从零开始学USB（二十四、最简单的USB驱动开始）

18年底，花了2个月啃学习USB2.0协议。现在终于开始要派上用场了，开始和代码打交道了。

当然，现在只是从简单的开始usb设备驱动开始，后面再慢慢的分析usb总线，usb的hub之类。

 

先给出代码，后面再一句一句分析。

#include 
#include 
#include 
#include 
#include 
#include 



static int usb_simple_probe(struct usb_interface *intf, const struct usb_device_id *id)
{

    printk(KERN_INFO"usb_simple_probe\n");

    return 0;
}


static void usb_simple_disconnect(struct usb_interface *intf)
{
    printk(KERN_INFO"usb_mouse_disconnect\n");
}

static const struct usb_device_id usb_simple_id_table[] = {
    { USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
        USB_INTERFACE_PROTOCOL_MOUSE) },
    {} /* Terminating entry */
};

static struct usb_driver usb_simple_driver = {
    .name       = "usb_simple",
    .probe      = usb_simple_probe,
    .disconnect = usb_simple_disconnect,
    .id_table   = usb_simple_id_table,
};


module_usb_driver(usb_simple_driver);
MODULE_LICENSE("GPL");

 

之前我们学习了platform总线，知道了一般每个platform设备都要有一个platform_driver，这里usb总线也不例外，设备设备都要有自己的驱动程序的。而usb_driver 就是一个usb的驱动程序的打包。

 

/**
 * struct usb_driver - identifies USB interface driver to usbcore
 * @name: The driver name should be unique among USB drivers,
 *	and should normally be the same as the module name.
 * @probe: Called to see if the driver is willing to manage a particular
 *	interface on a device.  If it is, probe returns zero and uses
 *	usb_set_intfdata() to associate driver-specific data with the
 *	interface.  It may also use usb_set_interface() to specify the
 *	appropriate altsetting.  If unwilling to manage the interface,
 *	return -ENODEV, if genuine IO errors occurred, an appropriate
 *	negative errno value.
 * @disconnect: Called when the interface is no longer accessible, usually
 *	because its device has been (or is being) disconnected or the
 *	driver module is being unloaded.
 * @unlocked_ioctl: Used for drivers that want to talk to userspace through
 *	the "usbfs" filesystem.  This lets devices provide ways to
 *	expose information to user space regardless of where they
 *	do (or don't) show up otherwise in the filesystem.
 * @suspend: Called when the device is going to be suspended by the
 *	system either from system sleep or runtime suspend context. The
 *	return value will be ignored in system sleep context, so do NOT
 *	try to continue using the device if suspend fails in this case.
 *	Instead, let the resume or reset-resume routine recover from
 *	the failure.
 * @resume: Called when the device is being resumed by the system.
 * @reset_resume: Called when the suspended device has been reset instead
 *	of being resumed.
 * @pre_reset: Called by usb_reset_device() when the device is about to be
 *	reset.  This routine must not return until the driver has no active
 *	URBs for the device, and no more URBs may be submitted until the
 *	post_reset method is called.
 * @post_reset: Called by usb_reset_device() after the device
 *	has been reset
 * @id_table: USB drivers use ID table to support hotplugging.
 *	Export this with MODULE_DEVICE_TABLE(usb,...).  This must be set
 *	or your driver's probe function will never get called.
 * @dynids: used internally to hold the list of dynamically added device
 *	ids for this driver.
 * @drvwrap: Driver-model core structure wrapper.
 * @no_dynamic_id: if set to 1, the USB core will not allow dynamic ids to be
 *	added to this driver by preventing the sysfs file from being created.
 * @supports_autosuspend: if set to 0, the USB core will not allow autosuspend
 *	for interfaces bound to this driver.
 * @soft_unbind: if set to 1, the USB core will not kill URBs and disable
 *	endpoints before calling the driver's disconnect method.
 * @disable_hub_initiated_lpm: if set to 1, the USB core will not allow hubs
 *	to initiate lower power link state transitions when an idle timeout
 *	occurs.  Device-initiated USB 3.0 link PM will still be allowed.
 *
 * USB interface drivers must provide a name, probe() and disconnect()
 * methods, and an id_table.  Other driver fields are optional.
 *
 * The id_table is used in hotplugging.  It holds a set of descriptors,
 * and specialized data may be associated with each entry.  That table
 * is used by both user and kernel mode hotplugging support.
 *
 * The probe() and disconnect() methods are called in a context where
 * they can sleep, but they should avoid abusing the privilege.  Most
 * work to connect to a device should be done when the device is opened,
 * and undone at the last close.  The disconnect code needs to address
 * concurrency issues with respect to open() and close() methods, as
 * well as forcing all pending I/O requests to complete (by unlinking
 * them as necessary, and blocking until the unlinks complete).
 */
struct usb_driver {
	const char *name;

