Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted

Pull networking updates from Jakub Kicinski:
 "Core:

   - Add dedicated kmem_cache for typical/small skb->head, avoid having
     to access struct page at kfree time, and improve memory use.

   - Introduce sysctl to set default RPS configuration for new netdevs.

   - Define Netlink protocol specification format which can be used to
     describe messages used by each family and auto-generate parsers.
     Add tools for generating kernel data structures and uAPI headers.

   - Expose all net/core sysctls inside netns.

   - Remove 4s sleep in netpoll if carrier is instantly detected on
     boot.

   - Add configurable limit of MDB entries per port, and port-vlan.

   - Continue populating drop reasons throughout the stack.

   - Retire a handful of legacy Qdiscs and classifiers.

  Protocols:

   - Support IPv4 big TCP (TSO frames larger than 64kB).

   - Add IP_LOCAL_PORT_RANGE socket option, to control local port range
     on socket by socket basis.

   - Track and report in procfs number of MPTCP sockets used.

   - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path
     manager.

   - IPv6: don't check net.ipv6.route.max_size and rely on garbage
     collection to free memory (similarly to IPv4).

   - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986).

   - ICMP: add per-rate limit counters.

   - Add support for user scanning requests in ieee802154.

   - Remove static WEP support.

   - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate
     reporting.

   - WiFi 7 EHT channel puncturing support (client & AP).

  BPF:

   - Add a rbtree data structure following the "next-gen data structure"
     precedent set by recently added linked list, that is, by using
     kfunc + kptr instead of adding a new BPF map type.

   - Expose XDP hints via kfuncs with initial support for RX hash and
     timestamp metadata.

   - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to
     better support decap on GRE tunnel devices not operating in collect
     metadata.

   - Improve x86 JIT's codegen for PROBE_MEM runtime error checks.

   - Remove the need for trace_printk_lock for bpf_trace_printk and
     bpf_trace_vprintk helpers.

   - Extend libbpf's bpf_tracing.h support for tracing arguments of
     kprobes/uprobes and syscall as a special case.

   - Significantly reduce the search time for module symbols by
     livepatch and BPF.

   - Enable cpumasks to be used as kptrs, which is useful for tracing
     programs tracking which tasks end up running on which CPUs in
     different time intervals.

   - Add support for BPF trampoline on s390x and riscv64.

   - Add capability to export the XDP features supported by the NIC.

   - Add __bpf_kfunc tag for marking kernel functions as kfuncs.

   - Add cgroup.memory=nobpf kernel parameter option to disable BPF
     memory accounting for container environments.

  Netfilter:

   - Remove the CLUSTERIP target. It has been marked as obsolete for
     years, and we still have WARN splats wrt races of the out-of-band
     /proc interface installed by this target.

   - Add 'destroy' commands to nf_tables. They are identical to the
     existing 'delete' commands, but do not return an error if the
     referenced object (set, chain, rule...) did not exist.

  Driver API:

   - Improve cpumask_local_spread() locality to help NICs set the right
     IRQ affinity on AMD platforms.

   - Separate C22 and C45 MDIO bus transactions more clearly.

   - Introduce new DCB table to control DSCP rewrite on egress.

   - Support configuration of Physical Layer Collision Avoidance (PLCA)
     Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of
     shared medium Ethernet.

   - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing
     preemption of low priority frames by high priority frames.

   - Add support for controlling MACSec offload using netlink SET.

   - Rework devlink instance refcounts to allow registration and
     de-registration under the instance lock. Split the code into
     multiple files, drop some of the unnecessarily granular locks and
     factor out common parts of netlink operation handling.

   - Add TX frame aggregation parameters (for USB drivers).

   - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning
     messages with notifications for debug.

   - Allow offloading of UDP NEW connections via act_ct.

   - Add support for per action HW stats in TC.

   - Support hardware miss to TC action (continue processing in SW from
     a specific point in the action chain).

   - Warn if old Wireless Extension user space interface is used with
     modern cfg80211/mac80211 drivers. Do not support Wireless
     Extensions for Wi-Fi 7 devices at all. Everyone should switch to
     using nl80211 interface instead.

