usb设备驱动程序usb gadget driver(4)

USB设备驱动程序-USB Gadget Driver(4)  Gadget 功能层Gadget功能层完成USB设备的具体功能,其表现的形式各不相同,如键盘、鼠标、存储和网卡等等。功能层不仅涉及到Gadget驱动相关的 内容 财务内部控制制度的内容财务内部控制制度的内容人员招聘与配置的内容项目成本控制的内容消防安全演练内容 ,还涉及到其功能相关的内核子系统。如存储还涉及到内核存储子系统,网卡还涉及到网络驱动子系统。因此,Gadget功能的代码非常复杂。这里以zero.c为例,这个模块只是简单地将接收的数据回显回去。一、数据结构首先需要实现 usb_composite_driver函数集:static struct usb_composite_driver zero_driver = { .name = "zero", .dev = &device_desc, .strings = dev_strings, .bind = zero_bind, .unbind = zero_unbind, .suspend = zero_suspend, .resume = zero_resume, }; 二、主要函数这个模块的实现就是这么简单:static int __init init(void) { return usb_composite_register(&zero_driver); } module_init(init); static void __exit cleanup(void) { usb_composite_unregister(&zero_driver); } Bind函数是功能层需要实现与设备层关联的重要函数:static int __init zero_bind(struct usb_composite_dev *cdev) { int gcnum; struct usb_gadget *gadget = cdev->gadget; //Gadget设备 int id; /* Allocate string descriptor numbers ... note that string * contents can be overridden by the composite_dev glue. */ /*分配字符串描述符的id,并赋值给设备描述符中字符串索引*/ id = usb_string_id(cdev); strings_dev[STRING_MANUFACTURER_IDX].id = id; device_desc.iManufacturer = id; id = usb_string_id(cdev); i strings_dev[STRING_PRODUCT_IDX].id = id; device_desc.iProduct = id; id = usb_string_id(cdev); strings_dev[STRING_SERIAL_IDX].id = id; device_desc.iSerialNumber = id; /*设置挂起后,设备自动恢复的定时器*/ setup_timer(&autoresume_timer, zero_autoresume, (unsigned long) cdev); /*核心代码,实现 功能*/ if (loopdefault) { loopback_add(cdev, autoresume != 0); //数据简单回显功能 if (!gadget_is_sh(gadget)) sourcesink_add(cdev, autoresume != 0); } else { sourcesink_add(cdev, autoresume != 0); if (!gadget_is_sh(gadget)) loopback_add(cdev, autoresume != 0); } /*初始化设备描述符*/ gcnum = usb_gadget_controller_number(gadget); if (gcnum >= 0) device_desc.bcdDevice = cpu_to_le16(0x0200 + gcnum); else { device_desc.bcdDevice = cpu_to_le16(0x9999); } return 0; } /*增加数据简单回显功能*/ int __init loopback_add(struct usb_composite_dev *cdev, bool autoresume) { int id; /*获取字符串描述符id索引*/ id = usb_string_id(cdev); strings_loopback[0].id = id; loopback_intf.iInterface = id; loopback_driver.iConfiguration = id; /* support autoresume for remote wakeup testing */ if (autoresume) sourcesink_driver.bmAttributes |= USB_CONFIG_ATT_WAKEUP; /* support OTG systems */ if (gadget_is_otg(cdev->gadget)) { loopback_driver.descriptors = otg_desc; loopback_driver.bmAttributes |= USB_CONFIG_ATT_WAKEUP; } return usb_add_config(cdev, &loopback_driver); //增加一个配置} /*loopback配置*/ static struct usb_configuration loopback_driver = { .label = "loopback", .strings = loopback_strings, .bind = loopback_bind_config, .bC onfigurationValue = 2, .bmAttributes = USB_CONFIG_ATT_SELFPOWER, /* .iConfiguration = DYNAMIC */ }; 将增加配置的 usb_add_config函数中会调用其bind函数,即 loopback_bind_config函数,来分配这个配置所需要的资源。struct f_loopback { struct usb_function function; struct usb_ep *in_ep; struct usb_ep *out_ep; }; static int __init loopback_bind_config(struct usb_configuration *c) { struct f_loopback *loop; int status; loop = kzalloc(sizeof *loop, GFP_KERNEL); //分配一个loop结构 if (!loop) return -ENOMEM; /*初始化一个功能*/ loop->function.name = "loopback"; loop->function.descriptors = fs_loopback_descs; loop->function.bind = loopback_bind; loop->function.unbind = loopback_unbind; loop->function.set_alt = loopback_set_alt; loop->function.disable = loopback_disable; status = usb_add_function(c, &loop->function); //加入这个功能if (status) kfree(loop); return status; } 在usb_add_function函数中,又会调用这个功能的bind函数,即loopback_bind函数:static int __init loopback_bind(struct usb_configuration *c, struct usb_function *f) { struct usb_composite_dev *cdev = c->cdev; struct f_loopback *loop = func_to_loop(f); int id; /* allocate interface ID(s) */ id = usb_interface_id(c, f); //分配一个接口id if (id < 0) return id; loopback_intf.bInterfaceNumber = id; /* allocate endpoints */ /*返回一个输入端点*/ loop->in_ep = usb_ep_autoconfig(cdev->gadget, &fs_loop_source_desc); if (!loop->in_ep) { autoco nf_fail: ERROR(cdev, "%s: can't autoconfigure on %s\n", f->name, cdev->gadget->name); return -ENODEV; } loop->in_ep->driver_data = cdev; /* claim */ /*返回一个输出端点,返回合适的端点*/ loop->out_ep = usb_ep_autoconfig(cdev->gadget, &fs_loop_sink_desc); if (!loop->out_ep) goto autoconf_fail; loop->out_ep->driver_data = cdev; /* claim */ /* support high speed hardware */ if (gadget_is_dualspeed(c->cdev->gadget)) { hs_loop_source_desc.bEndpointAddress = fs_loop_source_desc.bEndpointAddress; hs_loop_sink_desc.bEndpointAddress = fs_loop_sink_desc.bEndpointAddress; f->hs_descriptors = hs_loopback_descs; } DBG(cdev, "%s speed %s: IN/%s, OUT/%s\n", gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",f->name, loop->in_ep->name, loop->out_ep->name); return 0; } 功能的实现Loopback_set_alt函数将在设备层的setup函数中被调用,控制通信设置接口。static int loopback_set_alt(struct usb_function *f, unsigned intf, unsigned alt) { struct f_loopback *loop = func_to_loop(f); struct usb_composite_dev *cdev = f->config->cdev; /* we know alt is zero */ if (loop->in_ep->driver_data) disable_loopback(loop); return enable_loopback(cdev, loop); //开启功能} static int enable_loopback(struct usb_composite_dev *cdev, struct f_loopback *loop) { int result = 0; const struct usb_endpoint_descriptor *src, *sink; struct usb_ep *ep; struct usb_request *req; unsigned i; /*选择端点描述符*/ src = ep_choose(cdev->gadget, &hs_loop_source_desc, &fs_loop_source_desc); sink = ep_choose(cdev->gadget, &hs_loop_sink_desc, &fs_loop_sink_desc); /* one endpoint writes data back IN to the host */ /*输入输出端点使能*/ ep = loop->in_ep; result = usb_ep_enable(ep, src); if (result < 0) return result; ep->driver_data = loop; /* one endpoint just reads OUT packets */ ep = loop->out_ep; result = usb_ep_enable(ep, sink); if (result < 0) { fa il0: ep = loop->in_ep; usb_ep_disable(ep); ep->driver_data = NULL; return result; } ep->driver_data = loop; /* allocate a bunch of read buffers and queue them all at once. * we buffer at most 'qlen' transfers; fewer if any need more * than 'buflen' bytes each. */ /*qlen=32,分配32个请求,将这个请求放入输出端点队列,等待接收数据*/ for (i = 0; i < qlen && result == 0; i++) { req = alloc_ep_req(ep); if (req) { req->complete = loopback_complete; result = usb_ep_queue(ep, req, GFP_ATOMIC); if (result) ERROR(cdev, "%s queue req --> %d\n", ep->name, result); } else { usb_ep_disable(ep); ep->driver_data = NULL; result = -ENOMEM; goto fail0; } } DBG(cdev, "%s enabled\n", loop->function.name); return result; } /*接收到数据之后,将调用这个完成函数*/ static void loopback_complete(struct usb_ep *ep, struct usb_request *req) { struct f_loopback *loop = ep->driver_data; struct usb_composite_dev *cdev = loop->function.config->cdev; int status = req->status; switch (status) { case 0: /* normal completion? */ if (ep == loop->out_ep) { //将接收到的数据放入输入端点,返回给主机 /* loop this OUT packet back IN to the host */ req->zero = (req->actual < req->length); req->length = req->actual; status = usb_ep_queue(loop->in_ep, req, GFP_ATOMIC); if (status == 0) return; /* "should never get here" */ ERROR(cdev, "can't loop %s to %s: %d\n", ep->name, loop->in_ep->name,status); } /* queue the buffer for some later OUT packet */ req->length = buflen; //将输入端点完成的申请,重新放入输出队列,等待接收新的数据 status = usb_ep_queue(loop->out_ep, req, GFP_ATOMIC); if (status == 0) return; /* "should never get here" */ /* FALLTHROUGH */ default: ERROR(cdev, "%s loop complete --> %d, %d/%d\n", ep->name, status, req->actual, req->length); /* FALLTHROUGH */ /* NOTE: since this driver doesn't maintain an explicit record * of requests it submitted (just maintains qlen count), we * rely on the hardware driver to clean up on disconnect or * endpoint disable. */ case -ECONNABORTED: /* hardware forced ep reset */ case -ECONNRESET: /* request dequeued */ case -ESHUTDOWN: /* disconnect from host */ free_ep_req(ep, req); return; } }