Linux设备驱动之HID驱动

来源：互联网发布：飞鸽网络打印机编辑：程序博客网时间：2024/05/20 23:03

一:前言

继前面分析过UHCI和HUB驱动之后,接下来以HID设备驱动为例来做一个具体的USB设备驱动分析的例子.HID是Human Interface Devices的缩写.翻译成中文即为人机交互设备.这里的人机交互设备是一个宏观上面的概念,任何设备,只要符合HID spec,都可以称之为HID设备.常见的HID设备有鼠标键盘,游戏操纵杆等等.在接下来的代码分析中,可以参考HID的spec.这份spec可以在www.usb.org上找到.分析的代码主要集中在linux-2.6.25/drivers/hid目录下.

二:HID驱动入口分析

USB HID设备驱动入口位于linux-2.6.25/drivers/hid/usbhid/hid-core.c中.该module的入口为hid_init().代码如下:

static int __init hid_init(void)

{

int retval;

retval = usbhid_quirks_init(quirks_param);

if (retval)

goto usbhid_quirks_init_fail;

retval = hiddev_init();

if (retval)

goto hiddev_init_fail;

retval = usb_register(&hid_driver);

if (retval)

goto usb_register_fail;

info(DRIVER_VERSION ":" DRIVER_DESC);

return 0;

usb_register_fail:

hiddev_exit();

hiddev_init_fail:

usbhid_quirks_exit();

usbhid_quirks_init_fail:

return retval;

}

首先来看usbhid_quirks_init()函数.quirks我们在分析UHCI和HUB的时候也接触过,表示需要做某种修正的设备.该函数调用的参数是quirks_param.定义如下:

static char *quirks_param[MAX_USBHID_BOOT_QUIRKS] = { [ 0 ... (MAX_USBHID_BOOT_QUIRKS - 1) ] = NULL };

module_param_array_named(quirks, quirks_param, charp, NULL, 0444);

从此可以看出, quirks_param是MAX_USBHID_BOOT_QUIRKS元素的字符串数组.并且在加载module的时候,可以动态的指定这些值.

分析到这里.有人可以反应过来了,usbhid_quirks_init()是一种动态进行HID设备修正的方式.具体要修正哪些设备,要修正设备的那些方面,都可以由加载模块是所带参数来决定.

usbhid_quirks_init()的代码如下:

int usbhid_quirks_init(char **quirks_param)

{

u16 idVendor, idProduct;

u32 quirks;

int n = 0, m;

for (; quirks_param[n] && n < MAX_USBHID_BOOT_QUIRKS; n++) {

m = sscanf(quirks_param[n], "0x%hx:0x%hx:0x%x",

&idVendor, &idProduct, &quirks);

if (m != 3 ||

usbhid_modify_dquirk(idVendor, idProduct, quirks) != 0) {

printk(KERN_WARNING

"Could not parse HID quirk module param %s\n",

quirks_param[n]);

}

return 0;

}

由此可以看出, quirks_param数组中的每一项可以分为三个部份,分别是要修正设备的VendorID,ProductID和要修正的功能.比如0x1000 0x0001 0x0004就表示:要忽略掉VendorID为0x1000,ProductID为0x0004的设备.(在代码中,有 #define HID_QUIRK_IGNORE 0x00000004的定义)

跟进usbhid_modify_dquirk()函数,代码如下:

int usbhid_modify_dquirk(const u16 idVendor, const u16 idProduct,

const u32 quirks)

{

struct quirks_list_struct *q_new, *q;

int list_edited = 0;

if (!idVendor) {

dbg_hid("Cannot add a quirk with idVendor = 0\n");

return -EINVAL;

}

q_new = kmalloc(sizeof(struct quirks_list_struct), GFP_KERNEL);

if (!q_new) {

dbg_hid("Could not allocate quirks_list_struct\n");

return -ENOMEM;

}

q_new->hid_bl_item.idVendor = idVendor;

q_new->hid_bl_item.idProduct = idProduct;

q_new->hid_bl_item.quirks = quirks;

down_write(&dquirks_rwsem);

list_for_each_entry(q, &dquirks_list, node) {

if (q->hid_bl_item.idVendor == idVendor &&

q->hid_bl_item.idProduct == idProduct) {

list_replace(&q->node, &q_new->node);

kfree(q);

list_edited = 1;

break;

}

if (!list_edited)

list_add_tail(&q_new->node, &dquirks_list);

up_write(&dquirks_rwsem);

return 0;

}

这个函数比较简单,就把quirks_param数组项中的三个部份存入一个封装结构.然后将其结构挂载到dquirks_list表.如果dquirks_list有重复的VendorId和ProductID就更新其quirks信息.

经过usbhid_quirks_init()之后,所有要修正的设备的相关操作都会存放在dquirks_list中.

返回到hid_init(),继续往下面分析.

hiddev_init()是一个无关的操作,不会影响到后面的操作.忽略

后面就是我们今天要分析的重点了,如下:

retval = usb_register(&hid_driver);

通过前面对HUB的驱动分析,相信对usb_redister()应该很熟悉了.hid_driver定义如下:

static struct usb_driver hid_driver = {

.name = "usbhid",

.probe = hid_probe,

.disconnect = hid_disconnect,

.suspend = hid_suspend,

.resume = hid_resume,

.reset_resume = hid_post_reset,

.pre_reset = hid_pre_reset,

.post_reset = hid_post_reset,

.id_table = hid_usb_ids,

.supports_autosuspend = 1,

};

其中,id_table的结构为hid_usb_ids.定义如下:

static struct usb_device_id hid_usb_ids [] = {

{ .match_flags = USB_DEVICE_ID_MATCH_INT_CLASS,

.bInterfaceClass = USB_INTERFACE_CLASS_HID },

{ } /* Terminating entry */

};

也就是说,该驱动会匹配interface的ClassID,所有ClassID为USB_INTERFACE_CLASS_HID的设备都会被这个驱动所匹配.所以,所有USB HID设备都会由这个module来驱动.

三:HID驱动的probe过程

从上面的分析可看到,probe接口为hid_probe().定义如下:

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

{

struct hid_device *hid;

char path[64];

int i;

char *c;

dbg_hid("HID probe called for ifnum %d\n",

intf->altsetting->desc.bInterfaceNumber);

//config the hid device

if (!(hid = usb_hid_configure(intf)))

return -ENODEV;

usbhid_init_reports(hid);

hid_dump_device(hid);

if (hid->quirks & HID_QUIRK_RESET_LEDS)

usbhid_set_leds(hid);

if (!hidinput_connect(hid))

hid->claimed |= HID_CLAIMED_INPUT;

if (!hiddev_connect(hid))

hid->claimed |= HID_CLAIMED_HIDDEV;

if (!hidraw_connect(hid))

hid->claimed |= HID_CLAIMED_HIDRAW;

usb_set_intfdata(intf, hid);

if (!hid->claimed) {

printk ("HID device claimed by neither input, hiddev nor hidraw\n");

hid_disconnect(intf);

return -ENODEV;

}

if ((hid->claimed & HID_CLAIMED_INPUT))

hid_ff_init(hid);

if (hid->quirks & HID_QUIRK_SONY_PS3_CONTROLLER)

hid_fixup_sony_ps3_controller(interface_to_usbdev(intf),

intf->cur_altsetting->desc.bInterfaceNumber);

printk(KERN_INFO);

if (hid->claimed & HID_CLAIMED_INPUT)

printk("input");

if ((hid->claimed & HID_CLAIMED_INPUT) && ((hid->claimed & HID_CLAIMED_HIDDEV) ||

hid->claimed & HID_CLAIMED_HIDRAW))

printk(",");

if (hid->claimed & HID_CLAIMED_HIDDEV)

printk("hiddev%d", hid->minor);

if ((hid->claimed & HID_CLAIMED_INPUT) && (hid->claimed & HID_CLAIMED_HIDDEV) &&

(hid->claimed & HID_CLAIMED_HIDRAW))

printk(",");

if (hid->claimed & HID_CLAIMED_HIDRAW)

printk("hidraw%d", ((struct hidraw*)hid->hidraw)->minor);

c = "Device";

for (i = 0; i < hid->maxcollection; i++) {

if (hid->collection[i].type == HID_COLLECTION_APPLICATION &&

(hid->collection[i].usage & HID_USAGE_PAGE) == HID_UP_GENDESK &&

(hid->collection[i].usage & 0xffff) < ARRAY_SIZE(hid_types)) {

c = hid_types[hid->collection[i].usage & 0xffff];

break;

}

usb_make_path(interface_to_usbdev(intf), path, 63);

printk(": USB HID v%x.%02x %s [%s] on %s\n",

hid->version >> 8, hid->version & 0xff, c, hid->name, path);

return 0;

}

这个函数看起来是不是让人心慌慌?其实这个函数的最后一部份就是打印出一个Debug信息,我们根本就不需要去看. hiddev_connect()和hidraw_connect()是一个选择编译的操作,也不可以不要去理会.然后,剩下的就没多少了.

3.1:usb_hid_configure()函数分析

先来看usb_hid_configure().顾名思义,该接口用来配置hid设备.怎么配置呢?还是深入到代码来分析,该函数有一点长,分段分析如下:

static struct hid_device *usb_hid_configure(struct usb_interface *intf)

{

struct usb_host_interface *interface = intf->cur_altsetting;

struct usb_device *dev = interface_to_usbdev (intf);

struct hid_descriptor *hdesc;

struct hid_device *hid;

u32 quirks = 0;

unsigned rsize = 0;

char *rdesc;

int n, len, insize = 0;

struct usbhid_device *usbhid;

quirks = usbhid_lookup_quirk(le16_to_cpu(dev->descriptor.idVendor),

le16_to_cpu(dev->descriptor.idProduct));

/* Many keyboards and mice don't like to be polled for reports,

* so we will always set the HID_QUIRK_NOGET flag for them. */

//如果是boot设备,跳出.不由此驱动处理

if (interface->desc.bInterfaceSubClass == USB_INTERFACE_SUBCLASS_BOOT) {

if (interface->desc.bInterfaceProtocol == USB_INTERFACE_PROTOCOL_KEYBOARD ||

interface->desc.bInterfaceProtocol == USB_INTERFACE_PROTOCOL_MOUSE)

quirks |= HID_QUIRK_NOGET;

}

//如果是要忽略的

if (quirks & HID_QUIRK_IGNORE)

return NULL;

if ((quirks & HID_QUIRK_IGNORE_MOUSE) &&

(interface->desc.bInterfaceProtocol == USB_INTERFACE_PROTOCOL_MOUSE))

return NULL;

首先找到该接口需要修正的操作,也就是上面代码中的quirks值,如果没有修正操作,则quirks为0.另外,根据usb hid spec中的定义,subclass如果为1,则说明该设备是一个boot阶段使用的hid设备,然后Protocol Code为1和2时分别代表Keyboard和Mouse. 如果是boot阶段的Keyboard和Mouse是不会由这个驱动进行处理的.另外,quirks为HID_QUIRK_IGNORE表示忽略这个设备,为HID_QUIRK_IGNORE_MOUSE,表示,如果该设备是一个鼠标设备,则忽略.

