linux 内核的early_param

#define __setup_param(str, unique_id, fn, early)\
static const char __setup_str_##unique_id[] __initconst\
__aligned(1) = str; \
static struct obs_kernel_param __setup_##unique_id\
__used __section(.init.setup)\
__attribute__((aligned((sizeof(long)))))\
= { __setup_str_##unique_id, fn, early }
#define __setup(str, fn)\
__setup_param(str, fn, fn, 0)
/* NOTE: fn is as per module_param, not __setup!  Emits warning if fn
* returns non-zero. */
#define early_param(str, fn)\
__setup_param(str, fn, fn, 1)
early_param("debug", nf_debug_setup);

start_kernel->parse_early_param->parse_early_options

void __init parse_early_param(void)
{
static __initdata int done = 0;
static __initdata char tmp_cmdline[COMMAND_LINE_SIZE];
if (done)
return;
/* All fall through to do_early_param. */
strlcpy(tmp_cmdline, boot_command_line, COMMAND_LINE_SIZE);//复制启动命令行数据
parse_early_options(tmp_cmdline);
done = 1;
}

void __init parse_early_options(char *cmdline)
{
parse_args("early options", cmdline, NULL, 0, 0, 0, do_early_param);
}

/* Args looks like "foo=bar,bar2 baz=fuz wiz". */
int parse_args(const char *doing,//“early options”
char *args,//命令行参数
const struct kernel_param *params,//NULL
unsigned num,//0
s16 min_level,//0
s16 max_level,//0
int (*unknown)(char *param, char *val, const char *doing)//do_early_param)
{
char *param, *val;
/* Chew leading spaces */
args = skip_spaces(args);
if (*args)
pr_debug("doing %s, parsing ARGS: '%s'\n", doing, args);
while (*args) {
int ret;
int irq_was_disabled;
args = next_arg(args, ¶m, &val);
irq_was_disabled = irqs_disabled();
ret = parse_one(param, val, doing, params, num,
min_level, max_level, unknown);
if (irq_was_disabled && !irqs_disabled())
pr_warn("%s: option '%s' enabled irq's!\n",
doing, param);
switch (ret) {
case -ENOENT:
pr_err("%s: Unknown parameter `%s'\n", doing, param);
return ret;
case -ENOSPC:
pr_err("%s: `%s' too large for parameter `%s'\n",
doing, val ?: "", param);
return ret;
case 0:
break;
default:
pr_err("%s: `%s' invalid for parameter `%s'\n",
doing, val ?: "", param);
return ret;
}
}
/* All parsed OK. */
return 0;
}