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().
  ...

1 files changed, 428 insertions, 0 deletions

diff --git a/Documentation/i2c/writing-clients.rst b/Documentation/i2c/writing-clients.rst
new file mode 100644
index 000000000..b7d3ae745
--- /dev/null
+++ b/Documentation/i2c/writing-clients.rst
@@ -0,0 +1,428 @@
+===============================
+Implementing I2C device drivers
+===============================
+
+This is a small guide for those who want to write kernel drivers for I2C
+or SMBus devices, using Linux as the protocol host/master (not slave).
+
+To set up a driver, you need to do several things. Some are optional, and
+some things can be done slightly or completely different. Use this as a
+guide, not as a rule book!
+
+
+General remarks
+===============
+
+Try to keep the kernel namespace as clean as possible. The best way to
+do this is to use a unique prefix for all global symbols. This is
+especially important for exported symbols, but it is a good idea to do
+it for non-exported symbols too. We will use the prefix ``foo_`` in this
+tutorial.
+
+
+The driver structure
+====================
+
+Usually, you will implement a single driver structure, and instantiate
+all clients from it. Remember, a driver structure contains general access
+routines, and should be zero-initialized except for fields with data you
+provide.  A client structure holds device-specific information like the
+driver model device node, and its I2C address.
+
+::
+
+  static struct i2c_device_id foo_idtable[] = {
+	{ "foo", my_id_for_foo },
+	{ "bar", my_id_for_bar },
+	{ }
+  };
+
+  MODULE_DEVICE_TABLE(i2c, foo_idtable);
+
+  static struct i2c_driver foo_driver = {
+	.driver = {
+		.name	= "foo",
+		.pm	= &foo_pm_ops,	/* optional */
+	},
+
+	.id_table	= foo_idtable,
+	.probe_new	= foo_probe,
+	.remove		= foo_remove,
+	/* if device autodetection is needed: */
+	.class		= I2C_CLASS_SOMETHING,
+	.detect		= foo_detect,
+	.address_list	= normal_i2c,
+
+	.shutdown	= foo_shutdown,	/* optional */
+	.command	= foo_command,	/* optional, deprecated */
+  }
+
+The name field is the driver name, and must not contain spaces.  It
+should match the module name (if the driver can be compiled as a module),
+although you can use MODULE_ALIAS (passing "foo" in this example) to add
+another name for the module.  If the driver name doesn't match the module
+name, the module won't be automatically loaded (hotplug/coldplug).
+
+All other fields are for call-back functions which will be explained
+below.
+
+
+Extra client data
+=================
+
+Each client structure has a special ``data`` field that can point to any
+structure at all.  You should use this to keep device-specific data.
+
+::
+
+	/* store the value */
+	void i2c_set_clientdata(struct i2c_client *client, void *data);
+
+	/* retrieve the value */
+	void *i2c_get_clientdata(const struct i2c_client *client);
+
+Note that starting with kernel 2.6.34, you don't have to set the ``data`` field
+to NULL in remove() or if probe() failed anymore. The i2c-core does this
+automatically on these occasions. Those are also the only times the core will
+touch this field.
+
+
+Accessing the client
+====================
+
+Let's say we have a valid client structure. At some time, we will need
+to gather information from the client, or write new information to the
+client.
+
+I have found it useful to define foo_read and foo_write functions for this.
+For some cases, it will be easier to call the I2C functions directly,
+but many chips have some kind of register-value idea that can easily
+be encapsulated.
+
+The below functions are simple examples, and should not be copied
+literally::
+
+  int foo_read_value(struct i2c_client *client, u8 reg)
+  {
+	if (reg < 0x10)	/* byte-sized register */
+		return i2c_smbus_read_byte_data(client, reg);
+	else		/* word-sized register */
+		return i2c_smbus_read_word_data(client, reg);
+  }
+
+  int foo_write_value(struct i2c_client *client, u8 reg, u16 value)
+  {
+	if (reg == 0x10)	/* Impossible to write - driver error! */
+		return -EINVAL;
+	else if (reg < 0x10)	/* byte-sized register */
+		return i2c_smbus_write_byte_data(client, reg, value);
+	else			/* word-sized register */
+		return i2c_smbus_write_word_data(client, reg, value);
+  }
+
+
+Probing and attaching
+=====================
+
+The Linux I2C stack was originally written to support access to hardware
+monitoring chips on PC motherboards, and thus used to embed some assumptions
+that were more appropriate to SMBus (and PCs) than to I2C.  One of these
+assumptions was that most adapters and devices drivers support the SMBUS_QUICK
+protocol to probe device presence.  Another was that devices and their drivers
+can be sufficiently configured using only such probe primitives.
+
+As Linux and its I2C stack became more widely used in embedded systems
+and complex components such as DVB adapters, those assumptions became more
+problematic.  Drivers for I2C devices that issue interrupts need more (and
+different) configuration information, as do drivers handling chip variants
+that can't be distinguished by protocol probing, or which need some board
+specific information to operate correctly.
+
+
+Device/Driver Binding
+---------------------
+
+System infrastructure, typically board-specific initialization code or
+boot firmware, reports what I2C devices exist.  For example, there may be
+a table, in the kernel or from the boot loader, identifying I2C devices
+and linking them to board-specific configuration information about IRQs
+and other wiring artifacts, chip type, and so on.  That could be used to
+create i2c_client objects for each I2C device.
+
+I2C device drivers using this binding model work just like any other
+kind of driver in Linux:  they provide a probe() method to bind to
+those devices, and a remove() method to unbind.
