因为usb gadget驱动在实际应用中比较少见，通常usb口主要就两个功能，一是供电；二是接外部设备。而且如果是开发usb设备的话，很多是通过usb设备芯片配合firmware来提供成熟的解决方案，所以写这篇文章，以hid gadget驱动为例，来记录usb gadget驱动的开发使用过程。
一. usb gadget框架层次
usb gadget是通过驱动来使usb控制器扮演特定设备。为了方便，下面就把usb gadget简称为ugadget了。 ugadget分为三个层次，示例图如下：
对应的代码位于（以kernel 4.x为例）：
| 层次 | 位置 |
|---|---|
| 驱动层 | usb/gadget/legacy/* |
| 复合层 | usb/gadget下composite.c以及usb/gadget/function/* |
| 控制器驱动 | usb/gadget/udc/* |
1.1 驱动层
驱动层定义不同平台相关的驱动配置，然后负责和复合层进行交互，交互通过struct usb_composite_driver完成。
include/linux/usb/composite.h
struct usb_composite_driver {
const char *name;
const struct usb_device_descriptor *dev;
struct usb_gadget_strings **strings;
enum usb_device_speed max_speed;
unsigned needs_serial:1;
int (*bind)(struct usb_composite_dev *cdev);
int (*unbind)(struct usb_composite_dev *);
void (*disconnect)(struct usb_composite_dev *);
/* global suspend hooks */
void (*suspend)(struct usb_composite_dev *);
void (*resume)(struct usb_composite_dev *);
struct usb_gadget_driver gadget_driver;
};
1.2 复合层
复合层起到承上启下的作用，对上(驱动层)提供驱动接口，对下负责管理usb配置以及功能，所有function目录下的接口可以认为是供composite层调用的库。function目录汇集了很多功能层的接口代码，hid对应的文件为f_hid.c，其中必须实例化struct usb_function类型的结构体:
struct usb_function {
const char *name;
/*字符串描述符*/
struct usb_gadget_strings **strings;
/*全速，高速，超速设备描述符*/
struct usb_descriptor_header **fs_descriptors;
struct usb_descriptor_header **hs_descriptors;
struct usb_descriptor_header **ss_descriptors;
/*配置描述*/
struct usb_configuration *config;
/*os相关描述*/
struct usb_os_desc_table *os_desc_table;
unsigned os_desc_n;
/* REVISIT: bind() functions can be marked __init, which
* makes trouble for section mismatch analysis. See if
* we can't restructure things to avoid mismatching.
* Related: unbind() may kfree() but bind() won't...
*/
/* configuration management: bind/unbind */
int (*bind)(struct usb_configuration *,
struct usb_function *);
void (*unbind)(struct usb_configuration *,
struct usb_function *);
void (*free_func)(struct usb_function *f);
struct module *mod;
/* runtime state management */
int (*set_alt)(struct usb_function *,
unsigned interface, unsigned alt);
int (*get_alt)(struct usb_function *,
unsigned interface);
void (*disable)(struct usb_function *);
int (*setup)(struct usb_function *,
const struct usb_ctrlrequest *);
bool (*req_match)(struct usb_function *,
const struct usb_ctrlrequest *);
void (*suspend)(struct usb_function *);
void (*resume)(struct usb_function *);
/* USB 3.0 additions */
int (*get_status)(struct usb_function *);
int (*func_suspend)(struct usb_function *,
u8 suspend_opt);
/* private: */
/* internals */
struct list_head list;
DECLARE_BITMAP(endpoints, 32);
const struct usb_function_instance *fi;
unsigned int bind_deactivated:1;
};