	int (*probe) (struct usb_interface *intf,
		      const struct usb_device_id *id);

	void (*disconnect) (struct usb_interface *intf);

	int (*unlocked_ioctl) (struct usb_interface *intf, unsigned int code,
			void *buf);

	int (*suspend) (struct usb_interface *intf, pm_message_t message);
	int (*resume) (struct usb_interface *intf);
	int (*reset_resume)(struct usb_interface *intf);

	int (*pre_reset)(struct usb_interface *intf);
	int (*post_reset)(struct usb_interface *intf);

	const struct usb_device_id *id_table;

	struct usb_dynids dynids;
	struct usbdrv_wrap drvwrap;
	unsigned int no_dynamic_id:1;
	unsigned int supports_autosuspend:1;
	unsigned int disable_hub_initiated_lpm:1;
	unsigned int soft_unbind:1;
};

 

这里我们只用到4项，这里就先分析4项。

struct usb_driver {
	const char *name;

	int (*probe) (struct usb_interface *intf,
		      const struct usb_device_id *id);

	void (*disconnect) (struct usb_interface *intf);

        const struct usb_device_id *id_table;
};

name：方便用户查看设备的具体名称，逻辑上不重要。

probe：设备和驱动匹配后执行的初始化函数。

disconnect：设备移除后执行的函数（usb是支持热插拔的）。

usb_device_id ：和platform中原理一样都是用来驱动和设备做匹配的，但usb和platform不一样的是platform匹配的是name，而usb中支持匹配的项就比较对了，下面一一列出。

 

/**
 * struct usb_device_id - identifies USB devices for probing and hotplugging
 * @match_flags: Bit mask controlling which of the other fields are used to
 *	match against new devices. Any field except for driver_info may be
 *	used, although some only make sense in conjunction with other fields.
 *	This is usually set by a USB_DEVICE_*() macro, which sets all
 *	other fields in this structure except for driver_info.
 * @idVendor: USB vendor ID for a device; numbers are assigned
 *	by the USB forum to its members.
 * @idProduct: Vendor-assigned product ID.
 * @bcdDevice_lo: Low end of range of vendor-assigned product version numbers.
 *	This is also used to identify individual product versions, for
 *	a range consisting of a single device.
 * @bcdDevice_hi: High end of version number range.  The range of product
 *	versions is inclusive.
 * @bDeviceClass: Class of device; numbers are assigned
 *	by the USB forum.  Products may choose to implement classes,
 *	or be vendor-specific.  Device classes specify behavior of all
 *	the interfaces on a device.
 * @bDeviceSubClass: Subclass of device; associated with bDeviceClass.
 * @bDeviceProtocol: Protocol of device; associated with bDeviceClass.
 * @bInterfaceClass: Class of interface; numbers are assigned
 *	by the USB forum.  Products may choose to implement classes,
 *	or be vendor-specific.  Interface classes specify behavior only
 *	of a given interface; other interfaces may support other classes.
 * @bInterfaceSubClass: Subclass of interface; associated with bInterfaceClass.
 * @bInterfaceProtocol: Protocol of interface; associated with bInterfaceClass.
 * @bInterfaceNumber: Number of interface; composite devices may use
 *	fixed interface numbers to differentiate between vendor-specific
 *	interfaces.
 * @driver_info: Holds information used by the driver.  Usually it holds
 *	a pointer to a descriptor understood by the driver, or perhaps
 *	device flags.
 *
 * In most cases, drivers will create a table of device IDs by using
 * USB_DEVICE(), or similar macros designed for that purpose.
 * They will then export it to userspace using MODULE_DEVICE_TABLE(),
 * and provide it to the USB core through their usb_driver structure.
 *
 * See the usb_match_id() function for information about how matches are
 * performed.  Briefly, you will normally use one of several macros to help
 * construct these entries.  Each entry you provide will either identify
 * one or more specific products, or will identify a class of products
 * which have agreed to behave the same.  You should put the more specific
 * matches towards the beginning of your table, so that driver_info can
 * record quirks of specific products.
 */
struct usb_device_id {
	/* which fields to match against? */
	__u16		match_flags;

