[GitHub/moto-9609/android_kernel_motorola_exynos9610.git] / Documentation / usb / gadget-testing.txt

This file summarizes information on basic testing of USB functions
provided by gadgets.

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


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.
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>

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.
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>

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.
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>

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.txt:

$ ./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

http://www.linux-usb.org/usbtest/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.
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>

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://git.gitorious.org/usb/usb-tools.git master
Commit	Line	Data
e38eb2c8 AP	1	This file summarizes information on basic testing of USB functions
	2	provided by gadgets.
	3
	4	1. ACM function
d5862ca6	5	2. ECM function
7bfbc6e3	6	3. ECM subset function
4ca560a6	7	4. EEM function
2c0f62f9	8	5. FFS function
f7e3c3cd	9	6. HID function
ec91aff7	10	7. LOOPBACK function
cdbe287d	11	8. MASS STORAGE function
0d6be59a	12	9. MIDI function
4d0fa79e	13	10. NCM function
d81b85dc	14	11. OBEX function
e38eb2c8 AP	15
	16
	17	1. ACM function
	18	===============
	19
	20	The function is provided by usb_f_acm.ko module.
	21
	22	Function-specific configfs interface
	23	------------------------------------
	24
	25	The function name to use when creating the function directory is "acm".
	26	The ACM function provides just one attribute in its function directory:
	27
	28	port_num
	29
	30	The attribute is read-only.
	31
	32	There can be at most 4 ACM/generic serial/OBEX ports in the system.
	33
	34
	35	Testing the ACM function
	36	------------------------
	37
	38	On the host: cat > /dev/ttyACM<X>
	39	On the device : cat /dev/ttyGS<Y>
	40
	41	then the other way round
	42
	43	On the device: cat > /dev/ttyGS<Y>
	44	On the host: cat /dev/ttyACM<X>
d5862ca6 AP	45
	46	2. ECM function
	47	===============
	48
	49	The function is provided by usb_f_ecm.ko module.
	50
	51	Function-specific configfs interface
	52	------------------------------------
	53
	54	The function name to use when creating the function directory is "ecm".
	55	The ECM function provides these attributes in its function directory:
	56
	57	ifname - network device interface name associated with this
	58	function instance
	59	qmult - queue length multiplier for high and super speed
	60	host_addr - MAC address of host's end of this
	61	Ethernet over USB link
	62	dev_addr - MAC address of device's end of this
	63	Ethernet over USB link
	64
	65	and after creating the functions/ecm.<instance name> they contain default
	66	values: qmult is 5, dev_addr and host_addr are randomly selected.
	67	Except for ifname they can be written to until the function is linked to a
	68	configuration. The ifname is read-only and contains the name of the interface
	69	which was assigned by the net core, e. g. usb0.
	70
	71	Testing the ECM function
	72	------------------------
	73
	74	Configure IP addresses of the device and the host. Then:
	75
	76	On the device: ping <host's IP>
	77	On the host: ping <device's IP>
7bfbc6e3 AP	78
	79	3. ECM subset function
	80	======================
	81
	82	The function is provided by usb_f_ecm_subset.ko module.
	83
	84	Function-specific configfs interface
	85	------------------------------------
	86
	87	The function name to use when creating the function directory is "geth".
	88	The ECM subset function provides these attributes in its function directory:
	89
	90	ifname - network device interface name associated with this
	91	function instance
	92	qmult - queue length multiplier for high and super speed
	93	host_addr - MAC address of host's end of this
