系统升级系列六

void start_armboot (void)
{
    ...
    #ifdef CONFIG_ANDROID_RECOVERY
	check_recovery_mode();
	#endif
    ...
}

/* export to lib_arm/board.c */
void check_recovery_mode(void)
{
	if (check_key_pressing())// 检查按键
		setup_recovery_env();// 如果是组合按键方式则设置recovery的启动环境
	else if (check_recovery_cmd_file()) {// 如果按键不符合，则检查启动命令
		puts("Recovery command file founded!\n");
		setup_recovery_env();// 如果检查到有recovery命令，则设置recovery启动环境
	}
}

#ifdef CONFIG_MXC_KPD//按键驱动，相反的对应qwerty

#define PRESSED_HOME	0x01// home键值
#define PRESSED_POWER	0x02// power键值
#define RECOVERY_KEY_MASK (PRESSED_HOME | PRESSED_POWER)// recovery组合键的定义是power+home，这个是可以定制的

inline int test_key(int value, struct kpp_key_info *ki)
{
	return (ki->val == value) && (ki->evt == KDepress);
}

int check_key_pressing(void)
{
	struct kpp_key_info *key_info;
	int state = 0, keys, i;

	mxc_kpp_init();// mxc驱动初始化

	puts("Detecting HOME+POWER key for recovery ...\n");

	/* Check for home + power */
	keys = mxc_kpp_getc(&key_info);// 获取按键
	if (keys < 2)
		return 0;

	for (i = 0; i < keys; i++) {
		if (test_key(CONFIG_POWER_KEY, &key_info[i]))// 测试home键
			state |= PRESSED_HOME;
		else if (test_key(CONFIG_HOME_KEY, &key_info[i]))// 测试power键
			state |= PRESSED_POWER;
	}

	free(key_info);

	if ((state & RECOVERY_KEY_MASK) == RECOVERY_KEY_MASK)// 如果检测到home+power，则跟定义的recovery组合键符合
		return 1;

	return 0;
}
#else
/* If not using mxc keypad, currently we will detect power key on board */
int check_key_pressing(void)
{
	return 0;
}
#endif

int check_recovery_cmd_file(void)
{
	disk_partition_t info;
	ulong part_length;
	int filelen;
	char *env;

	/* For test only */
	/* When detecting android_recovery_switch,
	 * enter recovery mode directly */
	env = getenv("android_recovery_switch");
	if (!strcmp(env, "1")) {
		printf("Env recovery detected!\nEnter recovery mode!\n");
		return 1;
	}

	printf("Checking for recovery command file...\n");
	switch (get_boot_device()) {// 获取启动设备
	case MMC_BOOT:
	case SD_BOOT:
		{
			block_dev_desc_t *dev_desc = NULL;
            // 取到所有注册的mmc设备的设备号是0的
			struct mmc *mmc = find_mmc_device(0);

			dev_desc = get_dev("mmc", 0);// 取到块设备描述信息

			if (NULL == dev_desc) {
				puts("** Block device MMC 0 not supported\n");
				return 0;
			}

			mmc_init(mmc);
			// 从块设备描述信息了找到cache分区的信息
			if (get_partition_info(dev_desc,
					CONFIG_ANDROID_CACHE_PARTITION_MMC,
					&info)) {
				printf("** Bad partition %d **\n",
					CONFIG_ANDROID_CACHE_PARTITION_MMC);
				return 0;
			}

            // 计算cache分区大小
			part_length = ext2fs_set_blk_dev(dev_desc,
					CONFIG_ANDROID_CACHE_PARTITION_MMC);
			if (part_length == 0) {
				printf("** Bad partition - mmc 0:%d **\n",
					CONFIG_ANDROID_CACHE_PARTITION_MMC);
				ext2fs_close();
				return 0;
			}

            // 挂载cache分区
			if (!ext2fs_mount(part_length)) {
				printf("** Bad ext2 partition or "
					"disk - mmc 0:%d **\n",
					CONFIG_ANDROID_CACHE_PARTITION_MMC);
				ext2fs_close();
				return 0;
			}

            // #define CONFIG_ANDROID_RECOVERY_CMD_FILE "/recovery/command"
            // 打开cache/recovery/command文件
			filelen = ext2fs_open(CONFIG_ANDROID_RECOVERY_CMD_FILE);

			ext2fs_close();
		}
		break;
	case NAND_BOOT:
		return 0;
		break;
	case SPI_NOR_BOOT:
		return 0;
		break;
	case UNKNOWN_BOOT:
	default:
		return 0;
		break;
	}

    // 如果有command文件，则返回1，标示找到了recovery command文件，但是这里是不去判断command的内容的
	return (filelen > 0) ? 1 : 0;

}

void setup_recovery_env(void)
{
	char *env, *boot_args, *boot_cmd;
	int bootdev = get_boot_device();// 取到启动设备，MMC、SDCARD、NAND、SPI等

    // 取到驱动设备对应的启动命令
    // boot_cmd 实际就是
	// CONFIG_ANDROID_RECOVERY_BOOTCMD_MMC="run bootargs_android_recovery;mmc read ${loadaddr} ${kernel_offset} ${kernel_size};mmc read ${rd_loadaddr} ${recovery_offset} ${recovery_size};bootm ${loadaddr} ${rd_loadaddr}"
	boot_cmd = supported_reco_envs[bootdev].cmd;
    // 启动参数这里没有用到，有时候也会用，如下
    // boot_args = supported_reco_envs[bootdev].args;

	if (boot_cmd == NULL) {
		printf("Unsupported bootup device for recovery\n");
		return;
	}

	printf("setup env for recovery..\n");

	env = getenv("bootcmd_android_recovery");
	if (!env)
        // 将启动命令设置到环境变量中
		setenv("bootcmd_android_recovery", boot_cmd);
    // 设置bootcmd，去运行启动recovery的命令
	setenv("bootcmd", "run bootcmd_android_recovery");
}