Changes between Version 1 and Version 2 of linux/OTG


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Timestamp:
01/31/2018 10:53:54 PM (7 months ago)
Author:
Tim Harvey
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  • linux/OTG

    v1 v2  
    1 {{{#!html
    2           <div id="wikipage" class="trac-content"><p>
    3 </p><div class="wiki-toc">
    4 <ol>
    5   <li>
    6     <a href="#USBOn-The-GoOTG">USB On-The-Go (OTG)</a>
    7     <ol>
    8       <li>
    9         <a href="#USBHostMode">USB Host Mode</a>
    10       </li>
    11       <li>
    12         <a href="#USBDeviceModeUDC">USB Device Mode (UDC)</a>
    13         <ol>
    14           <li>
    15             <a href="#g_etherGadget">g_ether Gadget</a>
    16           </li>
    17           <li>
    18             <a href="#g_mass_storage-USBMassStorageDevice">g_mass_storage - USB Mass Storage Device</a>
    19           </li>
    20           <li>
    21             <a href="#g_file_storage-USBMassStorageDevice">g_file_storage - USB Mass Storage Device</a>
    22           </li>
    23           <li>
    24             <a href="#g_serial-SerialDeviceGadget">g_serial - Serial Device Gadget</a>
    25           </li>
    26           <li>
    27             <a href="#g_cdc-CompositeEthernetSerialGadget">g_cdc - Composite Ethernet + Serial Gadget</a>
    28           </li>
    29           <li>
    30             <a href="#g_multi-CompositeEthernetSerialMassStorageGadget">g_multi - Composite Ethernet + Serial + Mass Storage Gadget</a>
    31           </li>
    32           <li>
    33             <a href="#g_hid-HumanInterfaceDeviceHIDGadget">g_hid - Human Interface Device (HID) Gadget</a>
    34           </li>
    35           <li>
    36             <a href="#g_webcam-CompositeUSBAudioandVideoClassGadget">g_webcam - Composite USB Audio and Video Class Gadget</a>
    37           </li>
    38           <li>
    39             <a href="#g_ncm-USBCDCNCMsubclassEthernetGadget">g_ncm - USB CDC NCM subclass Ethernet Gadget</a>
    40           </li>
    41           <li>
    42             <a href="#ConfigFs">ConfigFs</a>
    43           </li>
    44         </ol>
    45       </li>
    46     </ol>
    47   </li>
    48   <li>
    49     <a href="#OpenWrtOTG">OpenWrt OTG</a>
    50   </li>
    51 </ol>
    52 </div><p>
    53 </p>
    54 <h1 id="USBOn-The-GoOTG">USB On-The-Go (OTG)</h1>
    55 <p>
    56 See <a class="wiki" href="/wiki/linux/OTG">OTG</a> for more info.
    57 </p>
    58 <h2 id="USBHostMode">USB Host Mode</h2>
    59 <p>
    60 A Host mode cable allows connecting to a USB device.  No special configuration is necessary for this.
    61 </p>
    62 <h2 id="USBDeviceModeUDC">USB Device Mode (UDC)</h2>
    63 <p>
    64 A Device mode cable allows connection to a USB host such as a PC. 
    65 </p>
    66 <p>
     1[[PageOutline]]
     2
     3= USB On-The-Go (OTG) =
     4Certain devices have USB Device Controllers or Dual-Role controllers that can be used in either host mode or device mode.
     5
     6This page aims to document how to use and configure USB OTG gadget devices on Linux for boards you wish to connect to a USB Host port and behave like a 'device'.
     7 
     8See also [wiki:USB_OTG USB_OTG]
     9
     10
     11[=#host]
     12== USB Host Mode ==
     13A Host mode cable allows connecting to a USB device. No special configuration is necessary for this.
     14
     15
     16[=#device]
     17== USB Device Mode ==
     18A Device mode cable allows connection to a USB host such as a PC.
     19
    6720When used in this mode, the device needs to have a 'Gadget driver' loaded which implements the personality of the device type you want.
    68 </p>
    69 <p>
    70 There are several Linux gadget drivers in today's linux kernel. These can be found under the <tt>Device Drivers -&gt; USB support -&gt; USB Gadget Support</tt> menu:
    71 </p>
    72 <ul><li>g_zero (CONFIG_USB_ZERO)
    73 </li><li>g_audio (CONFIG_USB_AUDIO)
    74 </li><li><a class="wiki" href="/wiki/linux/OTG#g_ether">g_ether</a> (CONFIG_USB_ETH) - implement a 'Communication Device Class' (CDC) Ethernet device to create a 'USB to Ethernet' network connection.
    75 </li><li><a class="wiki" href="/wiki/linux/OTG#g_ncm">g_ncm</a> (CONFIG_USB_G_NCM) - implement USB CDC NCM subclass standard. NCM is an advanced protocol for Ethernet encapsulation and allows grouping of several ethernet frames into one USB transfer.
    76 </li><li><a class="wiki" href="/wiki/linux/OTG#g_mass_storage">g_mass_storage</a> (CONFIG_USB_MASS_STORAGE) - acts as a USB Mass Storage disk driver. Its storage repository can use a regular file or a block device specified as a module parameter or sysfs option.
    77 </li><li><a class="wiki" href="/wiki/linux/OTG#g_serial">g_serial</a> (CONFIG_USB_G_SERIAL) - behave as a ACM Serial device to create a 'USB to Serial' connection which can be used to interoperate with MS-Windows hosts or with the Linux-USB 'cdc-acm' driver.
    78 </li><li>g_midi (CONFIG_USB_MIDI_GADGET) - acts as a USB Audio device with one MIDI input and one MIDI output.
    79 </li><li>g_printer (CONFIG_USB_G_PRINTER) - channels data between the USB host and a userspace program driving the print engine.
    80 </li><li><a class="wiki" href="/wiki/linux/OTG#g_cdc">g_cdc</a> (CONFIG_USB_CDC_COMPOSITE) - provides two functions in one configuration:  a CDC Ethernet (ECM) link, and a CDC ACM (serial port) link
    81 </li><li>g_acm_ms (CONFIG_USB_G_ACM_MS) - provides two functions in one configuration: a USB Mass Storage device and a CDC ACM (serial port) link
    82 </li><li><a class="wiki" href="/wiki/linux/OTG#g_multi">g_multi</a> (CONFIG_USB_G_MULTI) - A multifunction composite gadget that can provide Ethernet (RNDIS and/or CDC), mass storage, and ACM serial link interfaces
    83 </li><li><a class="wiki" href="/wiki/linux/OTG#g_hid">g_hid</a> (CONFIG_USB_G_HID) - A Human Interface Device (HID) gadget that provides a generic interface for things such as keyboards, mice, touchscreens
    84 </li><li><a class="wiki" href="/wiki/linux/OTG#g_webcam">g_webcam</a> - A Webcam Device
    85 </li></ul><p>
    86 Additionally The Linux <a class="wiki" href="/wiki/linux/OTG#configfs">Configfs</a> (CONFIG_CONFIGFS_FS) support allows complete dynamic configuration of gadget devices from userspace in which case you can create a single configuration or multi-configuration composite device with one or more of the functions available from drivers/usb/gadget/udc/functions. See <a class="wiki" href="/wiki/linux/OTG#configfs">below</a> for more details on how to use this.
