Linux 设备模型
设备驱动模型
总线
在linux内核中总线用数据结构bus_type表示。
struct bus_type {
const char *name;
const char *dev_name;
struct device *dev_root;
const struct attribute_group **bus_groups;
const struct attribute_group **dev_groups;
const struct attribute_group **drv_groups;
int (*match)(struct device *dev, struct device_driver *drv);
int (*uevent)(struct device *dev, struct kobj_uevent_env *env);
int (*probe)(struct device *dev);
void (*sync_state)(struct device *dev);
int (*remove)(struct device *dev);
void (*shutdown)(struct device *dev);
int (*online)(struct device *dev);
int (*offline)(struct device *dev);
int (*suspend)(struct device *dev, pm_message_t state);
int (*resume)(struct device *dev);
int (*num_vf)(struct device *dev);
int (*dma_configure)(struct device *dev);
const struct dev_pm_ops *pm;
const struct iommu_ops *iommu_ops;
struct subsys_private *p;
struct lock_class_key lock_key;
bool need_parent_lock;
};name/dev_name: 总线自己和下属设备的名字
bus/dev/drv_groups: 相关sysfs的文件
match/probe...: 匹配设备，操作设备的接口
p.subsys.kobj: kobj/sysfs 树的节点
p.subsys.devices_kset:下属设备的kobj/sysfs节点
p.subsys.drivers_kset:下属驱动的kobj/sysfs节点
bus_type
+------------------------------------+
|name |
|dev_name |
| (char *) |
+------------------------------------+
|bus_groups |
|dev_groups |
|drv_groups |
| (struct attribute_group**) |
+------------------------------------+
|match |
|uevent |
|probe |
|remove |
|shutdown |
| |
+------------------------------------+
|p |
| (struct subsys_private*) |
| +--------------------------------+
| |bus |
| | (struct bus_type*) |
| |subsys |
| | +----------------------------+
| | |kobj.name | = bus->name
| | |kobj.kset | = bus_kset
| | |kobj.ktype | = bus_ktype
| | +----------------------------+
| |devices_kset |
| |drivers_kset |
| | (struct kset) |
| |klist_devices |
| |klist_drivers |
| | (struct klist) |
| |class |
| | (struct class*) |
+---+--------------------------------+驱动
内核中用结构体device_driver来表示一个驱动。不过大家通常在驱动程序中看到是另外的结构体，比如pci驱动用的是pci_driver。但是我们打开这个pci_driver就可以看到其中包含了device_driver。所以驱动的核心数据结构还是device_driver。
struct device_driver {
const char *name;
struct bus_type *bus;
struct module *owner;
const char *mod_name; /* used for built-in modules */
bool suppress_bind_attrs; /* disables bind/unbind via sysfs */
enum probe_type probe_type;
const struct of_device_id *of_match_table;
const struct acpi_device_id *acpi_match_table;
int (*probe) (struct device *dev);
void (*sync_state)(struct device *dev);
int (*remove) (struct device *dev);
void (*shutdown) (struct device *dev);
int (*suspend) (struct device *dev, pm_message_t state);
int (*resume) (struct device *dev);
const struct attribute_group **groups;
const struct attribute_group **dev_groups;
const struct dev_pm_ops *pm;
void (*coredump) (struct device *dev);
struct driver_private *p;
}; device_driver
+----------------------------------+
|name |
| (char *) |
+----------------------------------+
|bus |
| (struct bus_type*) |
+----------------------------------+
|owner |
| (struct module*) |
+----------------------------------+
|probe |
|remove |
|shutdown |
|suspend |
|resume |
| |
+----------------------------------+
|p |
| (struct driver_private*) |
| +-----------------------------+
| |driver |
| | (struct device_driver*) |
| |kobj |
| | +------------------------+
| | |name | = device_driver->name
| | |kset | = device_driver->bus->p->drivers_kset
| | |ktype | = driver_ktype
| | +------------------------+
| |klist_devices |
| | |
+----+-----------------------------+name: 驱动名
bus: 对应的总线
probe/remove...: 驱动调用接口
p->kobj.name: kobj对应的名字
p->kobj.kset: kobj的父节点
p->kobj.kset设置成了对应总线的drivers_kset。这点表明了驱动在sysfs中的根是在对应的总线上。区别于设备！
设备
内核中用结构体device来表示一个设备。不过大家通常在驱动程序中看到是另外的结构体，比如pci设备用的是pci_dev。但是我们打开这个pci_dev就可以看到其中包含了device。所以设备的核心数据结构还是device。
struct device {
struct kobject kobj;
struct device *parent;
struct device_private *p;
const char *init_name; /* initial name of the device */
const struct device_type *type;
struct bus_type *bus; /* type of bus device is on */
struct device_driver *driver; /* which driver has allocated this
device */
void *platform_data; /* Platform specific data, device
core doesn't touch it */
void *driver_data; /* Driver data, set and get with
dev_set_drvdata/dev_get_drvdata */
#ifdef CONFIG_PROVE_LOCKING
struct mutex lockdep_mutex;
#endif
struct mutex mutex; /* mutex to synchronize calls to
* its driver.
