2019独角兽企业重金招聘Python工程师标准>>> 
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
//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- 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.