//get hid descriptors

if (usb_get_extra_descriptor(interface, HID_DT_HID, &hdesc) &&

(!interface->desc.bNumEndpoints ||

usb_get_extra_descriptor(&interface->endpoint[0], HID_DT_HID, &hdesc))) {

dbg_hid("class descriptor not present\n");

return NULL;

}

//bNumDescriptors:支持的附属描述符数目

for (n = 0; n < hdesc->bNumDescriptors; n++)

if (hdesc->desc[n].bDescriptorType == HID_DT_REPORT)

rsize = le16_to_cpu(hdesc->desc[n].wDescriptorLength);

//如果Report_Descriptors长度不合法

if (!rsize || rsize > HID_MAX_DESCRIPTOR_SIZE) {

dbg_hid("weird size of report descriptor (%u)\n", rsize);

return NULL;

}

if (!(rdesc = kmalloc(rsize, GFP_KERNEL))) {

dbg_hid("couldn't allocate rdesc memory\n");

return NULL;

}

//Set idle_time = 0

hid_set_idle(dev, interface->desc.bInterfaceNumber, 0, 0);

//Get Report_Descriptors

if ((n = hid_get_class_descriptor(dev, interface->desc.bInterfaceNumber, HID_DT_REPORT, rdesc, rsize)) < 0) {

dbg_hid("reading report descriptor failed\n");

kfree(rdesc);

return NULL;

}

//是否属于fixup?

usbhid_fixup_report_descriptor(le16_to_cpu(dev->descriptor.idVendor),

le16_to_cpu(dev->descriptor.idProduct), rdesc,

rsize, rdesc_quirks_param);

dbg_hid("report descriptor (size %u, read %d) = ", rsize, n);

for (n = 0; n < rsize; n++)

dbg_hid_line(" %02x", (unsigned char) rdesc[n]);

dbg_hid_line("\n");

对于HID设备来说,在interface description之后会附加一个hid description, hid description中的最后部份包含有Report description或者Physical Descriptors的长度.

在上面的代码中,首先取得附加在interface description之后的hid description,然后,再从hid description中取得report description的长度.最后,取得report description的详细信息.

在这里,还会将idle时间设备为0,表示无限时,即,从上一次报表传输后,只有在报表发生改变时,才会传送此报表内容,否则,传送NAK.

这段代码的最后一部份是相关的fixup操作,不做详细分析.

//pasrse the report_descriptor

if (!(hid = hid_parse_report(rdesc, n))) {

dbg_hid("parsing report descriptor failed\n");

kfree(rdesc);

return NULL;

}

kfree(rdesc);

hid->quirks = quirks;

if (!(usbhid = kzalloc(sizeof(struct usbhid_device), GFP_KERNEL)))

goto fail_no_usbhid;

hid->driver_data = usbhid;

usbhid->hid = hid;

解析获得的report description,解析之后的信息,存放在hid_device->collection和 hid_device->report_enum[ ]中,这个解析过程之后会做详细分析.然后,初始化一个usbhid_device结构,使usbhid_device->hid指向刚解析 report description获得的hid_device.同样,hid_device->driver_data关联到usbhid_device.

usbhid->bufsize = HID_MIN_BUFFER_SIZE;

//计算各传输方向的最大buffer

hid_find_max_report(hid, HID_INPUT_REPORT, &usbhid->bufsize);

hid_find_max_report(hid, HID_OUTPUT_REPORT, &usbhid->bufsize);

hid_find_max_report(hid, HID_FEATURE_REPORT, &usbhid->bufsize);

if (usbhid->bufsize > HID_MAX_BUFFER_SIZE)

usbhid->bufsize = HID_MAX_BUFFER_SIZE;

//in方向的传输最大值

hid_find_max_report(hid, HID_INPUT_REPORT, &insize);

if (insize > HID_MAX_BUFFER_SIZE)

insize = HID_MAX_BUFFER_SIZE;

if (hid_alloc_buffers(dev, hid)) {

hid_free_buffers(dev, hid);

goto fail;

}

计算传输数据的最大缓存区,并以这个大小为了hid设备的urb传输分配空间.另外,这里有一个最小值限制即代码中所看到的 HID_MIN_BUFFER_SIZE,为64, 即一个高速设备的一个端点一次传输的数据量.在这里定义最小值为64是为了照顾低速/全速/高速三种类型的端点传输数据量.

然后,调用hid_alloc_buffers()为hid的urb传输初始化传输缓冲区.

另外,需要注意的是,insize为INPUT方向的最大数据传输量.

// 初始化usbhid->urbin和usbhid->usbout

for (n = 0; n < interface->desc.bNumEndpoints; n++) {

struct usb_endpoint_descriptor *endpoint;

int pipe;

int interval;

endpoint = &interface->endpoint[n].desc;

//不是中断传输退出

if ((endpoint->bmAttributes & 3) != 3) /* Not an interrupt endpoint */

continue;

interval = endpoint->bInterval;

/* Change the polling interval of mice. */

//修正鼠标的双击时间

if (hid->collection->usage == HID_GD_MOUSE && hid_mousepoll_interval > 0)

interval = hid_mousepoll_interval;

if (usb_endpoint_dir_in(endpoint)) {

if (usbhid->urbin)

continue;

if (!(usbhid->urbin = usb_alloc_urb(0, GFP_KERNEL)))

goto fail;

pipe = usb_rcvintpipe(dev, endpoint->bEndpointAddress);

usb_fill_int_urb(usbhid->urbin, dev, pipe, usbhid->inbuf, insize,

hid_irq_in, hid, interval);

usbhid->urbin->transfer_dma = usbhid->inbuf_dma;

usbhid->urbin->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

} else {

if (usbhid->urbout)

continue;

if (!(usbhid->urbout = usb_alloc_urb(0, GFP_KERNEL)))

goto fail;

pipe = usb_sndintpipe(dev, endpoint->bEndpointAddress);

usb_fill_int_urb(usbhid->urbout, dev, pipe, usbhid->outbuf, 0,

hid_irq_out, hid, interval);

usbhid->urbout->transfer_dma = usbhid->outbuf_dma;

usbhid->urbout->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

}

if (!usbhid->urbin) {

err_hid("couldn't find an input interrupt endpoint");

goto fail;

}

遍历接口中的所有endpoint,并初始化in中断传输方向和out中断方向的urb.如果一个hid设备没有in方向的中断传输,非法.

另外,在这里要值得注意的是, 在为OUT方向urb初始化的时候,它的传输缓存区大小被设为了0.IN方向的中断传输缓存区大小被设为了insize,传输缓存区大小在submit的时候会修正的.

init_waitqueue_head(&hid->wait);

INIT_WORK(&usbhid->reset_work, hid_reset);

setup_timer(&usbhid->io_retry, hid_retry_timeout, (unsigned long) hid);

spin_lock_init(&usbhid->inlock);

spin_lock_init(&usbhid->outlock);

spin_lock_init(&usbhid->ctrllock);

hid->version = le16_to_cpu(hdesc->bcdHID);

hid->country = hdesc->bCountryCode;

hid->dev = &intf->dev;

usbhid->intf = intf;

usbhid->ifnum = interface->desc.bInterfaceNumber;

hid->name[0] = 0;

if (dev->manufacturer)

strlcpy(hid->name, dev->manufacturer, sizeof(hid->name));

if (dev->product) {

if (dev->manufacturer)

strlcat(hid->name, " ", sizeof(hid->name));

strlcat(hid->name, dev->product, sizeof(hid->name));

}

if (!strlen(hid->name))

snprintf(hid->name, sizeof(hid->name), "HID %04x:%04x",

le16_to_cpu(dev->descriptor.idVendor),

le16_to_cpu(dev->descriptor.idProduct));

hid->bus = BUS_USB;

hid->vendor = le16_to_cpu(dev->descriptor.idVendor);

hid->product = le16_to_cpu(dev->descriptor.idProduct);

usb_make_path(dev, hid->phys, sizeof(hid->phys));

strlcat(hid->phys, "/input", sizeof(hid->phys));

len = strlen(hid->phys);

if (len < sizeof(hid->phys) - 1)

snprintf(hid->phys + len, sizeof(hid->phys) - len,

"%d", intf->altsetting[0].desc.bInterfaceNumber);

if (usb_string(dev, dev->descriptor.iSerialNumber, hid->uniq, 64) <= 0)

hid->uniq[0] = 0;

初始化hid的相关信息.

//初始化hid 的ctrl传输

usbhid->urbctrl = usb_alloc_urb(0, GFP_KERNEL);

if (!usbhid->urbctrl)

goto fail;

usb_fill_control_urb(usbhid->urbctrl, dev, 0, (void *) usbhid->cr,

usbhid->ctrlbuf, 1, hid_ctrl, hid);

usbhid->urbctrl->setup_dma = usbhid->cr_dma;

usbhid->urbctrl->transfer_dma = usbhid->ctrlbuf_dma;

usbhid->urbctrl->transfer_flags |= (URB_NO_TRANSFER_DMA_MAP | URB_NO_SETUP_DMA_MAP);

hid->hidinput_input_event = usb_hidinput_input_event;

hid->hid_open = usbhid_open;

hid->hid_close = usbhid_close;

#ifdef CONFIG_USB_HIDDEV

hid->hiddev_hid_event = hiddev_hid_event;

hid->hiddev_report_event = hiddev_report_event;

#endif

hid->hid_output_raw_report = usbhid_output_raw_report;

return hid;

初始化usbhid的控制传输urb,之后又初始化了usbhid的几个操作函数.这个操作有什么用途,等用到的时候再来进行分析.

fail:

usb_free_urb(usbhid->urbin);

usb_free_urb(usbhid->urbout);

usb_free_urb(usbhid->urbctrl);

hid_free_buffers(dev, hid);

kfree(usbhid);

fail_no_usbhid:

hid_free_device(hid);

return NULL;

}

经过上面的分析之后,我们对这个函数的大概操作有了一定的了解.现在分析里面调用的一些重要的子调函数.等这些子函数全部分析完了之后,不妨回过头看下这个函数.

3.1.1:hid_parse_report()分析

第一个要分析的函数是hid_parse_report().该函数用来解析report description.

解析report description是一个繁杂的过程,对这个描述符不太清楚的,仔细看一下spec.在这里我们只会做代码上的分析.

