利用uboot传递参数进行内核的不同配置

如果一个硬件有不同的驱动支持，那么每次还得重新编译内核才能重新加载驱动吗？内核提供了一种很方便的机制，可以让我们通过uboot的命令参数来传递，调用不同的内核驱动。

__setup("xxx=", xxx_setup);

以内核下的文件Fbmem.c为例！

/**
 * fb_get_options - get kernel boot parameters
 * @name:   framebuffer name as it would appear in
 *          the boot parameter line
 *          (video=<name>:<options>)
 * @option: the option will be stored here
 *
 * NOTE: Needed to maintain backwards compatibility
 */
int fb_get_options(char *name, char **option)
{
	char *opt, *options = NULL;
	int retval = 0;
	int name_len = strlen(name), i;

	if (name_len && ofonly && strncmp(name, "offb", 4))
		retval = 1;

	if (name_len && !retval) {
		for (i = 0; i < FB_MAX; i++) {
			if (video_options[i] == NULL)
				continue;
			if (!video_options[i][0])
				continue;
			opt = video_options[i];
			if (!strncmp(name, opt, name_len) &&
			    opt[name_len] == ':')
				options = opt + name_len + 1;
		}
	}
	if (options && !strncmp(options, "off", 3))
		retval = 1;

	if (option)
		*option = options;

	return retval;
}

#ifndef MODULE
/**
 *	video_setup - process command line options
 *	@options: string of options
 *
 *	Process command line options for frame buffer subsystem.
 *
 *	NOTE: This function is a __setup and __init function.
 *            It only stores the options.  Drivers have to call
 *            fb_get_options() as necessary.
 *
 *	Returns zero.
 *
 */
static int __init video_setup(char *options)
{
	int i, global = 0;

	if (!options || !*options)
 		global = 1;

 	if (!global && !strncmp(options, "ofonly", 6)) {
 		ofonly = 1;
 		global = 1;
 	}

 	if (!global && !strstr(options,"fb:")) {
 		fb_mode_option = options;
 		global = 1;
 	}

 	if (!global) {
 		for (i = 0; i < FB_MAX; i++) {
 			if (video_options[i] == NULL) {
 				video_options[i] = options;
 				break;
 			}

		}
	}

	return 1;
}
__setup("video=", video_setup);

int fb_get_options(char *name, char **option)

得到不同的内核配置参数，之后依此可选择不同的文件进行驱动加载！