三星uboot1.1.6源码分析——start.s（9）--C语言部分(3)

上一篇我们分析了那个数组中的其中三个函数，这篇我们继续对那个数组中的函数进行分析。

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init_fnc_t *init_sequence[] = {
cpu_init, /* basic cpu dependent setup */
board_init, /* basic board dependent setup */
interrupt_init,/* set up exceptions */
env_init,/* initialize environment */
init_baudrate,/* initialze baudrate settings */
serial_init, /* serial communications setup */
console_init_f,/* stage 1 init of console */
display_banner,/* say that we are here */
#if defined(CONFIG_DISPLAY_CPUINFO)
print_cpuinfo,/* display cpu info (and speed) */
#endif
#if defined(CONFIG_DISPLAY_BOARDINFO)
checkboard, /* display board info */
#endif
dram_init, /* configure available RAM banks */
display_dram_config,
NULL,
};

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1、

env_init这个函数的源码应该在Env_nand.c (common)文件中，因为我们使用的是nand存储数据。

/* this is called before nand_init()
 * so we can't read Nand to validate env data.
 * Mark it OK for now. env_relocate() in env_common.c
 * will call our relocate function which will does
 * the real validation.
 *
 * When using a NAND boot image (like sequoia_nand), the environment
 * can be embedded（嵌入的） or attached（附着的） to the U-Boot image in NAND flash. This way
 * the SPL loads not only the U-Boot image from NAND but also the
 * environment.
 */
int env_init(void)
{
#if defined(ENV_IS_EMBEDDED)
ulong total;
int crc1_ok = 0, crc2_ok = 0;
env_t *tmp_env1, *tmp_env2;


total = CFG_ENV_SIZE;  ---#define CFG_ENV_SIZE0x80000 /* Total Size of Environment Sector */


tmp_env1 = env_ptr;
tmp_env2 = (env_t *)((ulong)env_ptr + CFG_ENV_SIZE);

------------------------------------------------------------------------

#ifdef ENV_IS_EMBEDDED
extern uchar environment[];
env_t *env_ptr = (env_t *)(&environment[0]);
#else /* ! ENV_IS_EMBEDDED */
env_t *env_ptr = 0;
#endif /* ENV_IS_EMBEDDED */

typedef struct environment_s {
unsigned long crc; /* CRC32 over data bytes*/
#ifdef CFG_REDUNDAND_ENVIRONMENT
unsigned char flags; /* active/obsolete flags*/
#endif
unsigned char data[ENV_SIZE]; /* Environment data */
} env_t;

------------------------------------------------------------------------


crc1_ok = (crc32(0, tmp_env1->data, ENV_SIZE) == tmp_env1->crc);
crc2_ok = (crc32(0, tmp_env2->data, ENV_SIZE) == tmp_env2->crc);

       ------------------和crc校验有关
------------------------------------------------------------

#define DO1(buf) crc = crc_table[((int)crc ^ (*buf++)) & 0xff] ^ (crc >> 8);
#define DO2(buf)  DO1(buf); DO1(buf);
#define DO4(buf)  DO2(buf); DO2(buf);
#define DO8(buf)  DO4(buf); DO4(buf);

/* ================================ */
uLong ZEXPORT crc32(crc, buf, len)
    uLong crc;
    const Bytef *buf;
    uInt len;
{
#ifdef DYNAMIC_CRC_TABLE
    if (crc_table_empty)
      make_crc_table();
#endif
    crc = crc ^ 0xffffffffL;
    while (len >= 8)
    {
      DO8(buf);
      len -= 8;
    }
    if (len) do {
      DO1(buf);
    } while (--len);
    return crc ^ 0xffffffffL;
}

------------------------------------------------------------

if (!crc1_ok && !crc2_ok)
gd->env_valid = 0;
else if(crc1_ok && !crc2_ok)
gd->env_valid = 1;
else if(!crc1_ok && crc2_ok)
gd->env_valid = 2;
else {
/* both ok - check serial */
if(tmp_env1->flags == 255 && tmp_env2->flags == 0)
gd->env_valid = 2;
else if(tmp_env2->flags == 255 && tmp_env1->flags == 0)
gd->env_valid = 1;
else if(tmp_env1->flags > tmp_env2->flags)
gd->env_valid = 1;
else if(tmp_env2->flags > tmp_env1->flags)
gd->env_valid = 2;
else /* flags are equal - almost impossible */
gd->env_valid = 1;
}
这里应该是根据校验结果，判断那个环境变量是可用的，然后设置gd->env_valid的值。从这里可以看出好像系统中有两个环境变量的存放空间？现在还不太清楚，有待以后查看。

if (gd->env_valid == 1)
env_ptr = tmp_env1;
else if (gd->env_valid == 2)
env_ptr = tmp_env2;
#else /* ENV_IS_EMBEDDED */
gd->env_addr  = (ulong)&default_environment[0];   这个应该是默认值
gd->env_valid = 1;