   - Improve the CAN bit timing configuration. Use extack to return
     error messages directly to user space, update the SJW handling,
     including the definition of a new default value that will benefit
     CAN-FD controllers, by increasing their oscillator tolerance.

  New hardware / drivers:

   - Ethernet:
      - nVidia BlueField-3 support (control traffic driver)
      - Ethernet support for imx93 SoCs
      - Motorcomm yt8531 gigabit Ethernet PHY
      - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA)
      - Microchip LAN8841 PHY (incl. cable diagnostics and PTP)
      - Amlogic gxl MDIO mux

   - WiFi:
      - RealTek RTL8188EU (rtl8xxxu)
      - Qualcomm Wi-Fi 7 devices (ath12k)

   - CAN:
      - Renesas R-Car V4H

  Drivers:

   - Bluetooth:
      - Set Per Platform Antenna Gain (PPAG) for Intel controllers.

   - Ethernet NICs:
      - Intel (1G, igc):
         - support TSN / Qbv / packet scheduling features of i226 model
      - Intel (100G, ice):
         - use GNSS subsystem instead of TTY
         - multi-buffer XDP support
         - extend support for GPIO pins to E823 devices
      - nVidia/Mellanox:
         - update the shared buffer configuration on PFC commands
         - implement PTP adjphase function for HW offset control
         - TC support for Geneve and GRE with VF tunnel offload
         - more efficient crypto key management method
         - multi-port eswitch support
      - Netronome/Corigine:
         - add DCB IEEE support
         - support IPsec offloading for NFP3800
      - Freescale/NXP (enetc):
         - support XDP_REDIRECT for XDP non-linear buffers
         - improve reconfig, avoid link flap and waiting for idle
         - support MAC Merge layer
      - Other NICs:
         - sfc/ef100: add basic devlink support for ef100
         - ionic: rx_push mode operation (writing descriptors via MMIO)
         - bnxt: use the auxiliary bus abstraction for RDMA
         - r8169: disable ASPM and reset bus in case of tx timeout
         - cpsw: support QSGMII mode for J721e CPSW9G
         - cpts: support pulse-per-second output
         - ngbe: add an mdio bus driver
         - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing
         - r8152: handle devices with FW with NCM support
         - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation
         - virtio-net: support multi buffer XDP
         - virtio/vsock: replace virtio_vsock_pkt with sk_buff
         - tsnep: XDP support

   - Ethernet high-speed switches:
      - nVidia/Mellanox (mlxsw):
         - add support for latency TLV (in FW control messages)
      - Microchip (sparx5):
         - separate explicit and implicit traffic forwarding rules, make
           the implicit rules always active
         - add support for egress DSCP rewrite
         - IS0 VCAP support (Ingress Classification)
         - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS
           etc.)
         - ES2 VCAP support (Egress Access Control)
         - support for Per-Stream Filtering and Policing (802.1Q,
           8.6.5.1)

   - Ethernet embedded switches:
      - Marvell (mv88e6xxx):
         - add MAB (port auth) offload support
         - enable PTP receive for mv88e6390
      - NXP (ocelot):
         - support MAC Merge layer
         - support for the the vsc7512 internal copper phys
      - Microchip:
         - lan9303: convert to PHYLINK
         - lan966x: support TC flower filter statistics
         - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x
         - lan937x: support Credit Based Shaper configuration
         - ksz9477: support Energy Efficient Ethernet
      - other:
         - qca8k: convert to regmap read/write API, use bulk operations
         - rswitch: Improve TX timestamp accuracy

   - Intel WiFi (iwlwifi):
      - EHT (Wi-Fi 7) rate reporting
      - STEP equalizer support: transfer some STEP (connection to radio
        on platforms with integrated wifi) related parameters from the
        BIOS to the firmware.

