On Fri, 15 Nov 2019, Andrey Konovalov wrote: > 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. ... > --- /dev/null > +++ b/Documentation/usb/raw-gadget.rst > +Userspace interface > +~~~~~~~~~~~~~~~~~~~ > + > +To create a Raw Gadget instance open /sys/kernel/debug/usb/raw-gadget > +(debugfs should be enabled and mounted). Multiple raw-gadget instances Looks like the documentation hasn't kept up with the more recent changes to the driver. > --- /dev/null > +++ b/drivers/usb/gadget/legacy/raw.c > @@ -0,0 +1,1057 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * USB Raw Gadget driver. > + * See Documentation/usb/raw-gadget.rst for more details. > + * > + * Andrey Konovalov <andreyknvl@xxxxxxxxx> > + */ > + > +#define pr_fmt(fmt) "raw: %s: " fmt, __func__ This macro isn't used anywhere now. Alan Stern