	94	Ethernet over USB link
	95	dev_addr - MAC address of device's end of this
	96	Ethernet over USB link
	97
	98	and after creating the functions/ecm.<instance name> they contain default
	99	values: qmult is 5, dev_addr and host_addr are randomly selected.
	100	Except for ifname they can be written to until the function is linked to a
	101	configuration. The ifname is read-only and contains the name of the interface
	102	which was assigned by the net core, e. g. usb0.
	103
	104	Testing the ECM subset function
	105	-------------------------------
	106
	107	Configure IP addresses of the device and the host. Then:
	108
	109	On the device: ping <host's IP>
	110	On the host: ping <device's IP>
4ca560a6 AP	111
	112	4. EEM function
	113	===============
	114
	115	The function is provided by usb_f_eem.ko module.
	116
	117	Function-specific configfs interface
	118	------------------------------------
	119
	120	The function name to use when creating the function directory is "eem".
	121	The EEM function provides these attributes in its function directory:
	122
	123	ifname - network device interface name associated with this
	124	function instance
	125	qmult - queue length multiplier for high and super speed
	126	host_addr - MAC address of host's end of this
	127	Ethernet over USB link
	128	dev_addr - MAC address of device's end of this
	129	Ethernet over USB link
	130
	131	and after creating the functions/eem.<instance name> they contain default
	132	values: qmult is 5, dev_addr and host_addr are randomly selected.
	133	Except for ifname they can be written to until the function is linked to a
	134	configuration. The ifname is read-only and contains the name of the interface
	135	which was assigned by the net core, e. g. usb0.
	136
	137	Testing the EEM function
	138	------------------------
	139
	140	Configure IP addresses of the device and the host. Then:
	141
	142	On the device: ping <host's IP>
	143	On the host: ping <device's IP>
2c0f62f9 AP	144
	145	5. FFS function
	146	===============
	147
	148	The function is provided by usb_f_fs.ko module.
	149
	150	Function-specific configfs interface
	151	------------------------------------
	152
	153	The function name to use when creating the function directory is "ffs".
	154	The function directory is intentionally empty and not modifiable.
	155
	156	After creating the directory there is a new instance (a "device") of FunctionFS
	157	available in the system. Once a "device" is available, the user should follow
	158	the standard procedure for using FunctionFS (mount it, run the userspace
	159	process which implements the function proper). The gadget should be enabled
	160	by writing a suitable string to usb_gadget/<gadget>/UDC.
	161
	162	Testing the FFS function
	163	------------------------
	164
	165	On the device: start the function's userspace daemon, enable the gadget
	166	On the host: use the USB function provided by the device
f7e3c3cd AP	167
	168	6. HID function
	169	===============
	170
	171	The function is provided by usb_f_hid.ko module.
	172
	173	Function-specific configfs interface
	174	------------------------------------
	175
	176	The function name to use when creating the function directory is "hid".
	177	The HID function provides these attributes in its function directory:
	178
	179	protocol - HID protocol to use
	180	report_desc - data to be used in HID reports, except data
	181	passed with /dev/hidg<X>
	182	report_length - HID report length
	183	subclass - HID subclass to use
	184
	185	For a keyboard the protocol and the subclass are 1, the report_length is 8,
	186	while the report_desc is:
	187
	188	$ hd my_report_desc
	189	00000000 05 01 09 06 a1 01 05 07 19 e0 29 e7 15 00 25 01 \|..........)...%.\|
	190	00000010 75 01 95 08 81 02 95 01 75 08 81 03 95 05 75 01 \|u.......u.....u.\|
	191	00000020 05 08 19 01 29 05 91 02 95 01 75 03 91 03 95 06 \|....).....u.....\|
	192	00000030 75 08 15 00 25 65 05 07 19 00 29 65 81 00 c0 \|u...%e....)e...\|
