2.7 console_init_f 控制台初始化,无关紧要
2.8 display_banner 打印代码段 BSS段等地址信息
2.9 dram_init
-
int dram_init (void)
-
{
-
gd->bd->bi_dram[0].start = PHYS_SDRAM_1;
-
gd->bd->bi_dram[0].size = PHYS_SDRAM_1_SIZE;
-
-
return 0;
-
}
在全局指针 gd 中标记内存范围
2.A display_dram_config 打印 sdram 信息
2.B norflash 初始化
-
#ifndef CFG_NO_FLASH
-
-
size = flash_init ();
2.C nandflash 初始化
-
#if (CONFIG_COMMANDS & CFG_CMD_NAND)
-
puts ("NAND: ");
-
nand_init();
2.D 环境变量重定位
-
void env_relocate (void)
-
{
-
DEBUGF ("%s[%d] offset = 0x%lx
", __FUNCTION__,__LINE__,
-
gd->reloc_off);
-
-
-
-
env_ptr = (env_t *)malloc (CFG_ENV_SIZE);
-
DEBUGF ("%s[%d] malloced ENV at %p
", __FUNCTION__,__LINE__,env_ptr);
-
-
-
-
-
env_get_char = env_get_char_memory;
-
-
if (gd->env_valid == 0)
-
puts ("*** Warning - bad CRC, using default environment
");
-
SHOW_BOOT_PROGRESS (-1);
-
-
-
if (sizeof(default_environment) > ENV_SIZE)
-
{
-
puts ("*** Error - default environment is too large
");
-
return;
-
}
-
-
memset (env_ptr, 0, sizeof(env_t));
-
memcpy (env_ptr->data,
-
default_environment,
-
sizeof(default_environment));
-
#ifdef CFG_REDUNDAND_ENVIRONMENT
-
env_ptr->flags = 0xFF;
-
#endif
-
env_crc_update ();
-
gd->env_valid = 1;
-
}
-
else {
-
-
env_relocate_spec ();
-
}
-
gd->env_addr = (ulong)&(env_ptr->data);
-
-
#ifdef CONFIG_AMIGAONEG3SE
-
disable_nvram();
-
#endif
-
}
-
-
#ifdef CONFIG_AUTO_COMPLETE
-
void env_relocate_spec (void)
-
{
-
-
-
memcpy (env_ptr, (void*)flash_addr, CFG_ENV_SIZE);
-
}
重定位之后,我们在uboot命令行读取到的环境变量都是内存中的,修改后要写回 norflash
-
#ifdef CMD_SAVEENV
-
-
int saveenv(void)
-
{
-
int len, rc;
-
ulong end_addr;
-
ulong flash_sect_addr;
-
-
uchar *env_buffer = (uchar *)env_ptr;
-
-
int rcode = 0;
-
-
flash_sect_addr = (ulong)flash_addr;
-
len = CFG_ENV_SIZE;
-
-
end_addr = flash_sect_addr + len - 1;
-
-
-
debug ("Protect off %08lX ... %08lX
",
-
(ulong)flash_sect_addr, end_addr);
-
-
if (flash_sect_protect (0, flash_sect_addr, end_addr))
-
return 1;
-
-
puts ("Erasing Flash...");
-
if (flash_sect_erase (flash_sect_addr, end_addr))
-
return 1;
-
-
puts ("Writing to Flash... ");
-
rc = flash_write((char *)env_buffer, flash_sect_addr, len);
-
if (rc != 0) {
-
flash_perror (rc);
-
rcode = 1;
-
} else {
-
puts ("done
");
-
}
-
-
-
(void) flash_sect_protect (1, flash_sect_addr, end_addr);
-
return rcode;
-
}
2.E 从环境变量中获取 ip mac 地址放入全局 gd 结构
-
-
gd->bd->bi_ip_addr = getenv_IPaddr ("ipaddr");
-
-
-
{
-
int i;
-
ulong reg;
-
char *s, *e;
-
char tmp[64];
-
-
i = getenv_r ("ethaddr", tmp, sizeof (tmp));
-
s = (i > 0) ? tmp : NULL;
-
-
for (reg = 0; reg < 6; ++reg) {
-
gd->bd->bi_enetaddr[reg] = s ? simple_strtoul (s, &e, 16) : 0;
-
if (s)
-
s = (*e) ? e + 1 : e;
-
}
-
-
#ifdef CONFIG_HAS_ETH1
-
i = getenv_r ("eth1addr", tmp, sizeof (tmp));
-
s = (i > 0) ? tmp : NULL;
-
-
for (reg = 0; reg < 6; ++reg) {
-
gd->bd->bi_enet1addr[reg] = s ? simple_strtoul (s, &e, 16) : 0;
-
if (s)
-
s = (*e) ? e + 1 : e;
-
}
有意思的是,这里用了一个{ },大概是为了防止变量名字冲突?