代码如下:

struct hid_device *hid_parse_report(__u8 *start, unsigned size)

{

struct hid_device *device;

struct hid_parser *parser;

struct hid_item item;

__u8 *end;

unsigned i;

static int (*dispatch_type[])(struct hid_parser *parser,

struct hid_item *item) = {

hid_parser_main,

hid_parser_global,

hid_parser_local,

hid_parser_reserved

};

if (!(device = kzalloc(sizeof(struct hid_device), GFP_KERNEL)))

return NULL;

//默认HID_DEFAULT_NUM_COLLECTIONS 项

if (!(device->collection = kzalloc(sizeof(struct hid_collection) *

HID_DEFAULT_NUM_COLLECTIONS, GFP_KERNEL))) {

kfree(device);

return NULL;

}

//hid_device->collection_size: collection的项数

device->collection_size = HID_DEFAULT_NUM_COLLECTIONS;

for (i = 0; i < HID_REPORT_TYPES; i++)

INIT_LIST_HEAD(&device->report_enum[i].report_list);

if (!(device->rdesc = kmalloc(size, GFP_KERNEL))) {

kfree(device->collection);

kfree(device);

return NULL;

}

//hid_device->rdesc存放report_descriptor,hid_device->size存放这个描述符的大小

memcpy(device->rdesc, start, size);

device->rsize = size;

if (!(parser = vmalloc(sizeof(struct hid_parser)))) {

kfree(device->rdesc);

kfree(device->collection);

kfree(device);

return NULL;

}

memset(parser, 0, sizeof(struct hid_parser));

parser->device = device;

end = start + size;

while ((start = fetch_item(start, end, &item)) != NULL) {

//long item在这里暂不做parse

if (item.format != HID_ITEM_FORMAT_SHORT) {

dbg_hid("unexpected long global item\n");

hid_free_device(device);

vfree(parser);

return NULL;

}

//parse the short item

if (dispatch_type[item.type](parser, &item)) {

dbg_hid("item %u %u %u %u parsing failed\n",

item.format, (unsigned)item.size, (unsigned)item.type, (unsigned)item.tag);

hid_free_device(device);

vfree(parser);

return NULL;

}

//如果全部解析完了

if (start == end) {

if (parser->collection_stack_ptr) {

dbg_hid("unbalanced collection at end of report description\n");

hid_free_device(device);

vfree(parser);

return NULL;

}

if (parser->local.delimiter_depth) {

dbg_hid("unbalanced delimiter at end of report description\n");

hid_free_device(device);

vfree(parser);

return NULL;

}

vfree(parser);

return device;

}

dbg_hid("item fetching failed at offset %d\n", (int)(end - start));

hid_free_device(device);

vfree(parser);

return NULL;

}

进入到这个函数,我们首先看到的是Main,Globa,Local标签的解析函数.然后,分配并初始化了hid_device结构和hid_ parser.在代码中我们看到,hid_ parser-> device指向了hid_device.后hid_device没有任何域指向hid_parser. 实际上hid_parser只是一个辅助结构.report description解析之后的信息全部都存放在hid_device结构中.

另外,hid_device-> rdesc保存了一份report description副本.

然后,就开始对report description的解析.函数fetch_item()用来取出report description的一项数据.代码如下:

static u8 *fetch_item(__u8 *start, __u8 *end, struct hid_item *item)

{

u8 b;

//合法性检测

if ((end - start) <= 0)

return NULL;

//取前面一个字节.对于短项.它的首个字节定义了bsize,bType,bTag.而对于长项,它的值为0xFE

b = *start++;

item->type = (b >> 2) & 3;

item->tag = (b >> 4) & 15;

//如果为长项.它的Type和Tag在其后的二个字节中.item->data.longdata指向数据的起始位置

if (item->tag == HID_ITEM_TAG_LONG) {

item->format = HID_ITEM_FORMAT_LONG;

if ((end - start) < 2)

return NULL;

item->size = *start++;

item->tag = *start++;

if ((end - start) < item->size)

return NULL;

item->data.longdata = start;

start += item->size;

return start;

}

//对于短项的情况.取得size值.并根据size值取得它的data域

item->format = HID_ITEM_FORMAT_SHORT;

item->size = b & 3;

switch (item->size) {

case 0:

return start;

case 1:

if ((end - start) < 1)

return NULL;

item->data.u8 = *start++;

return start;

case 2:

if ((end - start) < 2)

return NULL;

item->data.u16 = le16_to_cpu(get_unaligned((__le16*)start));

start = (__u8 *)((__le16 *)start + 1);

return start;

case 3:

item->size++;

if ((end - start) < 4)

return NULL;

item->data.u32 = le32_to_cpu(get_unaligned((__le32*)start));

start = (__u8 *)((__le32 *)start + 1);

return start;

}

return NULL;

}

对照代码中的注释,应该很容易看懂这个函数,不再详细分析.

返回到hid_parse_report()中,取得相应项之后,如果是长项,这里不会做处理.对于短项.为不同的type调用不同的解析函数.

3.1.1.1:Global项解析

Global的解析入口是hid_parser_global().代码如下:

static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)

{

switch (item->tag) {

//PUSH项

case HID_GLOBAL_ITEM_TAG_PUSH:

if (parser->global_stack_ptr == HID_GLOBAL_STACK_SIZE) {

dbg_hid("global enviroment stack overflow\n");

return -1;

}

memcpy(parser->global_stack + parser->global_stack_ptr++,

&parser->global, sizeof(struct hid_global));

return 0;

//POP项

case HID_GLOBAL_ITEM_TAG_POP:

if (!parser->global_stack_ptr) {

dbg_hid("global enviroment stack underflow\n");

return -1;

}

memcpy(&parser->global, parser->global_stack + --parser->global_stack_ptr,

sizeof(struct hid_global));

return 0;

case HID_GLOBAL_ITEM_TAG_USAGE_PAGE:

parser->global.usage_page = item_udata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_LOGICAL_MINIMUM:

parser->global.logical_minimum = item_sdata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_LOGICAL_MAXIMUM:

if (parser->global.logical_minimum < 0)

parser->global.logical_maximum = item_sdata(item);

else

parser->global.logical_maximum = item_udata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_PHYSICAL_MINIMUM:

parser->global.physical_minimum = item_sdata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_PHYSICAL_MAXIMUM:

if (parser->global.physical_minimum < 0)

parser->global.physical_maximum = item_sdata(item);

else

parser->global.physical_maximum = item_udata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_UNIT_EXPONENT:

parser->global.unit_exponent = item_sdata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_UNIT:

parser->global.unit = item_udata(item);

return 0;

case HID_GLOBAL_ITEM_TAG_REPORT_SIZE:

if ((parser->global.report_size = item_udata(item)) > 32) {

dbg_hid("invalid report_size %d\n", parser->global.report_size);

return -1;

}

return 0;

case HID_GLOBAL_ITEM_TAG_REPORT_COUNT:

if ((parser->global.report_count = item_udata(item)) > HID_MAX_USAGES) {

dbg_hid("invalid report_count %d\n", parser->global.report_count);

return -1;

}

return 0;

case HID_GLOBAL_ITEM_TAG_REPORT_ID:

if ((parser->global.report_id = item_udata(item)) == 0) {

dbg_hid("report_id 0 is invalid\n");

return -1;

}

return 0;

default:

dbg_hid("unknown global tag 0x%x\n", item->tag);

return -1;

}

这个函数虽然长,但是逻辑很简单,对于global信息,存放在hid_parse->global中.

如果遇到了PUSH项,将当前的global项入栈,栈即为hid_parse-> global_stack[ ].当前的栈顶位置由hid_parse-> global_stack_ptr指定.

如果遇到了POP项,就将栈中的global信息出栈.

3.1.1.2:Local项解析

Local项解析的相应接口为hid_parser_local().代码如下:

static int hid_parser_local(struct hid_parser *parser, struct hid_item *item)

{

__u32 data;

unsigned n;

if (item->size == 0) {

dbg_hid("item data expected for local item\n");

return -1;

}

data = item_udata(item);

switch (item->tag) {

//DELIMITER项,定义一个Local项的开始

case HID_LOCAL_ITEM_TAG_DELIMITER:

//data>1:一个local项开始,0:一个local项结束

//parse->local.delimiter_branch:表示local项计数.

//进入一个local项时,local.delimiter_depth为1,退出一个local项时local.delimiter_depth为0

// TODO: Local项不能嵌套

if (data) {

* We treat items before the first delimiter

* as global to all usage sets (branch 0).

* In the moment we process only these global

* items and the first delimiter set.

if (parser->local.delimiter_depth != 0) {

dbg_hid("nested delimiters\n");

return -1;

}

parser->local.delimiter_depth++;

parser->local.delimiter_branch++;

} else {

if (parser->local.delimiter_depth < 1) {

dbg_hid("bogus close delimiter\n");

return -1;

}

parser->local.delimiter_depth--;

}

return 1;

//以下各项不能出现在有DELIMITER标签的地方

case HID_LOCAL_ITEM_TAG_USAGE:

if (parser->local.delimiter_branch > 1) {

dbg_hid("alternative usage ignored\n");

return 0;

}

//local的usage项有扩展用法,它的高16可以定义usage_page.如果高16为空,它的//usage_page则定义在global中的usage_page

if (item->size <= 2)

data = (parser->global.usage_page << 16) + data;

//然后添加到parse->local的usage列表

return hid_add_usage(parser, data);

//对于有usage_min和usage_max的情况,将usage_min和usage_max之间的usage添加到//parse=>local的usage列表

case HID_LOCAL_ITEM_TAG_USAGE_MINIMUM:

if (parser->local.delimiter_branch > 1) {

dbg_hid("alternative usage ignored\n");

return 0;

}

if (item->size <= 2)

data = (parser->global.usage_page << 16) + data;

parser->local.usage_minimum = data;

return 0;

case HID_LOCAL_ITEM_TAG_USAGE_MAXIMUM:

if (parser->local.delimiter_branch > 1) {

dbg_hid("alternative usage ignored\n");

return 0;

}

if (item->size <= 2)

data = (parser->global.usage_page << 16) + data;

for (n = parser->local.usage_minimum; n <= data; n++)

if (hid_add_usage(parser, n)) {

dbg_hid("hid_add_usage failed\n");

return -1;

}

return 0;

default:

dbg_hid("unknown local item tag 0x%x\n", item->tag);

return 0;

}

return 0;

}

详细分析一下hid_add_usage().代码如下:

static int hid_add_usage(struct hid_parser *parser, unsigned usage)

{

if (parser->local.usage_index >= HID_MAX_USAGES) {

dbg_hid("usage index exceeded\n");

return -1;

}

parser->local.usage[parser->local.usage_index] = usage;

parser->local.collection_index[parser->local.usage_index] =

parser->collection_stack_ptr ?

parser->collection_stack[parser->collection_stack_ptr - 1] : 0;

parser->local.usage_index++;

return 0;

}

如果usage项超过了HID_MAX_USAGES,为非法.最大为8192项.

Parse->local.usage_index表示local的项数,当然也表示了parse->local.usage[ ]数组中的下一个可用项.

parser->local.collection_index表示该usage所在的collection项序号.具体的collection信息存放在hid_deivce->collection[ ]中.

关于collection我们在分析Main项解析的时候会详细分析.

3.1.1.3:Main项解析

Main项解析的入口为hid_parser_main().代码如下:

static int hid_parser_main(struct hid_parser *parser, struct hid_item *item)

{

__u32 data;

int ret;

//data域

data = item_udata(item);

switch (item->tag) {

//Collection

case HID_MAIN_ITEM_TAG_BEGIN_COLLECTION:

ret = open_collection(parser, data & 0xff);

break;

//End Collection

case HID_MAIN_ITEM_TAG_END_COLLECTION:

ret = close_collection(parser);

break;

//Input

case HID_MAIN_ITEM_TAG_INPUT:

ret = hid_add_field(parser, HID_INPUT_REPORT, data);

break;

//Outpput

case HID_MAIN_ITEM_TAG_OUTPUT:

ret = hid_add_field(parser, HID_OUTPUT_REPORT, data);

break;

//Feature

case HID_MAIN_ITEM_TAG_FEATURE:

ret = hid_add_field(parser, HID_FEATURE_REPORT, data);

break;

default:

dbg_hid("unknown main item tag 0x%x\n", item->tag);

ret = 0;

}

memset(&parser->local, 0, sizeof(parser->local)); /* Reset the local parser environment */

return ret;

}

对Main项的解析要稍微复杂一点,Main项主要有两个部份,一个是Collection,一个是Input/Output/Feature项.