提供了字符设备相关的操作接口，定义在struct file_operation中，如下所示：
static const struct file_operations f_hidg_fops = {
.owner = THIS_MODULE,
.open = f_hidg_open,
.release = f_hidg_release,
.write = f_hidg_write,
.read = f_hidg_read,
.poll = f_hidg_poll,
.llseek = noop_llseek,
};
1.3 控制器驱动层
核心代码位于usb/gadget/udc/udc-core.c，负责管理不同平台的gadget device，相关结构定义为
include/linux/usb/gadget.h
struct usb_gadget {
struct work_struct work;
struct usb_udc *udc;
/* readonly to gadget driver */
const struct usb_gadget_ops *ops;
struct usb_ep *ep0;
struct list_head ep_list; /* of usb_ep */
enum usb_device_speed speed;
enum usb_device_speed max_speed;
enum usb_device_state state;
const char *name;
struct device dev;
unsigned out_epnum;
unsigned in_epnum;
struct usb_otg_caps *otg_caps;
unsigned sg_supported:1;
unsigned is_otg:1;
unsigned is_a_peripheral:1;
unsigned b_hnp_enable:1;
unsigned a_hnp_support:1;
unsigned a_alt_hnp_support:1;
unsigned quirk_ep_out_aligned_size:1;
unsigned quirk_altset_not_supp:1;
unsigned quirk_stall_not_supp:1;
unsigned quirk_zlp_not_supp:1;
unsigned is_selfpowered:1;
unsigned deactivated:1;
unsigned connected:1;
};
以Marvell USB Controller为例，udc初始化入口为
usb/gadget/udc/mv_udc_core.c
/*mv_udc_probe*/
retval = usb_add_gadget_udc_release(&pdev->dev, &udc->gadget,
gadget_release);
if (retval)
goto err_create_workqueue;
其他类似的管理接口还有
void usb_gadget_udc_reset(struct usb_gadget *gadget,
struct usb_gadget_driver *driver);
static inline int usb_gadget_udc_start(struct usb_udc *udc);
...
...
可以看到udc层实际上有两个任务
- 用来管理不同平台的gadget device。
- 通过绑定gadget driver实例来为复合层提供服务。
二. 初始化流程
2.1 驱动层介绍
gadget驱动通过调用ugadget框架对应接口来进行初始化，所有的gadget驱动目前位于usb/gadget/legacy目录下。
legacy目录一览：
| 文件 | 实现功能 |
|---|---|
| webcam.c | usb摄像头 |
| hid.c | hid设备 |
| serial.c | 串口设备 |
| ether.c | 网络设备 |
| mass_storage.c | 存储设备 |
| audio.c | 音频设备 |
| printer.c | 打印机 |
| zero.c | 一个假设备，主要用来参考 |
现在来看hid设备对应的驱动文件hid.c
2.2 hidg驱动初始化详解
初始化分为两部分：首先按照驱动层级从上至下的绑定相关结构体，然后再自下而上进行具体的结构体初始化。
2.1 至上而下遍历：搜索绑定驱动和设备
驱动的入口为
usb/gadget/legacy/hid.c
static struct usb_composite_driver hidg_driver = {
.name = "g_hid",
.dev = &device_desc,
.strings = dev_strings,
.max_speed = USB_SPEED_HIGH,
.bind = hid_bind,
.unbind = hid_unbind,
};
static int __init hidg_init(void)
{
int status;
/*定义平台相关设备，在hidg_plat_driver_probe中绑定hid类协议参数，包括绑定报告描述符*/
status = platform_driver_probe(&hidg_plat_driver,
hidg_plat_driver_probe);
if (status < 0)
return status;
/*进入到复合设备层， hidg_driver为struct composite_driver类型*/
status = usb_composite_probe(&hidg_driver);
if (status < 0)
platform_driver_unregister(&hidg_plat_driver);
return status;
}
进入到usb_composite_probe之后，对composite_driver和gadget_driver进行绑定，然后通过usb_gadget_probe_driver进入udc层，来绑定udc和gadget driver
usb/gadget/composite.c
...
