USB Host Controller

• The Linux-USB Host Side API

• HCI(Host Controller Interface)

OHCI(Open Host Controller Interface)

• OHCI FireWire drivers
• supports USB 1.1 (full and low speeds) only
• If a computer provides non-x86 USB 1.1, or x86 USB 1.1 without an Intel or VIA chipset, it probably uses OHCI (Compaq, Microsoft and National Semiconductor)

UHCI(Universal Host Controller Interface)

• created by Intel for USB 1.0 (full and low speeds)
• USB_UHCI_HCD
  • The Linux kernel module supports Intel and VIA UHCI controllers

EHCI(Enhanced Host Controller Interface)

• EHCI only provides USB 2.0 (i.e. high speed USB)

• USB Core/HCD(Host Controller Driver)/URB(USB Request Block)

usb.h

• <kernel src>/include/linux/usb.h
  • struct usb_device(kernel's representation of a USB device)
    • struct device dev;
  • struct usb_interface(what usb device drivers talk to)
    • struct device dev; /* interface specific device info */
  • struct usb_class_driver(a USB driver that wants to use the USB major number)
    • const struct file_operations *fops;
  • struct urb
    • int status;
    • unsigned int transfer_flags;
      • URB_NO_TRANSFER_DMA_MAP: urb->transfer_dma are valid on submit
      • URB_NO_SETUP_DMA_MAP: urb->setup_dma are valid on submit
    • int interval; (isochronous and interrupt urbs)
      • Urb polling interval
      • For lowSpeed and fullSpeed devices, the interval unit is frames(ms)
      • For hiSpeed devices, the interval unit is microframes(1/8 ms)
    • usb_complete_t complete
      • Completion handler called when the transfer is complete
  • usb_fill_int_urb
  • usb_fill_bulk_urb
  • usb_fill_control_urb
  • usb_set_intfdata
    • save data private to the driver to struct usb_interface.device.driver_data
  • usb_get_intfdata
  • interface_to_usbdev
    • container_of(intf->dev.parent, struct usb_device, dev)

device.h

• <kernel src>/include/linux/device.h
  • struct device
    • struct device *parent; /* usb_inteface.dev.parent = &usb_device_dev */

urb.c

• <kernel src>/drivers/usb/core/urb.c
  • usb_alloc_urb/usb_free_urb
  • usb_buffer_alloc
    • allocate dma-consistent buffer
  • usb_buffer_free
  • usb_submit_urb
  • usb_unlink_urb
    • Canceling urbs asynchronously
    • Success: returns -EINPROGRESS
    • The corresponding completion handlers will still be run and will see urb->status == -ECONNRESET.
  • usb_kill_urb
    • Canceling urbs synchronously
    • The corresponding completion handlers will see urb->status == -ENOENT.
  • usb_get_dev
    • increments the reference count of usb_device.device.kobject
    • Drivers for USB interfaces should normally record such references in their probe() methods, when they bind to an interface

message.c

• <kernel src>/drivers/usb/core/message.c
  • usb_bulk_msg
  • usb_control_msg

file.c

• <kernel src>/drivers/usb/core/file.c
  • usb_register_dev(struct usb_interface *, struct usb_class_driver *)
  • usb_deregister_dev

hcd.h

• <kernel src>/drivers/usb/core/hcd.h
  • struct usb_hcd
    • const struct hc_driver *driver
    • unsigned long hcd_priv[0]
  • struct hc_driver
    • irqreturn_t (*irq)
• <kernel src>/drivers/usb/core/hcd.c
  • usb_create_hcd
  • usb_add_hcd
  • usb_remove_hcd

driver.c

• <kernel src>/drivers/usb/core/driver.c
  • usb_register_driver
    • register a USB interface driver
  • usb_deregister_driver
    • unregister a USB interface driver

• OHCI HCD

ohci.h

• <kernel src>/drivers/usb/host/ohci.h
  • hcd_to_ohci
  • ohci_to_hcd
  • struct ohci_hcd
    • the hcd_priv of usb_hcd

ohci-hcd.c

• <kernel src>/drivers/usb/host/ohci-hcd.c
  • for ohci_hcd
    • ohci_init
    • ohci_run
    • ohci_restart
  • for usb_hcd
    • ohci_irq
    • ohci_stop
    • ohci_shutdown
    • ohci_urb_enqueue
    • ohci_urb_dequeue
    • ohci_endpoint_disable
    • ohci_get_frame
    • ohci_ubs_suspend
    • ohci_bus_resume
    • ohci_start_port_reset