该系列文章总目录链接与各部分简介： Android Qcom USB Driver学习(零)
了解什么是dwc3 udc gadget hcd xhci， 差点被Chatgpt绕晕了，看的比较浅显就像知道这些都是什么作用的。
UDC-Gadget
UDC：(USB Device Controller)用于管理和控制USB设备与主机之间的通信。
Gadget：Android在此层实现了adb，mtp(Media Transfer Protocol 媒体传输协议)，mass_storage等。
早期的USB只支持单一的gadget设备，使用场景较为简单，随后加入了composite framework，用来支持多个function的gadget设备，多个function的绑定在内核中完成，若需要修改，则需要修改内核，不灵活也不方便。Linux3.11版本引入了基于configfs的usb gadget configfs。
usb gadget configfs重新实现了复合设备层，可以在用户空间配置和组合内核的function，灵活的构成USB复合设备，极大了提高了工作效率。
system/core/rootdir/init.usb.configfs.rc
[persist.sys.usb.config]: [diag,adb]
[sys.usb.config]: [mtp,adb]
on property:sys.usb.ffs.ready=1 && property:sys.usb.config=mtp,adb && property:sys.usb.configfs=1
write /config/usb_gadget/g1/configs/b.1/strings/0x409/configuration "mtp_adb"
write /config/usb_gadget/g1/idVendor 0x0c2e
write /config/usb_gadget/g1/idProduct 0x0ba3
symlink /config/usb_gadget/g1/functions/mtp.gs0 /config/usb_gadget/g1/configs/b.1/f1
symlink /config/usb_gadget/g1/functions/ffs.adb /config/usb_gadget/g1/configs/b.1/f2
write /config/usb_gadget/g1/UDC ${
sys.usb.controller}
setprop sys.usb.state ${
sys.usb.config}
drivers/usb/gadget/configfs.c
drivers\usb\gadget\composite.c
drivers/usb/gadget/udc/core.c
drivers/usb/gadget/function/f_mtp.c
USB总线-Linux内核USB3.0设备控制器复合设备之USB gadget configfs分析
gadget -> composite -> function
make_group -> function_make -> usb_get_function_instance -> alloc_inst -> mtp_alloc_inst
每个function driver创建的时候会分配一个usb_function_instance
echo 4e00000.dwc3 > configs/usb_gadget/g1/UDC
usb_udc_attch_driver-> udc_bind_to_driver-> configfs_composite_bind
-> usb_add_function -> function->bind -> mtp_function_bind
HCD-XHCI
HCD：(Host Controller Driver)是主机控制器驱动，它是对主机控制器硬件的抽象。
XHCI：(eXtensible Host Controller Interface)也是主机控制器驱动，XHIC是基于USB3.0并且向下兼容，其中集成了两个roothub，一个对应usb2.0的(main_hcd)，一个对应usb3.0的(shared_hcd)
struct xhci_hcd {
/* usb_hcd结构体：用于描述USB主机控制器驱动*/
struct usb_hcd *main_hcd;
struct usb_hcd *shared_hcd;
/* glue to PCI and HCD framework */
struct xhci_cap_regs __iomem *cap_regs;
struct xhci_op_regs __iomem *op_regs;
struct xhci_run_regs __iomem *run_regs;
struct xhci_doorbell_array __iomem *dba;
/* Our HCD's current interrupter register set */
struct xhci_intr_reg __iomem *ir_set;
/* Cached register copies of read-only HC data */
__u32 hcs_params1;
...
spinlock_t lock;
/* packed release number */
u8 sbrn;
u16 hci_version;
...
...
...