/*这里的赋值是结构体赋值*/
driver->gadget_driver = composite_driver_template;
gadget_driver = &driver->gadget_driver;
gadget_driver->function = (char *) driver->name;
gadget_driver->driver.name = driver->name;
gadget_driver->max_speed = driver->max_speed;
return usb_gadget_probe_driver(gadget_driver);
进入udc层后，首先根据驱动名字来匹配udc
usb/gadget/udc/udc-core.c
...
mutex_lock(&udc_lock);
if (driver->udc_name) {
list_for_each_entry(udc, &udc_list, list) {
ret = strcmp(driver->udc_name, dev_name(&udc->dev));
if (!ret)
break;
}
if (!ret && !udc->driver)
goto found;
} else {
list_for_each_entry(udc, &udc_list, list) {
/* For now we take the first one */
if (!udc->driver)
goto found;
}
}
匹配完成后进行绑定
found:
ret = udc_bind_to_driver(udc, driver);
注意，此时的driver为复合层composite.c提供的gadget driver模板
static const struct usb_gadget_driver composite_driver_template = {
.bind = composite_bind,
.unbind = composite_unbind,
.setup = composite_setup,
.reset = composite_disconnect,
.disconnect = composite_disconnect,
.suspend = composite_suspend,
.resume = composite_resume,
.driver = {
.owner = THIS_MODULE,
},
};
udc_bind_to_driver通过回调driver->bind进行复合层的初始化，代码如下，复合层初始化结束之后enable USB控制器。
/*driver is composite_driver_template，开始回调*/
ret = driver->bind(udc->gadget, driver);
if (ret)
goto err1;
/*start USB Device Controller*/
ret = usb_gadget_udc_start(udc);
if (ret) {
driver->unbind(udc->gadget);
goto err1;
}
usb_udc_connect_control(udc);
2.2 至下而上遍历：完成初始化
通过一系列的回调进行结构体的初始化，首先就是udc-core中driver->bind，对应的接口是
usb/gadget/composite.c
static int composite_bind(struct usb_gadget *gadget,
struct usb_gadget_driver *gdriver)
{
struct usb_composite_dev *cdev;
struct usb_composite_driver *composite = to_cdriver(gdriver);
int status = -ENOMEM;
cdev = kzalloc(sizeof *cdev, GFP_KERNEL);
if (!cdev)
return status;
spin_lock_init(&cdev->lock);
cdev->gadget = gadget;
set_gadget_data(gadget, cdev);
INIT_LIST_HEAD(&cdev->configs);
INIT_LIST_HEAD(&cdev->gstrings);
/*初始化复合设备，包括分配用来响应usb标准请求的request和buffer，创建设备文件，reset配置*/
status = composite_dev_prepare(composite, cdev);
if (status)
goto fail;
/* composite gadget needs to assign strings for whole device (like
* serial number), register function drivers, potentially update
* power state and consumption, etc
*/
status = composite->bind(cdev);
if (status < 0)
goto fail;
if (cdev->use_os_string) {
status = composite_os_desc_req_prepare(cdev, gadget->ep0);
if (status)
goto fail;
}
update_unchanged_dev_desc(&cdev->desc, composite->dev);
/* has userspace failed to provide a serial number? */
if (composite->needs_serial && !cdev->desc.iSerialNumber)
WARNING(cdev, "userspace failed to provide iSerialNumber\n");
INFO(cdev, "%s ready\n", composite->name);
return 0;
fail:
__composite_unbind(gadget, false);
return status;
}
在composite_bind获取第一步初始化时绑定的struct usb_composite_driver，回调composite->bind，此处的bind具体为
usb/gadget/legacy/hid.c hidg_driver->bind
static int hid_bind(struct usb_composite_dev *cdev)
{
struct usb_gadget *gadget = cdev->gadget;
struct list_head *tmp;
struct hidg_func_node *n, *m;
struct f_hid_opts *hid_opts;
int status, funcs = 0;
/*probe平台设备时候添加的function对象*/
list_for_each(tmp, &hidg_func_list)
funcs++;
if (!funcs)
return -ENODEV;
list_for_each_entry(n, &hidg_func_list, node) {
/*搜索功能function实例，在f_hid中初始化，初始化接口位于usb/gadget/functions.c*/
n->fi = usb_get_function_instance("hid");
if (IS_ERR(n->fi)) {
status = PTR_ERR(n->fi);
goto put;
}
/*把function实例和platform specific配置进行绑定*/
hid_opts = container_of(n->fi, struct f_hid_opts, func_inst);
hid_opts->subclass = n->func->subclass;
hid_opts->protocol = n->func->protocol;
hid_opts->report_length = n->func->report_length;
hid_opts->report_desc_length = n->func->report_desc_length;
hid_opts->report_desc = n->func->report_desc;
}
/* Allocate string descriptor numbers ... note that string
* contents can be overridden by the composite_dev glue.
