本文深入解析USBgadget机制，涵盖gadgetdriver与composite_driver的交互，详细阐述gadgetdriver的匹配过程，composite_bind函数的工作原理，以及USB请求的处理流程。文章还探讨了structusb_composite_dev和structusb_composite_driver的结构，ep0端点的配置，以及gadget与gadget_driver之间的绑定。同时，文中分析了USB设备描述符和字符串描述符的初始化，以及配置描述符的使用。
USB gadget----gadget driver
USB gadget Driver
USB gadget(1)----controller driver中，匹配gadget driver时，调用bind函数，这里调用的就是composite_bind。
struct usb_composite_driver 是struct usb_gadget_driver的子类，可以通过usb_gadget_driver获取相应的usb_composite_driver,执行子类的函数完成多态。
serial.c中初始化usb_composite_driver内的设备描述符和字符串描述符，实现多态需要的bind和unbind函数。
模块初始化函数init中，初始化配置描述符的相关字段，和设备描述符的设备类字段，iproduct的字符串描述符的index。
//drivers/usb/gadget/legacy/serial.c
struct usb_composite_dev {
struct usb_gadget *gadget;
struct usb_request *req;
struct usb_request *os_desc_req;
struct usb_configuration *config;
/* OS String is a custom (yet popular) extension to the USB standard. */
u8 qw_sign[OS_STRING_QW_SIGN_LEN];
u8 b_vendor_code;
struct usb_configuration *os_desc_config;
unsigned int use_os_string:1;
/* private: */
/* internals */
unsigned int suspended:1;
struct usb_device_descriptor desc;
struct list_head configs;
struct list_head gstrings;
struct usb_composite_driver *driver;
u8 next_string_id;
char *def_manufacturer;
/* the gadget driver won't enable the data pullup
* while the deactivation count is nonzero.
*/
unsigned deactivations;
/* the composite driver won't complete the control transfer's
* data/status stages till delayed_status is zero.
*/
int delayed_status;
/* protects deactivations and delayed_status counts*/
spinlock_t lock;
unsigned setup_pending:1;
unsigned os_desc_pending:1;
};
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 *);
//gadaget 结构，usb_composite_driver是gadget driver的子类。
struct usb_gadget_driver gadget_driver;
};
static struct usb_composite_driver gserial_driver = {
.name = "g_serial",
.dev = &device_desc,
.strings = dev_strings,
.max_speed = USB_SPEED_SUPER,
.bind = gs_bind,
.unbind = gs_unbind,
};
static int __init init(void)
{
/* We *could* export two configs; that'd be much cleaner...
* but neither of these product IDs was defined that way.
*/
if (use_acm) {
serial_config_driver.label = "CDC ACM config";
serial_config_driver.bConfigurationValue = 2;
device_desc.bDeviceClass = USB_CLASS_COMM;
device_desc.idProduct =
cpu_to_le16(GS_CDC_PRODUCT_ID);
} else if (use_obex) {
serial_config_driver.label = "CDC OBEX config";
serial_config_driver.bConfigurationValue = 3;
device_desc.bDeviceClass = USB_CLASS_COMM;
device_desc.idProduct =
cpu_to_le16(GS_CDC_OBEX_PRODUCT_ID);
} else {
serial_config_driver.label = "Generic Serial config";
serial_config_driver.bConfigurationValue = 1;
device_desc.bDeviceClass = USB_CLASS_VENDOR_SPEC;
device_desc.idProduct =
cpu_to_le16(GS_PRODUCT_ID);
}
strings_dev[STRING_DESCRIPTION_IDX].s = serial_config_driver.label;
return usb_composite_probe(&gserial_driver);
}
struct usb_configuration {
const char *label;
struct usb_gadget_strings **strings;
const struct usb_descriptor_header **descriptors;
/* REVISIT: bind() functions can be marked __init, which
* makes trouble for section mismatch analysis. See if
* we can't restructure things to avoid mismatching...
