This file summarizes information on basic testing of USB functions
provided by gadgets.
- ACM function
- ECM function
- ECM subset function
- EEM function
- FFS function
- HID function
- LOOPBACK function
- MASS STORAGE function
- MIDI function
- NCM function
- OBEX function
- PHONET function
- RNDIS function
- SERIAL function
- SOURCESINK function
- UAC1 function (legacy implementation)
- UAC2 function
- UVC function
- PRINTER function
- UAC1 function (new API)
The function is provided by usb_f_acm.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “acm”.
The ACM function provides just one attribute in its function directory:
port_num
The attribute is read-only.
There can be at most 4 ACM/generic serial/OBEX ports in the system.
Testing the ACM function
On the host: cat > /dev/ttyACM
On the device : cat /dev/ttyGS
then the other way round
On the device: cat > /dev/ttyGS
On the host: cat /dev/ttyACM
The function is provided by usb_f_ecm.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “ecm”.
The ECM function provides these attributes in its function directory:
ifname - network device interface name associated with this
function instance
qmult - queue length multiplier for high and super speed
host_addr - MAC address of host's end of this
Ethernet over USB link
dev_addr - MAC address of device's end of this
Ethernet over USB link
and after creating the functions/ecm.
values: qmult is 5, dev_addr and host_addr are randomly selected.
Except for ifname they can be written to until the function is linked to a
configuration. The ifname is read-only and contains the name of the interface
which was assigned by the net core, e. g. usb0.
Testing the ECM function
Configure IP addresses of the device and the host. Then:
On the device: ping <host’s IP>
On the host: ping <device’s IP>
The function is provided by usb_f_ecm_subset.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “geth”.
The ECM subset function provides these attributes in its function directory:
ifname - network device interface name associated with this
function instance
qmult - queue length multiplier for high and super speed
host_addr - MAC address of host's end of this
Ethernet over USB link
dev_addr - MAC address of device's end of this
Ethernet over USB link
and after creating the functions/ecm.
values: qmult is 5, dev_addr and host_addr are randomly selected.
Except for ifname they can be written to until the function is linked to a
configuration. The ifname is read-only and contains the name of the interface
which was assigned by the net core, e. g. usb0.
Testing the ECM subset function
Configure IP addresses of the device and the host. Then:
On the device: ping <host’s IP>
On the host: ping <device’s IP>
The function is provided by usb_f_eem.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “eem”.
The EEM function provides these attributes in its function directory:
ifname - network device interface name associated with this
function instance
qmult - queue length multiplier for high and super speed
host_addr - MAC address of host's end of this
Ethernet over USB link
dev_addr - MAC address of device's end of this
Ethernet over USB link
and after creating the functions/eem.
values: qmult is 5, dev_addr and host_addr are randomly selected.
Except for ifname they can be written to until the function is linked to a
configuration. The ifname is read-only and contains the name of the interface
which was assigned by the net core, e. g. usb0.
Testing the EEM function
Configure IP addresses of the device and the host. Then:
On the device: ping <host’s IP>
On the host: ping <device’s IP>
The function is provided by usb_f_fs.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “ffs”.
The function directory is intentionally empty and not modifiable.
After creating the directory there is a new instance (a “device”) of FunctionFS
available in the system. Once a “device” is available, the user should follow
the standard procedure for using FunctionFS (mount it, run the userspace
process which implements the function proper). The gadget should be enabled
by writing a suitable string to usb_gadget/
Testing the FFS function
On the device: start the function’s userspace daemon, enable the gadget
On the host: use the USB function provided by the device
The function is provided by usb_f_hid.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “hid”.
The HID function provides these attributes in its function directory:
protocol - HID protocol to use
report_desc - data to be used in HID reports, except data
passed with /dev/hidg<X>
report_length - HID report length
subclass - HID subclass to use
For a keyboard the protocol and the subclass are 1, the report_length is 8,
while the report_desc is:
$ hd my_report_desc
00000000 05 01 09 06 a1 01 05 07 19 e0 29 e7 15 00 25 01 |……….)…%.|
00000010 75 01 95 08 81 02 95 01 75 08 81 03 95 05 75 01 |u…….u…..u.|
00000020 05 08 19 01 29 05 91 02 95 01 75 03 91 03 95 06 |….)…..u…..|
00000030 75 08 15 00 25 65 05 07 19 00 29 65 81 00 c0 |u…%e….)e…|
0000003f
Such a sequence of bytes can be stored to the attribute with echo:
$ echo -ne \x05\x01\x09\x06\xa1…..
