• Andrey Konovalov's avatar
    usb: gadget: add raw-gadget interface · f2c2e717
    Andrey Konovalov authored
    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: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    Signed-off-by: default avatarAndrey Konovalov <andreyknvl@google.com>
    Signed-off-by: default avatarFelipe Balbi <balbi@kernel.org>
    f2c2e717
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