先来看Collection项的解析.

所有的collection信息都存放在hid_device->collection[ ]中.而Collection项又有嵌套的情况,每遇到一个Collection项就将collection的序号入栈,栈为 parser_device->collection_stack[ ].栈顶指针为parser_device->collection_stack_ptr .遇到了一个end collection之后,就parser_device->collection_stack_ptr减1,表示出栈.

熟悉这个大概的情况之后,就可以跟进open_collection()了.代码如下:

//所有的collection都存放在hid_dev->collection 中, 而hid_dev->maxcollection 表示collection[]中的下一个空闲位置

//paser->collection_stack[ ]存放的是当前解析的collection在hid_dev->collection[ ]中的序号

static int open_collection(struct hid_parser *parser, unsigned type)

{

struct hid_collection *collection;

unsigned usage;

usage = parser->local.usage[0];

//colletcion嵌套过多

if (parser->collection_stack_ptr == HID_COLLECTION_STACK_SIZE) {

dbg_hid("collection stack overflow\n");

return -1;

}

//device->maxcollection:存放的collection个数

//device->collection[ ]太小,必须扩大存放空间

if (parser->device->maxcollection == parser->device->collection_size) {

collection = kmalloc(sizeof(struct hid_collection) *

parser->device->collection_size * 2, GFP_KERNEL);

if (collection == NULL) {

dbg_hid("failed to reallocate collection array\n");

return -1;

}

memcpy(collection, parser->device->collection,

sizeof(struct hid_collection) *

parser->device->collection_size);

memset(collection + parser->device->collection_size, 0,

sizeof(struct hid_collection) *

parser->device->collection_size);

kfree(parser->device->collection);

parser->device->collection = collection;

parser->device->collection_size *= 2;

}

//将collection序号入栈

parser->collection_stack[parser->collection_stack_ptr++] =

parser->device->maxcollection;

//存入hid_device->collection[]

collection = parser->device->collection +

parser->device->maxcollection++;

collection->type = type;

collection->usage = usage;

//collection的深度

collection->level = parser->collection_stack_ptr - 1;

if (type == HID_COLLECTION_APPLICATION)

parser->device->maxapplication++;

return 0;

}

对照上面的分析和函数中的注释,理解这个函数应该很简单,不做详细分析.

对于Input/Output/Feature项的解析:

先来看一下hid_device结构的定义片段:

struct hid_device

{

……

struct hid_report_enum report_enum[HID_REPORT_TYPES];

……

}

对于INPUT/OUTPUT/FEATURE,每种类型都对应report_enum[ ]中的一项.

Struct hid_report_enum定义如下:

struct hid_report_enum {

unsigned numbered;

struct list_head report_list;

struct hid_report *report_id_hash[256];

};

对于每一个report_id,对应report_id_hash[ ]中的一项,同时,将所对应的hid_report添加到report_list链表中.如果有多个report_id 的情况,numbered被赋为1.

Struct hid_report定义如下:

struct hid_report {

struct list_head list;

unsigned id; /* id of this report */

unsigned type; /* report type */

struct hid_field *field[HID_MAX_FIELDS]; /* fields of the report */

unsigned maxfield; /* maximum valid field index */

unsigned size; /* size of the report (bits) */

struct hid_device *device; /* associated device */

}

List:用来形成链表

Id:表示report_id

Type: INPUT/OUTPUT/FEATURE

Field[ ]:成员列表,对应一个report_id有多个INPUT(OUTPUT/FEATURE)项

Maxfield: field[ ]中的有效项数

Size: 该report的大小

Device:所属的hid_device

了解了这些之后,就可以来看一下代码了:

如下:

static int hid_add_field(struct hid_parser *parser, unsigned report_type, unsigned flags)

{

struct hid_report *report;

struct hid_field *field;

int usages;

unsigned offset;

int i;

//找到类型和对应report_id所在的report.如果不存在,则新建之

if (!(report = hid_register_report(parser->device, report_type, parser->global.report_id))) {

dbg_hid("hid_register_report failed\n");

return -1;

}

//对当前global数据的有效性判断

if (parser->global.logical_maximum < parser->global.logical_minimum) {

dbg_hid("logical range invalid %d %d\n", parser->global.logical_minimum, parser->global.logical_maximum);

return -1;

}

//当前项在整个report中的数据偏移位置

offset = report->size;

//更新report->size

report->size += parser->global.report_size * parser->global.report_count;

//在local中没有定义usage项.该项是一个padding项

if (!parser->local.usage_index) /* Ignore padding fields */

return 0;

//计算parser->local.usage_index与parser->global.report_count的最大值

//1: parser->global.report_count >parser->local.usage_index :则后续的report项共用最后一个usage

//2: parser->global.report_count <parser->local.usage_index:在report项为Arrary类型的时候最为常

//见.

//3:相等的情况.每一个report项对应一个usage

usages = max_t(int, parser->local.usage_index, parser->global.report_count);

//注册这个report项

if ((field = hid_register_field(report, usages, parser->global.report_count)) == NULL)

return 0;

//初始化field的相关成员

field->physical = hid_lookup_collection(parser, HID_COLLECTION_PHYSICAL);

field->logical = hid_lookup_collection(parser, HID_COLLECTION_LOGICAL);

field->application = hid_lookup_collection(parser, HID_COLLECTION_APPLICATION);

//保存usage值

for (i = 0; i < usages; i++) {

int j = i;

/* Duplicate the last usage we parsed if we have excess values */

if (i >= parser->local.usage_index)

j = parser->local.usage_index - 1;

field->usage[i].hid = parser->local.usage[j];

field->usage[i].collection_index =

parser->local.collection_index[j];

}

field->maxusage = usages;

field->flags = flags;

field->report_offset = offset;

field->report_type = report_type;

field->report_size = parser->global.report_size;

field->report_count = parser->global.report_count;

field->logical_minimum = parser->global.logical_minimum;

field->logical_maximum = parser->global.logical_maximum;

field->physical_minimum = parser->global.physical_minimum;

field->physical_maximum = parser->global.physical_maximum;

field->unit_exponent = parser->global.unit_exponent;

field->unit = parser->global.unit;

return 0;

}

对照前面的分析和函数中的注释可以自行分析该函数.这里不再详细分析.

另外,要注意的是在hid_parser_main()处理的最后,有这样的一段代码:

memset(&parser->local, 0, sizeof(parser->local)); /* Reset the local parser environment */

即把local项清0.因为一个local项目只对它下面的第一个Main有效.

到这里,hid_parse_report()就分析完了.由于这个过程涉及到的数据结构有一点,用图的方式列出如下:

3.1.2:hid_find_max_report()函数分析

第二个要分析的函数是hid_find_max_report().代码如下:

static void hid_find_max_report(struct hid_device *hid, unsigned int type, int *max)

{

struct hid_report *report;

int size;

list_for_each_entry(report, &hid->report_enum[type].report_list, list) {

size = ((report->size - 1) >> 3) + 1;

if (type == HID_INPUT_REPORT && hid->report_enum[type].numbered)

size++;

if (*max < size)

*max = size;

}

经过前面的分析,我们可以得到,对于同种类型,不同report_id的report都会链接在对应类型的hid_device->report_enum[ ] ->report_list.

该函数就是遍历这个链表,取得最大的report size.

在这里之所以将这个函数单独列出.是因为在这里需要注意以下两点:

1: report->size这里存放的大小并不是以字节计数,而是位计算的

2:在INPUT类型,并有多个report_id的情,size会加1的原因:

在有多个report_id的情况下,input的数据最前面有一个字节会表示它的report_id

3.2: usbhid_init_reports()函数分析

返回到hid_probe()中,继续来分析probe过程.分析完usb_hid_configure()之后,紧接着就是usbhid_init_reports().代码如下:

void usbhid_init_reports(struct hid_device *hid)

{

struct hid_report *report;

struct usbhid_device *usbhid = hid->driver_data;

int err, ret;

//提交INPUT类型的,in方向的urb

list_for_each_entry(report, &hid->report_enum[HID_INPUT_REPORT].report_list, list)

usbhid_submit_report(hid, report, USB_DIR_IN);

//提交Feature类型的,in方向的urb

list_for_each_entry(report, &hid->report_enum[HID_FEATURE_REPORT].report_list, list)

usbhid_submit_report(hid, report, USB_DIR_IN);

err = 0;

//等待提交的信息传输完成.如果在定义时间内传输完成,返回0.否则-1

ret = usbhid_wait_io(hid);

//如果传输超时.清除传输的相关urb

while (ret) {

err |= ret;

if (test_bit(HID_CTRL_RUNNING, &usbhid->iofl))

usb_kill_urb(usbhid->urbctrl);

if (test_bit(HID_OUT_RUNNING, &usbhid->iofl))

usb_kill_urb(usbhid->urbout);

ret = usbhid_wait_io(hid);

}

if (err)

warn("timeout initializing reports");

}

在这里会遇到两个标志,分别是HID_CTRL_RUNNING, HID_OUT_RUNNING,表示正在提交usbhid->urbctrl和usbhid->urbout.

跟进去看一下usbhid_submit_report()的代码.如下:

void usbhid_submit_report(struct hid_device *hid, struct hid_report *report, unsigned char dir)

{

int head;

unsigned long flags;

struct usbhid_device *usbhid = hid->driver_data;

if ((hid->quirks & HID_QUIRK_NOGET) && dir == USB_DIR_IN)

return;

if (usbhid->urbout && dir == USB_DIR_OUT && report->type == HID_OUTPUT_REPORT) {

spin_lock_irqsave(&usbhid->outlock, flags);

if ((head = (usbhid->outhead + 1) & (HID_OUTPUT_FIFO_SIZE - 1)) == usbhid->outtail) {

spin_unlock_irqrestore(&usbhid->outlock, flags);

warn("output queue full");

return;

}

usbhid->out[usbhid->outhead] = report;

usbhid->outhead = head;

if (!test_and_set_bit(HID_OUT_RUNNING, &usbhid->iofl))

if (hid_submit_out(hid))

clear_bit(HID_OUT_RUNNING, &usbhid->iofl);

spin_unlock_irqrestore(&usbhid->outlock, flags);

return;

}

spin_lock_irqsave(&usbhid->ctrllock, flags);

//Control Queue Full

if ((head = (usbhid->ctrlhead + 1) & (HID_CONTROL_FIFO_SIZE - 1)) == usbhid->ctrltail) {

spin_unlock_irqrestore(&usbhid->ctrllock, flags);

warn("control queue full");

return;

}

usbhid->ctrl[usbhid->ctrlhead].report = report;

usbhid->ctrl[usbhid->ctrlhead].dir = dir;

usbhid->ctrlhead = head;

if (!test_and_set_bit(HID_CTRL_RUNNING, &usbhid->iofl))

if (hid_submit_ctrl(hid))

clear_bit(HID_CTRL_RUNNING, &usbhid->iofl);

spin_unlock_irqrestore(&usbhid->ctrllock, flags);

}

这个函数有三个参数,第一个为hid,表示操作的hid_deivce.第二个参数为report,表示要操作的report,dir表示提交URB的方向.有USB_DIR_IN / USB_DIR_OUT可选.

虽然我们在上面看到是以USB_DIR_IN调用此函数.不过在分析代码的时候,顺带把USB_DIR_OUT的情况也给分析一下.