*/
/* configuration management: unbind/setup */
void (*unbind)(struct usb_configuration *);
int (*setup)(struct usb_configuration *,
const struct usb_ctrlrequest *);
/* fields in the config descriptor */
u8 bConfigurationValue; //configuration的编号
u8 iConfiguration; //configuration字符串描述符的index
u8 bmAttributes;
u16 MaxPower;
struct usb_composite_dev *cdev;
/* private: */
/* internals */
struct list_head list;
struct list_head functions;
u8 next_interface_id;
unsigned superspeed:1;
unsigned highspeed:1;
unsigned fullspeed:1;
unsigned superspeed_plus:1;
struct usb_function *interface[MAX_CONFIG_INTERFACES];
};
usb_composite_probe(&gserial_driver)函数开始gadget和gadget_driver的匹配，gadget_driver在composite_driver中。usb_composite_probe(struct usb_composite_driver *driver) 函数中使用composite_driver_template模板将composite_driver中的gadget_driver初始化。usb_gadget_probe_driver(gadget_driver)真正开始gadget和gadget_driver的匹配。匹配成功后调用composite_dirver回调函数开始bind。composite_bind的动作如下：
- 通过gadget_driver获取composite_driver. 通过父类获取子类。
- 使用composite_dev_prepare(composite, cdev)创建composite_dev。
- 调用composite_driver中的bind回调函数
struct usb_composite_dev有如下的一些关键元素： - ep0 使用的struct usb_request
struct usb_request *req;
- struct usb_device_descriptor desc 设备描述符在composite_bind函数中从composite_driver中拷贝初始化。
- struct list_head configs， struct usb_configuration链表，在usb_add_config_only() 中将传递的usb_configuration加入到链表中。
///drivers/usb/gadget/composite.c
int usb_composite_probe(struct usb_composite_driver *driver)
{
struct usb_gadget_driver *gadget_driver;
if (!driver || !driver->dev || !driver->bind)
return -EINVAL;
if (!driver->name)
driver->name = "composite";
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);//与udc进行匹配
}
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,
.filteroutdata = composite_filteroutdata,
.driver = {
.owner = THIS_MODULE,
},
};
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);
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;
}
composite_dev_prepare(composite, cdev) 分配ep0用到的usb request
int composite_dev_prepare(struct usb_composite_driver *composite,
struct usb_composite_dev *cdev)
{
struct usb_gadget *gadget = cdev->gadget;
int ret = -ENOMEM;
/* preallocate control response and buffer */
/*分配ep0用到request*/
cdev->req = usb_ep_alloc_request(gadget->ep0, GFP_KERNEL);
if (!cdev->req)
return -ENOMEM;
cdev->req->buf = kmalloc(USB_COMP_EP0_BUFSIZ, GFP_KERNEL);
if (!cdev->req->buf)
goto fail;
ret = device_create_file(&gadget->dev, &dev_attr_suspended);
if (ret)
goto fail_dev;
cdev->req->complete = composite_setup_complete;
cdev->req->context = cdev;
gadget->ep0->driver_data = cdev;
cdev->driver = composite;
/*
* As per USB compliance update, a device that is actively drawing
* more than 100mA from USB must report itself as bus-powered in
* the GetStatus(DEVICE) call.
*/
if (CONFIG_USB_GADGET_VBUS_DRAW <= USB_SELF_POWER_VBUS_MAX_DRAW)
usb_gadget_set_selfpowered(gadget);
/* interface and string IDs start at zero via kzalloc.
* we force endpoints to start unassigned; few controller
* drivers will zero ep->driver_data.
*/
usb_ep_autoconfig_reset(gadget);
return 0;
fail_dev:
kfree(cdev->req->buf);
fail:
usb_ep_free_request(gadget->ep0, cdev->req);
cdev->req = NULL;
return ret;
}
static void composite_setup_complete(struct usb_ep *ep, struct usb_request *req)
{
struct usb_composite_dev *cdev;
if (req->status || req->actual != req->length)
DBG((struct usb_composite_dev *) ep->driver_data,
"setup complete --> %d, %d/%d\n",
req->status, req->actual, req->length);
/*
* REVIST The same ep0 requests are shared with function drivers
* so they don't have to maintain the same ->complete() stubs.
*
* Because of that, we need to check for the validity of ->context
* here, even though we know we've set it to something useful.