    87 </p>
    88 <p>
    89 Note that only one gadget driver (device personality) can be loaded at a time but there are some 'composite' gadget drivers that behave as 'composite devices' meaning they have multiple endpoints per USB device.  This will seem familiar if you think of how a modern smart-phone works.  Take an Android phone for example:  When plugged into a host PC via micro-USB OTG, it will behave as a storage device (MTP), however if you want to have it behave as a serial debug device you have to go into the developer menu and select this option.  Note that modern smartphones no longer behave as 'USB Mass Storage' devices as this protocol does not allow the device OS to access the filesystem at the same time the host PC does - instead these devices act as an MTP (<a class="ext-link" href="http://en.wikipedia.org/wiki/Media_Transfer_Protocol"><span class="icon">​</span>Media Transfer Protocol</a>) device.
    90 </p>
    91 <p>
    92 Note that the Vendor ID (VID) and Device ID (DID) that is presented to the USB host is configuable (see <a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/gadget_configfs.txt"><span class="icon">​</span>here</a> for details)
    93 </p>
    94 <p>
    95 <span class="wikianchor" id="g_ether"></span>
    96 </p>
    97 <h3 id="g_etherGadget">g_ether Gadget</h3>
    98 <p>
    99 The g_ether gadget driver behaves as a USB-to-Ethernet dongle.  Once loaded the device-mode system will add a 'usb&lt;n&gt;' network device which can be used the same as any other network device.  On the USB host system, a similar network device will appear as long as a driver supporting the 'CDC Ethernet' standard is available.
    100 </p>
    101 <p>
     21
     22There are several Linux gadget drivers in today's linux kernel. These can be found under the {{{Device Drivers -> USB support -> USB Gadget Support menu}}}:
     23 * g_zero (CONFIG_USB_ZERO)
     24 * g_audio (CONFIG_USB_AUDIO)
     25 * [#g_ether g_ether] (CONFIG_USB_ETH) - implement a 'Communication Device Class' (CDC) Ethernet device to create a 'USB to Ethernet' network connection.
     26 * [#g_ncm g_ncm] (CONFIG_USB_G_NCM) - implement USB CDC NCM subclass standard. NCM is an advanced protocol for Ethernet encapsulation and allows grouping of several ethernet frames into one USB transfer.
     27 * [#g_mass_storage g_mass_storage] (CONFIG_USB_MASS_STORAGE) - acts as a USB Mass Storage disk driver. Its storage repository can use a regular file or a block device specified as a module parameter or sysfs option.
     28 * [#g_serial g_serial] (CONFIG_USB_G_SERIAL) - behave as a ACM Serial device to create a 'USB to Serial' connection which can be used to interoperate with MS-Windows hosts or with the Linux-USB 'cdc-acm' driver.
     29 * g_midi (CONFIG_USB_MIDI_GADGET) - acts as a USB Audio device with one MIDI input and one MIDI output.
     30 * g_printer (CONFIG_USB_G_PRINTER) - channels data between the USB host and a userspace program driving the print engine.
     31 * [#g_cdc g_cdc] (CONFIG_USB_CDC_COMPOSITE) - provides two functions in one configuration: a CDC Ethernet (ECM) link, and a CDC ACM (serial port) link
     32 * g_acm_ms (CONFIG_USB_G_ACM_MS) - provides two functions in one configuration: a USB Mass Storage device and a CDC ACM (serial port) link
     33 * [#g_multi g_multi] (CONFIG_USB_G_MULTI) - A multifunction composite gadget that can provide Ethernet (RNDIS and/or CDC), mass storage, and ACM serial link interfaces
     34 * [#g_hid g_hid] (CONFIG_USB_G_HID) - A Human Interface Device (HID) gadget that provides a generic interface for things such as keyboards, mice, touchscreens
     35 * [#g_webcam g_webcam] - A Webcam Device
     36
     37Additionally The Linux [#configfs Configfs] (CONFIG_CONFIGFS_FS) support allows complete dynamic configuration of gadget devices from userspace in which case you can create a single configuration or multi-configuration composite device with one or more of the functions available from drivers/usb/gadget/udc/functions. See [#configfs below] for more details on how to use this.
     38
     39Note that only one gadget driver (device personality) can be loaded at a time but there are some 'composite' gadget drivers that behave as 'composite devices' meaning they have multiple endpoints per USB device. This will seem familiar if you think of how a modern smart-phone works. Take an Android phone for example: When plugged into a host PC via micro-USB OTG, it will behave as a storage device (MTP), however if you want to have it behave as a serial debug device you have to go into the developer menu and select this option. Note that modern smartphones no longer behave as 'USB Mass Storage' devices as this protocol does not allow the device OS to access the filesystem at the same time the host PC does - instead these devices act as an MTP (​[http://en.wikipedia.org/wiki/Media_Transfer_Protocol Media Transfer Protocol]) device.
     40
     41Note that the Vendor ID (VID) and Device ID (DID) that is presented to the USB host is configurable (see [https://www.kernel.org/doc/Documentation/usb/gadget_configfs.txt ​here] for details)
     42
     43
     44[=#g_ether]
     45=== g_ether Gadget ===
     46The g_ether gadget driver behaves as a USB-to-Ethernet dongle. Once loaded the device-mode system will add a 'usb<n>' network device which can be used the same as any other network device. On the USB host system, a similar network device will appear as long as a driver supporting the 'CDC Ethernet' standard is available.
     47
    10248This module can be built with additional support:
    103 </p>
    104 <ul><li>EEM: CDC Ethernet Emulation Model (EEM) is a newer standard that has a a simpler interface that can be used by more USB host hardware.
    105 </li><li>RNDIS: RNDIS support is an additional option (more CPU intensive) that may be more compatible with Windows drivers.