这个函数其实很简单,如果要提交的是OUT方向的,就将相关信息存入usbhid->out[ ]这个环形缓存区.然后调用hid_submit_out()提交hid->urbout. 如果要提交的是IN方向的,就将相关信息存放usbhid->in[ ]这个环形缓冲,然后调用hid_submit_ctrl()提交hid->urbctrl.

分别来看一下hid_submit_out()和hid_submit_ctrl().

static int hid_submit_out(struct hid_device *hid)

{

struct hid_report *report;

struct usbhid_device *usbhid = hid->driver_data;

report = usbhid->out[usbhid->outtail];

hid_output_report(report, usbhid->outbuf);

usbhid->urbout->transfer_buffer_length = ((report->size - 1) >> 3) + 1 + (report->id > 0);

usbhid->urbout->dev = hid_to_usb_dev(hid);

dbg_hid("submitting out urb\n");

if (usb_submit_urb(usbhid->urbout, GFP_ATOMIC)) {

err_hid("usb_submit_urb(out) failed");

return -1;

}

return 0;

}

首先从hid_device->out[ ]环形缓冲区中取得要操作的信息,然后调用hid_output_report( )将该report项的所有值存放到usbhid->outbuf中,然后将hid->urbout提交.

不要忘记了,在初始化hid->urbout的时候,它的传输缓存区是usbhid->outbuf.另外在这里重新定义了urbout传输缓存区的大小.(在初始化的时候,它的传输长度被置为了1)

static int hid_submit_ctrl(struct hid_device *hid)

{

struct hid_report *report;

unsigned char dir;

int len;

struct usbhid_device *usbhid = hid->driver_data;

report = usbhid->ctrl[usbhid->ctrltail].report;

dir = usbhid->ctrl[usbhid->ctrltail].dir;

len = ((report->size - 1) >> 3) + 1 + (report->id > 0);

if (dir == USB_DIR_OUT) {

hid_output_report(report, usbhid->ctrlbuf);

usbhid->urbctrl->pipe = usb_sndctrlpipe(hid_to_usb_dev(hid), 0);

usbhid->urbctrl->transfer_buffer_length = len;

} else {

int maxpacket, padlen;

usbhid->urbctrl->pipe = usb_rcvctrlpipe(hid_to_usb_dev(hid), 0);

maxpacket = usb_maxpacket(hid_to_usb_dev(hid), usbhid->urbctrl->pipe, 0);

if (maxpacket > 0) {

padlen = DIV_ROUND_UP(len, maxpacket);

padlen *= maxpacket;

if (padlen > usbhid->bufsize)

padlen = usbhid->bufsize;

} else

padlen = 0;

usbhid->urbctrl->transfer_buffer_length = padlen;

}

usbhid->urbctrl->dev = hid_to_usb_dev(hid);

usbhid->cr->bRequestType = USB_TYPE_CLASS | USB_RECIP_INTERFACE | dir;

usbhid->cr->bRequest = (dir == USB_DIR_OUT) ? HID_REQ_SET_REPORT : HID_REQ_GET_REPORT;

usbhid->cr->wValue = cpu_to_le16(((report->type + 1) << 8) | report->id);

usbhid->cr->wIndex = cpu_to_le16(usbhid->ifnum);

usbhid->cr->wLength = cpu_to_le16(len);

dbg_hid("submitting ctrl urb: %s wValue=0x%04x wIndex=0x%04x wLength=%u\n",

usbhid->cr->bRequest == HID_REQ_SET_REPORT ? "Set_Report" : "Get_Report",

usbhid->cr->wValue, usbhid->cr->wIndex, usbhid->cr->wLength);

if (usb_submit_urb(usbhid->urbctrl, GFP_ATOMIC)) {

err_hid("usb_submit_urb(ctrl) failed");

return -1;

}

return 0;

}

不要被这里的USB_DIR_OUT和上面的hid_submit_out()情况的USB_DIR_OUT相混淆.在这里是指Feature类型的,而在上面,是指OUTPUT类型.

在这里,是以Get_Report/Set_Report的方式接收或者向设备发送信息.

对于OUT方向的,传输的缓存区长度即为report的大小,而对于IN方向,.每次传一个endport最大支持长度.因此,对于IN方向.可能有些填充位.

之后.将hid->urbctrl提交.

提交了hid->urbout和hid->urbctrl之后会做什么呢?我们来看下它们的传输完成处理函数.

3.2.1: hid_submit_out()/hid_submit_ctrl()的后续处理

注意下面的几个代码片段:

static struct hid_device *usb_hid_configure(struct usb_interface *intf)

{

……

usb_fill_int_urb(usbhid->urbout, dev, pipe, usbhid->outbuf, 0,

hid_irq_out, hid, interval);

……

usb_fill_control_urb(usbhid->urbctrl, dev, 0, (void *) usbhid->cr,

usbhid->ctrlbuf, 1, hid_ctrl, hid);

……

}

也就是说,如果hid->urbout和hid->urbctrl传输完成之后,分别会调用hid_irq_out()和usbhid->ctr()

下面对这两个操作进行分析.

Hid_irq_out()代码如下:

static void hid_irq_out(struct urb *urb)

{

struct hid_device *hid = urb->context;

struct usbhid_device *usbhid = hid->driver_data;

unsigned long flags;

int unplug = 0;

switch (urb->status) {

case 0: /* success */

break;

case -ESHUTDOWN: /* unplug */

unplug = 1;

case -EILSEQ: /* protocol error or unplug */

case -EPROTO: /* protocol error or unplug */

case -ECONNRESET: /* unlink */

case -ENOENT:

break;

default: /* error */

warn("output irq status %d received", urb->status);

}

spin_lock_irqsave(&usbhid->outlock, flags);

if (unplug)

usbhid->outtail = usbhid->outhead;

else

usbhid->outtail = (usbhid->outtail + 1) & (HID_OUTPUT_FIFO_SIZE - 1);

if (usbhid->outhead != usbhid->outtail) {

if (hid_submit_out(hid)) {

clear_bit(HID_OUT_RUNNING, &usbhid->iofl);

wake_up(&hid->wait);

}

spin_unlock_irqrestore(&usbhid->outlock, flags);

return;

}

clear_bit(HID_OUT_RUNNING, &usbhid->iofl);

spin_unlock_irqrestore(&usbhid->outlock, flags);

wake_up(&hid->wait);

}

从该代码看出,在hid->urbout传输完全之后,会取usbhid->out[ ]环形缓冲区中的数据取出.调用hid_submit_out( )再次将对应report的相关信息通过hid->urbout提交.如果缓存区中report全部处理完全或者是传输出现了错误,清除掉 HID_OUT_RUNNING标志.

hid_ctrl()代码如下:

static void hid_ctrl(struct urb *urb)

{

struct hid_device *hid = urb->context;

struct usbhid_device *usbhid = hid->driver_data;

unsigned long flags;

int unplug = 0;

spin_lock_irqsave(&usbhid->ctrllock, flags);

switch (urb->status) {

case 0: /* success */

if (usbhid->ctrl[usbhid->ctrltail].dir == USB_DIR_IN)

hid_input_report(urb->context, usbhid->ctrl[usbhid->ctrltail].report->type,

urb->transfer_buffer, urb->actual_length, 0);

break;

case -ESHUTDOWN: /* unplug */

unplug = 1;

case -EILSEQ: /* protocol error or unplug */

case -EPROTO: /* protocol error or unplug */

case -ECONNRESET: /* unlink */

case -ENOENT:

case -EPIPE: /* report not available */

break;

default: /* error */

warn("ctrl urb status %d received", urb->status);

}

if (unplug)

usbhid->ctrltail = usbhid->ctrlhead;

else

usbhid->ctrltail = (usbhid->ctrltail + 1) & (HID_CONTROL_FIFO_SIZE - 1);

if (usbhid->ctrlhead != usbhid->ctrltail) {

if (hid_submit_ctrl(hid)) {

clear_bit(HID_CTRL_RUNNING, &usbhid->iofl);

wake_up(&hid->wait);

}

spin_unlock_irqrestore(&usbhid->ctrllock, flags);

return;

}

clear_bit(HID_CTRL_RUNNING, &usbhid->iofl);

spin_unlock_irqrestore(&usbhid->ctrllock, flags);

wake_up(&hid->wait);

}

该函数的处理流程跟上面分析的hid_irq_out()差不多,不同的是,如果是IN方向的数据,则必须要调用hid_input_report()进行处理了.

3.2.2: hid_input_report()函数分析

hid_input_report()函数是一个很重要的函数.代码如下:

int hid_input_report(struct hid_device *hid, int type, u8 *data, int size, int interrupt)

{

struct hid_report_enum *report_enum = hid->report_enum + type;

struct hid_report *report;

int n, rsize, i;

if (!hid)

return -ENODEV;

if (!size) {

dbg_hid("empty report\n");

return -1;

}

dbg_hid("report (size %u) (%snumbered)\n", size, report_enum->numbered ? "" : "un");

n = 0; /* Normally report number is 0 */

if (report_enum->numbered) { /* Device uses numbered reports, data[0] is report number */

n = *data++;

size--;

}

/* dump the report */

dbg_hid("report %d (size %u) = ", n, size);

for (i = 0; i < size; i++)

dbg_hid_line(" %02x", data[i]);

dbg_hid_line("\n");

if (!(report = report_enum->report_id_hash[n])) {

dbg_hid("undefined report_id %d received\n", n);

return -1;

}

rsize = ((report->size - 1) >> 3) + 1;

if (size < rsize) {

dbg_hid("report %d is too short, (%d < %d)\n", report->id, size, rsize);

memset(data + size, 0, rsize - size);

}

if ((hid->claimed & HID_CLAIMED_HIDDEV) && hid->hiddev_report_event)

hid->hiddev_report_event(hid, report);

if (hid->claimed & HID_CLAIMED_HIDRAW)

hidraw_report_event(hid, data, size);

for (n = 0; n < report->maxfield; n++)

hid_input_field(hid, report->field[n], data, interrupt);

if (hid->claimed & HID_CLAIMED_INPUT)

hidinput_report_event(hid, report);

return 0;

}

首先判断report_enum->numbered是否为1,如果为1,则说明该report类型有多个report_id.那INPUT传回来的数据的第一个字节是report_id值.

根据report的类型和report_id就可以在hid_device中找到相应的report了.

如果传回来的数据比report size要小,就把后面的无效数据全部置为0.

然后,对于HID_CLAIMED_HIDDEV和HID_CLAIMED_HIDRAW是选择编译部份,忽略这一部份.

如果一个设备是INPUT设备,我们会在后面看到,会在hid->claimed设置HID_CLAIMED_INPUT标志.

对于hidinput_report_event()函数十分简单,就是将hid关联的input_deivce全部发送EV_SYN.表示上报的信息已经结束了.

最后,我们要分析的重点就是下面的这段代码:

for (n = 0; n < report->maxfield; n++)

hid_input_field(hid, report->field[n], data, interrupt);

在这里会涉及到hid_deivce和input_deivce的关联,所以我们先留个尾巴.等分析完后面的流程再来分析.

3.3:hidinput_connect()函数分析

返回hid_probe().继续下面的流程,调用usbhid_init_reports()之后,接着的一个重要的操作就是hidinput_connect().这是我们对porbe过程最后要分析的函数了.