2.F devices_init (); 没研究过,不知道干啥的,应该没啥影响
2.G jumptable_init ()
-
void jumptable_init (void)
-
{
-
int i;
-
-
gd->jt = (void **) malloc (XF_MAX * sizeof (void *));
-
for (i = 0; i < XF_MAX; i++)
-
gd->jt[i] = (void *) dummy;
-
-
gd->jt[XF_get_version] = (void *) get_version;
-
gd->jt[XF_malloc] = (void *) malloc;
-
gd->jt[XF_free] = (void *) free;
-
gd->jt[XF_getenv] = (void *) getenv;
-
gd->jt[XF_setenv] = (void *) setenv;
-
gd->jt[XF_get_timer] = (void *) get_timer;
-
gd->jt[XF_simple_strtoul] = (void *) simple_strtoul;
-
gd->jt[XF_udelay] = (void *) udelay;
-
#if defined(CONFIG_I386) || defined(CONFIG_PPC)
-
gd->jt[XF_install_hdlr] = (void *) irq_install_handler;
-
gd->jt[XF_free_hdlr] = (void *) irq_free_handler;
-
#endif /* I386 || PPC */
-
#if (CONFIG_COMMANDS & CFG_CMD_I2C)
-
gd->jt[XF_i2c_write] = (void *) i2c_write;
-
gd->jt[XF_i2c_read] = (void *) i2c_read;
-
#endif /* CFG_CMD_I2C */
在全局结构 gd 中记录 这些函数,不太懂。
2.H enable_interrupts 在 cpsr 中使能 irq fiq
-
void enable_interrupts (void)
-
{
-
unsigned long temp;
-
__asm__ __volatile__("mrs %0, cpsr
"
-
"bic %0, %0, #0x80
"
-
"msr cpsr_c, %0"
-
: "=r" (temp)
-
:
-
: "memory");
-
}
2.I 网卡初始化
-
#if (CONFIG_COMMANDS & CFG_CMD_NET)
-
#if defined(CONFIG_NET_MULTI)
-
puts ("Net: ");
-
#endif
-
eth_initialize(gd->bd);
2.J 跳转到 uboot 菜单
-
for (;;) {
-
main_loop ();
-
}
三、第三阶段 启动内核
我们在 uboot 中输入 bootm 命令,U-Boot接收输入的字符串“bootm”,传递给 run_command 函数。run_command 函数调用 common/command.c 中实现的 find_cmd 函数在 __u_boot_cmd_start 与 __u_boot_cmd_end间查找命令,并返回
bootm 命令的 cmd_tbl_t 结构。然后 run_command 函数使用返回的 cmd_tbl_t 结构中的函数指针调用 bootm 命令的响应函数 do_bootm。
-
int do_bootm (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
-
{
-
......
-
image_header_t *hdr = &header;
-
......
-
if (argc < 2) {
-
addr = load_addr;
-
} else {
-
addr = simple_strtoul(argv[1], NULL, 16);
-
}
-
......
-
switch (hdr->ih_comp) {
-
case IH_COMP_NONE:
-
if(ntohl(hdr->ih_load) == addr) {
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
printf (" XIP %s ... ", name);
-
} else {
-
......do_bootm_linux (cmdtp, flag, argc, argv,addr, len_ptr, verify);
-
}
-
lib_arm/armlinux.c
-
void do_bootm_linux (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[],
-
ulong addr, ulong *len_ptr, int verify)
-
{
-
ulong len = 0, checksum;
-
ulong initrd_start, initrd_end;
-
ulong data;
-
-
void (*theKernel)(int zero, int arch, uint params);
-
image_header_t *hdr = &header;
-
bd_t *bd = gd->bd;
-
-
#ifdef CONFIG_CMDLINE_TAG
-
char *commandline = getenv ("bootargs");
-
#endif
-
-
theKernel = (void (*)(int, int, uint))ntohl(hdr->ih_ep)
-
-
#if defined (CONFIG_SETUP_MEMORY_TAGS) ||
-
defined (CONFIG_CMDLINE_TAG) ||
-
defined (CONFIG_INITRD_TAG) ||
-
defined (CONFIG_SERIAL_TAG) ||
-
defined (CONFIG_REVISION_TAG) ||
-
defined (CONFIG_LCD) ||
-
defined (CONFIG_VFD)
-
setup_start_tag (bd);
-
-
-
#ifdef CONFIG_SERIAL_TAG
-
setup_serial_tag (¶ms);
-
#endif
-
#ifdef CONFIG_REVISION_TAG
-
setup_revision_tag (¶ms);
-
#endif
-
#ifdef CONFIG_SETUP_MEMORY_TAGS
-
setup_memory_tags (bd);
-
#endif
-
#ifdef CONFIG_CMDLINE_TAG
-
setup_commandline_tag (bd, commandline);
-
#endif
-
#ifdef CONFIG_INITRD_TAG
-
if (initrd_start && initrd_end)
-
setup_initrd_tag (bd, initrd_start, initrd_end);
-
#endif
-
#if defined (CONFIG_VFD) || defined (CONFIG_LCD)
-
setup_videolfb_tag ((gd_t *) gd);
-
#endif
-
setup_end_tag (bd);
-
#endif
-
-
-
printf ("
Starting kernel ...