*/
status = usb_string_ids_tab(cdev, strings_dev);
if (status < 0)
goto put;
device_desc.iManufacturer = strings_dev[USB_GADGET_MANUFACTURER_IDX].id;
device_desc.iProduct = strings_dev[USB_GADGET_PRODUCT_IDX].id;
if (gadget_is_otg(gadget) && !otg_desc[0]) {
struct usb_descriptor_header *usb_desc;
usb_desc = usb_otg_descriptor_alloc(gadget);
if (!usb_desc)
goto put;
usb_otg_descriptor_init(gadget, usb_desc);
otg_desc[0] = usb_desc;
otg_desc[1] = NULL;
}
/* register our configuration */
status = usb_add_config(cdev, &config_driver, do_config);
if (status < 0)
goto free_otg_desc;
usb_composite_overwrite_options(cdev, &coverwrite);
dev_info(&gadget->dev, DRIVER_DESC ", version: " DRIVER_VERSION "\n");
return 0;
free_otg_desc:
kfree(otg_desc[0]);
otg_desc[0] = NULL;
put:
list_for_each_entry(m, &hidg_func_list, node) {
if (m == n)
break;
usb_put_function_instance(m->fi);
}
return status;
}
在复合层绑定的过程中，最关键的是通过
status = usb_add_config(cdev, &config_driver, do_config);
if (status < 0)
goto free_otg_desc;
进行配置的初始化，配置完成之后，这个ugadget就具有hid的功能了。
int usb_add_config(struct usb_composite_dev *cdev,
struct usb_configuration *config,
int (*bind)(struct usb_configuration *))
{
int status = -EINVAL;
if (!bind)
goto done;
DBG(cdev, "adding config #%u '%s'/%p\n",
config->bConfigurationValue,
config->label, config);
/*把config交给cdev管理*/
status = usb_add_config_only(cdev, config);
if (status)
goto done;
/*do_config, 往config中添加function*/
status = bind(config);
if (status < 0) {
/*绑定config和function失败*/
while (!list_empty(&config->functions)) {
struct usb_function *f;
f = list_first_entry(&config->functions,
struct usb_function, list);
list_del(&f->list);
if (f->unbind) {
DBG(cdev, "unbind function '%s'/%p\n",
f->name, f);
f->unbind(config, f);
/* may free memory for "f" */
}
}
list_del(&config->list);
config->cdev = NULL;
} else {
/*绑定成功，报告配置信息*/
unsigned i;
DBG(cdev, "cfg %d/%p speeds:%s%s%s\n",
config->bConfigurationValue, config,
config->superspeed ? " super" : "",
config->highspeed ? " high" : "",
config->fullspeed
? (gadget_is_dualspeed(cdev->gadget)
? " full"
: " full/low")
: "");
for (i = 0; i < MAX_CONFIG_INTERFACES; i++) {
struct usb_function *f = config->interface[i];
if (!f)
continue;
DBG(cdev, " interface %d = %s/%p\n",
i, f->name, f);
}
}
/* set_alt(), or next bind(), sets up ep->claimed as needed */
usb_ep_autoconfig_reset(cdev->gadget);
done:
if (status)
DBG(cdev, "added config '%s'/%u --> %d\n", config->label,
config->bConfigurationValue, status);
return status;
}
最后一步绑定的关键在于上面的bind回调，也就是do_config函数
usb/gadget/legacy/hid.c
static int do_config(struct usb_configuration *c)
{
struct hidg_func_node *e, *n;
int status = 0;
if (gadget_is_otg(c->cdev->gadget)) {
c->descriptors = otg_desc;
c->bmAttributes |= USB_CONFIG_ATT_WAKEUP;
}
list_for_each_entry(e, &hidg_func_list, node) {
e->f = usb_get_function(e->fi);