*/
if (!req->context)
return;
cdev = req->context;
if (cdev->req == req)
cdev->setup_pending = false;
else if (cdev->os_desc_req == req)
cdev->os_desc_pending = false;
else
WARN(1, "unknown request %p\n", req);
}
struct usb_gadget_driver {
char *function;
enum usb_device_speed max_speed;
int (*bind)(struct usb_gadget *gadget,
struct usb_gadget_driver *driver);
void (*unbind)(struct usb_gadget *);
int (*setup)(struct usb_gadget *,
const struct usb_ctrlrequest *);
void (*disconnect)(struct usb_gadget *);
void (*suspend)(struct usb_gadget *);
void (*resume)(struct usb_gadget *);
void (*reset)(struct usb_gadget *);
int (*filteroutdata)(struct usb_gadget *,
const struct usb_ctrlrequest *,
u8 *, int);
/* FIXME support safe rmmod */
struct device_driver driver;
char *udc_name;
struct list_head pending;
unsigned match_existing_only:1;
};
struct usb_request {
void *buf;
unsigned length;
dma_addr_t dma;
struct scatterlist *sg;
unsigned num_sgs;
unsigned num_mapped_sgs;
unsigned stream_id:16;
unsigned no_interrupt:1;
unsigned zero:1;
unsigned short_not_ok:1;
void (*complete)(struct usb_ep *ep,
struct usb_request *req);
void *context;
struct list_head list;
int status;
unsigned actual;
};
usb_get_function_instance()函数根据name参数去查找func_list链表中已经注册的function_driver, 找到之后调用alloc_inst()回调函数反回struct usb_function_instance.
gser_alloc_inst(void)中做了两件事情：
- 分配struct usb_function_instance结构。
- 调用gserial_alloc_line()创建usb serial上层的串口设施。
struct usb_function_instance {
struct config_group group;
struct list_head cfs_list;
struct usb_function_driver *fd;
int (*set_inst_name)(struct usb_function_instance *inst,
const char *name);
void (*free_func_inst)(struct usb_function_instance *inst);
};
struct usb_function_driver {
const char *name;
struct module *mod;
struct list_head list;
struct usb_function_instance *(*alloc_inst)(void);
struct usb_function *(*alloc_func)(struct usb_function_instance *inst);
};
struct f_serial_opts {
struct usb_function_instance func_inst;
u8 port_num;
};
static struct usb_function_instance *gser_alloc_inst(void)
{
struct f_serial_opts *opts;
int ret;
opts = kzalloc(sizeof(*opts), GFP_KERNEL);
if (!opts)
return ERR_PTR(-ENOMEM);
opts->func_inst.free_func_inst = gser_free_inst;
ret = gserial_alloc_line(&opts->port_num);
if (ret) {
kfree(opts);
return ERR_PTR(ret);
}
config_group_init_type_name(&opts->func_inst.group, "",
&serial_func_type);
return &opts->func_inst;
}
usb_get_funtion()使用struct usb_function_instance的struct usb_function_driver元素的alloc_func()回调函数分配struct usb_function结构
struct usb_function {
const char *name;
struct usb_gadget_strings **strings;
struct usb_descriptor_header **fs_descriptors;
struct usb_descriptor_header **hs_descriptors;
struct usb_descriptor_header **ss_descriptors;
struct usb_descriptor_header **ssp_descriptors;
struct usb_configuration *config; /*当前使能的配置*/
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 运行时状态管理*/
int (*set_alt)(struct usb_function *,
unsigned interface, unsigned alt); /*使能注册的每个接口，包括*/
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 *,
bool config0);
void (*suspend)(struct usb_function *);
void (*resume)(struct usb_function *);
int (*filteroutdata)(struct usb_function *,
const struct usb_ctrlrequest *,
u8 *buf,
int len);
/* 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;
};
struct f_acm {
struct gserial port;
u8 ctrl_id, data_id;
u8 port_num;
u8 pending;
/* lock is mostly for pending and notify_req ... they get accessed
* by callbacks both from tty (open/close/break) under its spinlock,
* and notify_req.complete() which can't use that lock.
