Trying to google ‘USB over IP’ doesn’t give much except some business web pages
that give you it as a service. This brings some information about potential on
the market IMHO. Main idea is well presented on open source project page for
usbip. I really recommend to read
USB/IP - a Peripheral Bus Extension for Device Sharing over IP Network
technical paper it describe briefly technical details and capability.
In short USB over IP is a sharing system aim to expose USB devices from server
to client encapsulating USB I/O messages in TCP/IP payload.
usbip contain client and server side (called stub and VHCI (Virtual Host
Controller Interface). Stub is used on server side to hijack USB traffic
from/to connected device and send/receive it over the network. VHCI expose
stubbed device on client side and also send and receive data to/from server. We
can say that stub-VHCI pair working as intermediate layer in USB stack, giving
ability to connect over the netowork. usbip project provided both Linux and
Windows version. In mid of 2008 usbip was introduced to Linux kernel and
matured a while in staging directory. Few days ago I read thread where
Greg KH mention that if it will be possible he will include usbip in
3.17-rc2.
As you can expect the biggest problem with USB over IP is how to handle
480Mbit/s (USB2.0) or more over TCP/IP payload. The answer is it can’t.
Recommended use case for usbip is LAN environment with low latency. Of course
you can try to use it over long distance but you will get best effort, which
varies according to device and application profile. Author of the idea (Takahiro
Hirofuchi) tested his solution and created some models for queue management for
different devices - you can read about it in technical paper. Below I present
Kingston USB stick test in function of delay.
Setting up usbip
What I tried to do was setting up my Raspberry Pi and connect it through my home
LAN to share USB device (Kingston DataTraveler). My configuration looks like
that:
First I installed latest Raspbian.
Assuming SD card is /dev/sdb:
With fresh SD card we can boot and push finish on initial setup screen. If you
have DHCP set on your router that’s great if not you have to manually configure
network inside RPi.
usbip kernel modules for RPi
usbip package is available in Raspbian default repository. Fortunately for our
learning purposes, usbip-core.ko and usbip-host.ko modules are not compiled
in the kernel. What you can see when trying to run usbipd:
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usbipd: error: please load usbip-core.ko and usbip-host.ko!
Let’s see if support for USBIP is in kernel:
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pi@raspberrypi /boot $ zcat /proc/config.gz |grep USBIP
# CONFIG_USBIP_CORE is not set
Compiling Linux kernel on RPi can take number of hours. I saw different values
like 5-6, 10 and even 22. It depends on many factors. But we should not bother
and try to cross compile RPi on development machine. I will use my Y510P laptop
with i7 4700MQ 2.4GHz (4 cores).
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git clone https://github.com/raspberrypi/tools tools-rpi
git clone --depth=1 https://github.com/raspberrypi/linux linux-rpi
exportPATH=${PWD}/tools-rpi/arm-bcm2708/gcc-linaro-arm-linux-gnueabihf-raspbian-x64/bin:${PATH}cd linux-rpi
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- bcmrpi_defconfig
make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- menuconfig
I compiled kernel on 3.12.y branch. Go to
Device Drivers -> Staging drivers -> USB/IP support. I choose to compile
usbip-core as loadable module.
Device Drivers-> Staging drivers -> USB/IP support -> Host driver also is
needed it compiles usbip-host module. Optionally Debug messages for USB/IP can
be set if you want to see kernel debug messages from driver. After saving
changes to config file we can start compilation:
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make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- -j8
After finishing compilation we can move our image to SD card. First mount your
SD card (it won’t automatically) and run compile modules with correct install
path.
busid 1-1.2 (0951:1625) is my Kingstone pendrive. If you are unsure which
busid is for device that you want to share compare device id and vendor id with
output of lsusb. To bind device to usbip-host.ko we should use:
As you can see communication to usbip-host module is through writing into
sysfs file.
NOTE : if you will try to bind device without root privileges or when modules
are not loaded you will get errors like below:
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pi@raspberrypi ~ $ usbip bind -b 1-1.2
usbip: error: could not unbind driver from device on busid 1-1.2
pi@raspberrypi ~ $ sudo usbip bind -b 1-1.2
usbip: error: unable to bind device on 1-1.2
usbip - client side
Our device should wait for communication. Let’s go to client side of our LAN and
try to check if we can use our USB device. To check if device is available:
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[22:29:37] pietrushnic:~ $ sudo usbip list -r 192.168.1.3
Exportable USB devices======================
- 192.168.1.3
1-1.2: Kingston Technology : DataTraveler 101 II (0951:1625)
: /sys/devices/platform/bcm2708_usb/usb1/1-1/1-1.2
: (Defined at Interface level)(00/00/00)
: 0 - Mass Storage / SCSI / Bulk-Only (08/06/50)
Where 192.168.1.3 is an IP of RPi. Everything seems to be ok. So let’s try to
attach it and do some test:
[ 676.126820] usbip_core: module is from the staging directory, the quality is unknown, you have been warned.
[ 676.127246] usbip_core: USB/IP Core v1.0.0
[ 676.127964] vhci_hcd: module is from the staging directory, the quality is unknown, you have been warned.
