Linux usb2ether

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Copyright © 2009 by Tom J.P.Sun All rights reserved.

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Linux USB to Ethernet development

spec. overviewkernel backenddriver interfaces

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USB Overview(1)USB Overview(1)

USB 1.1/2.0 Spec. For S/W engineer:Chap 5 “USB Data Flow Model”Chap 9 “USB Device Framework”Chap 10 “USB Host : H/W and S/W”

client

USB system

USB Bus interface

function

USB device

USB Bus interface

Logical connection

Physicalconnection

S/W

H/W

USB cable

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USB Overview(2)USB Overview(2)

client

USB system

Usbcore (bus driver)

HC driver

HC H/W SIEUSB device H/W

USB device F/W

USB bus

UHCI or OHCI

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USB communication flowUSB communication flow

Client S/W, driver

buffers

pipes

End points

Communicationflow

Interface

USB logical device

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USB transfer typesUSB transfer types

Control Transferdevice enumeration use this type ( issued by USBD (bus driver))client driver can use it ( same concept as “IOCTL”) for “device specific commands”

Bulk Transferreliable, but not realtime scanner,printer

Isochronous Transfernear realtime, but not reliable usbcam

Interrupt Transferreliable, realtime, but limit in bandwidth mouse

Important ConceptUSB is MasterSlave modelUSBOnTheGo is peertopeer model

cncpt

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USB Descriptor HierarchyUSB Descriptor Hierarchy

device descriptor

Configuration1

Configuration2

Interface 0AS0

Interface 1AS0

Interface 1AS1

Interface 0AS1

Interface 1AS0

Endpoint1

Endpoint2

Endpoint3

More endpoint descriptors

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USB device requestUSB device request

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USB standard commandsUSB standard commands(bRequest value)(bRequest value)

GET_STATUS 0CLEAR_FEATURE 1Reserved for future use 2SET_FEATURE 3Reserved for future use 4SET_ADDRESS 5GET_DESCRIPTOR 6SET_DESCRIPTOR 7GET_CONFIGURATION 8SET_CONFIGURATION 9GET_INTERFACE 10SET_INTERFACE 11SYNCH_FRAME 12

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9620 vendor commands9620 vendor commands(bRequest value)(bRequest value)

DM_READ_REGS 0DM_WRITE_REGS 1DM_READ_MEMS 2DM_WRITE_REG 3DM_WRITE_MEMS 5DM_WRITE_MEM 7

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Configure DeviceConfigure Device

When USB Device Plugged in, USBD + driver should complete the device enumeration steps

Host Device

1 get dev descriptor

dev descriptor

2 set address

3 get dev descriptor

4 set cfg

1 2

3 4

done by USBD

done by client

5 set itf

dev descriptor

5CATC can see these transfers...

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USB Core API LayersUSB Core API Layers

USB device driver

USB device driver

USB device driver

USBD = USB core ( usb.c )

USB UHCI driver

USB OHCI driver

other USB HC driver

upperAPI

lowerAPI

ready

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USB


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USB driver structure(1)USB driver structure(1)

@name: module name @probe: called to see if the driver will handle this USB interface , if it is, return zero, otherwise return a negative error code.@disconnect: called when the interface is no longer accessible.@id_table: USB use this table to support hotplugging, export this id_table with MODULE_DEVICE_TABLE( ) macro.@driver: driver modle core driver structure

struct usb_driver {const char *name;void* (*probe) (

struct usb_interface *const struct usb_device_id *id_table);

void (*disconnect)(struct usb_device *, void *);

...const struct usb_device_id *id_table;struct device_driver driver;

};

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USB driver structure(2)USB driver structure(2)

usb_driver

USBD

usb_register( )

my_probe( )…my_disconnect( )…

First enter point on device match

On device detachment, USB framework call this.

id_table : match list1st match dev2nd match dev…

On device attachment, USB framework walk through the id_table

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Standard CommandsStandard Commands

USBD provides USB standard commands

usb_set_configuration( struct usb_device* dev, int cfg);usb_set_interface(struct usb_device*, int itf, int alt);usb_get_descriptor(…);usb_get_string(…);usb_get_status(…);

kenrel_source/drivers/usb/core/message.c

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The USB data pathThe USB data path

PCIdriver

App

Linux O.S. Interface

App

Network(TCP/IP)

USB subsystem

FS

InKernel

PCI subsystem

EtherNetChip

H/W

USBdriver

EtherNetChip

PCI bus

USBHC

App open socket,data transferred byNetwork and USB driver

App open the usb device interface, direct transferdata to the USB HC

Can isolate driver, when proving h/w

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The usbnet minidriverThe usbnet minidriver

Network(TCP/IP)

usbnetdriver

framework

asix

dm9601

...other client

drivers

The mini-driver interface...tx_fixup( )rx_fixup( )...