*/
spinlock_t lock;
struct usb_ep *notify;
struct usb_request *notify_req;
struct usb_cdc_line_coding port_line_coding; /* 8-N-1 etc */
/* SetControlLineState request -- CDC 1.1 section 6.2.14 (INPUT) */
u16 port_handshake_bits;
#define ACM_CTRL_RTS (1 << 1) /* unused with full duplex */
#define ACM_CTRL_DTR (1 << 0) /* host is ready for data r/w */
/* SerialState notification -- CDC 1.1 section 6.3.5 (OUTPUT) */
u16 serial_state;
#define ACM_CTRL_OVERRUN (1 << 6)
#define ACM_CTRL_PARITY (1 << 5)
#define ACM_CTRL_FRAMING (1 << 4)
#define ACM_CTRL_RI (1 << 3)
#define ACM_CTRL_BRK (1 << 2)
#define ACM_CTRL_DSR (1 << 1)
#define ACM_CTRL_DCD (1 << 0)
};
struct gserial {
struct usb_function func;
/* port is managed by gserial_{connect,disconnect} */
struct gs_port *ioport;
struct usb_ep *in;
struct usb_ep *out;
/* REVISIT avoid this CDC-ACM support harder ... */
struct usb_cdc_line_coding port_line_coding; /* 9600-8-N-1 etc */
/* notification callbacks */
void (*connect)(struct gserial *p);
void (*disconnect)(struct gserial *p);
int (*send_break)(struct gserial *p, int duration);
};
static struct usb_function *acm_alloc_func(struct usb_function_instance *fi)
{
struct f_serial_opts *opts;
struct f_acm *acm;
acm = kzalloc(sizeof(*acm), GFP_KERNEL);
if (!acm)
return ERR_PTR(-ENOMEM);
spin_lock_init(&acm->lock);
acm->port.connect = acm_connect;
acm->port.disconnect = acm_disconnect;
acm->port.send_break = acm_send_break;
acm->port.func.name = "acm";
acm->port.func.strings = acm_strings;
/* descriptors are per-instance copies */
acm->port.func.bind = acm_bind;
acm->port.func.set_alt = acm_set_alt;
acm->port.func.setup = acm_setup;
acm->port.func.disable = acm_disable;
opts = container_of(fi, struct f_serial_opts, func_inst);
acm->port_num = opts->port_num;
acm->port.func.unbind = acm_unbind;
acm->port.func.free_func = acm_free_func;
return &acm->port.func;
}
static struct usb_function *acm_alloc_func(struct usb_function_instance *fi) 分配struct f_acm结构，填充内部struct gserial port中的回调函数和port中struct usb_function的回调函数。
获取到struct usb_function 后最后调用到acm_bind()
/* ACM function driver setup/binding */
static int
acm_bind(struct usb_configuration *c, struct usb_function *f)
{
struct usb_composite_dev *cdev = c->cdev;
struct f_acm *acm = func_to_acm(f);
struct usb_string *us;
int status;
struct usb_ep *ep;
/* REVISIT might want instance-specific strings to help
* distinguish instances ...
*/
/* maybe allocate device-global string IDs, and patch descriptors */
us = usb_gstrings_attach(cdev, acm_strings,
ARRAY_SIZE(acm_string_defs));
if (IS_ERR(us))
return PTR_ERR(us);
acm_control_interface_desc.iInterface = us[ACM_CTRL_IDX].id;
acm_data_interface_desc.iInterface = us[ACM_DATA_IDX].id;
acm_iad_descriptor.iFunction = us[ACM_IAD_IDX].id;
/* allocate instance-specific interface IDs, and patch descriptors */
status = usb_interface_id(c, f);
if (status < 0)
goto fail;
acm->ctrl_id = status;
acm_iad_descriptor.bFirstInterface = status;
acm_control_interface_desc.bInterfaceNumber = status;
acm_union_desc .bMasterInterface0 = status;
status = usb_interface_id(c, f);
if (status < 0)
goto fail;
acm->data_id = status;
acm_data_interface_desc.bInterfaceNumber = status;
acm_union_desc.bSlaveInterface0 = status;
acm_call_mgmt_descriptor.bDataInterface = status;
status = -ENODEV;
/* allocate instance-specific endpoints */
ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_in_desc);
if (!ep)
goto fail;
acm->port.in = ep;
ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_out_desc);
if (!ep)
goto fail;
acm->port.out = ep;
ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_notify_desc);
if (!ep)
goto fail;
acm->notify = ep;
/* allocate notification */
acm->notify_req = gs_alloc_req(ep,
sizeof(struct usb_cdc_notification) + 2,
GFP_KERNEL);
if (!acm->notify_req)
goto fail;
acm->notify_req->complete = acm_cdc_notify_complete;
acm->notify_req->context = acm;