   - Qualcomm 802.11ax WiFi (ath11k):
      - IPQ5018 support
      - Fine Timing Measurement (FTM) responder role support
      - channel 177 support

   - MediaTek WiFi (mt76):
      - per-PHY LED support
      - mt7996: EHT (Wi-Fi 7) support
      - Wireless Ethernet Dispatch (WED) reset support
      - switch to using page pool allocator

   - RealTek WiFi (rtw89):
      - support new version of Bluetooth co-existance

   - Mobile:
      - rmnet: support TX aggregation"

* tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits)
  page_pool: add a comment explaining the fragment counter usage
  net: ethtool: fix __ethtool_dev_mm_supported() implementation
  ethtool: pse-pd: Fix double word in comments
  xsk: add linux/vmalloc.h to xsk.c
  sefltests: netdevsim: wait for devlink instance after netns removal
  selftest: fib_tests: Always cleanup before exit
  net/mlx5e: Align IPsec ASO result memory to be as required by hardware
  net/mlx5e: TC, Set CT miss to the specific ct action instance
  net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG
  net/mlx5: Refactor tc miss handling to a single function
  net/mlx5: Kconfig: Make tc offload depend on tc skb extension
  net/sched: flower: Support hardware miss to tc action
  net/sched: flower: Move filter handle initialization earlier
  net/sched: cls_api: Support hardware miss to tc action
  net/sched: Rename user cookie and act cookie
  sfc: fix builds without CONFIG_RTC_LIB
  sfc: clean up some inconsistent indentings
  net/mlx4_en: Introduce flexible array to silence overflow warning
  net: lan966x: Fix possible deadlock inside PTP
  net/ulp: Remove redundant ->clone() test in inet_clone_ulp().
  ...

