acpi_hardware_id可以通过HID/CLD/UID/CLS/method/path获得

一般情况下在acpi_set_pnp_ids函数中通过bios传递的HID/CLD/UID/CLS/method/path等flags来识别不同的device。static void acpi_set_pnp_ids(acpi_handle handle, struct acpi_device_pnp *pnp,int device_type){acpi_status status;struct acpi_device_info *info;struct acpi_pnp_device_id_list *cid_list;int i;switch (device_type) {case ACPI_BUS_TYPE_DEVICE:if (handle == ACPI_ROOT_OBJECT) {acpi_add_id(pnp, ACPI_SYSTEM_HID);break;}status = acpi_get_object_info(handle, &info);if (ACPI_FAILURE(status)) {pr_err(PREFIX "%s: Error reading device info\n",__func__);return;}//通过HID 识别deviceif (info->valid & ACPI_VALID_HID) {acpi_add_id(pnp, info->hardware_id.string);pnp->type.platform_id = 1;}//通过CID 识别deviceif (info->valid & ACPI_VALID_CID) {cid_list = &info->compatible_id_list;for (i = 0; i < cid_list->count; i++)acpi_add_id(pnp, cid_list->ids[i].string);}//通过UID 识别deviceif (info->valid & ACPI_VALID_UID)pnp->unique_id = kstrdup(info->unique_id.string,GFP_KERNEL);if (info->valid & ACPI_VALID_CLS)acpi_add_id(pnp, info->class_code.string);kfree(info);/* * Some devices don't reliably have _HIDs & _CIDs, so add * synthetic HIDs to make sure drivers can find them. *///通过method来识别deviceif (acpi_is_video_device(handle))acpi_add_id(pnp, ACPI_VIDEO_HID);else if (acpi_bay_match(handle))acpi_add_id(pnp, ACPI_BAY_HID);else if (acpi_dock_match(handle))acpi_add_id(pnp, ACPI_DOCK_HID);else if (acpi_ibm_smbus_match(handle))acpi_add_id(pnp, ACPI_SMBUS_IBM_HID);//通过path识别deviceelse if (list_empty(&pnp->ids) && acpi_object_is_system_bus(handle)) {/* \_SB, \_TZ, LNXSYBUS */acpi_add_id(pnp, ACPI_BUS_HID);strcpy(pnp->device_name, ACPI_BUS_DEVICE_NAME);strcpy(pnp->device_class, ACPI_BUS_CLASS);}break;}}通过HID/CLD/UID/CLS识别device 比较好理解，先看看通过method来识别devicelong acpi_is_video_device(acpi_handle handle){long video_caps = 0;//可见主要是通过判断这个handle是否有相关的method。/* Is this device able to support video switching ? */if (acpi_has_method(handle, "_DOD") || acpi_has_method(handle, "_DOS"))video_caps |= ACPI_VIDEO_OUTPUT_SWITCHING;return video_caps;}再看看通过path识别device的static bool acpi_object_is_system_bus(acpi_handle handle){acpi_handle tmp;if (ACPI_SUCCESS(acpi_get_handle(NULL, "\\_SB", &tmp)) &&    tmp == handle)return true;if (ACPI_SUCCESS(acpi_get_handle(NULL, "\\_TZ", &tmp)) &&    tmp == handle)return true;return false;}其中acpi_get_handle的原型如下：可见本例是通过\\_SB 这个路径下的handle是否等于要识别device的handle来确认是否是同一个device的acpi_status   acpi_get_handle(acpi_handle parent,  acpi_string pathname,acpi_handle *ret_handle)