if (IS_ERR(e->f))
goto put;
/*向config中添加function*/
status = usb_add_function(c, e->f);
if (status < 0) {
usb_put_function(e->f);
goto put;
}
}
return 0;
put:
list_for_each_entry(n, &hidg_func_list, node) {
if (n == e)
break;
usb_remove_function(c, n->f);
usb_put_function(n->f);
}
return status;
}
do_config通过usb_add_dunction完成config和function的绑定
usb/gadget/composite.c
int usb_add_function(struct usb_configuration *config,
struct usb_function *function)
{
int value = -EINVAL;
DBG(config->cdev, "adding '%s'/%p to config '%s'/%p\n",
function->name, function,
config->label, config);
if (!function->set_alt || !function->disable)
goto done;
function->config = config;
list_add_tail(&function->list, &config->functions);
if (function->bind_deactivated) {
value = usb_function_deactivate(function);
if (value)
goto done;
}
/* REVISIT *require* function->bind? */
if (function->bind) {
value = function->bind(config, function);
if (value < 0) {
list_del(&function->list);
function->config = NULL;
}
} else
value = 0;
/* We allow configurations that don't work at both speeds.
* If we run into a lowspeed Linux system, treat it the same
* as full speed ... it's the function drivers that will need
* to avoid bulk and ISO transfers.
*/
if (!config->fullspeed && function->fs_descriptors)
config->fullspeed = true;
if (!config->highspeed && function->hs_descriptors)
config->highspeed = true;
if (!config->superspeed && function->ss_descriptors)
config->superspeed = true;
done:
if (value)
DBG(config->cdev, "adding '%s'/%p --> %d\n",
function->name, function, value);
return value;
}
这里通过function->bind完成最终usb function的初始化。function->bind指向
usb/gadget/function/f_hid.c
/*
* 分配interrupt-in端点和interrupt-out端点；
* 配置接口描述符和端点描述符;
* 注册字符设备
*/
static int hidg_bind(struct usb_configuration *c, struct usb_function *f);
至此，一个hid gadget就添加完成了，操作系统可以看到一个hidg设备文件。
三. hid gadget应用
关于如何应用可以参考kernel/Documentation/usb/gadget_hid.txt
这里摘出了其中的Sample code部分，以供参考。
/* hid_gadget_test */
#include <pthread.h>
#include <string.h>
#include <stdio.h>
#include <ctype.h>
#include <fcntl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#define BUF_LEN 512
struct options {
const char *opt;
unsigned char val;
};
static struct options kmod[] = {
{.opt = "--left-ctrl", .val = 0x01},
{.opt = "--right-ctrl", .val = 0x10},
{.opt = "--left-shift", .val = 0x02},
{.opt = "--right-shift", .val = 0x20},
{.opt = "--left-alt", .val = 0x04},
{.opt = "--right-alt", .val = 0x40},
{.opt = "--left-meta", .val = 0x08},
{.opt = "--right-meta", .val = 0x80},
{.opt = NULL}
};
static struct options kval[] = {
{.opt = "--return", .val = 0x28},
{.opt = "--esc", .val = 0x29},
{.opt = "--bckspc", .val = 0x2a},
{.opt = "--tab", .val = 0x2b},
{.opt = "--spacebar", .val = 0x2c},
{.opt = "--caps-lock", .val = 0x39},
{.opt = "--f1", .val = 0x3a},
{.opt = "--f2", .val = 0x3b},
{.opt = "--f3", .val = 0x3c},