");
-
-
cleanup_before_linux ();
-
-
theKernel (0, bd->bi_arch_number, bd->bi_boot_params);
-
}
至此,uboot 的生命周期结束,控制权交给内核~
四、添加自定义命令
下面以添加menu命令(启动菜单)为例讲解U-Boot添加命令的方法。
1、建立common/cmd_menu.c
习惯上通用命令源代码放在common目录下,与开发板专有命令源代码则放在board/<board_dir>目录下,并且习惯以“cmd_<命令名>.c”为文件名。
2、定义“menu”命令
在 cmd_menu.c中使用如下的代码定义“menu”命令:参考 cmd_bootm.c
-
U_BOOT_CMD(
-
bootm, CFG_MAXARGS, 1, do_bootm,
-
"bootm - boot application image from memory
",
-
"[addr [arg ...]]
- boot application image stored in memory
"
-
" passing arguments 'arg ...'; when booting a Linux kernel,
"
-
" 'arg' can be the address of an initrd image
"
-
#ifdef CONFIG_OF_FLAT_TREE
-
" When booting a Linux kernel which requires a flat device-tree
"
-
" a third argument is required which is the address of the of the
"
-
" device-tree blob. To boot that kernel without an initrd image,
"
-
" use a '-' for the second argument. If you do not pass a third
"
-
" a bd_info struct will be passed instead
"
-
#endif
-
);
-
U_BOOT_CMD(
-
menu, 3, 0, do_menu,
-
"menu - display a menu, to select the items to do something
",
-
" - display a menu, to select the items to do something"
-
);
U_BOOT_CMD(name,maxargs,rep,cmd,usage,help)
各个参数的意义如下:
name:命令名,非字符串,但在U_BOOT_CMD中用“#”符号转化为字符串
maxargs:命令的最大参数个数
rep:是否自动重复(按Enter键是否会重复执行)
cmd:该命令对应的响应函数
usage:简短的使用说明(字符串)
help:较详细的使用说明(字符串)
U_BOOT_CMD宏在include/command.h中定义,分为有无帮助信息两种:
-
#define Struct_Section __attribute__ ((unused,section (".u_boot_cmd")))
-
-
#ifdef CFG_LONGHELP
-
-
#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help)
-
cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage, help}
-
-
#else /* no long help info */
-
-
#define U_BOOT_CMD(name,maxargs,rep,cmd,usage,help)
-
cmd_tbl_t __u_boot_cmd_##name Struct_Section = {#name, maxargs, rep, cmd, usage}
-
-
#endif /* CFG_LONGHELP */
定义一个 cmd_tbl_t 类型的结构体,比如 bootm 名字叫 __u_boot_cmd_bootm 放在 .u_boot_cmd 段。执行命令时就可以在“u_boot_cmd”段查找到对应的 cmd_tbl_t 类型结构体。
-
struct cmd_tbl_s {
-
char *name;
-
int maxargs;
-
int repeatable;
-
int (*cmd)(struct cmd_tbl_s *, int, int, char *[]);
-
char *usage;
-
#ifdef CONFIG_SYS_LONGHELP
-
char *help;
-
#endif
-
#ifdef CONFIG_AUTO_COMPLETE
-
-
-
int (*complete)(int argc, char *argv[], char last_char, int maxv, char *cmdv[]);
-
#endif
-
};
-
typedef struct cmd_tbl_s cmd_tbl_t;
一个cmd_tbl_t结构体变量包含了调用一条命令的所需要的信息。
3、实现命令的函数
在cmd_menu.c中添加“menu”命令的响应函数的实现。具体的实现代码略:
-
int do_menu (cmd_tbl_t *cmdtp, int flag, int argc, char *argv[])
-
{
-
-
}
4、将common/cmd_menu.c编译进u-boot.bin
在common/Makefile中加入如下代码:
COBJS-$(CONFIG_BOOT_MENU) += cmd_menu.o
在include/configs/smdk2410.h加入如代码:
#define CONFIG_BOOT_MENU 1
重新编译下载U-Boot就可以使用menu命令了