usb驱动开发15——设备生命线

最新推荐文章于 2022-11-22 19:12:29 发布

kcyuan

最新推荐文章于 2022-11-22 19:12:29 发布

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分类专栏： USB驱动开发文章标签：驱动开发 linux 网络 c语言 usb

本文链接：https://blog.youkuaiyun.com/eryunyong/article/details/122661799

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本文详细探讨了USB驱动开发中的关键结构体`struct usb_hcd`和`struct usb_bus`，阐述了两者之间的关系以及在Linux设备模型中的作用。通过对`struct usb_bus`成员的分析，揭示了USB总线的编号、名称、DMA支持以及带宽管理等核心概念，并介绍了如何在设备模型和sysfs中体现。此外，还提到了USB监视器在内核中的实现。

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总算是进入了HCD的片儿区，既然来到一个片区，怎么都要去拜会一下山头几个大哥吧。，先回忆一些我们怎么到这里的？给你列举一个调用函数过程usb_control_msg->usb_internal_control_msg->usb_start_wait_urb->usb_submit_urb->usb_hcd_submit_urb。这个山头儿，王中之王就是drivers/usb/core/hcd.h里定义的struct usb_hcd。

/*-------------------------------------------------------------------------*/

/*

* USB Host Controller Driver (usb_hcd) framework

*

* Since "struct usb_bus" is so thin, you can't share much code in it.

* This framework is a layer over that, and should be more sharable.

*/

/*-------------------------------------------------------------------------*/

struct usb_hcd {
   

/*

* housekeeping

*/

struct usb_bus self; /* hcd is-a bus */

struct kref kref; /* reference counter */

const char *product_desc; /* product/vendor string */

char irq_descr[24]; /* driver + bus # */

struct timer_list rh_timer; /* drives root-hub polling */

struct urb *status_urb; /* the current status urb */

#ifdef CONFIG_PM

struct work_struct wakeup_work; /* for remote wakeup */

#endif

/*

* hardware info/state

*/

const struct hc_driver *driver; /* hw-specific hooks */

/* Flags that need to be manipulated atomically */

unsigned long flags;

#define HCD_FLAG_HW_ACCESSIBLE 0x00000001

#define HCD_FLAG_SAW_IRQ 0x00000002

unsigned rh_registered:1;/* is root hub registered? */

/* The next flag is a stopgap, to be removed when all the HCDs

* support the new root-hub polling mechanism. */

unsigned uses_new_polling:1;

unsigned poll_rh:1; /* poll for rh status? */

unsigned poll_pending:1; /* status has changed? */

unsigned wireless:1; /* Wireless USB HCD */

int irq; /* irq allocated */

void __iomem *regs; /* device memory/io */

u64 rsrc_start; /* memory/io resource start */

u64 rsrc_len; /* memory/io resource length */