3 files changed, 356 insertions, 0 deletions

diff --git a/Documentation/driver-api/nfc/index.rst b/Documentation/driver-api/nfc/index.rst
new file mode 100644
index 000000000..b6e9eedbf
--- /dev/null
+++ b/Documentation/driver-api/nfc/index.rst
@@ -0,0 +1,11 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+========================
+Near Field Communication
+========================
+
+.. toctree::
+   :maxdepth: 1
+
+   nfc-hci
+   nfc-pn544
diff --git a/Documentation/driver-api/nfc/nfc-hci.rst b/Documentation/driver-api/nfc/nfc-hci.rst
new file mode 100644
index 000000000..f10fe53aa
--- /dev/null
+++ b/Documentation/driver-api/nfc/nfc-hci.rst
@@ -0,0 +1,311 @@
+========================
+HCI backend for NFC Core
+========================
+
+- Author: Eric Lapuyade, Samuel Ortiz
+- Contact: eric.lapuyade@intel.com, samuel.ortiz@intel.com
+
+General
+-------
+
+The HCI layer implements much of the ETSI TS 102 622 V10.2.0 specification. It
+enables easy writing of HCI-based NFC drivers. The HCI layer runs as an NFC Core
+backend, implementing an abstract nfc device and translating NFC Core API
+to HCI commands and events.
+
+HCI
+---
+
+HCI registers as an nfc device with NFC Core. Requests coming from userspace are
+routed through netlink sockets to NFC Core and then to HCI. From this point,
+they are translated in a sequence of HCI commands sent to the HCI layer in the
+host controller (the chip). Commands can be executed synchronously (the sending
+context blocks waiting for response) or asynchronously (the response is returned
+from HCI Rx context).
+HCI events can also be received from the host controller. They will be handled
+and a translation will be forwarded to NFC Core as needed. There are hooks to
+let the HCI driver handle proprietary events or override standard behavior.
+HCI uses 2 execution contexts:
+
+- one for executing commands : nfc_hci_msg_tx_work(). Only one command
+  can be executing at any given moment.
+- one for dispatching received events and commands : nfc_hci_msg_rx_work().
+
+HCI Session initialization
+--------------------------
+
+The Session initialization is an HCI standard which must unfortunately
+support proprietary gates. This is the reason why the driver will pass a list
+of proprietary gates that must be part of the session. HCI will ensure all
+those gates have pipes connected when the hci device is set up.
+In case the chip supports pre-opened gates and pseudo-static pipes, the driver
+can pass that information to HCI core.
+
+HCI Gates and Pipes
+-------------------
+
+A gate defines the 'port' where some service can be found. In order to access
+a service, one must create a pipe to that gate and open it. In this
+implementation, pipes are totally hidden. The public API only knows gates.
+This is consistent with the driver need to send commands to proprietary gates
+without knowing the pipe connected to it.
+
+Driver interface
+----------------
+
+A driver is generally written in two parts : the physical link management and
+the HCI management. This makes it easier to maintain a driver for a chip that
+can be connected using various phy (i2c, spi, ...)
+
+HCI Management
+--------------
+
+A driver would normally register itself with HCI and provide the following
+entry points::
+
+  struct nfc_hci_ops {
+	int (*open)(struct nfc_hci_dev *hdev);
+	void (*close)(struct nfc_hci_dev *hdev);
+	int (*hci_ready) (struct nfc_hci_dev *hdev);
+	int (*xmit) (struct nfc_hci_dev *hdev, struct sk_buff *skb);
+	int (*start_poll) (struct nfc_hci_dev *hdev,
+			   u32 im_protocols, u32 tm_protocols);
+	int (*dep_link_up)(struct nfc_hci_dev *hdev, struct nfc_target *target,
+			   u8 comm_mode, u8 *gb, size_t gb_len);
+	int (*dep_link_down)(struct nfc_hci_dev *hdev);
+	int (*target_from_gate) (struct nfc_hci_dev *hdev, u8 gate,
+				 struct nfc_target *target);
+	int (*complete_target_discovered) (struct nfc_hci_dev *hdev, u8 gate,
+					   struct nfc_target *target);
+	int (*im_transceive) (struct nfc_hci_dev *hdev,
+			      struct nfc_target *target, struct sk_buff *skb,
+			      data_exchange_cb_t cb, void *cb_context);
+	int (*tm_send)(struct nfc_hci_dev *hdev, struct sk_buff *skb);
+	int (*check_presence)(struct nfc_hci_dev *hdev,
+			      struct nfc_target *target);
+	int (*event_received)(struct nfc_hci_dev *hdev, u8 gate, u8 event,
+			      struct sk_buff *skb);
+  };
+
+- open() and close() shall turn the hardware on and off.
+- hci_ready() is an optional entry point that is called right after the hci
+  session has been set up. The driver can use it to do additional initialization
+  that must be performed using HCI commands.
+- xmit() shall simply write a frame to the physical link.
+- start_poll() is an optional entrypoint that shall set the hardware in polling
+  mode. This must be implemented only if the hardware uses proprietary gates or a
+  mechanism slightly different from the HCI standard.
+- dep_link_up() is called after a p2p target has been detected, to finish
+  the p2p connection setup with hardware parameters that need to be passed back
+  to nfc core.
+- dep_link_down() is called to bring the p2p link down.
+- target_from_gate() is an optional entrypoint to return the nfc protocols
