ecefae6db0
While there are a mix of things here, most of the stuff were written from Kernel developer's PoV. So, add them to the driver-api book. A follow up for this patch would be to move documents from there that are specific to sysadmins, adding them to the admin-guide. Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org> Acked-by: Johan Hovold <johan@kernel.org> Acked-by: Felipe Balbi <felipe.balbi@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
517 lines
16 KiB
Plaintext
517 lines
16 KiB
Plaintext
# SPDX-License-Identifier: GPL-2.0
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#
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# USB Gadget support on a system involves
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# (a) a peripheral controller, and
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# (b) the gadget driver using it.
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#
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# NOTE: Gadget support ** DOES NOT ** depend on host-side CONFIG_USB !!
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#
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# - Host systems (like PCs) need CONFIG_USB (with "A" jacks).
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# - Peripherals (like PDAs) need CONFIG_USB_GADGET (with "B" jacks).
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# - Some systems have both kinds of controllers.
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#
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# With help from a special transceiver and a "Mini-AB" jack, systems with
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# both kinds of controller can also support "USB On-the-Go" (CONFIG_USB_OTG).
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#
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menuconfig USB_GADGET
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tristate "USB Gadget Support"
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select USB_COMMON
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select NLS
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help
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USB is a master/slave protocol, organized with one master
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host (such as a PC) controlling up to 127 peripheral devices.
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The USB hardware is asymmetric, which makes it easier to set up:
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you can't connect a "to-the-host" connector to a peripheral.
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Linux can run in the host, or in the peripheral. In both cases
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you need a low level bus controller driver, and some software
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talking to it. Peripheral controllers are often discrete silicon,
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or are integrated with the CPU in a microcontroller. The more
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familiar host side controllers have names like "EHCI", "OHCI",
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or "UHCI", and are usually integrated into southbridges on PC
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motherboards.
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Enable this configuration option if you want to run Linux inside
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a USB peripheral device. Configure one hardware driver for your
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peripheral/device side bus controller, and a "gadget driver" for
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your peripheral protocol. (If you use modular gadget drivers,
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you may configure more than one.)
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If in doubt, say "N" and don't enable these drivers; most people
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don't have this kind of hardware (except maybe inside Linux PDAs).
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For more information, see <http://www.linux-usb.org/gadget> and
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the kernel documentation for this API.
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if USB_GADGET
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config USB_GADGET_DEBUG
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bool "Debugging messages (DEVELOPMENT)"
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depends on DEBUG_KERNEL
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help
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Many controller and gadget drivers will print some debugging
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messages if you use this option to ask for those messages.
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Avoid enabling these messages, even if you're actively
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debugging such a driver. Many drivers will emit so many
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messages that the driver timings are affected, which will
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either create new failure modes or remove the one you're
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trying to track down. Never enable these messages for a
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production build.
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config USB_GADGET_VERBOSE
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bool "Verbose debugging Messages (DEVELOPMENT)"
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depends on USB_GADGET_DEBUG
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help
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Many controller and gadget drivers will print verbose debugging
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messages if you use this option to ask for those messages.
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Avoid enabling these messages, even if you're actively
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debugging such a driver. Many drivers will emit so many
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messages that the driver timings are affected, which will
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either create new failure modes or remove the one you're
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trying to track down. Never enable these messages for a
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production build.
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config USB_GADGET_DEBUG_FILES
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bool "Debugging information files (DEVELOPMENT)"
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depends on PROC_FS
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help
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Some of the drivers in the "gadget" framework can expose
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debugging information in files such as /proc/driver/udc
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(for a peripheral controller). The information in these
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files may help when you're troubleshooting or bringing up a
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driver on a new board. Enable these files by choosing "Y"
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here. If in doubt, or to conserve kernel memory, say "N".
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config USB_GADGET_DEBUG_FS
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bool "Debugging information files in debugfs (DEVELOPMENT)"
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depends on DEBUG_FS
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help
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Some of the drivers in the "gadget" framework can expose
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debugging information in files under /sys/kernel/debug/.
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The information in these files may help when you're
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troubleshooting or bringing up a driver on a new board.
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Enable these files by choosing "Y" here. If in doubt, or
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to conserve kernel memory, say "N".
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config USB_GADGET_VBUS_DRAW
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int "Maximum VBUS Power usage (2-500 mA)"
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range 2 500
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default 2
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help
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Some devices need to draw power from USB when they are
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configured, perhaps to operate circuitry or to recharge
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batteries. This is in addition to any local power supply,
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such as an AC adapter or batteries.