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uchar default_environment[] = {
#ifdef CONFIG_BOOTARGS
"bootargs=" CONFIG_BOOTARGS "\0"
#endif

--------------------------------------------------------

#define CONFIG_BOOTARGS     "root=/dev/mtdblock2 rootfstype=cramfs console=ttySAC0,115200"

--------------------------------------------------------
#ifdef CONFIG_BOOTCOMMAND
"bootcmd=" CONFIG_BOOTCOMMAND "\0"
#endif
#ifdef CONFIG_RAMBOOTCOMMAND
"ramboot=" CONFIG_RAMBOOTCOMMAND "\0"
#endif
#ifdef CONFIG_NFSBOOTCOMMAND
"nfsboot=" CONFIG_NFSBOOTCOMMAND "\0"
#endif

-------------------------------------------------------------

上面这些都和最上面那个很类似，就不详细说了，应该都是在Smdk6410.h (include\configs)文件中定义。

-------------------------------------------------------------
#if defined(CONFIG_BOOTDELAY) && (CONFIG_BOOTDELAY >= 0)
"bootdelay=" MK_STR(CONFIG_BOOTDELAY) "\0"
#endif
#if defined(CONFIG_BAUDRATE) && (CONFIG_BAUDRATE >= 0)
"baudrate=" MK_STR(CONFIG_BAUDRATE) "\0"
#endif
#ifdef CONFIG_LOADS_ECHO
"loads_echo=" MK_STR(CONFIG_LOADS_ECHO) "\0"
#endif
#ifdef CONFIG_ETHADDR
"ethaddr=" MK_STR(CONFIG_ETHADDR) "\0"
#endif
#ifdef CONFIG_ETH1ADDR
"eth1addr=" MK_STR(CONFIG_ETH1ADDR) "\0"
#endif
#ifdef CONFIG_ETH2ADDR
"eth2addr=" MK_STR(CONFIG_ETH2ADDR) "\0"
#endif
#ifdef CONFIG_ETH3ADDR
"eth3addr=" MK_STR(CONFIG_ETH3ADDR) "\0"
#endif
#ifdef CONFIG_IPADDR
"ipaddr=" MK_STR(CONFIG_IPADDR) "\0"
#endif
#ifdef CONFIG_SERVERIP
"serverip=" MK_STR(CONFIG_SERVERIP) "\0"
#endif
#ifdef CFG_AUTOLOAD
"autoload=" CFG_AUTOLOAD "\0"
#endif
#ifdef CONFIG_PREBOOT
"preboot=" CONFIG_PREBOOT "\0"
#endif
#ifdef CONFIG_ROOTPATH
"rootpath=" MK_STR(CONFIG_ROOTPATH) "\0"
#endif
#ifdef CONFIG_GATEWAYIP
"gatewayip=" MK_STR(CONFIG_GATEWAYIP) "\0"
#endif
#ifdef CONFIG_NETMASK
"netmask=" MK_STR(CONFIG_NETMASK) "\0"
#endif
#ifdef CONFIG_HOSTNAME
"hostname=" MK_STR(CONFIG_HOSTNAME) "\0"
#endif
#ifdef CONFIG_BOOTFILE
"bootfile=" MK_STR(CONFIG_BOOTFILE) "\0"
#endif
#ifdef CONFIG_LOADADDR
"loadaddr=" MK_STR(CONFIG_LOADADDR) "\0"
#endif

-------------------------------------------------------------------------

/*
 * Macros to transform values
 * into environment strings.
 */
#define XMK_STR(x) #x
#define MK_STR(x) XMK_STR(x)

-------------------------------------------------------------------------
#ifdef  CONFIG_CLOCKS_IN_MHZ
"clocks_in_mhz=1\0"
#endif
#if defined(CONFIG_PCI_BOOTDELAY) && (CONFIG_PCI_BOOTDELAY > 0)
"pcidelay=" MK_STR(CONFIG_PCI_BOOTDELAY) "\0"
#endif
#ifdef  CONFIG_EXTRA_ENV_SETTINGS
CONFIG_EXTRA_ENV_SETTINGS
#endif
"\0"
};

上面这些环境变量都是在Smdk6410.h (include\configs)文件中定义，因为我们关心的就是6410平台。这些环境变量的具体含义也没啥好说的，网上资料很多，而且这些我们都经常用，就不多说了。

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#endif /* ENV_IS_EMBEDDED */


return (0);
}

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总：这一篇博客重点说了一个与环境变量有关的函数env_init，下一篇，我们接着说其他函数。

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