驱动笔记
驱动
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WiFi
ath9k
ATH9K Driver Learning Part II: Important Transmission Functions data path 优秀
接口
PCIE
疑问:内存到内存为什么还需要 DMA ?
回答:你得有人来操作呀,内存又不会自我拷贝,还不得靠 CPU 来读写。不用 CPU 的话,就要用 DMA 喽。
设备管理机制
参考:RK3399平台开发系列讲解(设备管理篇)Linux 设备管理机制 - 视频介绍
一生二
内核生出:kobject 和 kset
二生三
kobject 和 kset 生出:bus_type、device、device_driver
三生万物
bus_type
struct bus_type {
const char *name;
const char *dev_name;
struct device *dev_root;
struct device_attribute *dev_attrs; /* use dev_groups instead */
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);
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);
const struct dev_pm_ops *pm;
const struct iommu_ops *iommu_ops;
struct subsys_private *p;
struct lock_class_key lock_key;
};
subsys_private
struct subsys_private {
struct kset subsys;
struct kset *devices_kset;
struct list_head interfaces;
struct mutex mutex;
struct kset *drivers_kset;
struct klist klist_devices; // 挂载总线上所有设备的链表
struct klist klist_drivers; // 挂载总线上所有驱动的链表
struct blocking_notifier_head bus_notifier;
unsigned int drivers_autoprobe:1;
struct bus_type *bus;
struct kset glue_dirs;
struct class *class;
};
当 bus 中的 devices 注册进去的时候,它会扫 drivers 的链表,当 drivers 注册进去的时候,它会扫 devices 的链表。进行一个 name 匹配,这就是 device bus 怎么管理 devices 和 drivers 的核心。
device
struct device {
struct device *parent;
struct device_private *p; // 重要
struct kobject kobj;
const char *init_name; /* initial name of the device */
const struct device_type *type;
struct mutex mutex; /* mutex to synchronize calls to its driver. */
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 ev_set/get_drvdata */
struct dev_pm_info power;
struct dev_pm_domain *pm_domain;
#ifdef CONFIG_PINCTRL
struct dev_pin_info *pins;
#endif
#ifdef CONFIG_NUMA
int numa_node; /* NUMA node this device is close to */
#endif
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. */
unsigned long dma_pfn_offset;
struct device_dma_parameters *dma_parms;
struct list_head dma_pools; /* dma pools (if dma'ble) */
struct dma_coherent_mem *dma_mem; /* internal for coherent mem override */
#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 */
dev_t devt; /* dev_t, creates the sysfs "dev" */
u32 id; /* device instance */
spinlock_t devres_lock;
struct list_head devres_head;
struct klist_node knode_class;
struct class *class;
const struct attribute_group **groups; /* optional groups */
void (*release)(struct device *dev);
struct iommu_group *iommu_group;
bool offline_disabled:1;
bool offline:1;
};
系统下挂载的形形色色的设备都是通过 struct device 结构体来描述的。其中 dts 里定义的很多节点,最终都会转换为 struct device 结构体,用于描述一个设备的信息,管理设备用到的资源等。
device 结构体下一个重要的结构是 device_private,该结构体成员 knode_bus 就是用于挂载到上面提到的 bus 下的 subsys_private 结构体中的 klist_devices。
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 */
const struct of_device_id *of_match_table;
const struct acpi_device_id *acpi_match_table;
int (*probe) (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 dev_pm_ops *pm;
struct driver_private *p; // 重要
};
driver_private 用于链接到 bus 下 subsys_private 结构体中的 klist_drivers