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Enter the maximum power your device draws through USB, in
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milliAmperes. The permitted range of values is 2 - 500 mA;
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0 mA would be legal, but can make some hosts misbehave.
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This value will be used except for system-specific gadget
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drivers that have more specific information.
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config USB_GADGET_STORAGE_NUM_BUFFERS
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int "Number of storage pipeline buffers"
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range 2 256
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default 2
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help
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Usually 2 buffers are enough to establish a good buffering
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pipeline. The number may be increased in order to compensate
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for a bursty VFS behaviour. For instance there may be CPU wake up
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latencies that makes the VFS to appear bursty in a system with
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an CPU on-demand governor. Especially if DMA is doing IO to
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offload the CPU. In this case the CPU will go into power
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save often and spin up occasionally to move data within VFS.
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If selecting USB_GADGET_DEBUG_FILES this value may be set by
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a module parameter as well.
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If unsure, say 2.
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config U_SERIAL_CONSOLE
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bool "Serial gadget console support"
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depends on USB_U_SERIAL
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help
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It supports the serial gadget can be used as a console.
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source "drivers/usb/gadget/udc/Kconfig"
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#
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# USB Gadget Drivers
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#
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# composite based drivers
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config USB_LIBCOMPOSITE
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tristate
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select CONFIGFS_FS
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depends on USB_GADGET
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config USB_F_ACM
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tristate
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config USB_F_SS_LB
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tristate
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config USB_U_SERIAL
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tristate
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config USB_U_ETHER
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tristate
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config USB_U_AUDIO
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tristate
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config USB_F_SERIAL
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tristate
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config USB_F_OBEX
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tristate
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config USB_F_NCM
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tristate
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config USB_F_ECM
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tristate
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config USB_F_PHONET
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tristate
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config USB_F_EEM
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tristate
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config USB_F_SUBSET
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tristate
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config USB_F_RNDIS
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tristate
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config USB_F_MASS_STORAGE
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tristate
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config USB_F_FS
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tristate
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config USB_F_UAC1
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tristate
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config USB_F_UAC1_LEGACY
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tristate
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config USB_F_UAC2
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tristate
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config USB_F_UVC
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tristate
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config USB_F_MIDI
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tristate
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config USB_F_HID
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tristate
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config USB_F_PRINTER
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tristate
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config USB_F_TCM
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tristate
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# this first set of drivers all depend on bulk-capable hardware.
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config USB_CONFIGFS
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tristate "USB Gadget functions configurable through configfs"
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select USB_LIBCOMPOSITE
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help
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A Linux USB "gadget" can be set up through configfs.
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If this is the case, the USB functions (which from the host's
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perspective are seen as interfaces) and configurations are
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specified simply by creating appropriate directories in configfs.
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Associating functions with configurations is done by creating
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appropriate symbolic links.
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For more information see Documentation/usb/gadget_configfs.rst.
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config USB_CONFIGFS_SERIAL
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bool "Generic serial bulk in/out"
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depends on USB_CONFIGFS
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depends on TTY
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select USB_U_SERIAL
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select USB_F_SERIAL
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help
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The function talks to the Linux-USB generic serial driver.
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config USB_CONFIGFS_ACM
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bool "Abstract Control Model (CDC ACM)"
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depends on USB_CONFIGFS
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depends on TTY
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select USB_U_SERIAL
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select USB_F_ACM
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help
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ACM serial link. This function can be used to interoperate with
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MS-Windows hosts or with the Linux-USB "cdc-acm" driver.
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config USB_CONFIGFS_OBEX
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bool "Object Exchange Model (CDC OBEX)"
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depends on USB_CONFIGFS
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depends on TTY
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select USB_U_SERIAL
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select USB_F_OBEX
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help
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You will need a user space OBEX server talking to /dev/ttyGS*,
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since the kernel itself doesn't implement the OBEX protocol.
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config USB_CONFIGFS_NCM
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bool "Network Control Model (CDC NCM)"
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depends on USB_CONFIGFS
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depends on NET
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select USB_U_ETHER
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select USB_F_NCM
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help
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NCM is an advanced protocol for Ethernet encapsulation, allows
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grouping of several ethernet frames into one USB transfer and
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different alignment possibilities.
