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linux/Documentation/usb/gadget-testing.rst
Lorenzo Colitti 63d152149b usb: gadget: u_ether: support configuring interface names. 
This patch allows the administrator to configure the interface
name of a function using u_ether (e.g., eem, ncm, rndis).

Currently, all such interfaces, regardless of function type, are
always called usb0, usb1, etc. This makes it very cumbersome to
use more than one such type at a time, because userspace cannnot
easily tell the interfaces apart and apply the right
configuration to each one. Interface renaming in userspace based
on driver doesn't help, because the interfaces all have the same
driver. Without this patch, doing this require hacks/workarounds
such as setting fixed MAC addresses on the functions, and then
renaming by MAC address, or scraping configfs after each
interface is created to find out what it is.

Setting the interface name is done by writing to the same
"ifname" configfs attribute that reports the interface name after
the function is bound. The write must contain an interface
pattern such as "usb%d" (which will cause the net core to pick
the next available interface name starting with "usb").
This patch does not allow writing an exact interface name (as
opposed to a pattern) because if the interface already exists at
bind time, the bind will fail and the whole gadget will fail to
activate. This could be allowed in a future patch.

For compatibility with current userspace, when reading an ifname
that has not currently been set, the result is still "(unnamed
net_device)". Once a write to ifname happens, then reading ifname
will return whatever was last written.

Tested by configuring an rndis function and an ncm function on
the same gadget, and writing "rndis%d" to ifname on the rndis
function and "ncm%d" to ifname on the ncm function. When the
gadget was bound, the rndis interface was rndis0 and the ncm
interface was ncm0.

Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Link: https://lore.kernel.org/r/20210113234222.3272933-1-lorenzo@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-01-15 16:08:53 +01:00

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==============
Gadget Testing
==============
This file summarizes information on basic testing of USB functions
provided by gadgets.
.. contents
1. ACM function
2. ECM function
3. ECM subset function
4. EEM function
5. FFS function
6. HID function
7. LOOPBACK function
8. MASS STORAGE function
9. MIDI function
10. NCM function
11. OBEX function
12. PHONET function
13. RNDIS function
14. SERIAL function
15. SOURCESINK function
16. UAC1 function (legacy implementation)
17. UAC2 function
18. UVC function
19. PRINTER function
20. UAC1 function (new API)
1. ACM function
===============
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<X>
On the device::
cat /dev/ttyGS<Y>
then the other way round
On the device::
cat > /dev/ttyGS<Y>
On the host::
cat /dev/ttyACM<X>
2. ECM function
===============
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.<instance name> they contain default
values: qmult is 5, dev_addr and host_addr are randomly selected.
The ifname can be written to if the function is not bound. A write must be an
interface pattern such as "usb%d", which will cause the net core to choose the
next free usbX interface. By default, it is set to "usb%d".
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>
3. ECM subset function
======================
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.<instance name> they contain default
values: qmult is 5, dev_addr and host_addr are randomly selected.
The ifname can be written to if the function is not bound. A write must be an
interface pattern such as "usb%d", which will cause the net core to choose the
next free usbX interface. By default, it is set to "usb%d".
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>
4. EEM function
===============
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.<instance name> they contain default
values: qmult is 5, dev_addr and host_addr are randomly selected.
The ifname can be written to if the function is not bound. A write must be an
interface pattern such as "usb%d", which will cause the net core to choose the
next free usbX interface. By default, it is set to "usb%d".
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>
5. FFS function
===============
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/<gadget>/UDC.
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
6. HID function
===============
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<N>, e.g.
a userspace program found in Documentation/usb/gadget_hid.rst::
$ ./hid_gadget_test /dev/hidg0 keyboard
Host:
- observe the keystrokes from the gadget
7. LOOPBACK function
====================
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)
8. MASS STORAGE function
========================
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 <name>.<number> scheme. The numbers can be 0..8.
Probably a good convention is to name the luns "lun.<number>",
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)
9. MIDI function
================
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.
1) 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
2) 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.
10. NCM function
================
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.<instance name> they contain default
values: qmult is 5, dev_addr and host_addr are randomly selected.
The ifname can be written to if the function is not bound. A write must be an
interface pattern such as "usb%d", which will cause the net core to choose the
next free usbX interface. By default, it is set to "usb%d".
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>
11. OBEX function
=================
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<Y> -s 1024
On host::
serialc -v <vendorID> -p <productID> -i<interface#> -a1 -s1024 \
-t<out endpoint addr> -r<in endpoint addr>
where seriald and serialc are Felipe's utilities found here:
https://github.com/felipebalbi/usb-tools.git master
12. PHONET function
===================
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
13. RNDIS function
==================
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.<instance name> they contain default
values: qmult is 5, dev_addr and host_addr are randomly selected.
The ifname can be written to if the function is not bound. A write must be an
interface pattern such as "usb%d", which will cause the net core to choose the
next free usbX interface. By default, it is set to "usb%d".
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>
14. SERIAL function
===================
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<X>
On target::
cat /dev/ttyGS<Y>
then the other way round
On target::
cat > /dev/ttyGS<Y>
On host::
cat /dev/ttyUSB<X>
15. SOURCESINK function
=======================
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)
16. UAC1 function (legacy implementation)
=========================================
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
17. UAC2 function
=================
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
18. UVC function
================
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 <<EOF > 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
19. PRINTER function
====================
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<number>.
If udev is active, then /dev/g_printer<number> should appear automatically.
host:
If udev is active, then e.g. /dev/usb/lp0 should appear.
host->device transmission:
device::
# cat /dev/g_printer<number>
host::
# cat > /dev/usb/lp0
device->host transmission::
# cat > /dev/g_printer<number>
host::
# cat /dev/usb/lp0
More advanced testing can be done with the prn_example
described in Documentation/usb/gadget_printer.rst.
20. UAC1 function (virtual ALSA card, using u_audio API)
========================================================
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
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