/* support all relevant hardware speeds... we expect that when
* hardware is dual speed, all bulk-capable endpoints work at
* both speeds
*/
acm_hs_in_desc.bEndpointAddress = acm_fs_in_desc.bEndpointAddress;
acm_hs_out_desc.bEndpointAddress = acm_fs_out_desc.bEndpointAddress;
acm_hs_notify_desc.bEndpointAddress =
acm_fs_notify_desc.bEndpointAddress;
acm_ss_in_desc.bEndpointAddress = acm_fs_in_desc.bEndpointAddress;
acm_ss_out_desc.bEndpointAddress = acm_fs_out_desc.bEndpointAddress;
status = usb_assign_descriptors(f, acm_fs_function, acm_hs_function,
acm_ss_function, NULL);
if (status)
goto fail;
dev_dbg(&cdev->gadget->dev,
"acm ttyGS%d: %s speed IN/%s OUT/%s NOTIFY/%s\n",
acm->port_num,
gadget_is_superspeed(c->cdev->gadget) ? "super" :
gadget_is_dualspeed(c->cdev->gadget) ? "dual" : "full",
acm->port.in->name, acm->port.out->name,
acm->notify->name);
return 0;
fail:
if (acm->notify_req)
gs_free_req(acm->notify, acm->notify_req);
ERROR(cdev, "%s/%p: can't bind, err %d\n", f->name, f, status);
return status;
}
usb_gstrings_attach(cdev, acm_strings,
ARRAY_SIZE(acm_string_defs));
上面的函数将struct usb_gadget_string 和struct usb_string 组建为协议中规定的格式。
status = usb_interface_id(c, f);
分配可用的interface id，相关的变量为struct usb_configuration 中的next_interface_id.
ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_in_desc);
if (!ep)
goto fail;
acm->port.in = ep;
ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_out_desc);
if (!ep)
goto fail;
acm->port.out = ep;
ep = usb_ep_autoconfig(cdev->gadget, &acm_fs_notify_desc);
if (!ep)
goto fail;
acm->notify = ep;
根据给出的端点描述符选择合适端点，ep_list在controller driver中初始化，ep_list由gadget管理。
//epautoconf.c
struct usb_ep *usb_ep_autoconfig(
struct usb_gadget *gadget,
struct usb_endpoint_descriptor *desc
)
{
return usb_ep_autoconfig_ss(gadget, desc, NULL);
}
struct usb_ep *usb_ep_autoconfig_ss(
struct usb_gadget *gadget,
struct usb_endpoint_descriptor *desc,
struct usb_ss_ep_comp_descriptor *ep_comp
)
{
struct usb_ep *ep;
u8 type;
type = desc->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK;
if (gadget->ops->match_ep) {
ep = gadget->ops->match_ep(gadget, desc, ep_comp);
if (ep)
goto found_ep;
}
/* Second, look at endpoints until an unclaimed one looks usable */
list_for_each_entry (ep, &gadget->ep_list, ep_list) {
if (usb_gadget_ep_match_desc(gadget, ep, desc, ep_comp))
goto found_ep;
}
/* Fail */
return NULL;
found_ep:
/*
* If the protocol driver hasn't yet decided on wMaxPacketSize
* and wants to know the maximum possible, provide the info.
*/
if (desc->wMaxPacketSize == 0)
desc->wMaxPacketSize = cpu_to_le16(ep->maxpacket_limit);
/* report address */
desc->bEndpointAddress &= USB_DIR_IN;
if (isdigit(ep->name[2])) {
u8 num = simple_strtoul(&ep->name[2], NULL, 10);
desc->bEndpointAddress |= num;
} else if (desc->bEndpointAddress & USB_DIR_IN) {
if (++gadget->in_epnum > 15)
return NULL;
desc->bEndpointAddress = USB_DIR_IN | gadget->in_epnum;
} else {
if (++gadget->out_epnum > 15)
return NULL;
desc->bEndpointAddress |= gadget->out_epnum;
}
/* report (variable) full speed bulk maxpacket */
if ((type == USB_ENDPOINT_XFER_BULK) && !ep_comp) {
int size = ep->maxpacket_limit;
/* min() doesn't work on bitfields with gcc-3.5 */
if (size > 64)
size = 64;
desc->wMaxPacketSize = cpu_to_le16(size);
}
ep->address = desc->bEndpointAddress;
ep->desc = NULL;
ep->comp_desc = NULL;
ep->claimed = true;
return ep;
}
acm->notify_req = gs_alloc_req(ep,
sizeof(struct usb_cdc_notification) + 2,
GFP_KERNEL);
if (!acm->notify_req)
goto fail;
acm->notify_req->complete = acm_cdc_notify_complete;
acm->notify_req->context = acm;
分配struct usb_request, 端点的回调函数定义参考USB gadget(1)----controller driver
/*-------------------------------------------------------------------------*/
/* I/O glue between TTY (upper) and USB function (lower) driver layers */
/*
* gs_alloc_req
*
* Allocate a usb_request and its buffer. Returns a pointer to the
* usb_request or NULL if there is an error.
