Updated: 2022/Sep/29

Please read Privacy Policy. It's for your privacy.

USBNET(9)                  Kernel Developer's Manual                 USBNET(9)

     usbnet - common USB Ethernet driver framework

     #include <dev/usb/usbnet.h>

   Functions offered by usbnet.h
     usbnet_set_link(struct usbnet *un, bool link);

     struct ifnet *
     usbnet_ifp(struct usbnet *un);

     struct ethercom *
     usbnet_ec(struct usbnet *un);

     struct mii_data *
     usbnet_mii(struct usbnet *un);

     krndsource_t *
     usbnet_rndsrc(struct usbnet *un);

     void *
     usbnet_softc(struct usbnet *un);

     usbnet_havelink(struct usbnet *un);

     usbnet_ispromisc(struct usbnet *un);

     usbnet_isdying(struct usbnet *un);

     usbnet_enqueue(struct usbnet *un, uint8_t *buf, size_t buflen,
         int csum_flags, uint32_t csum_data, int mbuf_flags);

     usbnet_input(struct usbnet *un, uint8_t *buf, size_t buflen);

     usbnet_attach(struct usbnet *un);

     usbnet_attach_ifp(struct usbnet *un, unsigned if_flags,
         unsigned if_extflags, const struct usbnet_mii *unm);

     usbnet_detach(device_t dev, int flags);

     usbnet_activate(device_t dev, devact_t act);

     The usbnet framework provides methods usable for USB Ethernet drivers.
     The framework has support for these features:

                Partial autoconf handling

                USB endpoint pipe handling

                Rx and Tx chain handling

                Generic handlers or support for several struct ifnet

                Network stack locking protocol

                Interrupt handling

     usbnet provides many or all of the traditional "softc" members inside
     struct usbnet, which can be used directly as the device softc structure
     if no additional storage is required.  A structure exists for receive and
     transmit chain management, struct usbnet_chain, that tracks the metadata
     for each transfer descriptor available, minimum of one each for Rx and Tx
     slot, and will be passed to the Rx and Tx callbacks.

     There is a struct usbnet_ops structure that provides a number of optional
     and required callbacks that will be described below.

     For autoconfiguration the device attach routine is expected to ensure
     that this device's struct usbnet is the first member of the device softc,
     if it can not be used directly as the device softc, as well as set up the
     necessary structure members, find end-points, find the Ethernet address
     if relevant, call usbnet_attach(), set up interface, Ethernet, and MII
     capabilities, and finally call usbnet_attach_ifp().  The device detach
     routine should free any resources allocated by attach and then call
     usbnet_detach(), possibly directly using usbnet_detach() as most
     consumers have no additional resources not owned and released by the
     usbnet framework itself.  The device activate function should be set to

     When bringing an interface up from if_init(9), which happens under
     IFNET_LOCK(9), usbnet will:

     1.   call "uno_init" to initialize the hardware for sending and receiving

     2.   open the USB pipes,

     3.   allocate Rx and Tx buffers for transfers,

     4.   call "uno_mcast" to initially program the hardware multicast filter,
          and finally

     5.   start the Rx transfers so packets can be received.

     See the RECEIVE AND SEND section for details on using the chains.

     When bringing an interface down from if_stop(9), which happens under
     IFNET_LOCK(9), usbnet will:

     1.   abort the USB pipes,

     2.   call "uno_stop" to stop the hardware from receiving packets (unless
          the device is detaching),

     3.   free Rx and Tx buffers for transfers, and

     4.   close the USB pipes.

     For interface ioctl, most of the handling is in the framework.  While the
     interface is running, the optional "uno_mcast" callback is invoked after
     handling the SIOCADDMULTI and SIOCDELMULTI ioctl commands to update the
     hardware's multicast filter from the ethersubr(9) lists.  The optional
     "uno_ioctl" callback, which is invoked under IFNET_LOCK(9), can be used
     to program special settings like offload handling.

     If ioctl handling requires capturing device-specific ioctls then the
     "uno_override_ioctl" callback may be used instead to replace the
     framework's ioctl handler completely (i.e., the replacement should call
     any generic ioctl handlers such as ether_ioctl() as required.)  For
     sending packets, the "uno_tx_prepare" callback must be used to convert an
     mbuf into a chain buffer ready for transmission.

     For devices requiring MII handling there are callbacks for reading and
     writing registers, and for status change events.  Access to all the MII
     functions is serialized by usbnet.

