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usb hid gadget驱动
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一. usb gadget框架层次
1.1 驱动层
1.2 复合层
1.3 控制器驱动层
二. 初始化流程
2.1 驱动层介绍
2.2 hidg驱动初始化详解
2.1 至上而下遍历：搜索绑定驱动和设备
2.2 至下而上遍历：完成初始化
三. hid gadget应用
四. 参考文献:
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 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 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 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 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 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 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 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 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 #include #include #include #include #include #include #include #include #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 |
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