	/* Used for product specific matches; range is inclusive */
	__u16		idVendor;
	__u16		idProduct;
	__u16		bcdDevice_lo;
	__u16		bcdDevice_hi;

	/* Used for device class matches */
	__u8		bDeviceClass;
	__u8		bDeviceSubClass;
	__u8		bDeviceProtocol;

	/* Used for interface class matches */
	__u8		bInterfaceClass;
	__u8		bInterfaceSubClass;
	__u8		bInterfaceProtocol;

	/* Used for vendor-specific interface matches */
	__u8		bInterfaceNumber;

	/* not matched against */
	kernel_ulong_t	driver_info
		__attribute__((aligned(sizeof(kernel_ulong_t))));
};

struct usb_device_id  - 识别用于探测和热插拔的USB设备
@match_flags：位掩码控制哪些其他字段用于匹配新设备。可以使用除driver_info之外的任何字段，但有些字段仅与其他字段一起使用。这通常由USB_DEVICE _ *（）宏设置，该宏设置此结构中除driver_info之外的所有其他字段。
@idVendor：设备的USB供应商ID; USB论坛将号码分配给其成员。
@idProduct：供应商分配的产品ID。
@bcdDevice_lo：供应商分配的产品版本号范围的低端。此选项还用于标识单个产品版本，包括单个设备。
@bcdDevice_hi：版本号范围的高端。产品版本范围包括在内。
@bDeviceClass：设备类;号码由USB论坛分配。产品可以选择实现类，或者是特定于供应商的。设备类指定设备上所有接口的行为。
@bDeviceSubClass：设备的子类;与bDeviceClass相关联。
@bDeviceProtocol：设备协议;与bDeviceClass相关联。
@bInterfaceClass：接口类;号码由USB论坛分配。产品可以选择实现类，或者是特定于供应商的。接口类仅指定给定接口的行为;其他接口可能支持其他类。
@bInterfaceSubClass：接口的子类;与bInterfaceClass相关联。
@bInterfaceProtocol：接口协议;与bInterfaceClass相关联。
@bInterfaceNumber：接口数量;复合设备可以使用固定的接口号来区分特定于供应商的接口。

@driver_info：保存驱动程序使用的信息。 通常它包含一个指向驱动程序所理解的描述符的指针，或者可能是设备标志。 在大多数情况下，驱动程序将使用USB_DEVICE（）或为此目的设计的类似宏来创建设备ID表。然后，他们将使用MODULE_DEVICE_TABLE（）将其导出到用户空间，并通过其usb_driver结构将其提供给USB内核。 有关如何执行匹配的信息，请参阅usb_match_id（）函数。 简而言之，您通常会使用多个宏中的一个来帮助构造这些条目。 您提供的每个条目将标识一个或多个特定产品，或者将标识已同意行为相同的一类产品。 您应该将更具体的匹配放在表的开头，以便driver_info可以记录特定产品的怪癖。

 

可以看到这里主要就是一些USB设备的信息，这些信息一般都是usb设备接入usb总线进行枚举后获得的信息。某个usb的驱动程序可以选择性的支持某些usb的特性。比如，我们这里的usb鼠标，一般就没必要支持供应商信息，毕竟鼠标是一个标准设备，一个驱动理论上是要支持所有鼠标的才对。

 

这里我们要重点说一下match_flags这个标志，它表示这个设备，支持哪些匹配，可以用那个下面的USB_DEVICE_ID_MATCH_XXXX匹配。

 

