[RK3288][Android6.0] DeviceTree中的status属性使用规则

Platform: Rockchip
OS: Android 6.0
Kernel: 3.10.92

有看到网友在讨论device tree中的status到底该如何设置，默认状态是什么，知识点如下:

1. 默认情况下不设置status属性的话表示此节点的功能是enable的
2. 如果要设置status,那么值必须是”okay”或者”ok”
3. dts里的status属性值会覆盖dtsi中的值(编译dtb的时候会覆盖)

对应代码在kernel/drivers/of/base.c:

/**
 *  of_device_is_available - check if a device is available for use
 *
 *  @device: Node to check for availability
 *
 *  Returns 1 if the status property is absent or set to "okay" or "ok",
 *  0 otherwise
 */
int of_device_is_available(const struct device_node *device)
{
    unsigned long flags;
int res;

    raw_spin_lock_irqsave(&devtree_lock, flags);
    res = __of_device_is_available(device);
    raw_spin_unlock_irqrestore(&devtree_lock, flags);
    return res;

}

__of_device_is_available():

/**
 * __of_device_is_available - check if a device is available for use
 *
 *  @device: Node to check for availability, with locks already held
 *
 * Returns 1 if the status property is absent or set to "okay" or "ok",
 * 0 otherwise
 */
static int __of_device_is_available(const struct device_node *device)
{
const char *status;
int statlen;

    status = __of_get_property(device, "status", &statlen);
if (status == NULL)
return 1;

if (statlen > 0) {
if (!strcmp(status, "okay") || !strcmp(status, "ok"))
return 1;
    }

return 0;
}

参考：
Linux Device Tree: What those status = “okay” are about