acpi_evaluate_integer

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acpi_evaluate_integer 用于执行acpi表格中的函数并返回值
以status = acpi_evaluate_integer(ac->device->handle, "_PSR", NULL,&ac->state);为例
acpi_status
acpi_evaluate_integer(acpi_handle handle,
              acpi_string pathname,
              struct acpi_object_list *arguments, unsigned long long *data)
{
   acpi_status status = AE_OK;
   union acpi_object element;
   struct acpi_buffer buffer = { 0, NULL };

   if (!data)
       return AE_BAD_PARAMETER;

   buffer.length = sizeof(union acpi_object);
   buffer.pointer = &element;
   status = acpi_evaluate_object(handle, pathname, arguments, &buffer);
   if (ACPI_FAILURE(status)) {
       acpi_util_eval_error(handle, pathname, status);
       return status;
   }

   if (element.type != ACPI_TYPE_INTEGER) {
       acpi_util_eval_error(handle, pathname, AE_BAD_DATA);
       return AE_BAD_DATA;
   }

   *data = element.integer.value;

   ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Return value [%llu]\n", *data));

   return AE_OK;
}
acpi_evaluate_integer 首先调用acpi_evaluate_object 运行acpi 中定义的函数，然后返回值存在buffer中
最后将*data = element.integer.value; 返回.

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