*/
struct usb_request *
gs_alloc_req(struct usb_ep *ep, unsigned len, gfp_t kmalloc_flags)
{
struct usb_request *req;
req = usb_ep_alloc_request(ep, kmalloc_flags);
if (req != NULL) {
req->length = len;
req->buf = kmalloc(len, kmalloc_flags);
if (req->buf == NULL) {
usb_ep_free_request(ep, req);
return NULL;
}
}
return req;
}
struct usb_request *usb_ep_alloc_request(struct usb_ep *ep,
gfp_t gfp_flags)
{
struct usb_request *req = NULL;
req = ep->ops->alloc_request(ep, gfp_flags);
trace_usb_ep_alloc_request(ep, req, req ? 0 : -ENOMEM);
return req;
}
void usb_ep_free_request(struct usb_ep *ep,
struct usb_request *req)
{
trace_usb_ep_free_request(ep, req, 0);
ep->ops->free_request(ep, req);
}
status = usb_assign_descriptors(f, acm_fs_function, acm_hs_function,
acm_ss_function, NULL);
将相关的描述符拷贝到struct usb_function中。
int usb_assign_descriptors(struct usb_function *f,
struct usb_descriptor_header **fs,
struct usb_descriptor_header **hs,
struct usb_descriptor_header **ss,
struct usb_descriptor_header **ssp)
{
struct usb_gadget *g = f->config->cdev->gadget;
if (fs) {
f->fs_descriptors = usb_copy_descriptors(fs);
if (!f->fs_descriptors)
goto err;
}
if (hs && gadget_is_dualspeed(g)) {
f->hs_descriptors = usb_copy_descriptors(hs);
if (!f->hs_descriptors)
goto err;
}
if (ss && gadget_is_superspeed(g)) {
f->ss_descriptors = usb_copy_descriptors(ss);
if (!f->ss_descriptors)
goto err;
}
if (ssp && gadget_is_superspeed_plus(g)) {
f->ssp_descriptors = usb_copy_descriptors(ssp);
if (!f->ssp_descriptors)
goto err;
}
return 0;
err:
usb_free_all_descriptors(f);
return -ENOMEM;
}
utilities for usb gadget function
usb gadget function 是做为usb设备来实现上层的特殊功能，usb 目录下u_前缀的文件是实现特定功能的基础和组件。以u_serial为例。
userial_init 中主要分配了struct tty_driver结构，tty_driver是tty终端设备的核心结构。
参考Linux UART Console Driver(1)–硬件设备的注册和UART Driver的注册
static int userial_init(void)
{
unsigned i;
int status;
gs_tty_driver = alloc_tty_driver(MAX_U_SERIAL_PORTS);
if (!gs_tty_driver)
return -ENOMEM;
gs_tty_driver->driver_name = "g_serial";
gs_tty_driver->name = "ttyGS";
/* uses dynamically assigned dev_t values */
gs_tty_driver->type = TTY_DRIVER_TYPE_SERIAL;
gs_tty_driver->subtype = SERIAL_TYPE_NORMAL;
gs_tty_driver->flags = TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV;
gs_tty_driver->init_termios = tty_std_termios;
/* 9600-8-N-1 ... matches defaults expected by "usbser.sys" on
* MS-Windows. Otherwise, most of these flags shouldn't affect
* anything unless we were to actually hook up to a serial line.