The mini-driver only take simple work for device-specific fixups.

The usbnet module manages:

1. skb flow control with the Network layer2. urb flow control with the USB bus driver

so, the performance issue should be little between each mini-driver, (Yes ! performance depends major on the H/W)

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USB


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dm9601_rx_fixup( )dm9601_rx_fixup( )Object: correct the contents of skb ( data for the network layer ), which is device specific. e.g. dm9620 h/w give us data with length in the first 2 bytes, rx_fixup( ) should remove it before passing to the network layer

static const struct driver_info dm9601_info = {.description = "Davicom DM9601 USB Ethernet",.flags = FLAG_ETHER,.bind = dm9601_bind,.rx_fixup = dm9601_rx_fixup,.tx_fixup = dm9601_tx_fixup,.status = dm9601_status,.link_reset = dm9601_link_reset,.reset = dm9601_link_reset,

};

Mini-driver interface

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dm9601_tx_fixup( )dm9601_tx_fixup( )

static const struct driver_info dm9601_info = {.description = "Davicom DM9601 USB Ethernet",.flags = FLAG_ETHER,.bind = dm9601_bind,.rx_fixup = dm9601_rx_fixup,.tx_fixup = dm9601_tx_fixup,.status = dm9601_status,.link_reset = dm9601_link_reset,.reset = dm9601_link_reset,

};

Object: correct the contents of skb ( data for the network layer ), which is device specific. e.g. dm9620 h/w need data with length in the first 2 bytes, tx_fixup( ) should add it before passing to the chip

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vendor commands(1)vendor commands(1)

static int dm_read(struct usbnet *dev, u8 reg, u16 length, void *data){

devdbg(dev, "dm_read() reg=0x%02x length=%d", reg, length);return usb_control_msg(dev->udev,

usb_rcvctrlpipe(dev->udev, 0), DM_READ_REGS, USB_DIR_IN | USB_TYPE_VENDOR |

USB_RECIP_DEVICE, 0, reg, data, length,

USB_CTRL_SET_TIMEOUT);}

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vendor commands (2)vendor commands (2)

static int dm_write(struct usbnet *dev, u8 reg, u16 length, void *data){

return usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0), DM_WRITE_REGS, USB_DIR_OUT | USB_TYPE_VENDOR |

USB_RECIP_DEVICE, 0, reg, data, length,

USB_CTRL_SET_TIMEOUT);}

Concept: The vendor commands are used to setup h/w , whilethe real data are transferred by b-in , b-out pipes, not the control pipe.

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Device ID & Vendor ID Device ID & Vendor ID

use Use this information to

load driver when plug-in...

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Appendix : libusbAppendix : libusb

Bypass driver, direct call via the USB subsystem.Package 0.1.12 (simple, but not well support thread )

we need header files:#> apt-get src libusb-dev(get libusb-0.1.12 under the same directory)

Makefile:usbtest: usbtest.c gcc -g -Wall $< -o $@ -I./libusb-0.1.12 -lusb

( assume usbtest.c is the our test program using the libusb , use root to test...)

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Example usage of libusb (1)Example usage of libusb (1)Include headers:

#include "linux.h"#include "usbi.h"

Initial setup provided by libusb

usb_init();usb_find_busses();usb_find_devices();

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Example usage of libusb (2)Example usage of libusb (2)Get our device:

for (usb_bus = usb_busses; usb_bus; usb_bus = usb_bus->next) { for (dev = usb_bus->devices; dev; dev = dev->next) { if ((dev->descriptor.idVendor == VENDOR_ID) && (dev->descriptor.idProduct == PRODUCT_ID)) return dev; } }

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Example usage of libusb (3)Example usage of libusb (3)Open:

usb_handle = usb_open(usb_dev);

B-out:

mk_raw(buf, SZBUF); /* prepare data in buf*/retval = usb_bulk_write(usb_handle, ep_bulk_out, (char*)buf, SZBUF, 5000);

B-in:

memset(buf, 0, SZBUF);retval = usb_bulk_read(usb_handle, ep_bulk_in, (char*)buf, SZBUF, 5000);

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Example usage of libusb (4)Example usage of libusb (4)

Control pipe:usb_control_msg(handle, 0x000000c0, DM_READ_REGS, 0,0xff & reg,data,length,5000);

prototype: libusb-0.1.12/linux.cint usb_control_msg(

usb_dev_handle *dev, int requesttype, int request,int value, int index, char *bytes, int size, int timeout);

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The EndThe End

Date post:	18-Jan-2015
Category:	Technology
Upload:	tom-sun
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Linux usb2ether

Technology