{.opt = "--f4", .val = 0x3d},
{.opt = "--f5", .val = 0x3e},
{.opt = "--f6", .val = 0x3f},
{.opt = "--f7", .val = 0x40},
{.opt = "--f8", .val = 0x41},
{.opt = "--f9", .val = 0x42},
{.opt = "--f10", .val = 0x43},
{.opt = "--f11", .val = 0x44},
{.opt = "--f12", .val = 0x45},
{.opt = "--insert", .val = 0x49},
{.opt = "--home", .val = 0x4a},
{.opt = "--pageup", .val = 0x4b},
{.opt = "--del", .val = 0x4c},
{.opt = "--end", .val = 0x4d},
{.opt = "--pagedown", .val = 0x4e},
{.opt = "--right", .val = 0x4f},
{.opt = "--left", .val = 0x50},
{.opt = "--down", .val = 0x51},
{.opt = "--kp-enter", .val = 0x58},
{.opt = "--up", .val = 0x52},
{.opt = "--num-lock", .val = 0x53},
{.opt = NULL}
};
int keyboard_fill_report(char report[8], char buf[BUF_LEN], int *hold)
{
char *tok = strtok(buf, " ");
int key = 0;
int i = 0;
for (; tok != NULL; tok = strtok(NULL, " ")) {
if (strcmp(tok, "--quit") == 0)
return -1;
if (strcmp(tok, "--hold") == 0) {
*hold = 1;
continue;
}
if (key < 6) {
for (i = 0; kval[i].opt != NULL; i++)
if (strcmp(tok, kval[i].opt) == 0) {
report[2 + key++] = kval[i].val;
break;
}
if (kval[i].opt != NULL)
continue;
}
if (key < 6)
if (islower(tok[0])) {
report[2 + key++] = (tok[0] - ('a' - 0x04));
continue;
}
for (i = 0; kmod[i].opt != NULL; i++)
if (strcmp(tok, kmod[i].opt) == 0) {
report[0] = report[0] | kmod[i].val;
break;
}
if (kmod[i].opt != NULL)
continue;
if (key < 6)
fprintf(stderr, "unknown option: %s\n", tok);
}
return 8;
}
static struct options mmod[] = {
{.opt = "--b1", .val = 0x01},
{.opt = "--b2", .val = 0x02},
{.opt = "--b3", .val = 0x04},
{.opt = NULL}
};
int mouse_fill_report(char report[8], char buf[BUF_LEN], int *hold)
{
char *tok = strtok(buf, " ");
int mvt = 0;
int i = 0;
for (; tok != NULL; tok = strtok(NULL, " ")) {
if (strcmp(tok, "--quit") == 0)
return -1;
if (strcmp(tok, "--hold") == 0) {
*hold = 1;
continue;
}
for (i = 0; mmod[i].opt != NULL; i++)
if (strcmp(tok, mmod[i].opt) == 0) {
report[0] = report[0] | mmod[i].val;
break;
}
if (mmod[i].opt != NULL)
continue;
if (!(tok[0] == '-' && tok[1] == '-') && mvt < 2) {
errno = 0;
report[1 + mvt++] = (char)strtol(tok, NULL, 0);
if (errno != 0) {
fprintf(stderr, "Bad value:'%s'\n", tok);
report[1 + mvt--] = 0;
}
continue;
}
fprintf(stderr, "unknown option: %s\n", tok);
}
return 3;
}
static struct options jmod[] = {
{.opt = "--b1", .val = 0x10},
{.opt = "--b2", .val = 0x20},
{.opt = "--b3", .val = 0x40},
{.opt = "--b4", .val = 0x80},
{.opt = "--hat1", .val = 0x00},
{.opt = "--hat2", .val = 0x01},
{.opt = "--hat3", .val = 0x02},
{.opt = "--hat4", .val = 0x03},
{.opt = "--hatneutral", .val = 0x04},
{.opt = NULL}
};
int joystick_fill_report(char report[8], char buf[BUF_LEN], int *hold)
{
char *tok = strtok(buf, " ");
int mvt = 0;
int i = 0;
*hold = 1;
/* set default hat position: neutral */
report[3] = 0x04;