Testing the HID function
Device:
- create the gadget
- connect the gadget to a host, preferably not the one used
to control the gadget - run a program which writes to /dev/hidg
, e.g.
a userspace program found in Documentation/usb/gadget_hid.txt:
$ ./hid_gadget_test /dev/hidg0 keyboard
Host:
- observe the keystrokes from the gadget
The function is provided by usb_f_ss_lb.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “Loopback”.
The LOOPBACK function provides these attributes in its function directory:
qlen - depth of loopback queue
bulk_buflen - buffer length
Testing the LOOPBACK function
device: run the gadget
host: test-usb (tools/usb/testusb.c)
The function is provided by usb_f_mass_storage.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “mass_storage”.
The MASS STORAGE function provides these attributes in its directory:
files:
stall - Set to permit function to halt bulk endpoints.
Disabled on some USB devices known not to work
correctly. You should set it to true.
num_buffers - Number of pipeline buffers. Valid numbers
are 2..4. Available only if
CONFIG_USB_GADGET_DEBUG_FILES is set.
and a default lun.0 directory corresponding to SCSI LUN #0.
A new lun can be added with mkdir:
$ mkdir functions/mass_storage.0/partition.5
Lun numbering does not have to be continuous, except for lun #0 which is
created by default. A maximum of 8 luns can be specified and they all must be
named following the
Probably a good convention is to name the luns “lun.
although it is not mandatory.
In each lun directory there are the following attribute files:
file - The path to the backing file for the LUN.
Required if LUN is not marked as removable.
ro - Flag specifying access to the LUN shall be
read-only. This is implied if CD-ROM emulation
is enabled as well as when it was impossible
to open "filename" in R/W mode.
removable - Flag specifying that LUN shall be indicated as
being removable.
cdrom - Flag specifying that LUN shall be reported as
being a CD-ROM.
nofua - Flag specifying that FUA flag
in SCSI WRITE(10,12)
Testing the MASS STORAGE function
device: connect the gadget, enable it
host: dmesg, see the USB drives appear (if system configured to automatically
mount)
The function is provided by usb_f_midi.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “midi”.
The MIDI function provides these attributes in its function directory:
buflen - MIDI buffer length
id - ID string for the USB MIDI adapter
in_ports - number of MIDI input ports
index - index value for the USB MIDI adapter
out_ports - number of MIDI output ports
qlen - USB read request queue length
Testing the MIDI function
There are two cases: playing a mid from the gadget to
the host and playing a mid from the host to the gadget.
- Playing a mid from the gadget to the host
host)
$ arecordmidi -l
Port Client name Port name
14:0 Midi Through Midi Through Port-0
24:0 MIDI Gadget MIDI Gadget MIDI 1
$ arecordmidi -p 24:0 from_gadget.mid
gadget)
$ aplaymidi -l
Port Client name Port name
20:0 f_midi f_midi
$ aplaymidi -p 20:0 to_host.mid
- Playing a mid from the host to the gadget
gadget)
$ arecordmidi -l
Port Client name Port name
20:0 f_midi f_midi
$ arecordmidi -p 20:0 from_host.mid
host)
$ aplaymidi -l
Port Client name Port name
14:0 Midi Through Midi Through Port-0
24:0 MIDI Gadget MIDI Gadget MIDI 1
$ aplaymidi -p24:0 to_gadget.mid
The from_gadget.mid should sound identical to the to_host.mid.
The from_host.id should sound identical to the to_gadget.mid.
MIDI files can be played to speakers/headphones with e.g. timidity installed
$ aplaymidi -l
Port Client name Port name
14:0 Midi Through Midi Through Port-0
24:0 MIDI Gadget MIDI Gadget MIDI 1
128:0 TiMidity TiMidity port 0
128:1 TiMidity TiMidity port 1
128:2 TiMidity TiMidity port 2
128:3 TiMidity TiMidity port 3
$ aplaymidi -p 128:0 file.mid
MIDI ports can be logically connected using the aconnect utility, e.g.:
$ aconnect 24:0 128:0 # try it on the host
After the gadget’s MIDI port is connected to timidity’s MIDI port,
whatever is played at the gadget side with aplaymidi -l is audible
in host’s speakers/headphones.
The function is provided by usb_f_ncm.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “ncm”.
The NCM function provides these attributes in its function directory:
ifname - network device interface name associated with this
function instance
qmult - queue length multiplier for high and super speed
host_addr - MAC address of host's end of this
Ethernet over USB link
dev_addr - MAC address of device's end of this
Ethernet over USB link
and after creating the functions/ncm.
values: qmult is 5, dev_addr and host_addr are randomly selected.
