On Fri, Nov 15, 2019 at 4:38 PM Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> wrote: > > 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. Right, will fix in v3, thanks! > > > --- /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. It's used internally by pr_debug(). I didn't remove all of the debugging messages, I've left the ones that are printed in cases or errors, since ftrace might not always help to distinguish between some of those.