    106 </li></ul><p>
    107 Example:
    108 </p>
    109 <ul><li>on target device (Gateworks board with OTG controller):
    110 <pre class="wiki">modprobe g_ether
    111 </pre><ul><li>usb0 network interface appears on target (treat like any other network interface)
    112 </li></ul></li><li>on host device (ie PC) a device with VID:PID 0525:a4a2 will appear conforming to the <a class="ext-link" href="http://en.wikipedia.org/wiki/USB_communications_device_class"><span class="icon">​</span>CDC Ethernet</a> standard
    113 <ul><li>usb0 appears on Linux host (using the cdc_ether driver)
    114 </li></ul></li><li>module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
    115 </li><li>module parameters can specify the device and host ethernet address and whether or not to use CDC EEM mode
    116 </li></ul><p>
     49 * EEM: CDC Ethernet Emulation Model (EEM) is a newer standard that has a a simpler interface that can be used by more USB host hardware.
     50 * RNDIS: RNDIS support is an additional option (more CPU intensive) that may be more compatible with Windows drivers.
     51Example:
     52 * on target device (Gateworks board with OTG controller):
     53{{{#!bash
     54modprobe g_ether
     55}}}
     56  - usb0 network interface appears on target (treat like any other network interface)
     57 * on host device (ie PC) a device with VID:PID 0525:a4a2 will appear conforming to the ​CDC Ethernet standard
     58  - usb0 appears on Linux host (using the cdc_ether driver)
     59 * module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
     60 * module parameters can specify the device and host ethernet address and whether or not to use CDC EEM mode
     61
    11762Linux Host Notes:
    118 </p>
    119 <ul><li>cdc_ether driver supports this and will create a 'usb&lt;n&gt;' device on the USB host
    120 </li></ul><p>
     63 * cdc_ether driver supports this and will create a 'usb<n>' device on the USB host
     64
    12165Windows Host Notes:
    122 </p>
    123 <ul><li>the g_ether driver is typically built with RNDIS support enabled which will make it compatible with drivers in Windows7 and above which will appear in the device manager as a 'USB Ethernet/RNDIS Gadget' and can be configured just as any other network interface.
    124 </li></ul><p>
     66 * the g_ether driver is typically built with RNDIS support enabled which will make it compatible with drivers in Windows7 and above which will appear in the device manager as a 'USB Ethernet/RNDIS Gadget' and can be configured just as any other network interface.
     67
    12568Reference:
    126 </p>
    127 <ul><li><a class="ext-link" href="http://en.wikipedia.org/wiki/USB_communications_device_class"><span class="icon">​</span>http://en.wikipedia.org/wiki/USB_communications_device_class</a>
    128 </li><li><a class="ext-link" href="http://en.wikipedia.org/wiki/Ethernet_over_USB"><span class="icon">​</span>http://en.wikipedia.org/wiki/Ethernet_over_USB</a>
    129 </li></ul><p>
    130 <span class="wikianchor" id="g_mass_storage"></span>
    131 </p>
    132 <h3 id="g_mass_storage-USBMassStorageDevice">g_mass_storage - USB Mass Storage Device</h3>
    133 <p>
     69 * ​http://en.wikipedia.org/wiki/USB_communications_device_class
     70 * http://en.wikipedia.org/wiki/Ethernet_over_USB
     71
     72
     73[=#g_mass_storage]
     74=== g_mass_storage - USB Mass Storage Device ===
    13475The g_file_storage driver behaves as a USB Mass Storage device such as a USB hard-disk or USB flash drive. You can decide whether to use a 'file' as a backing store, or a block device (ie a flash partition, or a physical disk). The file/device is provided to the module via the 'file' module parameter.
    135 </p>
    136 <p>
     76
    13777If using a backing storage 'file' you must create it beforehand with its desired size. For example to create a 64MB backing store:
    138 </p>
    139 <pre class="wiki">dd bs=1M count=64 if=/dev/zero of=/backing_file
    140 </pre><p>
     78{{{#!bash
     79dd bs=1M count=64 if=/dev/zero of=/backing_file
     80}}}
     81
    14182To use this as a backing store:
    142 </p>
    143 <pre class="wiki">modprobe g_mass_storage file=/backing_file
    144 </pre><p>
     83{{{#!bash
     84modprobe g_mass_storage file=/backing_file
     85}}}
     86
    14587References:
    146 </p>
    147 <ul><li><a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/mass-storage.txt"><span class="icon">​</span>https://www.kernel.org/doc/Documentation/usb/mass-storage.txt</a>
    148 </li><li><a class="ext-link" href="http://www.linux-usb.org/gadget/file_storage.html"><span class="icon">​</span>http://www.linux-usb.org/gadget/file_storage.html</a>
    149 </li></ul><p>
    150 <span class="wikianchor" id="g_file_storage"></span>
    151 </p>
    152 <h3 id="g_file_storage-USBMassStorageDevice">g_file_storage - USB Mass Storage Device</h3>
    153 <p>
    154 The g_file_storage driver behaves as a USB Mass Storage device such as a USB hard-disk or USB flash drive.  You can decide whether to use a 'file' as a backing store, or a block device (ie a flash partition, or a physical disk).  The file/device is provided to the module via the 'file' module parameter.
    155 </p>
    156 <p>
    157 <strong>This gadget driver was repaced with <tt>g_mass_storage</tt> in Linux 3.8</strong>
    158 </p>
    159 <p>
    160 Example (using the first physical disk (/dev/sda) as a backing store):
    161 </p>
    162 <ul><li>on target device  (Gateworks board with OTG controller):
    163 <ul><li>load module specifying block device (ie /dev/sda the first physical disk device)
    164 <pre class="wiki">modprobe g_file_storage file=/dev/sda
    165 </pre></li></ul></li><li>on host device (ie PC) a USB Mass Storage device (VID:PID 0525:a4a5 by default) will appear and behave as any other USB Mass Storage device (ie flash stick) would.
    166 </li><li>module parameters can specify the serialnumber, number of luns to support as well as some other low-level features (see 'modinfo g_file_storage' for details)
    167 </li></ul><p>
    168 Using a file as a backing store:
    169 </p>
    170 <ul><li>Create backing storage file (done once, before you load the gadget module)
    171 <pre class="wiki">dd bs=1M count=64 if=/dev/zero of=/tmp/backing_file # create empty file
    172 </pre><ul><li>you can choose to partition it (ie 'printf "<sub>L</sub>\n" | sfdisk -uS /tmp/backing_file' for a single linux partition) or partition/format it from the host after connection
    173 </li><li>make sure you choose a partition/filesystem scheme that is compatible with the USB Host PC you are going to use (ie, Windows doesn't know how to deal with ext2/ext3/ext4 partitions, so you may want to use VFAT or NTFS)
    174 </li><li>specify the path to the backing store via the file parameter (ie 'modprobe g_mass_storage file=/tmp/backing_file')
    175 </li></ul></li></ul><p>
     88 * ​https://www.kernel.org/doc/Documentation/usb/mass-storage.txt
     89 * http://www.linux-usb.org/gadget/file_storage.html
     90
     91
     92[=#g_serial]
     93=== g_serial - Serial Device Gadget ===
     94The Serial Gadget supports CDC-ACM and CDC-OBEX which can inter-operate with the MS-Windows hosts or with Linux hosts using the 'cdc-acm' driver to create a 'USB-to-Serial' connection.