Except for ifname they can be written to until the function is linked to a
configuration. The ifname is read-only and contains the name of the interface
which was assigned by the net core, e. g. usb0.
Testing the NCM function
Configure IP addresses of the device and the host. Then:
On the device: ping <host’s IP>
On the host: ping <device’s IP>
The function is provided by usb_f_obex.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “obex”.
The OBEX function provides just one attribute in its function directory:
port_num
The attribute is read-only.
There can be at most 4 ACM/generic serial/OBEX ports in the system.
Testing the OBEX function
On device: seriald -f /dev/ttyGS
On host: serialc -v
-t
where seriald and serialc are Felipe’s utilities found here:
https://github.com/felipebalbi/usb-tools.git master
The function is provided by usb_f_phonet.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “phonet”.
The PHONET function provides just one attribute in its function directory:
ifname - network device interface name associated with this
function instance
Testing the PHONET function
It is not possible to test the SOCK_STREAM protocol without a specific piece
of hardware, so only SOCK_DGRAM has been tested. For the latter to work,
in the past I had to apply the patch mentioned here:
http://www.spinics.net/lists/linux-usb/msg85689.html
These tools are required:
git://git.gitorious.org/meego-cellular/phonet-utils.git
On the host:
$ ./phonet -a 0x10 -i usbpn0
$ ./pnroute add 0x6c usbpn0
$./pnroute add 0x10 usbpn0
$ ifconfig usbpn0 up
On the device:
$ ./phonet -a 0x6c -i upnlink0
$ ./pnroute add 0x10 upnlink0
$ ifconfig upnlink0 up
Then a test program can be used:
http://www.spinics.net/lists/linux-usb/msg85690.html
On the device:
$ ./pnxmit -a 0x6c -r
On the host:
$ ./pnxmit -a 0x10 -s 0x6c
As a result some data should be sent from host to device.
Then the other way round:
On the host:
$ ./pnxmit -a 0x10 -r
On the device:
$ ./pnxmit -a 0x6c -s 0x10
The function is provided by usb_f_rndis.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “rndis”.
The RNDIS function provides these attributes in its function directory:
ifname - network device interface name associated with this
function instance
qmult - queue length multiplier for high and super speed
host_addr - MAC address of host's end of this
Ethernet over USB link
dev_addr - MAC address of device's end of this
Ethernet over USB link
and after creating the functions/rndis.
values: qmult is 5, dev_addr and host_addr are randomly selected.
Except for ifname they can be written to until the function is linked to a
configuration. The ifname is read-only and contains the name of the interface
which was assigned by the net core, e. g. usb0.
Testing the RNDIS function
Configure IP addresses of the device and the host. Then:
On the device: ping <host’s IP>
On the host: ping <device’s IP>
The function is provided by usb_f_gser.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “gser”.
The SERIAL function provides just one attribute in its function directory:
port_num
The attribute is read-only.
There can be at most 4 ACM/generic serial/OBEX ports in the system.
Testing the SERIAL function
On host: insmod usbserial
echo VID PID >/sys/bus/usb-serial/drivers/generic/new_id
On host: cat > /dev/ttyUSB
On target: cat /dev/ttyGS
then the other way round
On target: cat > /dev/ttyGS
On host: cat /dev/ttyUSB
The function is provided by usb_f_ss_lb.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “SourceSink”.
The SOURCESINK function provides these attributes in its function directory:
pattern - 0 (all zeros), 1 (mod63), 2 (none)
isoc_interval - 1..16
isoc_maxpacket - 0 - 1023 (fs), 0 - 1024 (hs/ss)
isoc_mult - 0..2 (hs/ss only)
isoc_maxburst - 0..15 (ss only)
bulk_buflen - buffer length
bulk_qlen - depth of queue for bulk
iso_qlen - depth of queue for iso
Testing the SOURCESINK function
device: run the gadget
host: test-usb (tools/usb/testusb.c)
The function is provided by usb_f_uac1_legacy.ko module.
Function-specific configfs interface
The function name to use when creating the function directory
is “uac1_legacy”.
The uac1 function provides these attributes in its function directory:
audio_buf_size - audio buffer size
fn_cap - capture pcm device file name
fn_cntl - control device file name
fn_play - playback pcm device file name
req_buf_size - ISO OUT endpoint request buffer size
req_count - ISO OUT endpoint request count
The attributes have sane default values.
Testing the UAC1 function
device: run the gadget
host: aplay -l # should list our USB Audio Gadget
The function is provided by usb_f_uac2.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “uac2”.