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config USB_CONFIGFS_ECM
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bool "Ethernet Control Model (CDC ECM)"
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depends on USB_CONFIGFS
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depends on NET
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select USB_U_ETHER
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select USB_F_ECM
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help
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The "Communication Device Class" (CDC) Ethernet Control Model.
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That protocol is often avoided with pure Ethernet adapters, in
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favor of simpler vendor-specific hardware, but is widely
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supported by firmware for smart network devices.
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config USB_CONFIGFS_ECM_SUBSET
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bool "Ethernet Control Model (CDC ECM) subset"
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depends on USB_CONFIGFS
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depends on NET
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select USB_U_ETHER
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select USB_F_SUBSET
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help
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On hardware that can't implement the full protocol,
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a simple CDC subset is used, placing fewer demands on USB.
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config USB_CONFIGFS_RNDIS
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bool "RNDIS"
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depends on USB_CONFIGFS
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depends on NET
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select USB_U_ETHER
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select USB_F_RNDIS
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help
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Microsoft Windows XP bundles the "Remote NDIS" (RNDIS) protocol,
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and Microsoft provides redistributable binary RNDIS drivers for
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older versions of Windows.
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To make MS-Windows work with this, use Documentation/usb/linux.inf
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as the "driver info file". For versions of MS-Windows older than
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XP, you'll need to download drivers from Microsoft's website; a URL
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is given in comments found in that info file.
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config USB_CONFIGFS_EEM
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bool "Ethernet Emulation Model (EEM)"
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depends on USB_CONFIGFS
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depends on NET
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select USB_U_ETHER
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select USB_F_EEM
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help
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CDC EEM is a newer USB standard that is somewhat simpler than CDC ECM
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and therefore can be supported by more hardware. Technically ECM and
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EEM are designed for different applications. The ECM model extends
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the network interface to the target (e.g. a USB cable modem), and the
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EEM model is for mobile devices to communicate with hosts using
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ethernet over USB. For Linux gadgets, however, the interface with
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the host is the same (a usbX device), so the differences are minimal.
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config USB_CONFIGFS_PHONET
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bool "Phonet protocol"
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depends on USB_CONFIGFS
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depends on NET
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depends on PHONET
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select USB_U_ETHER
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select USB_F_PHONET
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help
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The Phonet protocol implementation for USB device.
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config USB_CONFIGFS_MASS_STORAGE
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bool "Mass storage"
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depends on USB_CONFIGFS
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depends on BLOCK
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select USB_F_MASS_STORAGE
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help
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The Mass Storage Gadget acts as a USB Mass Storage disk drive.
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As its storage repository it can use a regular file or a block
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device (in much the same way as the "loop" device driver),
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specified as a module parameter or sysfs option.
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config USB_CONFIGFS_F_LB_SS
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bool "Loopback and sourcesink function (for testing)"
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depends on USB_CONFIGFS
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select USB_F_SS_LB
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help
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Loopback function loops back a configurable number of transfers.
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Sourcesink function either sinks and sources bulk data.
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It also implements control requests, for "chapter 9" conformance.
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Make this be the first driver you try using on top of any new
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USB peripheral controller driver. Then you can use host-side
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test software, like the "usbtest" driver, to put your hardware
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and its driver through a basic set of functional tests.
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config USB_CONFIGFS_F_FS
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bool "Function filesystem (FunctionFS)"
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depends on USB_CONFIGFS
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select USB_F_FS
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help
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The Function Filesystem (FunctionFS) lets one create USB
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composite functions in user space in the same way GadgetFS
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lets one create USB gadgets in user space. This allows creation
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of composite gadgets such that some of the functions are
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implemented in kernel space (for instance Ethernet, serial or
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mass storage) and other are implemented in user space.
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config USB_CONFIGFS_F_UAC1
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bool "Audio Class 1.0"
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depends on USB_CONFIGFS
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depends on SND
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select USB_LIBCOMPOSITE
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select SND_PCM
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select USB_U_AUDIO
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select USB_F_UAC1
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help
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This Audio function implements 1 AudioControl interface,
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1 AudioStreaming Interface each for USB-OUT and USB-IN.
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This driver doesn't expect any real Audio codec to be present
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on the device - the audio streams are simply sinked to and
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sourced from a virtual ALSA sound card created. The user-space
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application may choose to do whatever it wants with the data
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received from the USB Host and choose to provide whatever it
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wants as audio data to the USB Host.