     95
     96Example:
     97 * on target device (Gateworks board with OTG controller):
     98{{{#!bash
     99modprobe g_serial
     100}}}
     101 * on host device (ie PC) a USB CDC ACM device (VID:PID 0525:a4a7 by default) will appear and behave as a serial device
     102 * module parameters can specify the VID, PID, device version,
     103manufacturer string, product string, serialnumber
     104 * module parameters can specify whether or not to use CDC ACM, CDC OBEX, and the number of ports to create
     105
     106Linux USB Host notes:
     107 * the cdc_acm driver will enumerate this device as '/dev/ttyACM<n>'
     108
     109Windows USB Host notes:
     110 * see ​https://www.kernel.org/doc/Documentation/usb/gadget_serial.txt
     111
    176112Reference:
    177 </p>
    178 <ul><li><a class="ext-link" href="http://www.linux-usb.org/gadget/file_storage.html"><span class="icon">​</span>http://www.linux-usb.org/gadget/file_storage.html</a>
    179 </li></ul><p>
    180 <span class="wikianchor" id="g_serial"></span>
    181 </p>
    182 <h3 id="g_serial-SerialDeviceGadget">g_serial - Serial Device Gadget</h3>
    183 <p>
    184 The Serial Gadget supports CDC-ACM and CDC-OBEX which can inter-operate with the MS-Windows hosts or with Linux hosts using the 'cdc-acm' driver to create a 'USB-to-Serial' connection.
    185 </p>
    186 <p>
    187 Example:
    188 </p>
    189 <ul><li>on target device  (Gateworks board with OTG controller):
    190 <ul><li>load module
    191 <pre class="wiki">modprobe g_serial
    192 </pre></li></ul></li><li>on host device (ie PC) a USB CDC ACM device (VID:PID 0525:a4a7 by default) will appear and behave as a serial device
    193 </li><li>module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
    194 </li><li>module parameters can specify whether or not to use CDC ACM, CDC OBEX, and the number of ports to create
    195 </li></ul><p>
    196 Linux USB Host notes:
    197 </p>
    198 <ul><li>the cdc_acm driver will enumerate this device as '/dev/ttyACM&lt;n&gt;'
    199 </li></ul><p>
    200 Windows USB Host notes:
    201 </p>
    202 <ul><li>see <a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/gadget_serial.txt"><span class="icon">​</span>https://www.kernel.org/doc/Documentation/usb/gadget_serial.txt</a>
    203 </li></ul><p>
    204 Reference:
    205 </p>
    206 <ul><li><a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/gadget_serial.txt"><span class="icon">​</span>https://www.kernel.org/doc/Documentation/usb/gadget_serial.txt</a>
    207 </li></ul><p>
    208 <span class="wikianchor" id="g_cdc"></span>
    209 </p>
    210 <h3 id="g_cdc-CompositeEthernetSerialGadget">g_cdc - Composite Ethernet + Serial Gadget</h3>
    211 <p>
     113 * ​https://www.kernel.org/doc/Documentation/usb/gadget_serial.txt
     114
     115
     116[=#g_cdc]
     117=== g_cdc - Composite Ethernet + Serial Gadget ===
    212118The g_cdc gadget supports two functions in one configuration:
    213 </p>
    214 <ul><li>a CDC Ethernet (ECM) link (USB-to-Ethernet connection)
    215 </li><li>a CDC ACM (serial port) link (USB-to-Serial connection)
    216 </li></ul><p>
    217 Example:
    218 </p>
    219 <ul><li>on target device  (Gateworks board with OTG controller):
    220 <ul><li>load module
    221 <pre class="wiki">modprobe g_cdc
    222 </pre></li></ul></li><li>on host device (ie PC) a USB CDC ACM device (VID:PID 0525:a4aa) will appear
    223 </li></ul><p>
    224 Linux USB Host notes:
    225 </p>
    226 <ul><li>the cdc_acm driver will enumerate this device as '/dev/ttyACM&lt;n&gt;'
    227 </li><li>the cdc_ether driver will enumerate this device as a 'usb&lt;n&gt;' network device
    228 </li></ul><p>
    229 Windows USB Host notes:
    230 </p>
    231 <ul><li>A CDC Composite Gadget device will appear in Device Manager
    232 </li><li>TODO: Is there a driver available that can use this in Windows?  See g_multi below
    233 </li></ul><p>
    234 <span class="wikianchor" id="g_multi"></span>
    235 </p>
    236 <h3 id="g_multi-CompositeEthernetSerialMassStorageGadget">g_multi - Composite Ethernet + Serial + Mass Storage Gadget</h3>
    237 <p>
     119 * a CDC Ethernet (ECM) link (USB-to-Ethernet connection)
     120 * a CDC ACM (serial port) link (USB-to-Serial connection)
     121
     122Example:
     123 * on target device (Gateworks board with OTG controller):
     124{{{#!bash
     125modprobe g_cdc
     126}}}
     127 * on host device (ie PC) a USB CDC ACM device (VID:PID 0525:a4aa) will appear
     128
     129Linux USB Host notes:
     130 * the cdc_acm driver will enumerate this device as '/dev/ttyACM<n>'
     131 * the cdc_ether driver will enumerate this device as a 'usb<n>' network device
     132
     133Windows USB Host notes:
     134 * A CDC Composite Gadget device will appear in Device Manager
     135 * TODO: Is there a driver available that can use this in Windows? See [#g_multi g_multi below]
     136
     137
     138[=#g_multi]
     139=== g_multi - Composite Ethernet + Serial + Mass Storage Gadget ===
    238140The g_multi gadget supports multiple functions in one configuration:
    239 </p>
    240 <ul><li>a CDC Ethernet (ECM) link
    241 </li><li>a CDC ACM (serial port) link
    242 </li><li>a USB Mass Storage device
    243 </li></ul><p>
    244 Example:
    245 </p>
    246 <ul><li>on target device  (Gateworks board with OTG controller):
    247 <ul><li>load module
    248 <pre class="wiki">modprobe g_cdc