for (; tok != NULL; tok = strtok(NULL, " ")) {
if (strcmp(tok, "--quit") == 0)
return -1;
for (i = 0; jmod[i].opt != NULL; i++)
if (strcmp(tok, jmod[i].opt) == 0) {
report[3] = (report[3] & 0xF0) | jmod[i].val;
break;
}
if (jmod[i].opt != NULL)
continue;
if (!(tok[0] == '-' && tok[1] == '-') && mvt < 3) {
errno = 0;
report[mvt++] = (char)strtol(tok, NULL, 0);
if (errno != 0) {
fprintf(stderr, "Bad value:'%s'\n", tok);
report[mvt--] = 0;
}
continue;
}
fprintf(stderr, "unknown option: %s\n", tok);
}
return 4;
}
void print_options(char c)
{
int i = 0;
if (c == 'k') {
printf(" keyboard options:\n"
" --hold\n");
for (i = 0; kmod[i].opt != NULL; i++)
printf("\t\t%s\n", kmod[i].opt);
printf("\n keyboard values:\n"
" [a-z] or\n");
for (i = 0; kval[i].opt != NULL; i++)
printf("\t\t%-8s%s", kval[i].opt, i % 2 ? "\n" : "");
printf("\n");
} else if (c == 'm') {
printf(" mouse options:\n"
" --hold\n");
for (i = 0; mmod[i].opt != NULL; i++)
printf("\t\t%s\n", mmod[i].opt);
printf("\n mouse values:\n"
" Two signed numbers\n"
"--quit to close\n");
} else {
printf(" joystick options:\n");
for (i = 0; jmod[i].opt != NULL; i++)
printf("\t\t%s\n", jmod[i].opt);
printf("\n joystick values:\n"
" three signed numbers\n"
"--quit to close\n");
}
}
int main(int argc, const char *argv[])
{
const char *filename = NULL;
int fd = 0;
char buf[BUF_LEN];
int cmd_len;
char report[8];
int to_send = 8;
int hold = 0;
fd_set rfds;
int retval, i;
if (argc < 3) {
fprintf(stderr, "Usage: %s devname mouse|keyboard|joystick\n",
argv[0]);
return 1;
}
if (argv[2][0] != 'k' && argv[2][0] != 'm' && argv[2][0] != 'j')
return 2;
filename = argv[1];
if ((fd = open(filename, O_RDWR, 0666)) == -1) {
perror(filename);
return 3;
}
print_options(argv[2][0]);
while (42) {
FD_ZERO(&rfds);
FD_SET(STDIN_FILENO, &rfds);
FD_SET(fd, &rfds);
retval = select(fd + 1, &rfds, NULL, NULL, NULL);
if (retval == -1 && errno == EINTR)
continue;
if (retval < 0) {
perror("select()");
return 4;
}
if (FD_ISSET(fd, &rfds)) {
cmd_len = read(fd, buf, BUF_LEN - 1);
printf("recv report:");
for (i = 0; i < cmd_len; i++)
printf(" %02x", buf[i]);
printf("\n");
}
if (FD_ISSET(STDIN_FILENO, &rfds)) {
memset(report, 0x0, sizeof(report));
cmd_len = read(STDIN_FILENO, buf, BUF_LEN - 1);
if (cmd_len == 0)
break;
buf[cmd_len - 1] = '\0';
hold = 0;
memset(report, 0x0, sizeof(report));
if (argv[2][0] == 'k')
to_send = keyboard_fill_report(report, buf, &hold);
else if (argv[2][0] == 'm')
to_send = mouse_fill_report(report, buf, &hold);
else
to_send = joystick_fill_report(report, buf, &hold);
if (to_send == -1)
break;
if (write(fd, report, to_send) != to_send) {
perror(filename);
return 5;
}
if (!hold) {
memset(report, 0x0, sizeof(report));
if (write(fd, report, to_send) != to_send) {
perror(filename);
return 6;
}
}
}
}
close(fd);
return 0;
}
四. 参考文献:
[1] $(kernel_root)/Documentation/usb/gadget_hid.txt