代码如下:

int hidinput_connect(struct hid_device *hid)

{

struct hid_report *report;

struct hid_input *hidinput = NULL;

struct input_dev *input_dev;

int i, j, k;

int max_report_type = HID_OUTPUT_REPORT;

if (hid->quirks & HID_QUIRK_IGNORE_HIDINPUT)

return -1;

//初始化hid->inputs链表

INIT_LIST_HEAD(&hid->inputs);

for (i = 0; i < hid->maxcollection; i++)

if (hid->collection[i].type == HID_COLLECTION_APPLICATION ||

hid->collection[i].type == HID_COLLECTION_PHYSICAL)

if (IS_INPUT_APPLICATION(hid->collection[i].usage))

break;

if (i == hid->maxcollection && (hid->quirks & HID_QUIRK_HIDINPUT) == 0)

return -1;

if (hid->quirks & HID_QUIRK_SKIP_OUTPUT_REPORTS)

max_report_type = HID_INPUT_REPORT;

for (k = HID_INPUT_REPORT; k <= max_report_type; k++)

list_for_each_entry(report, &hid->report_enum[k].report_list, list) {

if (!report->maxfield)

continue;

//如果不存在hidinput,分配并初始化它,并将其链入hid-<inputs链表

if (!hidinput) {

hidinput = kzalloc(sizeof(*hidinput), GFP_KERNEL);

input_dev = input_allocate_device();

if (!hidinput || !input_dev) {

kfree(hidinput);

input_free_device(input_dev);

err_hid("Out of memory during hid input probe");

goto out_unwind;

}

input_set_drvdata(input_dev, hid);

input_dev->event = hid->hidinput_input_event;

input_dev->open = hidinput_open;

input_dev->close = hidinput_close;

input_dev->setkeycode = hidinput_setkeycode;

input_dev->getkeycode = hidinput_getkeycode;

input_dev->name = hid->name;

input_dev->phys = hid->phys;

input_dev->uniq = hid->uniq;

input_dev->id.bustype = hid->bus;

input_dev->id.vendor = hid->vendor;

input_dev->id.product = hid->product;

input_dev->id.version = hid->version;

input_dev->dev.parent = hid->dev;

hidinput->input = input_dev;

list_add_tail(&hidinput->list, &hid->inputs);

}

//遍历report的filed项

for (i = 0; i < report->maxfield; i++)

//遍历filed中的usage

for (j = 0; j < report->field[i]->maxusage; j++)

hidinput_configure_usage(hidinput, report->field[i],

report->field[i]->usage + j);

if (hid->quirks & HID_QUIRK_MULTI_INPUT) {

/* This will leave hidinput NULL, so that it

* allocates another one if we have more inputs on

* the same interface. Some devices (e.g. Happ's

* UGCI) cram a lot of unrelated inputs into the

* same interface. */

hidinput->report = report;

if (input_register_device(hidinput->input))

goto out_cleanup;

hidinput = NULL;

}

//注册这个input_device

if (hidinput && input_register_device(hidinput->input))

goto out_cleanup;

return 0;

out_cleanup:

input_free_device(hidinput->input);

kfree(hidinput);

out_unwind:

/* unwind the ones we already registered */

hidinput_disconnect(hid);

return -1;

}

很容易看出,这个函数的重点是在中间的那个for循环上,

首先.如果hidinput为空.分配空间并初始化它,同时,分配并初始化hidinput->input域.然后将该hidinput链接到hid_deivce->inputs链表.

另外,从代码中看出.如果hid->quirks中没有定义HID_QUIRK_MULTI_INPUT.那hidinput只会初始化一次,对应的,hid_deivce->inputs链表上只有一个hidinput.

跟踪hidinput_configure_usage().代码如下:

static void hidinput_configure_usage(struct hid_input *hidinput, struct hid_field *field,

struct hid_usage *usage)

{

struct input_dev *input = hidinput->input;

struct hid_device *device = input_get_drvdata(input);

int max = 0, code, ret;

unsigned long *bit = NULL;

//使field的hidinput域指向hidinput

field->hidinput = hidinput;

//Debug,忽略

dbg_hid("Mapping: ");

hid_resolv_usage(usage->hid);

dbg_hid_line(" ---> ");

if (field->flags & HID_MAIN_ITEM_CONSTANT)

goto ignore;

/* only LED usages are supported in output fields */

//如果是否个输出设备但却不是LED,忽略

if (field->report_type == HID_OUTPUT_REPORT &&

(usage->hid & HID_USAGE_PAGE) != HID_UP_LED) {

dbg_hid_line(" [non-LED output field] ");

goto ignore;

}

/* handle input mappings for quirky devices */

//关于quirks的东东,忽略

ret = hidinput_mapping_quirks(usage, input, &bit, &max);

if (ret)

goto mapped;

//取usage的高16位,即usage_page

switch (usage->hid & HID_USAGE_PAGE) {

case HID_UP_UNDEFINED:

goto ignore;

//键盘类型的设备

case HID_UP_KEYBOARD:

//使input device支持重复按键

set_bit(EV_REP, input->evbit);

if ((usage->hid & HID_USAGE) < 256) {

if (!hid_keyboard[usage->hid & HID_USAGE]) goto ignore;

map_key_clear(hid_keyboard[usage->hid & HID_USAGE]);

} else

map_key(KEY_UNKNOWN);

break;

case HID_UP_BUTTON:

code = ((usage->hid - 1) & 0xf);

switch (field->application) {

case HID_GD_MOUSE:

case HID_GD_POINTER: code += 0x110; break;

case HID_GD_JOYSTICK: code += 0x120; break;

case HID_GD_GAMEPAD: code += 0x130; break;

default:

switch (field->physical) {

case HID_GD_MOUSE:

case HID_GD_POINTER: code += 0x110; break;

case HID_GD_JOYSTICK: code += 0x120; break;

case HID_GD_GAMEPAD: code += 0x130; break;

default: code += 0x100;

}

/* Special handling for Logitech Cordless Desktop */

if (field->application != HID_GD_MOUSE) {

if (device->quirks & HID_QUIRK_LOGITECH_EXPANDED_KEYMAP) {

int hid = usage->hid & HID_USAGE;

if (hid < LOGITECH_EXPANDED_KEYMAP_SIZE && logitech_expanded_keymap[hid] != 0)

code = logitech_expanded_keymap[hid];

}

} else {

if (device->quirks & HID_QUIRK_LOGITECH_IGNORE_DOUBLED_WHEEL) {

int hid = usage->hid & HID_USAGE;

if (hid == 7 || hid == 8)

goto ignore;

}

map_key(code);

break;

case HID_UP_SIMULATION:

switch (usage->hid & 0xffff) {

case 0xba: map_abs(ABS_RUDDER); break;

case 0xbb: map_abs(ABS_THROTTLE); break;

case 0xc4: map_abs(ABS_GAS); break;

case 0xc5: map_abs(ABS_BRAKE); break;

case 0xc8: map_abs(ABS_WHEEL); break;

default: goto ignore;

}

break;

case HID_UP_GENDESK:

if ((usage->hid & 0xf0) == 0x80) { /* SystemControl */

switch (usage->hid & 0xf) {

case 0x1: map_key_clear(KEY_POWER); break;

case 0x2: map_key_clear(KEY_SLEEP); break;

case 0x3: map_key_clear(KEY_WAKEUP); break;

default: goto unknown;

}

break;

}

if ((usage->hid & 0xf0) == 0x90) { /* D-pad */

switch (usage->hid) {

case HID_GD_UP: usage->hat_dir = 1; break;

case HID_GD_DOWN: usage->hat_dir = 5; break;

case HID_GD_RIGHT: usage->hat_dir = 3; break;

case HID_GD_LEFT: usage->hat_dir = 7; break;

default: goto unknown;

}

if (field->dpad) {

map_abs(field->dpad);

goto ignore;

}

map_abs(ABS_HAT0X);

break;

}

switch (usage->hid) {

/* These usage IDs map directly to the usage codes. */

case HID_GD_X: case HID_GD_Y: case HID_GD_Z:

case HID_GD_RX: case HID_GD_RY: case HID_GD_RZ:

case HID_GD_SLIDER: case HID_GD_DIAL: case HID_GD_WHEEL:

if (field->flags & HID_MAIN_ITEM_RELATIVE)

map_rel(usage->hid & 0xf);

else

map_abs(usage->hid & 0xf);

break;

case HID_GD_HATSWITCH:

usage->hat_min = field->logical_minimum;

usage->hat_max = field->logical_maximum;

map_abs(ABS_HAT0X);

break;

case HID_GD_START: map_key_clear(BTN_START); break;

case HID_GD_SELECT: map_key_clear(BTN_SELECT); break;

default: goto unknown;

}

break;

case HID_UP_LED:

switch (usage->hid & 0xffff) { /* HID-Value: */

case 0x01: map_led (LED_NUML); break; /* "Num Lock" */

case 0x02: map_led (LED_CAPSL); break; /* "Caps Lock" */

case 0x03: map_led (LED_SCROLLL); break; /* "Scroll Lock" */

case 0x04: map_led (LED_COMPOSE); break; /* "Compose" */

case 0x05: map_led (LED_KANA); break; /* "Kana" */

case 0x27: map_led (LED_SLEEP); break; /* "Stand-By" */

case 0x4c: map_led (LED_SUSPEND); break; /* "System Suspend" */

case 0x09: map_led (LED_MUTE); break; /* "Mute" */

case 0x4b: map_led (LED_MISC); break; /* "Generic Indicator" */

case 0x19: map_led (LED_MAIL); break; /* "Message Waiting" */

case 0x4d: map_led (LED_CHARGING); break; /* "External Power Connected" */

default: goto ignore;

}

break;

case HID_UP_DIGITIZER:

switch (usage->hid & 0xff) {

case 0x30: /* TipPressure */

if (!test_bit(BTN_TOUCH, input->keybit)) {

device->quirks |= HID_QUIRK_NOTOUCH;

set_bit(EV_KEY, input->evbit);

set_bit(BTN_TOUCH, input->keybit);

}

map_abs_clear(ABS_PRESSURE);

break;

case 0x32: /* InRange */

switch (field->physical & 0xff) {

case 0x21: map_key(BTN_TOOL_MOUSE); break;

case 0x22: map_key(BTN_TOOL_FINGER); break;

default: map_key(BTN_TOOL_PEN); break;

}

break;

case 0x3c: /* Invert */

map_key_clear(BTN_TOOL_RUBBER);

break;

case 0x33: /* Touch */

case 0x42: /* TipSwitch */

case 0x43: /* TipSwitch2 */

device->quirks &= ~HID_QUIRK_NOTOUCH;

map_key_clear(BTN_TOUCH);

break;

case 0x44: /* BarrelSwitch */

map_key_clear(BTN_STYLUS);

break;

default: goto unknown;