*/
struct dev_links_info links;
struct dev_pm_info power;
struct dev_pm_domain *pm_domain;
#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
struct irq_domain *msi_domain;
#endif
#ifdef CONFIG_PINCTRL
struct dev_pin_info *pins;
#endif
#ifdef CONFIG_GENERIC_MSI_IRQ
struct list_head msi_list;
#endif
const struct dma_map_ops *dma_ops;
u64 *dma_mask; /* dma mask (if dma'able device) */
u64 coherent_dma_mask;/* Like dma_mask, but for
alloc_coherent mappings as
not all hardware supports
64 bit addresses for consistent
allocations such descriptors. */
u64 bus_dma_mask; /* upstream dma_mask constraint */
unsigned long dma_pfn_offset;
struct device_dma_parameters *dma_parms;
struct list_head dma_pools; /* dma pools (if dma'ble) */
#ifdef CONFIG_DMA_DECLARE_COHERENT
struct dma_coherent_mem *dma_mem; /* internal for coherent mem
override */
#endif
#ifdef CONFIG_DMA_CMA
struct cma *cma_area; /* contiguous memory area for dma
allocations */
#endif
/* arch specific additions */
struct dev_archdata archdata;
struct device_node *of_node; /* associated device tree node */
struct fwnode_handle *fwnode; /* firmware device node */
#ifdef CONFIG_NUMA
int numa_node; /* NUMA node this device is close to */
#endif
dev_t devt; /* dev_t, creates the sysfs "dev" */
u32 id; /* device instance */
spinlock_t devres_lock;
struct list_head devres_head;
struct class *class;
const struct attribute_group **groups; /* optional groups */
void (*release)(struct device *dev);
struct iommu_group *iommu_group;
struct iommu_fwspec *iommu_fwspec;
struct iommu_param *iommu_param;
bool offline_disabled:1;
bool offline:1;
bool of_node_reused:1;
bool state_synced:1;
#if defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_DEVICE) || \
defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU) || \
defined(CONFIG_ARCH_HAS_SYNC_DMA_FOR_CPU_ALL)
bool dma_coherent:1;
#endif
#if defined(CONFIG_DMA_COHERENT_HINT_CACHED)
bool dma_coherent_hint_cached:1;
#endif
};简化为：
device
+----------------------------------------+
|init_name |
| (char *) |
|devt |
| (dev_t) |
|id |
| (u32) |
+----------------------------------------+
|kobj |
| (struct kobject) |
| +-----------------------------------+
| |name | = device->init_name or
| | | device->bus->dev_name + id
| |kset | = devices_kset
| |ktype | = device_ktype
+----+-----------------------------------+
|type |
| (struct device_type*) |
+----------------------------------------+
|bus | = [pci_bus_type|nvdimm_bus_type]
| (struct bus_type) |
+----------------------------------------+
|driver |
| (struct device_driver*) |
+----------------------------------------+
|p |
| (struct device_private *) |
+----------------------------------------+init_name: 设备名（如果有的话）
id: 设备号
bus: 对应的总线
driver: 对应的驱动
kobj.name: kobj对应的名字，真正的设备名
kobj.kset: kobj的父节点
这里着重强调一点kobj.kset，这个值和驱动的父节点有所不同。驱动的父节点指向了总线，而设备的父节点是另一个根节点。这个时候我们可以来看看有了驱动和设备后，kobj树形结构的样子了。
总线，驱动和设备的树
bus(bus_kset) <-------------+ devices(devices_kset)
| | |
--+-----------+------+----- | ----+----+-------------
| | | |
+- drivers +- devices | |
| | | |
+- drvA <- - - +- devA - * - * | > +- devA
| | | | |
| | +- subsystem --+ |
| | | |
+- drvB <- - - +- devB - * - * | > +- devB
| | | | |
| | +- subsystem --+ |
| | | |
+- drvC <- - - +- devC - * - * | > +- devC
| | | | |
| | +- subsystem --+ |
| | |
+- drvD <- - - +- devD - * - * - > +- devD总线下有驱动和设备
设备和驱动存在着关联
总线下的设备实际是一个软链接
设备真正的根在devices_kset
Bind
在内核中驱动和设备发生关联称之为绑定bind。而且有意思的是绑定的过程可以在两个地方发生。
驱动加载
设备发现
不过这两个地方最后都会通过函数__driver_attach()来处理。而这个过程又可以分成两步：
匹配
探测
匹配
匹配的过程由总线的match函数来处理。
static inline int driver_match_device(struct device_driver *drv,
struct device *dev)
{
return drv->bus->match ? drv->bus->match(dev, drv) : 1;
}那具体的操作就由总线来决定。比如pci总线上的match函数就是pci_match_device()。它的过程就是匹配pci的厂商号和设备号。
探测
找到了匹配的设备和驱动后，就可以执行探测了。这个过程相对比较复杂，在当前的内核中，大多最后由总线的probe函数执行。
比如pci总线上的probe函数就是pci_device_probe()。它的作用就是去调用pci_driver中的probe函数。
流程图
__driver_attach
driver_match_device()
bus->match()
driver_probe_device()
bus->probe()Last updated