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config USB_CONFIGFS_F_UAC1_LEGACY
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bool "Audio Class 1.0 (legacy implementation)"
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depends on USB_CONFIGFS
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depends on SND
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select USB_LIBCOMPOSITE
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select SND_PCM
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select USB_F_UAC1_LEGACY
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help
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This Audio function implements 1 AudioControl interface,
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1 AudioStreaming Interface each for USB-OUT and USB-IN.
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This is a legacy driver and requires a real Audio codec
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to be present on the device.
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config USB_CONFIGFS_F_UAC2
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bool "Audio Class 2.0"
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depends on USB_CONFIGFS
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depends on SND
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select USB_LIBCOMPOSITE
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select SND_PCM
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select USB_U_AUDIO
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select USB_F_UAC2
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help
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This Audio function is compatible with USB Audio Class
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specification 2.0. It implements 1 AudioControl interface,
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1 AudioStreaming Interface each for USB-OUT and USB-IN.
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This driver doesn't expect any real Audio codec to be present
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on the device - the audio streams are simply sinked to and
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sourced from a virtual ALSA sound card created. The user-space
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application may choose to do whatever it wants with the data
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received from the USB Host and choose to provide whatever it
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wants as audio data to the USB Host.
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config USB_CONFIGFS_F_MIDI
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bool "MIDI function"
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depends on USB_CONFIGFS
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depends on SND
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select USB_LIBCOMPOSITE
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select SND_RAWMIDI
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select USB_F_MIDI
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help
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The MIDI Function acts as a USB Audio device, with one MIDI
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input and one MIDI output. These MIDI jacks appear as
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a sound "card" in the ALSA sound system. Other MIDI
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connections can then be made on the gadget system, using
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ALSA's aconnect utility etc.
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config USB_CONFIGFS_F_HID
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bool "HID function"
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depends on USB_CONFIGFS
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select USB_F_HID
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help
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The HID function driver provides generic emulation of USB
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Human Interface Devices (HID).
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For more information, see Documentation/usb/gadget_hid.rst.
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config USB_CONFIGFS_F_UVC
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bool "USB Webcam function"
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depends on USB_CONFIGFS
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depends on VIDEO_V4L2
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depends on VIDEO_DEV
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select VIDEOBUF2_VMALLOC
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select USB_F_UVC
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help
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The Webcam function acts as a composite USB Audio and Video Class
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device. It provides a userspace API to process UVC control requests
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and stream video data to the host.
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config USB_CONFIGFS_F_PRINTER
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bool "Printer function"
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select USB_F_PRINTER
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depends on USB_CONFIGFS
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help
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The Printer function channels data between the USB host and a
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userspace program driving the print engine. The user space
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program reads and writes the device file /dev/g_printer<X> to
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receive or send printer data. It can use ioctl calls to
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the device file to get or set printer status.
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For more information, see Documentation/usb/gadget_printer.rst
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which includes sample code for accessing the device file.
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config USB_CONFIGFS_F_TCM
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bool "USB Gadget Target Fabric"
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depends on TARGET_CORE
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depends on USB_CONFIGFS
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select USB_LIBCOMPOSITE
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select USB_F_TCM
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help
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This fabric is a USB gadget component. Two USB protocols are
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supported that is BBB or BOT (Bulk Only Transport) and UAS
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(USB Attached SCSI). BOT is advertised on alternative
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interface 0 (primary) and UAS is on alternative interface 1.
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Both protocols can work on USB2.0 and USB3.0.
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UAS utilizes the USB 3.0 feature called streams support.
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choice
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tristate "USB Gadget precomposed configurations"
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default USB_ETH
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optional
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help
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A Linux "Gadget Driver" talks to the USB Peripheral Controller
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driver through the abstract "gadget" API. Some other operating
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systems call these "client" drivers, of which "class drivers"
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are a subset (implementing a USB device class specification).
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A gadget driver implements one or more USB functions using
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the peripheral hardware.
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Gadget drivers are hardware-neutral, or "platform independent",
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except that they sometimes must understand quirks or limitations
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of the particular controllers they work with. For example, when
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a controller doesn't support alternate configurations or provide
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enough of the right types of endpoints, the gadget driver might
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not be able work with that controller, or might need to implement
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a less common variant of a device class protocol.
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The available choices each represent a single precomposed USB
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gadget configuration. In the device model, each option contains
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both the device instantiation as a child for a USB gadget
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controller, and the relevant drivers for each function declared
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by the device.
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source "drivers/usb/gadget/legacy/Kconfig"
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endchoice
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endif # USB_GADGET
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