}

break;

case HID_UP_CONSUMER: /* USB HUT v1.1, pages 56-62 */

switch (usage->hid & HID_USAGE) {

case 0x000: goto ignore;

case 0x034: map_key_clear(KEY_SLEEP); break;

case 0x036: map_key_clear(BTN_MISC); break;

case 0x040: map_key_clear(KEY_MENU); break;

case 0x045: map_key_clear(KEY_RADIO); break;

case 0x083: map_key_clear(KEY_LAST); break;

case 0x088: map_key_clear(KEY_PC); break;

case 0x089: map_key_clear(KEY_TV); break;

case 0x08a: map_key_clear(KEY_WWW); break;

case 0x08b: map_key_clear(KEY_DVD); break;

case 0x08c: map_key_clear(KEY_PHONE); break;

case 0x08d: map_key_clear(KEY_PROGRAM); break;

case 0x08e: map_key_clear(KEY_VIDEOPHONE); break;

case 0x08f: map_key_clear(KEY_GAMES); break;

case 0x090: map_key_clear(KEY_MEMO); break;

case 0x091: map_key_clear(KEY_CD); break;

case 0x092: map_key_clear(KEY_VCR); break;

case 0x093: map_key_clear(KEY_TUNER); break;

case 0x094: map_key_clear(KEY_EXIT); break;

case 0x095: map_key_clear(KEY_HELP); break;

case 0x096: map_key_clear(KEY_TAPE); break;

case 0x097: map_key_clear(KEY_TV2); break;

case 0x098: map_key_clear(KEY_SAT); break;

case 0x09a: map_key_clear(KEY_PVR); break;

case 0x09c: map_key_clear(KEY_CHANNELUP); break;

case 0x09d: map_key_clear(KEY_CHANNELDOWN); break;

case 0x0a0: map_key_clear(KEY_VCR2); break;

case 0x0b0: map_key_clear(KEY_PLAY); break;

case 0x0b1: map_key_clear(KEY_PAUSE); break;

case 0x0b2: map_key_clear(KEY_RECORD); break;

case 0x0b3: map_key_clear(KEY_FASTFORWARD); break;

case 0x0b4: map_key_clear(KEY_REWIND); break;

case 0x0b5: map_key_clear(KEY_NEXTSONG); break;

case 0x0b6: map_key_clear(KEY_PREVIOUSSONG); break;

case 0x0b7: map_key_clear(KEY_STOPCD); break;

case 0x0b8: map_key_clear(KEY_EJECTCD); break;

case 0x0cd: map_key_clear(KEY_PLAYPAUSE); break;

case 0x0e0: map_abs_clear(ABS_VOLUME); break;

case 0x0e2: map_key_clear(KEY_MUTE); break;

case 0x0e5: map_key_clear(KEY_BASSBOOST); break;

case 0x0e9: map_key_clear(KEY_VOLUMEUP); break;

case 0x0ea: map_key_clear(KEY_VOLUMEDOWN); break;

case 0x182: map_key_clear(KEY_BOOKMARKS); break;

case 0x183: map_key_clear(KEY_CONFIG); break;

case 0x184: map_key_clear(KEY_WORDPROCESSOR); break;

case 0x185: map_key_clear(KEY_EDITOR); break;

case 0x186: map_key_clear(KEY_SPREADSHEET); break;

case 0x187: map_key_clear(KEY_GRAPHICSEDITOR); break;

case 0x188: map_key_clear(KEY_PRESENTATION); break;

case 0x189: map_key_clear(KEY_DATABASE); break;

case 0x18a: map_key_clear(KEY_MAIL); break;

case 0x18b: map_key_clear(KEY_NEWS); break;

case 0x18c: map_key_clear(KEY_VOICEMAIL); break;

case 0x18d: map_key_clear(KEY_ADDRESSBOOK); break;

case 0x18e: map_key_clear(KEY_CALENDAR); break;

case 0x191: map_key_clear(KEY_FINANCE); break;

case 0x192: map_key_clear(KEY_CALC); break;

case 0x194: map_key_clear(KEY_FILE); break;

case 0x196: map_key_clear(KEY_WWW); break;

case 0x19c: map_key_clear(KEY_LOGOFF); break;

case 0x19e: map_key_clear(KEY_COFFEE); break;

case 0x1a6: map_key_clear(KEY_HELP); break;

case 0x1a7: map_key_clear(KEY_DOCUMENTS); break;

case 0x1ab: map_key_clear(KEY_SPELLCHECK); break;

case 0x1b6: map_key_clear(KEY_MEDIA); break;

case 0x1b7: map_key_clear(KEY_SOUND); break;

case 0x1bc: map_key_clear(KEY_MESSENGER); break;

case 0x1bd: map_key_clear(KEY_INFO); break;

case 0x201: map_key_clear(KEY_NEW); break;

case 0x202: map_key_clear(KEY_OPEN); break;

case 0x203: map_key_clear(KEY_CLOSE); break;

case 0x204: map_key_clear(KEY_EXIT); break;

case 0x207: map_key_clear(KEY_SAVE); break;

case 0x208: map_key_clear(KEY_PRINT); break;

case 0x209: map_key_clear(KEY_PROPS); break;

case 0x21a: map_key_clear(KEY_UNDO); break;

case 0x21b: map_key_clear(KEY_COPY); break;

case 0x21c: map_key_clear(KEY_CUT); break;

case 0x21d: map_key_clear(KEY_PASTE); break;

case 0x21f: map_key_clear(KEY_FIND); break;

case 0x221: map_key_clear(KEY_SEARCH); break;

case 0x222: map_key_clear(KEY_GOTO); break;

case 0x223: map_key_clear(KEY_HOMEPAGE); break;

case 0x224: map_key_clear(KEY_BACK); break;

case 0x225: map_key_clear(KEY_FORWARD); break;

case 0x226: map_key_clear(KEY_STOP); break;

case 0x227: map_key_clear(KEY_REFRESH); break;

case 0x22a: map_key_clear(KEY_BOOKMARKS); break;

case 0x22d: map_key_clear(KEY_ZOOMIN); break;

case 0x22e: map_key_clear(KEY_ZOOMOUT); break;

case 0x22f: map_key_clear(KEY_ZOOMRESET); break;

case 0x233: map_key_clear(KEY_SCROLLUP); break;

case 0x234: map_key_clear(KEY_SCROLLDOWN); break;

case 0x238: map_rel(REL_HWHEEL); break;

case 0x25f: map_key_clear(KEY_CANCEL); break;

case 0x279: map_key_clear(KEY_REDO); break;

case 0x289: map_key_clear(KEY_REPLY); break;

case 0x28b: map_key_clear(KEY_FORWARDMAIL); break;

case 0x28c: map_key_clear(KEY_SEND); break;

default: goto ignore;

}

break;

case HID_UP_HPVENDOR: /* Reported on a Dutch layout HP5308 */

set_bit(EV_REP, input->evbit);

switch (usage->hid & HID_USAGE) {

case 0x021: map_key_clear(KEY_PRINT); break;

case 0x070: map_key_clear(KEY_HP); break;

case 0x071: map_key_clear(KEY_CAMERA); break;

case 0x072: map_key_clear(KEY_SOUND); break;

case 0x073: map_key_clear(KEY_QUESTION); break;

case 0x080: map_key_clear(KEY_EMAIL); break;

case 0x081: map_key_clear(KEY_CHAT); break;

case 0x082: map_key_clear(KEY_SEARCH); break;

case 0x083: map_key_clear(KEY_CONNECT); break;

case 0x084: map_key_clear(KEY_FINANCE); break;

case 0x085: map_key_clear(KEY_SPORT); break;

case 0x086: map_key_clear(KEY_SHOP); break;

default: goto ignore;

}

break;

case HID_UP_MSVENDOR:

goto ignore;

case HID_UP_CUSTOM: /* Reported on Logitech and Apple USB keyboards */

set_bit(EV_REP, input->evbit);

switch(usage->hid & HID_USAGE) {

case 0x003:

/* The fn key on Apple USB keyboards */

map_key_clear(KEY_FN);

hidinput_apple_setup(input);

break;

default: goto ignore;

}

break;

case HID_UP_LOGIVENDOR:

goto ignore;

case HID_UP_PID:

switch(usage->hid & HID_USAGE) {

case 0xa4: map_key_clear(BTN_DEAD); break;

default: goto ignore;

}

break;

default:

unknown:

if (field->report_size == 1) {

if (field->report->type == HID_OUTPUT_REPORT) {

map_led(LED_MISC);

break;

}

map_key(BTN_MISC);

break;

}

if (field->flags & HID_MAIN_ITEM_RELATIVE) {

map_rel(REL_MISC);

break;

}

map_abs(ABS_MISC);

break;

}

mapped:

if (device->quirks & HID_QUIRK_MIGHTYMOUSE) {

if (usage->hid == HID_GD_Z)

map_rel(REL_HWHEEL);

else if (usage->code == BTN_1)

map_key(BTN_2);

else if (usage->code == BTN_2)

map_key(BTN_1);

}

if ((device->quirks & (HID_QUIRK_2WHEEL_MOUSE_HACK_7 | HID_QUIRK_2WHEEL_MOUSE_HACK_5 |

HID_QUIRK_2WHEEL_MOUSE_HACK_B8)) && (usage->type == EV_REL) &&

(usage->code == REL_WHEEL))

set_bit(REL_HWHEEL, bit);

if (((device->quirks & HID_QUIRK_2WHEEL_MOUSE_HACK_5) && (usage->hid == 0x00090005))

|| ((device->quirks & HID_QUIRK_2WHEEL_MOUSE_HACK_7) && (usage->hid == 0x00090007)))

goto ignore;

if ((device->quirks & HID_QUIRK_BAD_RELATIVE_KEYS) &&

usage->type == EV_KEY && (field->flags & HID_MAIN_ITEM_RELATIVE))

field->flags &= ~HID_MAIN_ITEM_RELATIVE;

set_bit(usage->type, input->evbit);

if (device->quirks & HID_QUIRK_DUPLICATE_USAGES &&

(usage->type == EV_KEY ||

usage->type == EV_REL ||

usage->type == EV_ABS))

clear_bit(usage->code, bit);

while (usage->code <= max && test_and_set_bit(usage->code, bit))

usage->code = find_next_zero_bit(bit, max + 1, usage->code);

if (usage->code > max)

goto ignore;

if (usage->type == EV_ABS) {

int a = field->logical_minimum;

int b = field->logical_maximum;

if ((device->quirks & HID_QUIRK_BADPAD) && (usage->code == ABS_X || usage->code == ABS_Y)) {

a = field->logical_minimum = 0;

b = field->logical_maximum = 255;

}

if (field->application == HID_GD_GAMEPAD || field->application == HID_GD_JOYSTICK)

input_set_abs_params(input, usage->code, a, b, (b - a) >> 8, (b - a) >> 4);

else input_set_abs_params(input, usage->code, a, b, 0, 0);

}

if (usage->type == EV_ABS &&

(usage->hat_min < usage->hat_max || usage->hat_dir)) {

int i;

for (i = usage->code; i < usage->code + 2 && i <= max; i++) {

input_set_abs_params(input, i, -1, 1, 0, 0);

set_bit(i, input->absbit);

}

if (usage->hat_dir && !field->dpad)

field->dpad = usage->code;

}

/* for those devices which produce Consumer volume usage as relative,

* we emulate pressing volumeup/volumedown appropriate number of times

* in hidinput_hid_event()

if ((usage->type == EV_ABS) && (field->flags & HID_MAIN_ITEM_RELATIVE) &&

(usage->code == ABS_VOLUME)) {

set_bit(KEY_VOLUMEUP, input->keybit);

set_bit(KEY_VOLUMEDOWN, input->keybit);

}

if (usage->type == EV_KEY) {

set_bit(EV_MSC, input->evbit);

set_bit(MSC_SCAN, input->mscbit);

}

hid_resolv_event(usage->type, usage->code);

dbg_hid_line("\n");

return;

ignore:

dbg_hid_line("IGNORED\n");

return;

}

乍看之下,这个函数超长,为们以keyboad为例,对它进行分析,同时忽略掉quirks和调试信息以及一些无关的操作.代码就缩减成下面这样了:

……

switch (usage->hid & HID_USAGE_PAGE) {

case HID_UP_UNDEFINED:

goto ignore;

//键盘类型的设备

case HID_UP_KEYBOARD:

//使input device支持重复按键

set_bit(EV_REP, input->evbit);

if ((usage->hid & HID_USAGE) < 256) {

if (!hid_keyboard[usage->hid & HID_USAGE]) goto ignore;

map_key_clear(hid_keyboard[usage->hid & HID_USAGE]);

} else

map_key(KEY_UNKNOWN);

break;

……

}

mapped:

set_bit(usage->type, input->evbit);

while (usage->code <= max && test_and_set_bit(usage->code, bit))

usage->code = find_next_zero_bit(bit, max + 1, usage->code);

if (usage->code > max)

goto ignore;

……

if (usage->type == EV_KEY) {

set_bit(EV_MSC, input->evbit);

set_bit(MSC_SCAN, input->mscbit);

}

……

return;

ignore:

dbg_hid_line("IGNORED\n");

return;

}

关于键盘这部份的usage 定义请自行参考 USB HID Usage Tables sepc.对照hid_keyboard[ ]和键盘的扫描码可以得知,其实hid_keyboard[ ]就是定义了按键的扫描码.

