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linux/Documentation/usb/gadget-testing.rst
Chris Wulff 82313624b2 usb: gadget: f_uac1: Change volume name and remove alt names 
This changes the UAPI to align with disussion of alt settings work.

fu_name is renamed to fu_vol_name, and alt settings mode names
are removed for now in favor of future work where they will be
settable in subdirectories for each alt mode.

discussion thread for api changes for alt mode settings:
https://lore.kernel.org/linux-usb/35be4668-58d3-894a-72cf-de1afaacae45@ivitera.com/T/

Signed-off-by: Chris Wulff <crwulff@gmail.com>
Link: https://lore.kernel.org/r/20240804002912.3293177-2-crwulff@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2024-08-13 18:11:35 +02:00

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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)
21. MIDI2 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.
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.
The FFS function provides just one attribute in its function directory:
ready
The attribute is read-only and signals if the function is ready (1) to be
used, E.G. if userspace has written descriptors and strings to ep0, so
the gadget can be enabled.
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)
forced_eject This write-only file is useful only when
the function is active. It causes the backing
file to be forcibly detached from the LUN,
regardless of whether the host has allowed it.
Any non-zero number of bytes written will
result in ejection.
=============== ==============================================
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
max_segment_size Segment size required for P2P connections. This
will set MTU to 14 bytes
======================= ==================================================
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 list of capture sampling rates (comma-separated)
c_ssize capture sample size (bytes)
c_sync capture synchronization type (async/adaptive)
c_mute_present capture mute control enable
c_volume_present capture volume control enable
c_volume_min capture volume control min value (in 1/256 dB)
c_volume_max capture volume control max value (in 1/256 dB)
c_volume_res capture volume control resolution (in 1/256 dB)
c_hs_bint capture bInterval for HS/SS (1-4: fixed, 0: auto)
fb_max maximum extra bandwidth in async mode
p_chmask playback channel mask
p_srate list of playback sampling rates (comma-separated)
p_ssize playback sample size (bytes)
p_mute_present playback mute control enable
p_volume_present playback volume control enable
p_volume_min playback volume control min value (in 1/256 dB)
p_volume_max playback volume control max value (in 1/256 dB)
p_volume_res playback volume control resolution (in 1/256 dB)
p_hs_bint playback bInterval for HS/SS (1-4: fixed, 0: auto)
req_number the number of pre-allocated request for both capture
and playback
function_name name of the interface
if_ctrl_name topology control name
clksrc_in_name input clock name
clksrc_out_name output clock name
p_it_name playback input terminal name
p_it_ch_name playback input first channel name
p_ot_name playback output terminal name
p_fu_vol_name playback function unit name
c_it_name capture input terminal name
c_it_ch_name capture input first channel name
c_ot_name capture output terminal name
c_fu_vol_name capture functional unit name
c_terminal_type code of the capture terminal type
p_terminal_type code of the playback terminal type
================ ====================================================
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
function_name name of the interface
=================== ================================================
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 interval 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 list of capture sampling rates (comma-separated)
c_ssize capture sample size (bytes)
c_mute_present capture mute control enable
c_volume_present capture volume control enable
c_volume_min capture volume control min value (in 1/256 dB)
c_volume_max capture volume control max value (in 1/256 dB)
c_volume_res capture volume control resolution (in 1/256 dB)
p_chmask playback channel mask
p_srate list of playback sampling rates (comma-separated)
p_ssize playback sample size (bytes)
p_mute_present playback mute control enable
p_volume_present playback volume control enable
p_volume_min playback volume control min value (in 1/256 dB)
p_volume_max playback volume control max value (in 1/256 dB)
p_volume_res playback volume control resolution (in 1/256 dB)
req_number the number of pre-allocated requests for both capture
and playback
function_name name of the interface
p_it_name playback input terminal name
p_it_ch_name playback channels name
p_ot_name playback output terminal name
p_fu_vol_name playback mute/volume functional unit name
c_it_name capture input terminal name
c_it_ch_name capture channels name
c_ot_name capture output terminal name
c_fu_vol_name capture mute/volume functional unit name
================ ====================================================
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
