uclinux内核参数处理(2)：parse_cmdline_early

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这是内核第一次对传递进来的参数进行分析，对此函数的调用出现在setup_arch函数中，此时，内核仅仅对CPU的基本参数进行的进行了设置，如运行频率，EBIU等等。

void __init setup_arch(char **cmdline_p)

{

……………………

/* Keep a copy of command line */

*cmdline_p = &command_line[0];

memcpy(boot_command_line, command_line, COMMAND_LINE_SIZE);

boot_command_line[COMMAND_LINE_SIZE - 1] = '\0';

/* setup memory defaults from the user config */

physical_mem_end = 0;

_ramend = CONFIG_MEM_SIZE * 1024 * 1024;

parse_cmdline_early(&command_line[0]);

…………………….

}

而parse_cmdline_early函数的实现则为：

/*

* Initial parsing of the command line. Currently, we support:

* - Controlling the linux memory size: mem=xxx[KMG]

* - Controlling the physical memory size: max_mem=xxx[KMG][$][#]

* $ -> reserved memory is dcacheable

* # -> reserved memory is icacheable

*/

static __init void parse_cmdline_early(char *cmdline_p)

{

char c = ' ', *to = cmdline_p;

unsigned int memsize;

for (;;) {

if (c == ' ') {

if (!memcmp(to, "mem=", 4)) {

to += 4;

memsize = memparse(to, &to);

if (memsize)

_ramend = memsize;

} else if (!memcmp(to, "max_mem=", 8)) {

to += 8;

memsize = memparse(to, &to);

if (memsize) {

physical_mem_end = memsize;

if (*to != ' ') {

if (*to == '$'

|| *(to + 1) == '$')

reserved_mem_dcache_on =

1;

if (*to == '#'

|| *(to + 1) == '#')

reserved_mem_icache_on =

1;

}

}

} else if (!memcmp(to, "earlyprintk=", 12)) {

to += 12;

setup_early_printk(to);

}

}

c = *(to++);

if (!c)

break;

}

}

从这段代码可以很容易看出此时内核只处理必要的3个参数：mem，max_mem和earlyprintk。

1 参考资料

uclinux内核参数处理(1)：参数接收(2009-1-29)