The uac2 function provides these attributes in its function directory:
c_chmask - capture channel mask
c_srate - capture sampling rate
c_ssize - capture sample size (bytes)
p_chmask - playback channel mask
p_srate - playback sampling rate
p_ssize - playback sample size (bytes)
req_number - the number of pre-allocated request for both capture
and playback
The attributes have sane default values.
Testing the UAC2 function
device: run the gadget
host: aplay -l # should list our USB Audio Gadget
This function does not require real hardware support, it just
sends a stream of audio data to/from the host. In order to
actually hear something at the device side, a command similar
to this must be used at the device side:
$ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
e.g.:
$ arecord -f dat -t wav -D hw:CARD=UAC2Gadget,DEV=0 |
aplay -D default:CARD=OdroidU3
The function is provided by usb_f_uvc.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “uvc”.
The uvc function provides these attributes in its function directory:
streaming_interval - interval for polling endpoint for data transfers
streaming_maxburst - bMaxBurst for super speed companion descriptor
streaming_maxpacket - maximum packet size this endpoint is capable of
sending or receiving when this configuration is
selected
There are also “control” and “streaming” subdirectories, each of which contain
a number of their subdirectories. There are some sane defaults provided, but
the user must provide the following:
control header - create in control/header, link from control/class/fs
and/or control/class/ss
streaming header - create in streaming/header, link from
streaming/class/fs and/or streaming/class/hs and/or
streaming/class/ss
format description - create in streaming/mjpeg and/or
streaming/uncompressed
frame description - create in streaming/mjpeg/<format> and/or in
streaming/uncompressed/<format>
Each frame description contains frame interval specification, and each
such specification consists of a number of lines with an inverval value
in each line. The rules stated above are best illustrated with an example:
mkdir functions/uvc.usb0/control/header/h
cd functions/uvc.usb0/control/
ln -s header/h class/fs
ln -s header/h class/ss
mkdir -p functions/uvc.usb0/streaming/uncompressed/u/360p
cat < functions/uvc.usb0/streaming/uncompressed/u/360p/dwFrameInterval
666666
1000000
5000000
EOF
cd $GADGET_CONFIGFS_ROOT
mkdir functions/uvc.usb0/streaming/header/h
cd functions/uvc.usb0/streaming/header/h
ln -s ../../uncompressed/u
cd ../../class/fs
ln -s ../../header/h
cd ../../class/hs
ln -s ../../header/h
cd ../../class/ss
ln -s ../../header/h
Testing the UVC function
device: run the gadget, modprobe vivid
uvc-gadget -u /dev/video<uvc video node #> -v /dev/video<vivid video node #>
where uvc-gadget is this program:
http://git.ideasonboard.org/uvc-gadget.git
with these patches:
http://www.spinics.net/lists/linux-usb/msg99220.html
host: luvcview -f yuv
The function is provided by usb_f_printer.ko module.
Function-specific configfs interface
The function name to use when creating the function directory is “printer”.
The printer function provides these attributes in its function directory:
pnp_string - Data to be passed to the host in pnp string
q_len - Number of requests per endpoint
Testing the PRINTER function
The most basic testing:
device: run the gadget
ls -l /devices/virtual/usb_printer_gadget/
should show g_printer
If udev is active, then /dev/g_printer
host:
If udev is active, then e.g. /dev/usb/lp0 should appear.
host->device transmission:
device:
cat /dev/g_printer
host:
cat > /dev/usb/lp0
device->host transmission:
cat > /dev/g_printer
host:
cat /dev/usb/lp0
More advanced testing can be done with the prn_example
described in Documentation/usb/gadget_printer.txt.
The function is provided by usb_f_uac1.ko module.
It will create a virtual ALSA card and the audio streams are simply
sinked to and sourced from it.
Function-specific configfs interface
The function name to use when creating the function directory is “uac1”.
The uac1 function provides these attributes in its function directory:
c_chmask - capture channel mask
c_srate - capture sampling rate
c_ssize - capture sample size (bytes)
p_chmask - playback channel mask
p_srate - playback sampling rate
p_ssize - playback sample size (bytes)
req_number - the number of pre-allocated request for both capture
and playback
The attributes have sane default values.
Testing the UAC1 function
device: run the gadget
host: aplay -l # should list our USB Audio Gadget
This function does not require real hardware support, it just
sends a stream of audio data to/from the host. In order to
actually hear something at the device side, a command similar
to this must be used at the device side:
$ arecord -f dat -t wav -D hw:2,0 | aplay -D hw:0,0 &
e.g.:
$ arecord -f dat -t wav -D hw:CARD=UAC1Gadget,DEV=0 |
aplay -D default:CARD=OdroidU3