	193	0000003f
	194
	195	Such a sequence of bytes can be stored to the attribute with echo:
	196
	197	$ echo -ne \\x05\\x01\\x09\\x06\\xa1.....
	198
	199	Testing the HID function
	200	------------------------
	201
	202	Device:
	203	- create the gadget
	204	- connect the gadget to a host, preferably not the one used
	205	to control the gadget
	206	- run a program which writes to /dev/hidg<N>, e.g.
	207	a userspace program found in Documentation/usb/gadget_hid.txt:
	208
	209	$ ./hid_gadget_test /dev/hidg0 keyboard
	210
	211	Host:
	212	- observe the keystrokes from the gadget
ec91aff7 AP	213
	214	7. LOOPBACK function
	215	====================
	216
	217	The function is provided by usb_f_ss_lb.ko module.
	218
	219	Function-specific configfs interface
	220	------------------------------------
	221
	222	The function name to use when creating the function directory is "Loopback".
	223	The LOOPBACK function provides these attributes in its function directory:
	224
	225	qlen - depth of loopback queue
	226	bulk_buflen - buffer length
	227
	228	Testing the LOOPBACK function
	229	-----------------------------
	230
	231	device: run the gadget
	232	host: test-usb
	233
	234	http://www.linux-usb.org/usbtest/testusb.c
cdbe287d AP	235
	236	8. MASS STORAGE function
	237	========================
	238
	239	The function is provided by usb_f_mass_storage.ko module.
	240
	241	Function-specific configfs interface
	242	------------------------------------
	243
	244	The function name to use when creating the function directory is "mass_storage".
	245	The MASS STORAGE function provides these attributes in its directory:
	246	files:
	247
	248	stall - Set to permit function to halt bulk endpoints.
	249	Disabled on some USB devices known not to work
	250	correctly. You should set it to true.
	251	num_buffers - Number of pipeline buffers. Valid numbers
	252	are 2..4. Available only if
	253	CONFIG_USB_GADGET_DEBUG_FILES is set.
	254
	255	and a default lun.0 directory corresponding to SCSI LUN #0.
	256
	257	A new lun can be added with mkdir:
	258
	259	$ mkdir functions/mass_storage.0/partition.5
	260
	261	Lun numbering does not have to be continuous, except for lun #0 which is
	262	created by default. A maximum of 8 luns can be specified and they all must be
	263	named following the <name>.<number> scheme. The numbers can be 0..8.
	264	Probably a good convention is to name the luns "lun.<number>",
	265	although it is not mandatory.
	266
	267	In each lun directory there are the following attribute files:
	268
	269	file - The path to the backing file for the LUN.
	270	Required if LUN is not marked as removable.
	271	ro - Flag specifying access to the LUN shall be
	272	read-only. This is implied if CD-ROM emulation
	273	is enabled as well as when it was impossible
	274	to open "filename" in R/W mode.
	275	removable - Flag specifying that LUN shall be indicated as
	276	being removable.
	277	cdrom - Flag specifying that LUN shall be reported as
	278	being a CD-ROM.
	279	nofua - Flag specifying that FUA flag
	280	in SCSI WRITE(10,12)
	281
	282	Testing the MASS STORAGE function
	283	---------------------------------
	284
	285	device: connect the gadget, enable it
	286	host: dmesg, see the USB drives appear (if system configured to automatically
	287	mount)
0d6be59a AP	288
	289	9. MIDI function
	290	================
	291
	292	The function is provided by usb_f_midi.ko module.
	293
	294	Function-specific configfs interface
	295	------------------------------------
	296
	297	The function name to use when creating the function directory is "midi".
	298	The MIDI function provides these attributes in its function directory:
	299
	300	buflen - MIDI buffer length
	301	id - ID string for the USB MIDI adapter
	302	in_ports - number of MIDI input ports
	303	index - index value for the USB MIDI adapter
	304	out_ports - number of MIDI output ports
	305	qlen - USB read request queue length
	306
	307	Testing the MIDI function