     As receive must handle the case of multiple packets in one buffer, the
     support is split between the driver and the framework.  A "uno_rx_loop"
     callback must be provided that loops over the incoming packet data found
     in a chain, performs necessary checking and passes the network frame up
     the stack via either usbnet_enqueue() or usbnet_input().  Typically
     Ethernet devices prefer usbnet_enqueue().

     General accessor functions for struct usbnet:

     usbnet_set_link(un, link)
           Set the link status for this un to link.

           Returns pointer to this un's struct ifnet.

           Returns pointer to this un's struct ethercom.

           Returns pointer to this un's struct mii_data.

           Returns pointer to this un's krndsource_t.

           Returns pointer to this un's device softc.

           Returns true if link is active.

           True if IFF_PROMISC is enabled, false if not.

           May be used only in "uno_init" and "uno_mcast".

           Drivers must use this in "uno_mcast" instead of reading

           Returns true if device is dying (has been pulled or deactivated,
           pending detach).  This should be used only to abort timeout loops

     Buffer enqueue handling for struct usbnet:

     usbnet_enqueue(un, buf, buflen, csum_flags, csum_data, mbuf_flags)
           Enqueue buffer buf for length buflen with higher layers, using the
           provided csum_flags, and csum_data, which are written directly to
           the mbuf packet header, and mbuf_flags, which is or-ed into the
           mbuf flags for the created mbuf.

     usbnet_input(un, buf, buflen)
           Enqueue buffer buf for length buflen with higher layers.

     Autoconfiguration handling for struct usbnet.  See the AUTOCONFIGURATION
     section for more details about these functions.

           Initial stage attach of a usb network device.  Performs internal
           initialization and memory allocation only -- nothing is published

     usbnet_attach_ifp(un, if_flags, if_extflags, unm)
           Final stage attach of usb network device.  Publishes the network
           interface to the rest of the system.

           If the passed in unm is non-NULL then an MII interface will be
           created using the values provided in the struct usbnet_mii
           structure, which has these members passed to mii_attach():

           un_mii_flags    Flags.

           un_mii_capmask  Capability mask.

           un_mii_phyloc   PHY location.

           un_mii_offset   PHY offset.

           A default unm can be set using the USBNET_MII_DECL_DEFAULT() macro.
           The if_flags and if_extflags will be or-ed into the interface flags
           and extflags.

     usbnet_detach(dev, flags)
           Device detach.  Stops all activity and frees memory.  Usable as
           driver(9) detach method.

     usbnet_activate(dev, act)
           Device activate (deactivate) method.  Usable as driver(9) activate

     The framework expects the usbnet structure to have these members filled
     in with valid values or functions:

     un_sc   Real softc allocated by autoconf and provided to attach, should
             be set to the usbnet structure if no device-specific softc is

     un_dev  device_t saved in attach, used for messages mostly.

             The USB iface handle for data interactions, see
             usbd_device2interface_handle() for more details.

             The struct usbd_device for this device, provided as the
             usb_attach_arg's uaa_device member.

     un_ops  Points to a struct usbnet_ops structure which contains these

             void (*uno_stop)(struct ifnet *ifp, int disable)
                   Stop hardware activity (optional).  Called under
                   IFNET_LOCK(9) when bringing the interface down, but skipped
                   when the device is detaching.

             int (*uno_ioctl)(struct ifnet *ifp, u_long cmd, void *data)
                   Handle driver-specific ioctls (optional).  Called under

             void (*uno_mcast)(struct ifnet *)
                   Program hardware multicast filters from ethersubr(9) lists
                   (optional).  Called between, and not during, "uno_init" and

             int (*uno_override_ioctl)(struct ifnet *ifp, u_long cmd, void
                   Handle all ioctls, including standard ethernet ioctls
                   normally handled internally by usbnet (optional).  May or
                   may not be called under IFNET_LOCK(9).

             int (*uno_init)(struct ifnet *ifp)
                   Initialize hardware activity (optional).  Called under
                   IFNET_LOCK(9) when bringing the interface up.

             int (*uno_read_reg)(struct usbnet *un, int phy, int reg, uint16_t
                   Read MII register.  Required with MII.  Serialized with
                   other MII functions, and only called after "uno_init" and
                   before "uno_stop".

             int (*uno_write_reg)(struct usbnet *un, int phy, int reg,
                   uint16_t val)
                   Write MII register.  Required with MII.  Serialized with
                   other MII functions, and only called after "uno_init" and
                   before "uno_stop".

             usbd_status (*uno_statchg)(struct ifnet *ifp)
                   Handle MII status change.  Required with MII.  Serialized
                   with other MII functions, and only called after "uno_init"
                   and before "uno_stop".

