Re: [PATCH 0/1] usb: gadget: add raw-gadget interface

[Alan Stern]

On Fri, 8 Nov 2019, Andrey Konovalov wrote:

> This patchset (currently a single patch) adds a new userspace interface
> for the USB Gadget subsystem called USB Raw Gadget (I don't mind changing
> the name to something else if there are better ideas). This is what
> currently being used to enable coverage-buided USB fuzzing with syzkaller:
> 
> https://github.com/google/syzkaller/blob/master/docs/linux/external_fuzzing_usb.md
> 
> Initially I was using GadgetFS (together with the Dummy HCD/UDC module)
> to perform emulation of USB devices for fuzzing, but later switched to a
> custom written interface. The incentive to implement a different interface
> was to provide a somewhat raw and direct access to the USB Gadget layer
> for the userspace, where every USB request is passed to the userspace to
> get a response. See documentation for the list of differences between
> Raw Gadget and GadgetFS.
> 
> This patchset has been pushed to the public Linux kernel Gerrit instance:
> 
> https://linux-review.googlesource.com/c/linux/kernel/git/torvalds/linux/+/2144
> 
> Andrey Konovalov (1):
>   usb: gadget: add raw-gadget interface
> 
>  Documentation/usb/index.rst         |    1 +
>  Documentation/usb/raw-gadget.rst    |   60 ++
>  drivers/usb/gadget/Kconfig          |    9 +
>  drivers/usb/gadget/Makefile         |    2 +
>  drivers/usb/gadget/raw.c            | 1150 +++++++++++++++++++++++++++

As a general rule, gadget drivers don't go directly in
drivers/usb/gadget.  raw.c counts as a legacy driver (because it's not
written to use the composite gadget framework), so it belongs in
drivers/usb/gadget/legacy.  That's where the gadgetfs driver lives, for
example.

Alan Stern

>  include/uapi/linux/usb/raw_gadget.h |  164 ++++
>  6 files changed, 1386 insertions(+)
>  create mode 100644 Documentation/usb/raw-gadget.rst
>  create mode 100644 drivers/usb/gadget/raw.c
>  create mode 100644 include/uapi/linux/usb/raw_gadget.h