	308	-------------------------
	309
	310	There are two cases: playing a mid from the gadget to
	311	the host and playing a mid from the host to the gadget.
	312
	313	1) Playing a mid from the gadget to the host
	314	host)
	315
	316	$ arecordmidi -l
	317	Port Client name Port name
	318	14:0 Midi Through Midi Through Port-0
	319	24:0 MIDI Gadget MIDI Gadget MIDI 1
	320	$ arecordmidi -p 24:0 from_gadget.mid
	321
	322	gadget)
	323
	324	$ aplaymidi -l
	325	Port Client name Port name
	326	20:0 f_midi f_midi
	327
	328	$ aplaymidi -p 20:0 to_host.mid
	329
	330	2) Playing a mid from the host to the gadget
	331	gadget)
	332
	333	$ arecordmidi -l
	334	Port Client name Port name
	335	20:0 f_midi f_midi
	336
	337	$ arecordmidi -p 20:0 from_host.mid
	338
	339	host)
	340
	341	$ aplaymidi -l
	342	Port Client name Port name
	343	14:0 Midi Through Midi Through Port-0
	344	24:0 MIDI Gadget MIDI Gadget MIDI 1
	345
	346	$ aplaymidi -p24:0 to_gadget.mid
	347
	348	The from_gadget.mid should sound identical to the to_host.mid.
	349	The from_host.id should sound identical to the to_gadget.mid.
	350
	351	MIDI files can be played to speakers/headphones with e.g. timidity installed
352
353	$ aplaymidi -l
354	Port Client name Port name
355	14:0 Midi Through Midi Through Port-0
356	24:0 MIDI Gadget MIDI Gadget MIDI 1
357	128:0 TiMidity TiMidity port 0
358	128:1 TiMidity TiMidity port 1
359	128:2 TiMidity TiMidity port 2
360	128:3 TiMidity TiMidity port 3
361
362	$ aplaymidi -p 128:0 file.mid
363
364	MIDI ports can be logically connected using the aconnect utility, e.g.:
365
366	$ aconnect 24:0 128:0 # try it on the host
367
368	After the gadget's MIDI port is connected to timidity's MIDI port,
369	whatever is played at the gadget side with aplaymidi -l is audible
370	in host's speakers/headphones.
4d0fa79e AP	371
	372	10. NCM function
	373	================
	374
	375	The function is provided by usb_f_ncm.ko module.
	376
	377	Function-specific configfs interface
	378	------------------------------------
	379
	380	The function name to use when creating the function directory is "ncm".
	381	The NCM function provides these attributes in its function directory:
	382
	383	ifname - network device interface name associated with this
	384	function instance
	385	qmult - queue length multiplier for high and super speed
	386	host_addr - MAC address of host's end of this
	387	Ethernet over USB link
	388	dev_addr - MAC address of device's end of this
	389	Ethernet over USB link
	390
	391	and after creating the functions/ncm.<instance name> they contain default
	392	values: qmult is 5, dev_addr and host_addr are randomly selected.
	393	Except for ifname they can be written to until the function is linked to a
	394	configuration. The ifname is read-only and contains the name of the interface
	395	which was assigned by the net core, e. g. usb0.
	396
	397	Testing the NCM function
	398	------------------------
	399
	400	Configure IP addresses of the device and the host. Then:
	401
	402	On the device: ping <host's IP>
	403	On the host: ping <device's IP>
d81b85dc AP	404
	405	11. OBEX function
	406	=================
	407
	408	The function is provided by usb_f_obex.ko module.
	409
	410	Function-specific configfs interface
	411	------------------------------------
	412
	413	The function name to use when creating the function directory is "obex".
	414	The OBEX function provides just one attribute in its function directory:
	415
	416	port_num
	417
	418	The attribute is read-only.
	419
	420	There can be at most 4 ACM/generic serial/OBEX ports in the system.
	421
	422	Testing the OBEX function
	423	-------------------------
	424
	425	On device: seriald -f /dev/ttyGS<Y> -s 1024
	426	On host: serialc -v <vendorID> -p <productID> -i<interface#> -a1 -s1024 \
	427	-t<out endpoint addr> -r<in endpoint addr>
	428
	429	where seriald and serialc are Felipe's utilities found here:
	430
	431	https://git.gitorious.org/usb/usb-tools.git master