[RK3288][Android6.0] DeviceTree中的status屬性使用規則

Platform: Rockchip

OS: Android 6.0

Kernel: 3.10.92

有看到網友在讨論device tree中的status到底該如何設定，預設狀态是什麼，知識點如下:

1. 預設情況下不設定status屬性的話表示此節點的功能是enable的
2. 如果要設定status,那麼值必須是”okay”或者”ok”
3. dts裡的status屬性值會覆寫dtsi中的值(編譯dtb的時候會覆寫)

對應代碼在kernel/drivers/of/base.c:

/**
 *  of_device_is_available - check if a device is available for use
 *
 *  @device: Node to check for availability
 *
 *  Returns  if the status property is absent or set to "okay" or "ok",
 *   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 ;

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

    return ;
}
           

參考：

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