             unsigned (*uno_tx_prepare)(struct usbnet *un, struct mbuf *m,
                   struct usbnet_chain *c)
                   Prepare an mbuf for transmit.  Required.  Called
                   sequentially between, and not during, "uno_init" and

             void (*uno_rx_loop)(struct usbnet *un, struct usbnet_chain *c,
                   uint32_t total_len)
                   Prepare one or more chain for enqueue.  Required.  Called
                   sequentially between, and not during, "uno_init" and

             void (*uno_intr)(struct usbnet *un, usbd_status status)
                   Process periodic interrupt (optional).  Called sequentially
                   between, and not during, "uno_init" and "uno_stop".

             void (*uno_tick)(struct usbnet *un)
                   Called every second with USB task thread context
                   (optional).  Called sequentially between, and not during,
                   "uno_init" and "uno_stop".

             Points to a struct usbnet_intr structure which should have these
             members set:

                   If non-NULL, points to a buffer passed to
                   usbd_open_pipe_intr() in the device init callback, along
                   with the size and interval.

                   Size of interrupt pipe buffer.

                   Frequency of the interrupt in milliseconds.

     un_ed   Array of endpoint descriptors.  There indexes are provided:
             and Tx endpoints are required.

             MII phy number.  Not used by usbnet.

             6 bytes of Ethernet address that must be provided before calling
             usbnet_attach_ifp() if the device has Ethernet.

             Device owned flags word.  The usbnet framework will not touch
             this value.

             Passed to usbd_setup_xfer() for receiving packets.

             Passed to usbd_setup_xfer() for sending packets.

             Number of chain elements to allocate for Rx.

             Number of chain elements to allocate for Tx.

             Rx buffer size.

             Tx buffer size.

     The device detach and activate callbacks can typically be set to
     usbnet_detach() and usbnet_activate() unless device-specific handling is
     required, in which case, they can be called before or after such

     The capabilities described in both struct ifp and struct ethercom must be
     set before calling usbnet_attach_ifp().

     Receive and send routines are structured around the usbnet_cdata and
     usbnet_chain structures, the un_ed, un_rx_xfer_flags, and
     un_tx_xfer_flags members, and the uno_init(), uno_tx_prepare(),
     uno_rx_loop(), and uno_stop() callbacks of usbnet_ops.

     Typically, the device attach routine will fill in members of the usbnet
     structure, as listed in AUTOCONFIGURATION.  The un_ed array should have
     the USBNET_ENDPT_RX and USBNET_ENDPT_TX array entries filled in, and
     optionally the USBNET_ENDPT_INTR entry filled in if applicable.

     The uno_init() callback enables the hardware, and if necessary reprograms
     the hardware multicast filter, before the framework initiates USB Tx/Rx
     transfers.  All USB transfer setup is handled by the framework.  The
     driver callbacks merely copy data in or out of a chain entry using what
     is typically a device-specific method.

     The uno_rx_loop() callback, called sequentially, converts the provided
     usbnet_chain data and length into a series (one or more) of packets that
     are enqueued with the higher layers using either usbnet_enqueue() (for
     most devices) or usbnet_input() for devices that use if_input().  (This
     currently relies upon the struct ifnet having the "_if_input" member set
     as well, which is true for current consumers.)

     The uno_tx_prepare() callback must convert the provided struct mbuf into
     the provided struct usbnet_chain performing any device-specific padding,
     checksum, header or other.  Note that this callback must check that it is
     not attempting to copy more than the chain buffer size, as set in the
     usbnet "un_tx_bufsz" member.  This callback is only called once per
     packet, sequentially.

     The struct usbnet_chain structure which contains a "unc_buf" member which
     has the chain buffer allocated where data should be copied to or from for
     receive or transmit operations.  It also contains pointers back to the
     owning struct usbnet, and the struct usbd_xfer associated with this

     After aborting all USB Tx/Rx transfers when bringing an interface down,
     the framework calls the optional uno_stop() callback to disable the

     For devices that have MII support these callbacks in struct usbnet_ops
     must be provided:

           Read an MII register for a particular PHY.  Returns standard
           errno(2).  Must initialize the result even on failure.

           Write an MII register for a particular PHY.  Returns standard

           Handle a status change event for this interface.

     The interrupt specific callback, "uno_intr", is an optional callback that
     can be called periodically, registered by usbnet using the
     usbd_open_pipe_intr() function (instead of the usbd_open_pipe()
     function.)  The usbnet framework provides most of the interrupt handling
     and the callback simply inspects the returned buffer as necessary.  To
     enable the this callback point the struct usbnet member "un_intr" to a
     struct usbnet_intr structure with these members set:

           Data buffer for interrupt status relies.