*/
gs_tty_driver->init_termios.c_cflag =
B9600 | CS8 | CREAD | HUPCL | CLOCAL;
gs_tty_driver->init_termios.c_ispeed = 9600;
gs_tty_driver->init_termios.c_ospeed = 9600;
tty_set_operations(gs_tty_driver, &gs_tty_ops);
for (i = 0; i < MAX_U_SERIAL_PORTS; i++)
mutex_init(&ports[i].lock);
/* export the driver ... */
status = tty_register_driver(gs_tty_driver);
if (status) {
pr_err("%s: cannot register, err %d\n",
__func__, status);
goto fail;
}
pr_debug("%s: registered %d ttyGS* device%s\n", __func__,
MAX_U_SERIAL_PORTS,
(MAX_U_SERIAL_PORTS == 1) ? "" : "s");
return status;
fail:
put_tty_driver(gs_tty_driver);
gs_tty_driver = NULL;
return status;
}
module_init(userial_init);
gserial_alloc_line() 函数创建gs_port, 添加ttyGS0。
int gserial_alloc_line(unsigned char *line_num)
{
struct usb_cdc_line_coding coding;
struct device *tty_dev;
int ret;
int port_num;
coding.dwDTERate = cpu_to_le32(9600);
coding.bCharFormat = 8;
coding.bParityType = USB_CDC_NO_PARITY;
coding.bDataBits = USB_CDC_1_STOP_BITS;
for (port_num = 0; port_num < MAX_U_SERIAL_PORTS; port_num++) {
ret = gs_port_alloc(port_num, &coding);
if (ret == -EBUSY)
continue;
if (ret)
return ret;
break;
}
if (ret)
return ret;
/* ... and sysfs class devices, so mdev/udev make /dev/ttyGS* */
tty_dev = tty_port_register_device(&ports[port_num].port->port,
gs_tty_driver, port_num, NULL);
if (IS_ERR(tty_dev)) {
struct gs_port *port;
pr_err("%s: failed to register tty for port %d, err %ld\n",
__func__, port_num, PTR_ERR(tty_dev));
ret = PTR_ERR(tty_dev);
port = ports[port_num].port;
ports[port_num].port = NULL;
gserial_free_port(port);
goto err;
}
*line_num = port_num;
gserial_console_init();
err:
return ret;
}
struct gs_port 结构类似Linux UART Console Driver(1)–硬件设备的注册和UART Driver的注册 中的struct uart_state结构，在串口驱动中底层硬件是uart，struct uart_state 内部包含struct tty_port, struct uart_state构成了串口下层的ringbuf系统。类似的gs_port跟struct uart_state结构类似。
static int
gs_port_alloc(unsigned port_num, struct usb_cdc_line_coding *coding)
{
struct gs_port *port;
int ret = 0;
mutex_lock(&ports[port_num].lock);
if (ports[port_num].port) {
ret = -EBUSY;
goto out;
}
port = kzalloc(sizeof(struct gs_port), GFP_KERNEL);
if (port == NULL) {
ret = -ENOMEM;
goto out;
}
tty_port_init(&port->port);
spin_lock_init(&port->port_lock);
init_waitqueue_head(&port->drain_wait);
init_waitqueue_head(&port->close_wait);
tasklet_init(&port->push, gs_rx_push, (unsigned long) port); // gs_rx_push 是解说tasklet负责将接收到的usb_request从read_pool
INIT_LIST_HEAD(&port->read_pool);
INIT_LIST_HEAD(&port->read_queue);
INIT_LIST_HEAD(&port->write_pool);
port->port_num = port_num;
port->port_line_coding = *coding;
ports[port_num].port = port;
out:
mutex_unlock(&ports[port_num].lock);
return ret;
}
struct gs_port {
struct tty_port port;
spinlock_t port_lock; /* guard port_* access */
struct gserial *port_usb;
bool openclose; /* open/close in progress */
u8 port_num;
struct list_head read_pool;
int read_started;
int read_allocated;
struct list_head read_queue;
unsigned n_read;
struct tasklet_struct push;
struct list_head write_pool;
int write_started;
int write_allocated;
struct gs_buf port_write_buf;
wait_queue_head_t drain_wait; /* wait while writes drain */
bool write_busy;
wait_queue_head_t close_wait;
/* REVISIT this state ... */
struct usb_cdc_line_coding port_line_coding; /* 8-N-1 etc */
};
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