+  corresponding to a proprietary gate.
+- complete_target_discovered() is an optional entry point to let the driver
+  perform additional proprietary processing necessary to auto activate the
+  discovered target.
+- im_transceive() must be implemented by the driver if proprietary HCI commands
+  are required to send data to the tag. Some tag types will require custom
+  commands, others can be written to using the standard HCI commands. The driver
+  can check the tag type and either do proprietary processing, or return 1 to ask
+  for standard processing. The data exchange command itself must be sent
+  asynchronously.
+- tm_send() is called to send data in the case of a p2p connection
+- check_presence() is an optional entry point that will be called regularly
+  by the core to check that an activated tag is still in the field. If this is
+  not implemented, the core will not be able to push tag_lost events to the user
+  space
+- event_received() is called to handle an event coming from the chip. Driver
+  can handle the event or return 1 to let HCI attempt standard processing.
+
+On the rx path, the driver is responsible to push incoming HCP frames to HCI
+using nfc_hci_recv_frame(). HCI will take care of re-aggregation and handling
+This must be done from a context that can sleep.
+
+PHY Management
+--------------
+
+The physical link (i2c, ...) management is defined by the following structure::
+
+  struct nfc_phy_ops {
+	int (*write)(void *dev_id, struct sk_buff *skb);
+	int (*enable)(void *dev_id);
+	void (*disable)(void *dev_id);
+  };
+
+enable():
+	turn the phy on (power on), make it ready to transfer data
+disable():
+	turn the phy off
+write():
+	Send a data frame to the chip. Note that to enable higher
+	layers such as an llc to store the frame for re-emission, this
+	function must not alter the skb. It must also not return a positive
+	result (return 0 for success, negative for failure).
+
+Data coming from the chip shall be sent directly to nfc_hci_recv_frame().
+
+LLC
+---
+
+Communication between the CPU and the chip often requires some link layer
+protocol. Those are isolated as modules managed by the HCI layer. There are
+currently two modules : nop (raw transfert) and shdlc.
+A new llc must implement the following functions::
+
+  struct nfc_llc_ops {
+	void *(*init) (struct nfc_hci_dev *hdev, xmit_to_drv_t xmit_to_drv,
+		       rcv_to_hci_t rcv_to_hci, int tx_headroom,
+		       int tx_tailroom, int *rx_headroom, int *rx_tailroom,
+		       llc_failure_t llc_failure);
+	void (*deinit) (struct nfc_llc *llc);
+	int (*start) (struct nfc_llc *llc);
+	int (*stop) (struct nfc_llc *llc);
+	void (*rcv_from_drv) (struct nfc_llc *llc, struct sk_buff *skb);
+	int (*xmit_from_hci) (struct nfc_llc *llc, struct sk_buff *skb);
+  };
+
+init():
+	allocate and init your private storage
+deinit():
+	cleanup
+start():
+	establish the logical connection
+stop ():
+	terminate the logical connection
+rcv_from_drv():
+	handle data coming from the chip, going to HCI
+xmit_from_hci():
+	handle data sent by HCI, going to the chip
+
+The llc must be registered with nfc before it can be used. Do that by
+calling::
+
+	nfc_llc_register(const char *name, const struct nfc_llc_ops *ops);
+
+Again, note that the llc does not handle the physical link. It is thus very
+easy to mix any physical link with any llc for a given chip driver.
+
+Included Drivers
+----------------
+
+An HCI based driver for an NXP PN544, connected through I2C bus, and using
+shdlc is included.
+
+Execution Contexts
+------------------
+
+The execution contexts are the following:
+- IRQ handler (IRQH):
+fast, cannot sleep. sends incoming frames to HCI where they are passed to
+the current llc. In case of shdlc, the frame is queued in shdlc rx queue.
+
+- SHDLC State Machine worker (SMW)
+
+  Only when llc_shdlc is used: handles shdlc rx & tx queues.
+
+  Dispatches HCI cmd responses.
+
+- HCI Tx Cmd worker (MSGTXWQ)
+
+  Serializes execution of HCI commands.
+
+  Completes execution in case of response timeout.
+
+- HCI Rx worker (MSGRXWQ)
+
+  Dispatches incoming HCI commands or events.
+
+- Syscall context from a userspace call (SYSCALL)
+
+  Any entrypoint in HCI called from NFC Core
+
+Workflow executing an HCI command (using shdlc)
+-----------------------------------------------
+
+Executing an HCI command can easily be performed synchronously using the
+following API::
+
+  int nfc_hci_send_cmd (struct nfc_hci_dev *hdev, u8 gate, u8 cmd,
+			const u8 *param, size_t param_len, struct sk_buff **skb)
+
+The API must be invoked from a context that can sleep. Most of the time, this
+will be the syscall context. skb will return the result that was received in
+the response.
+
+Internally, execution is asynchronous. So all this API does is to enqueue the
+HCI command, setup a local wait queue on stack, and wait_event() for completion.
+The wait is not interruptible because it is guaranteed that the command will
+complete after some short timeout anyway.
+
+MSGTXWQ context will then be scheduled and invoke nfc_hci_msg_tx_work().
+This function will dequeue the next pending command and send its HCP fragments