21. MIDI2 function
==================
The function is provided by usb_f_midi2.ko module.
It will create a virtual ALSA card containing a UMP rawmidi device
where the UMP packet is looped back. In addition, a legacy rawmidi
device is created. The UMP rawmidi is bound with ALSA sequencer
clients, too.
Function-specific configfs interface
------------------------------------
The function name to use when creating the function directory is "midi2".
The midi2 function provides these attributes in its function directory
as the card top-level information:
============= =================================================
process_ump Bool flag to process UMP Stream messages (0 or 1)
static_block Bool flag for static blocks (0 or 1)
iface_name Optional interface name string
============= =================================================
The directory contains a subdirectory "ep.0", and this provides the
attributes for a UMP Endpoint (which is a pair of USB MIDI Endpoints):
============= =================================================
protocol_caps MIDI protocol capabilities;
1: MIDI 1.0, 2: MIDI 2.0, or 3: both protocols
protocol Default MIDI protocol (either 1 or 2)
ep_name UMP Endpoint name string
product_id Product ID string
manufacturer Manufacture ID number (24 bit)
family Device family ID number (16 bit)
model Device model ID number (16 bit)
sw_revision Software revision (32 bit)
============= =================================================
Each Endpoint subdirectory contains a subdirectory "block.0", which
represents the Function Block for Block 0 information.
Its attributes are:
================= ===============================================
name Function Block name string
direction Direction of this FB
1: input, 2: output, or 3: bidirectional
first_group The first UMP Group number (0-15)
num_groups The number of groups in this FB (1-16)
midi1_first_group The first UMP Group number for MIDI 1.0 (0-15)
midi1_num_groups The number of groups for MIDI 1.0 (0-16)
ui_hint UI-hint of this FB
0: unknown, 1: receiver, 2: sender, 3: both
midi_ci_verison Supported MIDI-CI version number (8 bit)
is_midi1 Legacy MIDI 1.0 device (0-2)
0: MIDI 2.0 device,
1: MIDI 1.0 without restriction, or
2: MIDI 1.0 with low speed
sysex8_streams Max number of SysEx8 streams (8 bit)
active Bool flag for FB activity (0 or 1)
================= ===============================================
If multiple Function Blocks are required, you can add more Function
Blocks by creating subdirectories "block.<num>" with the corresponding
Function Block number (1, 2, ....). The FB subdirectories can be
dynamically removed, too. Note that the Function Block numbers must be
continuous.
Similarly, if you multiple UMP Endpoints are required, you can add
more Endpoints by creating subdirectories "ep.<num>". The number must
be continuous.
For emulating the old MIDI 2.0 device without UMP v1.1 support, pass 0
to `process_ump` flag. Then the whole UMP v1.1 requests are ignored.
Testing the MIDI2 function
--------------------------
On the device: run the gadget, and running::
$ cat /proc/asound/cards
will show a new sound card containing a MIDI2 device.
OTOH, on the host::
$ cat /proc/asound/cards
will show a new sound card containing either MIDI1 or MIDI2 device,
depending on the USB audio driver configuration.
On both, when ALSA sequencer is enabled on the host, you can find the
UMP MIDI client such as "MIDI 2.0 Gadget".
As the driver simply loops back the data, there is no need for a real
device just for testing.
For testing a MIDI input from the gadget to the host (e.g. emulating a
MIDI keyboard), you can send a MIDI stream like the following.
On the gadget::
$ aconnect -o
....
client 20: 'MIDI 2.0 Gadget' [type=kernel,card=1]
0 'MIDI 2.0 '
1 'Group 1 (MIDI 2.0 Gadget I/O)'
$ aplaymidi -p 20:1 to_host.mid
On the host::
$ aconnect -i
....
client 24: 'MIDI 2.0 Gadget' [type=kernel,card=2]
0 'MIDI 2.0 '
1 'Group 1 (MIDI 2.0 Gadget I/O)'
$ arecordmidi -p 24:1 from_gadget.mid
If you have a UMP-capable application, you can use the UMP port to
send/receive the raw UMP packets, too. For example, aseqdump program
with UMP support can receive from UMP port. On the host::
$ aseqdump -u 2 -p 24:1
Waiting for data. Press Ctrl+C to end.
Source Group Event Ch Data
24:1 Group 0, Program change 0, program 0, Bank select 0:0
24:1 Group 0, Channel pressure 0, value 0x80000000
For testing a MIDI output to the gadget to the host (e.g. emulating a
MIDI synth), it'll be just other way round.
On the gadget::
$ arecordmidi -p 20:1 from_host.mid
On the host::
$ aplaymidi -p 24:1 to_gadget.mid
The access to MIDI 1.0 on altset 0 on the host is supported, and it's
translated from/to UMP packets on the gadget. It's bound to only
Function Block 0.
The current operation mode can be observed in ALSA control element
"Operation Mode" for SND_CTL_IFACE_RAWMIDI. For example::
$ amixer -c1 contents
numid=1,iface=RAWMIDI,name='Operation Mode'
; type=INTEGER,access=r--v----,values=1,min=0,max=2,step=0
: values=2
where 0 = unused, 1 = MIDI 1.0 (altset 0), 2 = MIDI 2.0 (altset 1).
The example above shows it's running in 2, i.e. MIDI 2.0.
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