下面是所有的匹配的选项

/* Some useful macros to use to create struct usb_device_id */
#define USB_DEVICE_ID_MATCH_VENDOR		0x0001
#define USB_DEVICE_ID_MATCH_PRODUCT		0x0002
#define USB_DEVICE_ID_MATCH_DEV_LO		0x0004
#define USB_DEVICE_ID_MATCH_DEV_HI		0x0008
#define USB_DEVICE_ID_MATCH_DEV_CLASS		0x0010
#define USB_DEVICE_ID_MATCH_DEV_SUBCLASS	0x0020
#define USB_DEVICE_ID_MATCH_DEV_PROTOCOL	0x0040
//上面的都是对于一个usb设备(dev)的匹配标志,下面的是对于usb的接口(interface)的匹配标志
#define USB_DEVICE_ID_MATCH_INT_CLASS		0x0080
#define USB_DEVICE_ID_MATCH_INT_SUBCLASS	0x0100
#define USB_DEVICE_ID_MATCH_INT_PROTOCOL	0x0200
#define USB_DEVICE_ID_MATCH_INT_NUMBER		0x0400

//当然通常使用时是用对上面组合后的宏，这样书写简单一些

//比如下面这种,支持某个厂商的某款设备
#define USB_DEVICE_ID_MATCH_DEVICE \
		(USB_DEVICE_ID_MATCH_VENDOR | USB_DEVICE_ID_MATCH_PRODUCT)

#define USB_DEVICE_ID_MATCH_DEV_RANGE \
		(USB_DEVICE_ID_MATCH_DEV_LO | USB_DEVICE_ID_MATCH_DEV_HI)

//比如下面这种,既要匹配厂商的某款设备,又要匹配这个设备的版本
#define USB_DEVICE_ID_MATCH_DEVICE_AND_VERSION \
		(USB_DEVICE_ID_MATCH_DEVICE | USB_DEVICE_ID_MATCH_DEV_RANGE)

//下面这种就是要匹配设备的类信息
#define USB_DEVICE_ID_MATCH_DEV_INFO \
		(USB_DEVICE_ID_MATCH_DEV_CLASS | \
		USB_DEVICE_ID_MATCH_DEV_SUBCLASS | \
		USB_DEVICE_ID_MATCH_DEV_PROTOCOL)

//下面是支持某一类接口的类信息
#define USB_DEVICE_ID_MATCH_INT_INFO \
		(USB_DEVICE_ID_MATCH_INT_CLASS | \
		USB_DEVICE_ID_MATCH_INT_SUBCLASS | \
		USB_DEVICE_ID_MATCH_INT_PROTOCOL)

 

当然为了使用简单，内核开发者做了更进一步的简单化，如下：

/**
 * USB_DEVICE - macro used to describe a specific usb device
 * @vend: the 16 bit USB Vendor ID
 * @prod: the 16 bit USB Product ID
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific device.
 */
#define USB_DEVICE(vend, prod) \
	.match_flags = USB_DEVICE_ID_MATCH_DEVICE, \
	.idVendor = (vend), \
	.idProduct = (prod)
/**
 * USB_DEVICE_VER - describe a specific usb device with a version range
 * @vend: the 16 bit USB Vendor ID
 * @prod: the 16 bit USB Product ID
 * @lo: the bcdDevice_lo value
 * @hi: the bcdDevice_hi value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific device, with a version range.
 */
#define USB_DEVICE_VER(vend, prod, lo, hi) \
	.match_flags = USB_DEVICE_ID_MATCH_DEVICE_AND_VERSION, \
	.idVendor = (vend), \
	.idProduct = (prod), \
	.bcdDevice_lo = (lo), \
	.bcdDevice_hi = (hi)

/**
 * USB_DEVICE_INTERFACE_CLASS - describe a usb device with a specific interface class
 * @vend: the 16 bit USB Vendor ID
 * @prod: the 16 bit USB Product ID
 * @cl: bInterfaceClass value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific interface class of devices.
 */
#define USB_DEVICE_INTERFACE_CLASS(vend, prod, cl) \
	.match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
		       USB_DEVICE_ID_MATCH_INT_CLASS, \
	.idVendor = (vend), \
	.idProduct = (prod), \
	.bInterfaceClass = (cl)