+to the lower layer which happens to be shdlc. It will then start a timer to be
+able to complete the command with a timeout error if no response arrive.
+
+SMW context gets scheduled and invokes nfc_shdlc_sm_work(). This function
+handles shdlc framing in and out. It uses the driver xmit to send frames and
+receives incoming frames in an skb queue filled from the driver IRQ handler.
+SHDLC I(nformation) frames payload are HCP fragments. They are aggregated to
+form complete HCI frames, which can be a response, command, or event.
+
+HCI Responses are dispatched immediately from this context to unblock
+waiting command execution. Response processing involves invoking the completion
+callback that was provided by nfc_hci_msg_tx_work() when it sent the command.
+The completion callback will then wake the syscall context.
+
+It is also possible to execute the command asynchronously using this API::
+
+  static int nfc_hci_execute_cmd_async(struct nfc_hci_dev *hdev, u8 pipe, u8 cmd,
+				       const u8 *param, size_t param_len,
+				       data_exchange_cb_t cb, void *cb_context)
+
+The workflow is the same, except that the API call returns immediately, and
+the callback will be called with the result from the SMW context.
+
+Workflow receiving an HCI event or command
+------------------------------------------
+
+HCI commands or events are not dispatched from SMW context. Instead, they are
+queued to HCI rx_queue and will be dispatched from HCI rx worker
+context (MSGRXWQ). This is done this way to allow a cmd or event handler
+to also execute other commands (for example, handling the
+NFC_HCI_EVT_TARGET_DISCOVERED event from PN544 requires to issue an
+ANY_GET_PARAMETER to the reader A gate to get information on the target
+that was discovered).
+
+Typically, such an event will be propagated to NFC Core from MSGRXWQ context.
+
+Error management
+----------------
+
+Errors that occur synchronously with the execution of an NFC Core request are
+simply returned as the execution result of the request. These are easy.
+
+Errors that occur asynchronously (e.g. in a background protocol handling thread)
+must be reported such that upper layers don't stay ignorant that something
+went wrong below and know that expected events will probably never happen.
+Handling of these errors is done as follows:
+
+- driver (pn544) fails to deliver an incoming frame: it stores the error such
+  that any subsequent call to the driver will result in this error. Then it
+  calls the standard nfc_shdlc_recv_frame() with a NULL argument to report the
+  problem above. shdlc stores a EREMOTEIO sticky status, which will trigger
+  SMW to report above in turn.
+
+- SMW is basically a background thread to handle incoming and outgoing shdlc
+  frames. This thread will also check the shdlc sticky status and report to HCI
+  when it discovers it is not able to run anymore because of an unrecoverable
+  error that happened within shdlc or below. If the problem occurs during shdlc
+  connection, the error is reported through the connect completion.
+
+- HCI: if an internal HCI error happens (frame is lost), or HCI is reported an
+  error from a lower layer, HCI will either complete the currently executing
+  command with that error, or notify NFC Core directly if no command is
+  executing.
+
+- NFC Core: when NFC Core is notified of an error from below and polling is
+  active, it will send a tag discovered event with an empty tag list to the user
+  space to let it know that the poll operation will never be able to detect a
+  tag. If polling is not active and the error was sticky, lower levels will
+  return it at next invocation.
diff --git a/Documentation/driver-api/nfc/nfc-pn544.rst b/Documentation/driver-api/nfc/nfc-pn544.rst
new file mode 100644
index 000000000..6b2d8aae0
--- /dev/null
+++ b/Documentation/driver-api/nfc/nfc-pn544.rst
@@ -0,0 +1,34 @@
+============================================================================
+Kernel driver for the NXP Semiconductors PN544 Near Field Communication chip
+============================================================================
+
+
+General
+-------
+
+The PN544 is an integrated transmission module for contactless
+communication. The driver goes under drives/nfc/ and is compiled as a
+module named "pn544".
+
+Host Interfaces: I2C, SPI and HSU, this driver supports currently only I2C.
+
+Protocols
+---------
+
+In the normal (HCI) mode and in the firmware update mode read and
+write functions behave a bit differently because the message formats
+or the protocols are different.
+
+In the normal (HCI) mode the protocol used is derived from the ETSI
+HCI specification. The firmware is updated using a specific protocol,
+which is different from HCI.
+
+HCI messages consist of an eight bit header and the message body. The
+header contains the message length. Maximum size for an HCI message is
+33. In HCI mode sent messages are tested for a correct
+checksum. Firmware update messages have the length in the second (MSB)
+and third (LSB) bytes of the message. The maximum FW message length is
+1024 bytes.
+
+For the ETSI HCI specification see
+http://www.etsi.org/WebSite/Technologies/ProtocolSpecification.aspx