           Size of the above buffer.

           Interval in millieconds.

     These values will be passed to usbd_open_pipe_intr().

     The porting of an older driver to the usbnet framework is largely an
     effort in deleting code.  The process involves making these changes:

           Many headers are included in usbnet.h and can be removed from the
           driver, as well as headers no longer used, such as callout.h and
           rndsource.h, etc.

     Device softc
           The majority of the driver's existing "softc" structure can likely
           be replaced with usage of struct usbnet and its related
           functionality.  This includes at least the device_t pointer,
           Ethernet address, the ethercom and mii_data structures, end point
           descriptors, usbd device, interface, and task and callout
           structures (both these probably go away entirely) and all the
           associated watchdog handling, timevals, list size, buffer size and
           xfer flags for both Rx, and Tx, and interrupt notices, interface
           flags, device link, PHY number, chain data, locks including Rx, Tx,
           and MII.  There is a driver-only "un_flags" in the usbnet structure
           available for drivers to use.

           Many drivers can use the usbnet structure as the device private
           storage passed to CFATTACH_DECL_NEW.  Many internal functions to
           the driver may look better if switched to operate on the device's
           usbnet as, for example, the usbd_device value is now available (and
           must be set by the driver) in the usbnet, which may be needed for
           any call to usbd_do_request().  The standard endpoint values must
           be stored in the usbnet "un_ed[]" array.

           As usbnet manages xfer chains all code related to the opening,
           closing, aborting and transferring of data on pipes is performed by
           the framework based upon the buffer size and more provided in
           subnet, so all code related to them should be deleted.

     Interface setup
           The vast majority of interface specific code should be deleted.
           For device-specific interface values, the ifnet flags and exflags
           can be set, as well as the ethercom "ec_capabilities" member,
           before calling usbnet_attach_ifp().  All calls to ifmedia_init(),
           mii_attach(), ifmedia_add(), ifmedia_set(), if_attach(),
           ether_ifattach(), rnd_attach_source(), and usbd_add_drv_event()
           should be eliminated.  The device "ioctl" routine can use the
           default handling with a callback for additional device specific
           programming (multicast filters, etc.), which can be empty, or, the
           override ioctl can be used for heavier requirements.  The device
           "stop" routine is replaced with a simple call that turns off the
           device-specific transmitter and receiver if necessary, as the
           framework handles pipes and transfers and buffers.

     MII handling
           For devices with MII support the three normal callbacks (read,
           write, and status change) must be converted to usbnet.  Local
           "link" variables need to be replaced with accesses to
           usbnet_set_link() and usbnet_havelink().  Other ifmedia callbacks
           that were passed to ifmedia_init() should be deleted and any work
           moved into "uno_statchg".

     Receive and Transmit
           The usbnet framework handles the majority of handling of both
           network directions.  The interface init routine should keep all of
           the device specific setup but replace all pipe management with a
           call to usbnet_init_rx_tx().  The typical receive handling will
           normally be replaced with a receive loop functions that can accept
           one or more packets, "uno_rx_loop", which can use either
           usbnet_enqueue() or usbnet_input() to pass the packets up to higher
           layers.  The typical interface "if_start" function and any
           additional functions used will normal be replaced with a relatively
           simple "uno_tx_prepare" function that simply converts an mbuf into
           a usbnet_chain useful for this device that will be passed onto
           usbd_transfer().  The framework's handling of the Tx interrupt is
           all internal.

     Interrupt pipe handling
           For devices requiring special handling of the interrupt pipe (i.e.,
           they use the usbd_open_pipe_intr() method), most of the interrupt
           handler should be deleted, leaving only code that inspects the
           result of the interrupt transfer.

     Common errors
           It's common to forget to set link active on devices with MII.  Be
           sure to call usbent_set_link() during any status change event.

           Many locking issues are hidden without LOCKDEBUG, including hard-
           hangs.  It's highly recommended to develop with LOCKDEBUG.

           The usbnet "un_ed" array is unsigned and should use "0" as the no-
           endpoint value.

     usb(4), driver(9), usbd_status(9), usbdi(9)

     This usbnet interface first appeared in NetBSD 9.0.  Portions of the
     original design are based upon ideas from Nick Hudson <skrll@NetBSD.org>.

     Matthew R. Green <mrg@eterna.com.au>

NetBSD 9.99                     March 15, 2020                     NetBSD 9.99