nd_region
接着我们来看nd_region这个数据结构。
构造nd_region的函数
老规矩，先看看构造这个数据结构的函数样子。
acpi_nfit_register_regions()
list_for_each_entry(nfit_spa, &acpi_desc->spas, list) {
rc = acpi_nfit_register_region(acpi_desc, nfit_spa);
struct nd_region_desc *ndr_desc;
nfit_spa->nd_region = nvdimm_pmem_region_create(nvdimm_bus, ndr_desc);
}这是一个非常简略的构建流程，有几点含义想要表达：
nd_region的创建由一个acpi_desc->spa触发，并最后挂在spa上
构造的过程中由一个中间变量ndr_desc，由它构造了最后的nd_region
相关的数据结构
这次的牵扯到的数据结构比较多了。
acpi_nfit_desc
acpi_nfit_desc
+-----------------------------------------------+
|dev | = point to an acpi_device
| (struct device*) |
+-----------------------------------------------+
|acpi_header |
| (struct acpi_table_header) |
+-----------------------------------------------+
|spas | a list of nfit_spa
| (struct list_head) | added from acpi_table
| +------------------------------------------+
| |nd_region | * created from nfit_spa
| | (struct nd_region*) |
| |ars_state |
| | (unsigned long) |
| |spa[0] | looks just have one spa
| | (struct acpi_nfit_system_address) |
| | +-------------------------------------+
| | |header |
| | | (struct acpi_nfit_header) |
| | |range_guid[16] |
| | | (u8) |
| | |range_index |
| | |flags |
| | |address | spa address
| | |length |
| | | (u16) |
| | | |
| +----+-------------------------------------+
+-----------------------------------------------+首先来看一下acpi_nfit_desc。其中有一个叫spas的链表。这个的数据在前期从acpi中读取并解析后保存在此。而其中的信息就是构造nd_region的基础。
nd_region_desc
这个结构就是用来构造nd_region的描述结构。在nvdimm驱动中已经是第二次看到这种描述结构了，看来驱动的作者挺喜欢这种方式。
其中在mapping字段可以看出当前nd_region和nvdimm之间的一个关联。
nd_region_desc
+-----------------------------------------------+
|res |
| (struct resource*) |
| +-----------------------------------------+
| |name |
| |start | nfit_spa->address
| |end | nfit_spa->address + nfit_spa->length - 1
+-----+-----------------------------------------+
|provider_data | = nfit_spa
| (void*) |
|attr_groups | = acpi_nfit_region_attribute_groups
| (struct attribute_group**) |
|num_lanes |
|numa_node |
| (int) |
|flags |
| (unsigned logn) |
| |
| |
+-----------------------------------------------+
|num_mappings |
| (u16) |
|mapping | created from acpi_nfit_desc->memdev
| (struct nd_mapping_desc*) |
| +-----------------------------------------+
| |nvdimm |
| | (struct nvdimm*) |
| |start/size |
| | (u64) |
| |position |
| | (int) |
+-----+-----------------------------------------+
|nd_set | * will be used in nd_region
| (struct nd_interleave_set*) |
| +-----------------------------------------+
| |cookie1 |
| |cookie2 |
| |altcookie |
| | (u64) |
| |type_guid |
| | (guid_t) |
+-----+-----------------------------------------+nd_region
最后就是nd_region这个结构本身了。其中大部分的数据是从刚才的 nd_region_desc 中拷贝过来的。
不过有意思的是，这个nd_region_desc之后就消失了，没有人会记得曾经还有个这么重要的角色。
nd_region
+-------------------------------------------------+
|dev |
| (struct device) |
| +---------------------------------------------+
| |groups | = acpi_nfit_region_attribute_groups
| | (struct attr_groups**) |
| | |
| +---------------------------------------------+
| |type | = &nd_pmem_device_type
| | (struct device_type*) | &nd_blk_device_type
| | | &nd_volatile_device_type
| |driver_data | = nd_region_data
| | (void*) nd_region_data |
| | +----------------------------------------+
| | |ns_count |
| | |ns_active |
| | | (int) |
| | |hints_shift |
| | | (unsigned int) |
| | |flush_wpq[0] |
| | | (void*) |
+---+----+----------------------------------------+
|ns_ida |
|btt_ida |
|pfn_ida |
|dax_ida |
| (struct ida) |
+-------------------------------------------------+
|ns_seed |
|btt_seed |
|pfn_seed |
|dax_seed |
| (struct device*) |
+-------------------------------------------------+
|lane |
| (struct nd_percpu_lan) |
+-------------------------------------------------+
|provider_data | = ndr_desc->provider_data
| (void *) |
|ndr_mappings | = ndr_desc->num_mappings
| (u16) |
|ndr_start | = ndr_desc->res->start
|ndr_size | = ndr_desc->res:size
| (u16/u64) |
|num_lanes | = ndr_desc->num_lanes
|numa_node | = ndr_desc->numa_node
| (int) |
| |
|nd_set | = ndr_desc->nd_set
| (struct nd_interleave_set*) |
| |
+-------------------------------------------------+
|mapping[0] | copied from ndr_des->mapping
| (struct nd_mapping) |
| +-------------------------------------------+
| |start/size/position |
| | (u64/int) |
| |labels | a list of
| | (struct list_head) | nd_namespace_label
| | +--------------------------------------+
| | | uuid[NSLABEL_UUID_LEN] |
| | | name[NSLABEL_NAME_LEN] |
| | | flags |
| | | nlabel |
| | | position |
| | | dpa |
| | | |
| | | |
| | +--------------------------------------+
| |nvdimm |
| | (struct nvdimm*) |
| |ndd | = nvdimm->dev->driver_data
| | (struct nvdimm_drvdata*) |
| | |
| | |
+-----+-------------------------------------------+ 补充一点，nd_regioin一共有三种类型:
nd_pmem
nd_volatile
nd_blk
这个类型的区分由dev->type的值来区分，对应上面三种类型各自的type值为：
nd_pmem_device_type
nd_volatile_device_type
nd_blk_device_type
到这里基本算可以结束了，但是我还想再往回推一层。那就是这个type的值是谁来决定的。
在本节的开头我们也看到了，每个nd_region是在acpi_nfit_desc->spa的基础上创建的。而在代码中也正好印证了这一点。nd_region->type也是基于spa的类型决定的。
int nfit_spa_type(struct acpi_nfit_system_address *spa)
{
int i;
for (i = 0; i < NFIT_UUID_MAX; i++)
if (guid_equal(to_nfit_uuid(i), (guid_t *)&spa->range_guid))
return i;
return -1;
}这个函数将spa->range_guid和一个表比较，从而得出当前spa的类型，也就是nd_region的类型了。
nd_region_driver
当一个nd_region构造好了之后，其对应的驱动就该登场干活了。这次就是nd_region_driver，而且还干了不少活。
nd_region_probe()
nd_region_activate()
nd_blk_region_init()
nd_region_register_namespaces()
nd_region->btt_seed = nd_btt_create(nd_region);
nd_region->pfn_seed = nd_pfn_create(nd_region);
nd_region->dax_seed = nd_dax_create(nd_region);其做了一些初始化的工作后又做了几件重要的事：
创建namespace
创建btt/pfn/dax设备
接下来我们就分步骤看看这几个重要的设备的创建过程。
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