[ 676.128336] vhci_hcd vhci_hcd: USB/IP Virtual Host Controller
[ 676.128341] vhci_hcd vhci_hcd: new USB bus registered, assigned bus number 5[ 676.128493] usb usb5: New USB device found, idVendor=1d6b, idProduct=0002[ 676.128495] usb usb5: New USB device strings: Mfr=3, Product=2, SerialNumber=1[ 676.128497] usb usb5: Product: USB/IP Virtual Host Controller
[ 676.128498] usb usb5: Manufacturer: Linux 3.14-2-amd64 vhci_hcd
[ 676.128499] usb usb5: SerialNumber: vhci_hcd
[ 676.128603] hub 5-0:1.0: USB hub found
[ 676.128607] hub 5-0:1.0: 8 ports detected
[ 676.128732] vhci_hcd: USB/IP 'Virtual' Host Controller (VHCI) Driver v1.0.0
[ 676.228522] vhci_hcd: changed 0[ 694.052076] vhci_hcd vhci_hcd: rhport(0) sockfd(3) devid(65540) speed(3)[ 694.052289] vhci_hcd: changed 1[ 694.158844] vhci_hcd: changed 0[ 694.267024] usb 5-1: new high-speed USB device number 2 using vhci_hcd
[ 694.491154] usb 5-1: new high-speed USB device number 3 using vhci_hcd
[ 694.715339] usb 5-1: new high-speed USB device number 4 using vhci_hcd
[ 694.715356] usb 5-1: SetAddress Request (4) to port 0[ 694.758246] usb 5-1: New USB device found, idVendor=0951, idProduct=1625[ 694.758251] usb 5-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3[ 694.758252] usb 5-1: Product: DT 101 II
[ 694.758254] usb 5-1: Manufacturer: Kingston
[ 694.758255] usb 5-1: SerialNumber: 001CC0EC3519EA51A0000017
[ 694.809487] usb-storage 5-1:1.0: USB Mass Storage device detected
[ 694.809582] scsi6 : usb-storage 5-1:1.0
[ 694.809660] usbcore: registered new interface driver usb-storage
[ 695.816239] scsi 6:0:0:0: Direct-Access Kingston DT 101 II PMAP PQ: 0 ANSI: 0 CCS
[ 695.816627] sd 6:0:0:0: Attached scsi generic sg2 type0[ 695.825894] sd 6:0:0:0: [sdb]7815168 512-byte logical blocks: (4.00 GB/3.72 GiB)[ 695.833602] sd 6:0:0:0: [sdb] Write Protect is off
[ 695.833616] sd 6:0:0:0: [sdb] Mode Sense: 03410000[ 695.841427] sd 6:0:0:0: [sdb] No Caching mode page found
[ 695.841440] sd 6:0:0:0: [sdb] Assuming drive cache: write through
[ 695.883028] sd 6:0:0:0: [sdb] No Caching mode page found
[ 695.883044] sd 6:0:0:0: [sdb] Assuming drive cache: write through
[ 695.903869] sdb: sdb1 sdb2 < sdb5 >
[ 695.941208] sd 6:0:0:0: [sdb] No Caching mode page found
[ 695.941211] sd 6:0:0:0: [sdb] Assuming drive cache: write through
[ 695.941214] sd 6:0:0:0: [sdb] Attached SCSI removable disk
Device show correct information in lsusb output and /proc/partitions.
Testing usbip
From technical paper that I mentioned above I understand that probably the most
important factor for usbip performance is latency. Simplest method to emulate
WAN delays is tc from iproute2 package. It is available by as default tool
in Raspbian:
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sudo tc qdisc add dev eth0 root netem delay 100ms #add device and set delay
sudo tc qdisc change dev eth0 root netem delay 10ms #change delay
I see this as opportunity to debug, understand and fix the driver.
Arduino
There was no problem with Arduino. I was even able to program it successfully.
Unfortunately to big delay (in my case 300ms) cause software errors:
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Binary sketch size: 1,056 bytes (of a 30,720 byte maximum)
avrdude: stk500_getparm(): (a) protocol error, expect=0x14, resp=0x14
avrdude: stk500_getparm(): (a) protocol error, expect=0x14, resp=0x01
avrdude: stk500_initialize(): (a) protocol error, expect=0x14, resp=0x10
avrdude: initialization failed, rc=-1
Double check connections and try again, or use -F to override
this check.
Summary
Looks like usbip is usable in low delay network. It would be great to test it
in real WAN. It is possible to use usbip with more sophisticated devices but
potential driver tweaking is required. As a telecommunication graduate I cannot
say about possible improvements in queue algorithms, like adaptive queueing
which depends on data transfer profile. It was interesting experience to play
with usbip and probably I will back to it especially to testing part of this
post.
If you have questions, suggestions or comments please let me know.
Founder of 3mdeb, a passionate advocate for open-source firmware solutions, driven by a belief in transparency, innovation, and trustworthiness. Every day is a new opportunity to embody the company's vision, emphasizing user liberty, simplicity, and privacy. Beyond business, a casual chess and bridge player, finding peace in nature and nourishment in theology, philosophy, and psychology. A person striving to foster a healthy community, grounded in collaboration and shared growth, while nurturing a lifelong curiosity and a desire to deeply understand the world.
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