};
root hub设备注册(三)
drivers/usb/host/xhci-plat.c
drivers/usb/core/hcd.c
drivers/usb/host/xhci.c
drivers/usb/core/hub.c
dwc3_otg_start_host -> dwc3_host_init -> platform_device_add(xhci) -> xhci_plat_probe
xhci->main_hcd = hcd;
usb_add_hcd(hcd, irq, IRQF_SHARED); //roothub对应usb0
usb_add_hcd(xhci->shared_hcd, irq, IRQF_SHARED);
hcd->driver->start(hcd) //hc_driver
xhci_run(hcd)
xhci_try_enable_msi(hcd)
hci_setup_msix(xhci)
xhci_irq(hcd)
---------------------------------------------------------------------------------
| xhci_handle_event(xhci) |
| case: TRB_PORT_STATUS |
| handle_port_status(xhci, event); |
| case: TRB_TRANSFER |
| handle_tx_event(xhci, &event->trans_event); |
| usb_hcd_giveback_urb |
| tasklet_schedule(&bh->bh); |
| kick_hub_wq(hub); |
| queue_work(hub_wq, &hub->events) |
| hub_event->port_event->hub_port_connect_change |
| ->hub_port_connect -> usb_new_device(udev); |
----------------------------------------------------------------------------------
register_root_hub(hcd)
usb_get_device_descriptor(usb_dev, USB_DT_DEVICE_SIZE)
usb_new_device (usb_dev)
usb_enumerate_device(udev)
announce_device(udev)/* 打印New USB device found*/
device_add(&udev->dev)
DWC3
DWC3：(DesignWare USB 3.0 Controller) 在Android系统中，dwc3通常被用作USB3.0主机控制器，用于与XHCI驱动程序配合使用，控制USB3.0设备与主机之间的通信。同时，dwc3还可以与Gadget驱动程序配合使用，将linux设备转为USB设备，实现设备与主机间的通信。
dwc3控制器初始化的时候会将控制器设置为USB_DR_MODE_OTG模式，同时调用dwc3_host_init和dwc3_gadget_init函数初始化主机模式和设备模式所需的资源，控制器后续可以动态切换为主机模式和设备模式。
-> host mode xhci dwc3_host_init()
dwc3 controller -
-> device mode udc dwc3_gadget_init()
dual-role device (DRD) OTG State
enum dwc3_drd_state {
DRD_STATE_UNDEFINED = 0, //put controller and phy in suspend if no cable connected
//pm_runtime_putsync decrease usage_count
DRD_STATE_IDLE,
DRD_STATE_PERIPHERAL,
DRD_STATE_PERIPHERAL_SUSPEND,
DRD_STATE_HOST_IDLE,
DRD_STATE_HOST,
};
dual-role usb control(DR) works on a particular mode
enum usb_dr_mode {
USB_DR_MODE_UNKNOWN,
USB_DR_MODE_HOST,
USB_DR_MODE_PERIPHERAL,
USB_DR_MODE_OTG,
};
状态的切换通过dwc3_otg_sm_work -> dwc3_otg_start_host/dwc3_otg_start_peripheral
power/supply/qcom/qpnp-smb5.c devm_extcon_dev_register 发送广播
static const unsigned int smblib_extcon_cable[] = {
EXTCON_USB,
EXTCON_USB_HOST,
EXTCON_NONE,
};
smblib_notify_device_mode
extcon_set_state_sync(chg->extcon, EXTCON_USB, enable);
smblib_notify_usb_host
extcon_set_state_sync(chg->extcon, EXTCON_USB_HOST, enable);
usb/dwc3/dwc3-msm.c devm_extcon_register_notifier注册监听usb状态变化，接受广播
mdwc->extcon[idx].vbus_nb.notifier_call = dwc3_msm_vbus_notifier;
extcon_register_notifier(edev, EXTCON_USB, &mdwc->extcon[idx].vbus_nb);
extcon_register_notifier(edev, EXTCON_USB_HOST,&mdwc->extcon[idx].id_nb);
dwc3_msm_vbus_notifier(&mdwc->extcon[idx].vbus_nb,true, edev);
dwc3_msm_id_notifier(&mdwc->extcon[idx].id_nb,true, edev);