/**
 * USB_DEVICE_INTERFACE_PROTOCOL - describe a usb device with a specific interface protocol
 * @vend: the 16 bit USB Vendor ID
 * @prod: the 16 bit USB Product ID
 * @pr: bInterfaceProtocol value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific interface protocol of devices.
 */
#define USB_DEVICE_INTERFACE_PROTOCOL(vend, prod, pr) \
	.match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
		       USB_DEVICE_ID_MATCH_INT_PROTOCOL, \
	.idVendor = (vend), \
	.idProduct = (prod), \
	.bInterfaceProtocol = (pr)

/**
 * USB_DEVICE_INTERFACE_NUMBER - describe a usb device with a specific interface number
 * @vend: the 16 bit USB Vendor ID
 * @prod: the 16 bit USB Product ID
 * @num: bInterfaceNumber value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific interface number of devices.
 */
#define USB_DEVICE_INTERFACE_NUMBER(vend, prod, num) \
	.match_flags = USB_DEVICE_ID_MATCH_DEVICE | \
		       USB_DEVICE_ID_MATCH_INT_NUMBER, \
	.idVendor = (vend), \
	.idProduct = (prod), \
	.bInterfaceNumber = (num)

/**
 * USB_DEVICE_INFO - macro used to describe a class of usb devices
 * @cl: bDeviceClass value
 * @sc: bDeviceSubClass value
 * @pr: bDeviceProtocol value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific class of devices.
 */
#define USB_DEVICE_INFO(cl, sc, pr) \
	.match_flags = USB_DEVICE_ID_MATCH_DEV_INFO, \
	.bDeviceClass = (cl), \
	.bDeviceSubClass = (sc), \
	.bDeviceProtocol = (pr)

/**
 * USB_INTERFACE_INFO - macro used to describe a class of usb interfaces
 * @cl: bInterfaceClass value
 * @sc: bInterfaceSubClass value
 * @pr: bInterfaceProtocol value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific class of interfaces.
 */
#define USB_INTERFACE_INFO(cl, sc, pr) \
	.match_flags = USB_DEVICE_ID_MATCH_INT_INFO, \
	.bInterfaceClass = (cl), \
	.bInterfaceSubClass = (sc), \
	.bInterfaceProtocol = (pr)

/**
 * USB_DEVICE_AND_INTERFACE_INFO - describe a specific usb device with a class of usb interfaces
 * @vend: the 16 bit USB Vendor ID
 * @prod: the 16 bit USB Product ID
 * @cl: bInterfaceClass value
 * @sc: bInterfaceSubClass value
 * @pr: bInterfaceProtocol value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific device with a specific class of interfaces.
 *
 * This is especially useful when explicitly matching devices that have
 * vendor specific bDeviceClass values, but standards-compliant interfaces.
 */
#define USB_DEVICE_AND_INTERFACE_INFO(vend, prod, cl, sc, pr) \
	.match_flags = USB_DEVICE_ID_MATCH_INT_INFO \
		| USB_DEVICE_ID_MATCH_DEVICE, \
	.idVendor = (vend), \
	.idProduct = (prod), \
	.bInterfaceClass = (cl), \
	.bInterfaceSubClass = (sc), \
	.bInterfaceProtocol = (pr)

/**
 * USB_VENDOR_AND_INTERFACE_INFO - describe a specific usb vendor with a class of usb interfaces
 * @vend: the 16 bit USB Vendor ID
 * @cl: bInterfaceClass value
 * @sc: bInterfaceSubClass value
 * @pr: bInterfaceProtocol value
 *
 * This macro is used to create a struct usb_device_id that matches a
 * specific vendor with a specific class of interfaces.
 *
 * This is especially useful when explicitly matching devices that have
 * vendor specific bDeviceClass values, but standards-compliant interfaces.
 */
#define USB_VENDOR_AND_INTERFACE_INFO(vend, cl, sc, pr) \
	.match_flags = USB_DEVICE_ID_MATCH_INT_INFO \
		| USB_DEVICE_ID_MATCH_VENDOR, \
	.idVendor = (vend), \
	.bInterfaceClass = (cl), \
	.bInterfaceSubClass = (sc), \
	.bInterfaceProtocol = (pr)