    249 </pre></li></ul></li><li>on host device (ie PC) a USB CDC ACM device (VID:PID 1d6b:0104 by default) will appear
    250 </li><li>module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
    251 </li><li>module parameters can specify the ethernet device and host address and queue length multiplier at high speed
    252 </li></ul><p>
    253 Linux USB Host notes:
    254 </p>
    255 <ul><li>the cdc_acm driver will enumerate this device as '/dev/ttyACM&lt;n&gt;'
    256 </li><li>the cdc_ether driver will enumerate this device as a 'usb&lt;n&gt;' network device
    257 </li><li>the usb-storage driver will provide the USB Mass Storage feature
    258 </li></ul><p>
    259 Windows USB Host notes:
    260 </p>
    261 <ul><li>A Multifunction Composite Gadget device will appear in Device Manager
    262 </li><li>see <a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/gadget_multi.txt"><span class="icon">​</span>here</a> for details on Windows configuration
    263 </li></ul><p>
     141 * a CDC Ethernet (ECM) link
     142 * a CDC ACM (serial port) link
     143 * a USB Mass Storage device
     144
     145Example:
     146 * on target device (Gateworks board with OTG controller):
     147{{{#!bash
     148modprobe g_cdc
     149}}}
     150 * on host device (ie PC) a USB CDC ACM device (VID:PID 1d6b:0104 by default) will appear
     151 * module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
     152 * module parameters can specify the ethernet device and host address and queue length multiplier at high speed
     153
     154Linux USB Host notes:
     155 * the cdc_acm driver will enumerate this device as '/dev/ttyACM<n>'
     156 * the cdc_ether driver will enumerate this device as a 'usb<n>' network device
     157 * the usb-storage driver will provide the USB Mass Storage feature
     158
     159Windows USB Host notes:
     160 * A Multifunction Composite Gadget device will appear in Device Manager
     161 * see [https://www.kernel.org/doc/Documentation/usb/gadget_multi.txt ​here] for details on Windows configuration
     162
    264163References:
    265 </p>
    266 <ul><li><a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/gadget_multi.txt"><span class="icon">​</span>https://www.kernel.org/doc/Documentation/usb/gadget_multi.txt</a>
    267 </li></ul><p>
    268 <span class="wikianchor" id="g_hid"></span>
    269 </p>
    270 <h3 id="g_hid-HumanInterfaceDeviceHIDGadget">g_hid - Human Interface Device (HID) Gadget</h3>
    271 <p>
     164 * ​https://www.kernel.org/doc/Documentation/usb/gadget_multi.txt
     165
     166
     167[=#g_hid]
     168=== g_hid - Human Interface Device (HID) Gadget ===
    272169The HID gadget driver provides generic emulation of USB Human Interface Devices (HID), for example keyboards, mice, touchscreens, etc
    273 </p>
    274 <p>
    275 Example:
    276 </p>
    277 <ul><li>on target device  (Gateworks board with OTG controller):
    278 <ul><li>load module
    279 <pre class="wiki">modprobe g_hid
    280 </pre></li></ul></li><li>module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
    281 </li></ul><p>
     170
     171Example:
     172 * on target device (Gateworks board with OTG controller):
     173{{{#!bash
     174modprobe g_hid
     175}}}
     176 * module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
     177
    282178References:
    283 </p>
    284 <ul><li><a class="ext-link" href="https://www.kernel.org/doc/Documentation/usb/gadget_hid.txt"><span class="icon">​</span>https://www.kernel.org/doc/Documentation/usb/gadget_hid.txt</a>
    285 </li></ul><p>
    286 <span class="wikianchor" id="g_webcam"></span>
    287 </p>
    288 <h3 id="g_webcam-CompositeUSBAudioandVideoClassGadget">g_webcam - Composite USB Audio and Video Class Gadget</h3>
    289 <p>
     179 * ​https://www.kernel.org/doc/Documentation/usb/gadget_hid.txt
     180
     181
     182[=#g_webcam]
     183=== g_webcam - Composite USB Audio and Video Class Gadget ===
    290184The g_webcam gadget driver provides a Composite USB Audio and Video Class device.
    291 </p>
    292 <p>
    293 Example:
    294 </p>
    295 <ul><li>on target device (Gateworks board with OTG controller):
    296 <ul><li>load module
    297 <pre class="wiki">modprobe g_webcam
    298 </pre></li></ul></li><li>on host device (ie PC) a 'Linux Foundation Webcam Gadget' device (VID:PID 1d6b:0102 by default) will appear
    299 </li><li>on target device (Gateworks board) a /dev/video&lt;n&gt; device will be created and avialable as a Video4Linux output device supporting 320/240 YUYV video
    300 </li><li>module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
    301 </li></ul><p>
    302 Linux USB Host notes:
    303 </p>
    304 <ul><li>the uvcvideo driver will enumerate the device and create a /dev/video&lt;n&gt; video capture device
    305 </li></ul><p>
    306 Windows USB Host notes:
    307 </p>
    308 <ul><li>A USB Composite device will appear in Device Manager
    309 </li><li>A UVC Camera device will appear under Imaging devices in the device manager and be available to capture video
    310 </li></ul><p>
    311 <span class="wikianchor" id="g_ncm"></span>
    312 </p>
    313 <h3 id="g_ncm-USBCDCNCMsubclassEthernetGadget">g_ncm - USB CDC NCM subclass Ethernet Gadget</h3>
    314 <p>
    315 The g_ncm gadget driver provides a a USB CDC NCM subclass.  NCM is an advanced protocol for Ethernet encapsulation, allowing grouping of several ethernet frames into one USB transfer with various alignment possibilities.