如果filed的usage在hid_keyboard[ ]中有定义,则表示该设备支持这个类型的按键.在代码中,也就是会调用map_key_clear().跟踪看一下它的定义:

#define map_key_clear(c) do { map_key(c); clear_bit(c, bit); } while (0)

#define map_key(c) do { usage->code = c; usage->type = EV_KEY; bit = input->keybit; max = KEY_MAX; } while (0)

假设该设备支持的按键为C.则经过map_key_clear()后会变成:

Usage->code = C

Usage->type=EV_KEY

Bit 为input->keybit所支持的按键类型,不过已经将C位清除了.

接下来,在hidinput_configure_usage()函数中调用

set_bit(usage->type, input->evbit)

即让input device 支持EV_KEY事件

然后经过下列语句:

while (usage->code <= max && test_and_set_bit(usage->code, bit))

usage->code = find_next_zero_bit(bit, max + 1, usage->code);

会在bit中设置usage->code.即上面例子中的按键C.因为在前面已经在bit中usage->code清除.因此test_and_set_bit(usage->code, bit)是不会满足的.

最后会调用以下语句:

if (usage->type == EV_KEY) {

set_bit(EV_MSC, input->evbit);

set_bit(MSC_SCAN, input->mscbit);

}

即设置input_deivce的evbit和mscbit位.

到这里,这个函数已经分析完了.至于keyboard以外的设备,对照usage table spec,也很容易弄得,为了节省篇幅,这里就不将各种设备一一列出.

3.4:关于HID中的input_device操作

在前面分析hidinput_connect看到了hid的input_device初始化过程.为了描述方便，将相关的代码列出如下：

input_dev->event = hid->hidinput_input_event;

input_dev->open = hidinput_open;

input_dev->close = hidinput_close;

input_dev->setkeycode = hidinput_setkeycode;

input_dev->getkeycode = hidinput_getkeycode;

结合之前对input子系统的分析。所有的input device都会被终端控制台的input_handler匹配。在匹配过程中，会调用input_device->open。对这个过程不太清楚的，请参阅本站关于input子系统分析的文档。

对应的,open的接口如下示：

static int hidinput_open(struct input_dev *dev)

{

struct hid_device *hid = input_get_drvdata(dev);

return hid->hid_open(hid);

}

由此可见，它会转换到hid_device->open()。

在usb_hid_configure()中，hid_device的信息初始化如下：

static struct hid_device *usb_hid_configure(struct usb_interface *intf)

{

……

hid->hid_open = usbhid_open;

hid->hid_close = usbhid_close;

#ifdef CONFIG_USB_HIDDEV

hid->hiddev_hid_event = hiddev_hid_event;

hid->hiddev_report_event = hiddev_report_event;

#endif

hid->hid_output_raw_report = usbhid_output_raw_report;

return hid;

……

}

相应的接口如下示：

int usbhid_open(struct hid_device *hid)

{

struct usbhid_device *usbhid = hid->driver_data;

int res;

if (!hid->open++) {

res = usb_autopm_get_interface(usbhid->intf);

if (res < 0) {

hid->open--;

return -EIO;

}

if (hid_start_in(hid))

hid_io_error(hid);

return 0;

}

这个函数里会调用hid_start_in().代码如下：

static int hid_start_in(struct hid_device *hid)

{

unsigned long flags;

int rc = 0;

struct usbhid_device *usbhid = hid->driver_data;

spin_lock_irqsave(&usbhid->inlock, flags);

if (hid->open > 0 && !test_bit(HID_SUSPENDED, &usbhid->iofl) &&

!test_and_set_bit(HID_IN_RUNNING, &usbhid->iofl)) {

rc = usb_submit_urb(usbhid->urbin, GFP_ATOMIC);

if (rc != 0)

clear_bit(HID_IN_RUNNING, &usbhid->iofl);

}

spin_unlock_irqrestore(&usbhid->inlock, flags);

return rc;

}

由此看到，它会提交usbhid->urbin.

相对于整个过程来说，如果open了input_device.就要开始从设备读取数据了。

3.3.1: hid_irq_in()函数分析

Usbhid->urbin传输完成之后，会调用hid_irq_in（）。该函数代码如下：

static void hid_irq_in(struct urb *urb)

{

struct hid_device *hid = urb->context;

struct usbhid_device *usbhid = hid->driver_data;

int status;

switch (urb->status) {

case 0: /* success */

usbhid->retry_delay = 0;

hid_input_report(urb->context, HID_INPUT_REPORT,

urb->transfer_buffer,

urb->actual_length, 1);

break;

case -EPIPE: /* stall */

clear_bit(HID_IN_RUNNING, &usbhid->iofl);

set_bit(HID_CLEAR_HALT, &usbhid->iofl);

schedule_work(&usbhid->reset_work);

return;

case -ECONNRESET: /* unlink */

case -ENOENT:

case -ESHUTDOWN: /* unplug */

clear_bit(HID_IN_RUNNING, &usbhid->iofl);

return;

case -EILSEQ: /* protocol error or unplug */

case -EPROTO: /* protocol error or unplug */

case -ETIME: /* protocol error or unplug */

case -ETIMEDOUT: /* Should never happen, but... */

clear_bit(HID_IN_RUNNING, &usbhid->iofl);

hid_io_error(hid);

return;

default: /* error */

warn("input irq status %d received", urb->status);

}

status = usb_submit_urb(urb, GFP_ATOMIC);

if (status) {

clear_bit(HID_IN_RUNNING, &usbhid->iofl);

if (status != -EPERM) {

err_hid("can't resubmit intr, %s-%s/input%d, status %d",

hid_to_usb_dev(hid)->bus->bus_name,

hid_to_usb_dev(hid)->devpath,

usbhid->ifnum, status);

hid_io_error(hid);

}

从上面的代码可以看出，它会一直提交usbhid->urbin.以这样的方式轮询HID设备.直到发生错误，清除HID_IN_RUNNING标志退出。

另外，对于接收到的数据会调用hid_input_report().

这样函数我们在上面已经分析过，不过那时候还留下了一个尾巴，现在就把它补上

3.4:遗留的尾巴:hid_input_field()函数

代码如下:

void hid_input_field(struct hid_device *hid, struct hid_field *field, __u8 *data, int interrupt)

{

unsigned n;

unsigned count = field->report_count;

unsigned offset = field->report_offset;

unsigned size = field->report_size;

__s32 min = field->logical_minimum;

__s32 max = field->logical_maximum;

__s32 *value;

//每一项report的值都存放在一个32位的的buff中

if (!(value = kmalloc(sizeof(__s32) * count, GFP_ATOMIC)))

return;

for (n = 0; n < count; n++) {

value[n] = min < 0 ? snto32(extract(data, offset + n * size, size), size) :

extract(data, offset + n * size, size);

//Array类型的.且为ErrorRollOver .忽略

if (!(field->flags & HID_MAIN_ITEM_VARIABLE) /* Ignore report if ErrorRollOver */

&& value[n] >= min && value[n] <= max

&& field->usage[value[n] - min].hid == HID_UP_KEYBOARD + 1)

goto exit;

}

for (n = 0; n < count; n++) {

//如果field为variable 类型, 如果是var型的话,传递过来的数量应该为了0,1表示按键的状态

if (HID_MAIN_ITEM_VARIABLE & field->flags) {

hid_process_event(hid, field, &field->usage[n], value[n], interrupt);

continue;

}

//如果是Array类型,那传递过来的应该就是按键码的usage值(与min相减)

//如果field里原本有,但传递过来的按键却没有这个键了,表示上次的按键已经松开了.

if (field->value[n] >= min && field->value[n] <= max

&& field->usage[field->value[n] - min].hid

search(value, field->value[n], count))

hid_process_event(hid, field, &field->usage[field->value[n] - min], 0, interrupt);

//filed里没有,vaule里却有,表示这个键是新按下的

if (value[n] >= min && value[n] <= max

&& field->usage[value[n] - min].hid

&& search(field->value, value[n], count))

hid_process_event(hid, field, &field->usage[value[n] - min], 1, interrupt);

}

//把这一次的按键值保存到field->value中

memcpy(field->value, value, count * sizeof(__s32));

exit:

kfree(value);

}

在这个函数里,首先要注意的是field的value的部份.结合之前对report description的解析过程好好理解一下.再次给出field的结构.如下图:

上图中的value是附加部份,是在分配field空间的时候留出来的部份

每一个report项,对于value中的一项,用来存放上一次从设备读取的值或者是要传送给设备的值.

另外,还需要注意的是,对于array和variable类型的不同.以keyboard类型为例.对于variable,上面的usage数组分别表示了每一个按键的扫描码.因此从设备读取的信息,也就是value中的值表示的是按键的状态,0是松开,1是按下. 而对于array类型.usage保存的是可能出现的按键类型.从设备读取的信息就浊按键的扫描码.

对于array类型而言,上一次的按键可以从field->value[ ]中找到,就可以得到,上次的按键有没有被松开.或者对比从设备读取回来的值,就可以得知,哪些键是刚被按下去的.

最后,将读取到的信息更新回filed->value.供下一次按键的时候比较.

每次的按键上报都是调用hid_process_event()来完成的,这个是hid封装的一个input device上报消息的接触,最终会调用input_event()将事件上报.这个过程很简单,可以自行查阅.

四:总结

总的来说,HID的驱动不算复杂,只是对report description的解析比较晦涩一点.另外这个hid驱动封装了几乎所有类型的HID设备.因此,代码中的分支处理比较繁杂.研究代码的时候,最好是抓住一种类型的HID设备去深入研究.

转自：http://www.cnblogs.com/sdphome/archive/2011/09/29/2195799.html