比如某个驱动程序是支持某种匹配方式的，只需要在usb_device_id数组中，用这个宏设置就可以了。

 

比如我们上面的简单驱动程序，调用的就是用来匹配接口的信息：

#define USB_INTERFACE_INFO(cl, sc, pr) \
	.match_flags = USB_DEVICE_ID_MATCH_INT_INFO, \
	.bInterfaceClass = (cl), \
	.bInterfaceSubClass = (sc), \
	.bInterfaceProtocol = (pr)



static const struct usb_device_id usb_simple_id_table[] = {
    { USB_INTERFACE_INFO(USB_INTERFACE_CLASS_HID, USB_INTERFACE_SUBCLASS_BOOT,
        USB_INTERFACE_PROTOCOL_MOUSE) },
    {} /* Terminating entry */
};

可以看到，我们这里是要让这个驱动程序匹配的是一个usb的鼠标。

 

关于类，如果不知道可以查看我之前usb理论章节的内容。

https://blog.csdn.net/qq_16777851/article/details/86103430

 

可以看到有了match_flags 这个变量，可以在信息比较前先做一轮筛选，只匹配筛选match_flags支持的，这样可以加快匹配速度。

 

这里我们给出接口类的匹配函数。但这里不进行分析了，这个在usb总线学习的时候再分析。

/* returns 0 if no match, 1 if match */
int usb_match_one_id_intf(struct usb_device *dev,
			  struct usb_host_interface *intf,
			  const struct usb_device_id *id)
{
	/* The interface class, subclass, protocol and number should never be
	 * checked for a match if the device class is Vendor Specific,
	 * unless the match record specifies the Vendor ID. */
	if (dev->descriptor.bDeviceClass == USB_CLASS_VENDOR_SPEC &&
			!(id->match_flags & USB_DEVICE_ID_MATCH_VENDOR) &&
			(id->match_flags & (USB_DEVICE_ID_MATCH_INT_CLASS |
				USB_DEVICE_ID_MATCH_INT_SUBCLASS |
				USB_DEVICE_ID_MATCH_INT_PROTOCOL |
				USB_DEVICE_ID_MATCH_INT_NUMBER)))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_CLASS) &&
	    (id->bInterfaceClass != intf->desc.bInterfaceClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_SUBCLASS) &&
	    (id->bInterfaceSubClass != intf->desc.bInterfaceSubClass))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_PROTOCOL) &&
	    (id->bInterfaceProtocol != intf->desc.bInterfaceProtocol))
		return 0;

	if ((id->match_flags & USB_DEVICE_ID_MATCH_INT_NUMBER) &&
	    (id->bInterfaceNumber != intf->desc.bInterfaceNumber))
		return 0;

	return 1;
}

 

还有最后一个要说的module_usb_driver接口：

/**
 * module_usb_driver() - Helper macro for registering a USB driver
 * @__usb_driver: usb_driver struct
 *
 * Helper macro for USB drivers which do not do anything special in module
 * init/exit. This eliminates a lot of boilerplate. Each module may only
 * use this macro once, and calling it replaces module_init() and module_exit()
 */
#define module_usb_driver(__usb_driver) \
	module_driver(__usb_driver, usb_register, \
		       usb_deregister)



/**
 * module_driver() - Helper macro for drivers that don't do anything
 * special in module init/exit. This eliminates a lot of boilerplate.
 * Each module may only use this macro once, and calling it replaces
 * module_init() and module_exit().
 *
 * @__driver: driver name
 * @__register: register function for this driver type
 * @__unregister: unregister function for this driver type
 * @...: Additional arguments to be passed to __register and __unregister.
 *
 * Use this macro to construct bus specific macros for registering
 * drivers, and do not use it on its own.
 */
#define module_driver(__driver, __register, __unregister, ...) \
static int __init __driver##_init(void) \
{ \
	return __register(&(__driver) , ##__VA_ARGS__); \
} \
module_init(__driver##_init); \
static void __exit __driver##_exit(void) \
{ \
	__unregister(&(__driver) , ##__VA_ARGS__); \
} \
module_exit(__driver##_exit);

可以看到这个是几个宏组成的模块的注册和卸载函数。

 

用我们的例子带进去可以看到，和老版本内核的驱动一样，只不过这样，驱动工程师可少复制几行代码。

static struct usb_driver usb_simple_driver = {
    
    ......