    316 </p>
    317 <p>
    318 Example:
    319 </p>
    320 <ul><li>on target device (Gateworks board with OTG controller):
    321 <ul><li>load module
    322 <pre class="wiki">modprobe g_ncm
    323 </pre></li></ul></li><li>on host device (ie PC) a 'Linux-USB Ethernet Gadget' device (VID:PID 0525:a4a1 by default) will appear
    324 </li><li>on target device (Gateworks board) a usb&lt;n&gt; network device will be created
    325 </li><li>module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
    326 </li><li>module parameters can specify the device and host ethernet addresses and the queue length multiplier used at high speeds
    327 </li></ul><p>
    328 Linux USB Host notes:
    329 </p>
    330 <ul><li>the cdc_ncm driver will enumerate the device and create a /dev/video&lt;n&gt; video capture device
    331 </li></ul><p>
    332 Windows USB Host notes:
    333 </p>
    334 <ul><li>A NCM Gadget device will appear in Device Manager
    335 </li><li>see <a class="ext-link" href="http://www.thesycon.de/eng/usb_cdcncm.shtml"><span class="icon">​</span>here</a> for details about a Windows CDC NCM driver
    336 </li></ul><p>
    337 <span class="wikianchor" id="configfs"></span>
    338 </p>
    339 <h3 id="ConfigFs">ConfigFs</h3>
    340 <p>
     185
     186Example:
     187 * on target device (Gateworks board with OTG controller):
     188{{{#!bash
     189modprobe g_webcam
     190}}}
     191 * on host device (ie PC) a 'Linux Foundation Webcam Gadget' device (VID:PID 1d6b:0102 by default) will appear
     192 * on target device (Gateworks board) a /dev/video<n> device will be created and avialable as a Video4Linux output device supporting 320/240 YUYV video
     193 * module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
     194
     195Linux USB Host notes:
     196 * the uvcvideo driver will enumerate the device and create a {{{/dev/video<n>}}} video capture device
     197
     198Windows USB Host notes:
     199 * A USB Composite device will appear in Device Manager
     200 * A UVC Camera device will appear under Imaging devices in the device manager and be available to capture video
     201
     202
     203[=#g_ncm]
     204=== g_ncm - USB CDC NCM subclass Ethernet Gadget ===
     205The g_ncm gadget driver provides a a USB CDC NCM subclass. NCM is an advanced protocol for Ethernet encapsulation, allowing grouping of several ethernet frames into one USB transfer with various alignment possibilities.
     206
     207Example:
     208 * on target device (Gateworks board with OTG controller):
     209{{{#!bash
     210modprobe g_ncm
     211}}}
     212 * on host device (ie PC) a 'Linux-USB Ethernet Gadget' device (VID:PID 0525:a4a1 by default) will appear
     213 * on target device (Gateworks board) a usb<n> network device will be created
     214 * module parameters can specify the VID, PID, device version, manufacturer string, product string, serialnumber
     215 * module parameters can specify the device and host ethernet addresses and the queue length multiplier used at high speeds
     216
     217Linux USB Host notes:
     218 * the cdc_ncm driver will enumerate the device and create a network interface in {{{/sys/class/net}}}
     219
     220Windows USB Host notes:
     221 * A NCM Gadget device will appear in Device Manager
     222 * see [http://www.thesycon.de/eng/usb_cdcncm.shtml ​here] for details about a Windows CDC NCM driver
     223
     224
     225[=#configfs]
     226=== !ConfigFs ===
    341227The Linux Configfs (CONFIG_CONFIGFS_FS) support allows complete dynamic configuration of gadget devices from userspace in which case you can create a single configuration or multi-configuration composite device with one or more of the functions available from drivers/usb/gadget/udc/functions:
    342 </p>
    343 <ul><li>usb_f_acm - CDC Serial (ACM - Abstract Control Model)
    344 </li><li>usb_f_ecm - CDC Ethernet (ECM - Ethernet Networking Control Model)
    345 </li><li>usb_f_eem - CDC Ethernet (EEM - Ethernet Emulation Model)
    346 </li><li>usb_f_fs - Filesystem
    347 </li><li>usb_f_hid - HID Interface
    348 </li><li>usb_f_mass_storage - USB Mass Storage class
    349 </li><li>usb_f_midi - MIDI
    350 </li><li>usb_f_ncm - CDC Network (NCM - Network Control Model Ethernet)
    351 </li><li>usb_f_obex - CDC OBEX (Object Exchange Model)
    352 </li><li>usb_f_phonet - CDC Phonet
    353 </li><li>usb_f_printer - Printer function
    354 </li><li>usb_f_rndis - (Remote Network Driver Interface Specification - Microsoft Ethernet over USB)
    355 </li><li>usb_f_serial - Generic serial function
    356 </li><li>usb_f_subset - CDC Subset (Ethernet with no control mechanism - just raw data transfer)
    357 </li><li>usb_f_uac1 - USB Audio class
    358 </li><li>usb_f_uac2 - USB Audio class 2.0
    359 </li><li>usb_f_uvc - USB Video class
    360 </li></ul><p>
     228 * usb_f_acm - CDC Serial (ACM - Abstract Control Model)
     229 * usb_f_ecm - CDC Ethernet (ECM - Ethernet Networking Control Model)
     230 * usb_f_eem - CDC Ethernet (EEM - Ethernet Emulation Model)
     231 * usb_f_fs - Filesystem
     232 * usb_f_hid - HID Interface
     233 * usb_f_mass_storage - USB Mass Storage class
     234 * usb_f_midi - MIDI
     235 * usb_f_ncm - CDC Network (NCM - Network Control Model Ethernet)
     236 * usb_f_obex - CDC OBEX (Object Exchange Model)
     237 * usb_f_phonet - CDC Phonet
     238 * usb_f_printer - Printer function
     239 * usb_f_rndis - (Remote Network Driver Interface Specification - Microsoft Ethernet over USB)
     240 * usb_f_serial - Generic serial function
     241 * usb_f_subset - CDC Subset (Ethernet with no control mechanism - just raw data transfer)
     242 * usb_f_uac1 - USB Audio class
     243 * usb_f_uac2 - USB Audio class 2.0
     244 * usb_f_uvc - USB Video class
     245
    361246Note that not all of the above kernel modules may be available depending on your kernel configuration or BSP.
