linux-stable/Documentation/usb/index.rst
Andrey Konovalov f2c2e71764 usb: gadget: add raw-gadget interface
USB Raw Gadget is a kernel module that provides a userspace interface for
the USB Gadget subsystem. Essentially it allows to emulate USB devices
from userspace. Enabled with CONFIG_USB_RAW_GADGET. Raw Gadget is
currently a strictly debugging feature and shouldn't be used in
production.

Raw Gadget is similar to GadgetFS, but provides a more low-level and
direct access to the USB Gadget layer for the userspace. The key
differences are:

1. Every USB request is passed to the userspace to get a response, while
   GadgetFS responds to some USB requests internally based on the provided
   descriptors. However note, that the UDC driver might respond to some
   requests on its own and never forward them to the Gadget layer.

2. GadgetFS performs some sanity checks on the provided USB descriptors,
   while Raw Gadget allows you to provide arbitrary data as responses to
   USB requests.

3. Raw Gadget provides a way to select a UDC device/driver to bind to,
   while GadgetFS currently binds to the first available UDC.

4. Raw Gadget uses predictable endpoint names (handles) across different
   UDCs (as long as UDCs have enough endpoints of each required transfer
   type).

5. Raw Gadget has ioctl-based interface instead of a filesystem-based one.

Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>
2020-03-15 11:34:48 +02:00

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===========
USB support
===========
.. toctree::
:maxdepth: 1
acm
authorization
chipidea
dwc3
ehci
functionfs
gadget_configfs
gadget_hid
gadget_multi
gadget_printer
gadget_serial
gadget-testing
iuu_phoenix
mass-storage
misc_usbsevseg
mtouchusb
ohci
raw-gadget
usbip_protocol
usbmon
usb-serial
usb-help
text_files
.. only:: subproject and html
Indices
=======
* :ref:`genindex`