};


static int __init usb_simple_driver _init(void) 
{
	return usb_register(&(usb_simple_driver) ); 
}
module_init(usb_simple_driver _init); 
static void __exit usb_simple_driver _exit(void) 
{
	usb_deregister(&(usb_simple_driver) ); 
}
module_exit(usb_simple_driver _exit);

 

这里要对比platform总线中，usb的注册函数是用usb_register，卸载是用usb_deregister函数。

下面我们给出这两个函数的原型，当然这里不打算分析。后面章节，随着学习的深入再慢慢分析。

/* use a define to avoid include chaining to get THIS_MODULE & friends */
#define usb_register(driver) \
	usb_register_driver(driver, THIS_MODULE, KBUILD_MODNAME)




/**
 * usb_register_driver - register a USB interface driver
 * @new_driver: USB operations for the interface driver
 * @owner: module owner of this driver.
 * @mod_name: module name string
 *
 * Registers a USB interface driver with the USB core.  The list of
 * unattached interfaces will be rescanned whenever a new driver is
 * added, allowing the new driver to attach to any recognized interfaces.
 *
 * Return: A negative error code on failure and 0 on success.
 *
 * NOTE: if you want your driver to use the USB major number, you must call
 * usb_register_dev() to enable that functionality.  This function no longer
 * takes care of that.
 */
int usb_register_driver(struct usb_driver *new_driver, struct module *owner,
			const char *mod_name)
{
	int retval = 0;

	if (usb_disabled())
		return -ENODEV;

	new_driver->drvwrap.for_devices = 0;
	new_driver->drvwrap.driver.name = new_driver->name;
	new_driver->drvwrap.driver.bus = &usb_bus_type;
	new_driver->drvwrap.driver.probe = usb_probe_interface;
	new_driver->drvwrap.driver.remove = usb_unbind_interface;
	new_driver->drvwrap.driver.owner = owner;
	new_driver->drvwrap.driver.mod_name = mod_name;
	spin_lock_init(&new_driver->dynids.lock);
	INIT_LIST_HEAD(&new_driver->dynids.list);

	retval = driver_register(&new_driver->drvwrap.driver);
	if (retval)
		goto out;

	retval = usb_create_newid_files(new_driver);
	if (retval)
		goto out_newid;

	pr_info("%s: registered new interface driver %s\n",
			usbcore_name, new_driver->name);

out:
	return retval;

out_newid:
	driver_unregister(&new_driver->drvwrap.driver);

	printk(KERN_ERR "%s: error %d registering interface "
			"	driver %s\n",
			usbcore_name, retval, new_driver->name);
	goto out;
}


/**
 * usb_deregister - unregister a USB interface driver
 * @driver: USB operations of the interface driver to unregister
 * Context: must be able to sleep
 *
 * Unlinks the specified driver from the internal USB driver list.
 *
 * NOTE: If you called usb_register_dev(), you still need to call
 * usb_deregister_dev() to clean up your driver's allocated minor numbers,
 * this * call will no longer do it for you.
 */
void usb_deregister(struct usb_driver *driver)
{
	pr_info("%s: deregistering interface driver %s\n",
			usbcore_name, driver->name);

	usb_remove_newid_files(driver);
	driver_unregister(&driver->drvwrap.driver);
	usb_free_dynids(driver);
}

 

 

最后看一下测试结果:

注意：要先卸载内核自带的hid设备。

Device Driver
    HID Support --->
        < > HID bus support

我目前用的是4.18.4版本的内核。

 

安装usb驱动，usb的核心层会打印出，注册了一个接口驱动。

正真的插入和拔出鼠标也会，打印出我们前面函数中的内容。