    362 </p>
    363 <p>
     247
    364248Examples:
    365 </p>
    366 <ul><li>Create a CDC ACM Serial device:
    367 <div class="code"><pre><span class="c"># mount configfs
    368 </span>mount -t configfs none /sys/kernel/config
    369 <span class="c"># load libcomposite module
    370 </span>modprobe libcomposite
    371 <span class="c"># create a gadget
    372 </span>mkdir /sys/kernel/config/usb_gadget/g1
    373 <span class="c"># cd to its configfs node
    374 </span><span class="nb">cd</span> /sys/kernel/config/usb_gadget/g1
    375 <span class="c"># configure it (vid/pid can be anything if USB Class is used for driver compat)
    376 </span><span class="nb">echo </span>0xabcd &gt; idVendor
    377 <span class="nb">echo </span>0x1234 &gt; idProduct
    378 <span class="c"># configure its serial/mfg/product
    379 </span>mkdir strings/0x409
    380 <span class="nb">echo </span>myserial &gt; strings/0x409/serialnumber
    381 <span class="nb">echo </span>mymfg &gt; strings/0x409/manufacturer
    382 <span class="nb">echo </span>myproduct &gt; strings/0x409/product
    383 <span class="c"># create a config
    384 </span>mkdir configs/c.1
    385 <span class="c"># configure it with attributes if needed
    386 </span><span class="nb">echo </span>120 &gt; configs/c.1/MaxPower
    387 <span class="c"># ensure function is loaded
    388 </span>modprobe usb_f_acm
    389 <span class="c"># create the function (name must match a usb_f_&lt;name&gt; module such as 'acm')
    390 </span>mkdir functions/acm.0
    391 <span class="c"># associate function with config
    392 </span>ln -s functions/acm.0 configs/c.1
    393 <span class="c"># enable gadget by binding it to a UDC from /sys/class/udc
    394 </span><span class="nb">echo </span>0000:01:00.0 &gt; UDC
    395 <span class="c"># to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1
    396 </span></pre></div></li><li>Create a CDC ECM Ethernet device:
    397 <div class="code"><pre><span class="c"># mount configfs
    398 </span>mount -t configfs none /sys/kernel/config
    399 <span class="c"># load libcomposite module
    400 </span>modprobe libcomposite
    401 <span class="c"># create a gadget
    402 </span>mkdir /sys/kernel/config/usb_gadget/g1
    403 <span class="c"># cd to its configfs node
    404 </span><span class="nb">cd</span> /sys/kernel/config/usb_gadget/g1
    405 <span class="c"># configure it (vid/pid can be anything if USB Class is used for driver compat)
    406 </span><span class="nb">echo </span>0xabcd &gt; idVendor
    407 <span class="nb">echo </span>0x1234 &gt; idProduct
    408 <span class="c"># configure its serial/mfg/product
    409 </span>mkdir strings/0x409
    410 <span class="nb">echo </span>myserial &gt; strings/0x409/serialnumber
    411 <span class="nb">echo </span>mymfg &gt; strings/0x409/manufacturer
    412 <span class="nb">echo </span>myproduct &gt; strings/0x409/product
    413 <span class="c"># create a config
    414 </span>mkdir configs/c.1
    415 <span class="c"># configure it with attributes if needed
    416 </span><span class="nb">echo </span>120 &gt; configs/c.1/MaxPower
    417 <span class="c"># ensure function is loaded
    418 </span>modprobe usb_f_ecm
    419 <span class="c"># create the function (name must match a usb_f_&lt;name&gt; module such as 'ecm')
    420 </span>mkdir functions/ecm.0
    421 <span class="c"># associate function with config
    422 </span>ln -s functions/ecm.0 configs/c.1
    423 <span class="c"># enable gadget by binding it to a UDC from /sys/class/udc
    424 </span><span class="nb">echo </span>0000:01:00.0 &gt; UDC
    425 <span class="c"># to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1
    426 </span></pre></div></li><li>Create a USB Mass Storage device (with 2 LUN's 16MB each):
    427 <div class="code"><pre><span class="c"># mount configfs
    428 </span>mount -t configfs none /sys/kernel/config
    429 <span class="c"># load libcomposite module
    430 </span>modprobe libcomposite
    431 <span class="c"># create a gadget
    432 </span>mkdir /sys/kernel/config/usb_gadget/g1
    433 <span class="c"># cd to its configfs node
    434 </span><span class="nb">cd</span> /sys/kernel/config/usb_gadget/g1
    435 <span class="c"># configure it (vid/pid can be anything if USB Class is used for driver compat)
    436 </span><span class="nb">echo </span>0xabcd &gt; idVendor
    437 <span class="nb">echo </span>0x1234 &gt; idProduct
    438 <span class="c"># configure its serial/mfg/product
    439 </span>mkdir strings/0x409
    440 <span class="nb">echo </span>myserial &gt; strings/0x409/serialnumber
    441 <span class="nb">echo </span>mymfg &gt; strings/0x409/manufacturer
    442 <span class="nb">echo </span>myproduct &gt; strings/0x409/product
    443 <span class="c"># create configs
    444 </span>mkdir configs/c.1
     249 * Create a CDC ACM Serial device:
     250{{{#!bash
     251# mount configfs
     252mount -t configfs none /sys/kernel/config
     253# load libcomposite module
     254modprobe libcomposite
     255# create a gadget
     256mkdir /sys/kernel/config/usb_gadget/g1
     257# cd to its configfs node
     258cd /sys/kernel/config/usb_gadget/g1
     259# configure it (vid/pid can be anything if USB Class is used for driver compat)
     260echo 0xabcd > idVendor
     261echo 0x1234 > idProduct
     262# configure its serial/mfg/product
     263mkdir strings/0x409
     264echo myserial > strings/0x409/serialnumber
     265echo mymfg > strings/0x409/manufacturer
     266echo myproduct > strings/0x409/product
     267# create a config
     268mkdir configs/c.1
     269# configure it with attributes if needed
     270echo 120 > configs/c.1/MaxPower
     271# ensure function is loaded
     272modprobe usb_f_acm
     273# create the function (name must match a usb_f_<name> module such as 'acm')
     274mkdir functions/acm.0
     275# associate function with config
     276ln -s functions/acm.0 configs/c.1
     277# enable gadget by binding it to a UDC from /sys/class/udc
     278echo 0000:01:00.0 > UDC
     279# to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1
     280}}}
     281 * Create a CDC ECM Ethernet device:
     282{{{#!bash
     283# mount configfs
     284mount -t configfs none /sys/kernel/config
     285# load libcomposite module
     286modprobe libcomposite
     287# create a gadget
     288mkdir /sys/kernel/config/usb_gadget/g1
     289# cd to its configfs node
     290cd /sys/kernel/config/usb_gadget/g1
     291# configure it (vid/pid can be anything if USB Class is used for driver compat)
     292echo 0xabcd > idVendor
     293echo 0x1234 > idProduct
     294# configure its serial/mfg/product
     295mkdir strings/0x409
     296echo myserial > strings/0x409/serialnumber
     297echo mymfg > strings/0x409/manufacturer
     298echo myproduct > strings/0x409/product
     299# create a config
     300mkdir configs/c.1
     301# configure it with attributes if needed
     302echo 120 > configs/c.1/MaxPower
     303# ensure function is loaded
     304modprobe usb_f_ecm
     305# create the function (name must match a usb_f_<name> module such as 'ecm')
     306mkdir functions/ecm.0
     307# associate function with config
     308ln -s functions/ecm.0 configs/c.1
     309# enable gadget by binding it to a UDC from /sys/class/udc
     310echo 0000:01:00.0 > UDC
     311# to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1
     312}}}
     313 * Create a USB Mass Storage device (with 2 LUN's 16MB each):
     314{{{#!bash
     315# mount configfs
     316mount -t configfs none /sys/kernel/config
     317# load libcomposite module
     318modprobe libcomposite
     319# create a gadget
     320mkdir /sys/kernel/config/usb_gadget/g1
     321# cd to its configfs node
     322cd /sys/kernel/config/usb_gadget/g1
     323# configure it (vid/pid can be anything if USB Class is used for driver compat)
     324echo 0xabcd > idVendor
     325echo 0x1234 > idProduct
     326# configure its serial/mfg/product
     327mkdir strings/0x409
     328echo myserial > strings/0x409/serialnumber
     329echo mymfg > strings/0x409/manufacturer
     330echo myproduct > strings/0x409/product
     331# create configs
     332mkdir configs/c.1
    445333mkdir configs/c.2
    446334mkdir configs/c.3
    447 <span class="c"># configure them with attributes if needed
    448 </span><span class="nb">echo </span>120 &gt; configs/c.1/MaxPower
    449 <span class="nb">echo </span>120 &gt; configs/c.2/MaxPower
    450 <span class="nb">echo </span>120 &gt; configs/c.2/MaxPower
    451 <span class="c"># ensure function is loaded
    452 </span>modprobe usb_f_mass_storage
    453 <span class="c"># create the function (name must match a usb_f_&lt;name&gt; module such as 'acm')
    454 </span>mkdir functions/mass_storage.0
    455 <span class="c"># create backing store(s): in this example 2 LUN's 16MB each
    456 </span>dd <span class="nv">bs</span><span class="o">=</span>1M <span class="nv">count</span><span class="o">=</span>16 <span class="k">if</span><span class="o">=</span>/dev/zero <span class="nv">of</span><span class="o">=</span>/tmp/lun0.img <span class="c"># 16MB
    457 </span>dd <span class="nv">bs</span><span class="o">=</span>1M <span class="nv">count</span><span class="o">=</span>16 <span class="k">if</span><span class="o">=</span>/dev/zero <span class="nv">of</span><span class="o">=</span>/tmp/lun1.img <span class="c"># 16MB
     335# configure them with attributes if needed
     336echo 120 > configs/c.1/MaxPower
     337echo 120 > configs/c.2/MaxPower
     338echo 120 > configs/c.2/MaxPower
     339# ensure function is loaded
     340modprobe usb_f_mass_storage
     341# create the function (name must match a usb_f_<name> module such as 'acm')
     342mkdir functions/mass_storage.0
     343# create backing store(s): in this example 2 LUN's 16MB each
     344dd bs=1M count=16 if=/dev/zero of=/tmp/lun0.img # 16MB
     345dd bs=1M count=16 if=/dev/zero of=/tmp/lun1.img # 16MB
    458346# associate with partitions
    459 </span>mkdir functions/mass_storage.0/lun.0
    460 <span class="nb">echo</span> /tmp/lun0.img &gt; functions/mass_storage.0/lun.0/file
     347mkdir functions/mass_storage.0/lun.0
     348echo /tmp/lun0.img > functions/mass_storage.0/lun.0/file
    461349mkdir functions/mass_storage.0/lun.1
    462 <span class="nb">echo</span> /tmp/lun1.img &gt; functions/mass_storage.0/lun.1/file
    463 <span class="c"># associate function with config
    464 </span>ln -s functions/mass_storage.0 configs/c.1
    465 <span class="c"># enable gadget by binding it to a UDC from /sys/class/udc
    466 </span><span class="nb">echo </span>0000:01:00.0 &gt; UDC
    467 <span class="c"># to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1
    468 </span></pre></div></li></ul><p>
     350echo /tmp/lun1.img > functions/mass_storage.0/lun.1/file
     351# associate function with config
     352ln -s functions/mass_storage.0 configs/c.1
     353# enable gadget by binding it to a UDC from /sys/class/udc
     354echo 0000:01:00.0 > UDC
     355# to unbind it: echo "" UDC; sleep 1; rm -rf /sys/kernel/config/usb_gadget/g1
     356}}}
     357
    469358References:
    470 </p>
    471 <ul><li><a class="ext-link" href="https://lxr.missinglinkelectronics.com/linux/Documentation/usb/gadget_configfs.txt"><span class="icon">​</span>Documentation/usb/gadget_configfs.txt</a>
    472 </li><li><a class="ext-link" href="https://wiki.tizen.org/wiki/USB/Linux_USB_Layers/Configfs_Composite_Gadget/General_configuration"><span class="icon">​</span>https://wiki.tizen.org/wiki/USB/Linux_USB_Layers/Configfs_Composite_Gadget/General_configuration</a>
    473 </li></ul><h1 id="OpenWrtOTG"><a class="wiki" href="/wiki/OpenWrt">OpenWrt</a> OTG</h1>
    474 <p>
    475 <a class="wiki" href="/wiki/OpenWrt">OpenWrt</a> packages several of the above Linux kernel modules as packages:
    476 </p>
    477 <ul><li>g_ether - Kernel modules -&gt; USB Support -&gt; kmod-usb-eth-gadget
    478 </li><li>g_mass_storage - Kernel modules -&gt; USB Support -&gt; kmod-usb-mass-storage-gadget
    479 </li><li>g_serial - Kernel modules -&gt; USB Support -&gt; kmod-usb-serial-gadget
    480 </li></ul><p>
     359 * [https://lxr.missinglinkelectronics.com/linux/Documentation/usb/gadget_configfs.txt ​Documentation/usb/gadget_configfs.txt]
     360 * https://wiki.tizen.org/wiki/USB/Linux_USB_Layers/Configfs_Composite_Gadget/General_configuration
     361
     362
     363[=#openwrt]
     364== OpenWrt OTG ==
     365OpenWrt packages several of the above Linux kernel modules as packages:
     366 * g_ether - Kernel modules -> USB Support -> kmod-usb-eth-gadget
     367 * g_mass_storage - Kernel modules -> USB Support -> kmod-usb-mass-storage-gadget
     368 * g_serial - Kernel modules -> USB Support -> kmod-usb-serial-gadget
     369
    481370You must have gadget support enabled:
    482 </p>
    483 <ul><li>Kernel modules -&gt; USB Support (kmod-usb-gadget)
    484 </li></ul><p>
     371 * Kernel modules -> USB Support (kmod-usb-gadget)
     372
    485373Note that all of these packages will attempt to autoload their respective kernel module so whichever one is alphabetically first will be loaded. You can see what is loaded by looking at the current modules:
    486 </p>
    487 <div class="code"><pre>lsmod | grep g_*
    488 </pre></div
    489 }}}
     374{{{#!bash
     375lsmod | grep g_*
     376}}}