+
+::
+
+	static int foo_probe(struct i2c_client *client);
+	static void foo_remove(struct i2c_client *client);
+
+Remember that the i2c_driver does not create those client handles.  The
+handle may be used during foo_probe().  If foo_probe() reports success
+(zero not a negative status code) it may save the handle and use it until
+foo_remove() returns.  That binding model is used by most Linux drivers.
+
+The probe function is called when an entry in the id_table name field
+matches the device's name. If the probe function needs that entry, it
+can retrieve it using
+
+::
+
+	const struct i2c_device_id *id = i2c_match_id(foo_idtable, client);
+
+
+Device Creation
+---------------
+
+If you know for a fact that an I2C device is connected to a given I2C bus,
+you can instantiate that device by simply filling an i2c_board_info
+structure with the device address and driver name, and calling
+i2c_new_client_device().  This will create the device, then the driver core
+will take care of finding the right driver and will call its probe() method.
+If a driver supports different device types, you can specify the type you
+want using the type field.  You can also specify an IRQ and platform data
+if needed.
+
+Sometimes you know that a device is connected to a given I2C bus, but you
+don't know the exact address it uses.  This happens on TV adapters for
+example, where the same driver supports dozens of slightly different
+models, and I2C device addresses change from one model to the next.  In
+that case, you can use the i2c_new_scanned_device() variant, which is
+similar to i2c_new_client_device(), except that it takes an additional list
+of possible I2C addresses to probe.  A device is created for the first
+responsive address in the list.  If you expect more than one device to be
+present in the address range, simply call i2c_new_scanned_device() that
+many times.
+
+The call to i2c_new_client_device() or i2c_new_scanned_device() typically
+happens in the I2C bus driver. You may want to save the returned i2c_client
+reference for later use.
+
+
+Device Detection
+----------------
+
+Sometimes you do not know in advance which I2C devices are connected to
+a given I2C bus.  This is for example the case of hardware monitoring
+devices on a PC's SMBus.  In that case, you may want to let your driver
+detect supported devices automatically.  This is how the legacy model
+was working, and is now available as an extension to the standard
+driver model.
+
+You simply have to define a detect callback which will attempt to
+identify supported devices (returning 0 for supported ones and -ENODEV
+for unsupported ones), a list of addresses to probe, and a device type
+(or class) so that only I2C buses which may have that type of device
+connected (and not otherwise enumerated) will be probed.  For example,
+a driver for a hardware monitoring chip for which auto-detection is
+needed would set its class to I2C_CLASS_HWMON, and only I2C adapters
+with a class including I2C_CLASS_HWMON would be probed by this driver.
+Note that the absence of matching classes does not prevent the use of
+a device of that type on the given I2C adapter.  All it prevents is
+auto-detection; explicit instantiation of devices is still possible.
+
+Note that this mechanism is purely optional and not suitable for all
+devices.  You need some reliable way to identify the supported devices
+(typically using device-specific, dedicated identification registers),
+otherwise misdetections are likely to occur and things can get wrong
+quickly.  Keep in mind that the I2C protocol doesn't include any
+standard way to detect the presence of a chip at a given address, let
+alone a standard way to identify devices.  Even worse is the lack of
+semantics associated to bus transfers, which means that the same
+transfer can be seen as a read operation by a chip and as a write
+operation by another chip.  For these reasons, explicit device
+instantiation should always be preferred to auto-detection where
+possible.
+
+
+Device Deletion
+---------------
+
+Each I2C device which has been created using i2c_new_client_device()
+or i2c_new_scanned_device() can be unregistered by calling
+i2c_unregister_device().  If you don't call it explicitly, it will be
+called automatically before the underlying I2C bus itself is removed,
+as a device can't survive its parent in the device driver model.
+
+
+Initializing the driver
+=======================
+
+When the kernel is booted, or when your foo driver module is inserted,
+you have to do some initializing. Fortunately, just registering the
+driver module is usually enough.
+
+::
+
+  static int __init foo_init(void)
+  {
+	return i2c_add_driver(&foo_driver);
+  }
+  module_init(foo_init);
+
+  static void __exit foo_cleanup(void)
+  {
+	i2c_del_driver(&foo_driver);
+  }
+  module_exit(foo_cleanup);
+
+  The module_i2c_driver() macro can be used to reduce above code.
+
+  module_i2c_driver(foo_driver);
+
+Note that some functions are marked by ``__init``.  These functions can
+be removed after kernel booting (or module loading) is completed.
+Likewise, functions marked by ``__exit`` are dropped by the compiler when
+the code is built into the kernel, as they would never be called.
+
+
+Driver Information
+==================
+
+::
+
+  /* Substitute your own name and email address */
+  MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl>"
+  MODULE_DESCRIPTION("Driver for Barf Inc. Foo I2C devices");
+
+  /* a few non-GPL license types are also allowed */
+  MODULE_LICENSE("GPL");
+
+
+Power Management
+================
+
+If your I2C device needs special handling when entering a system low
+power state -- like putting a transceiver into a low power mode, or
+activating a system wakeup mechanism -- do that by implementing the
+appropriate callbacks for the dev_pm_ops of the driver (like suspend
+and resume).
+
+These are standard driver model calls, and they work just like they
+would for any other driver stack.  The calls can sleep, and can use
+I2C messaging to the device being suspended or resumed (since their
+parent I2C adapter is active when these calls are issued, and IRQs
+are still enabled).
+
+
+System Shutdown
+===============
+
+If your I2C device needs special handling when the system shuts down
+or reboots (including kexec) -- like turning something off -- use a
+shutdown() method.
+
+Again, this is a standard driver model call, working just like it
+would for any other driver stack:  the calls can sleep, and can use
+I2C messaging.
+
+
+Command function
+================
+
+A generic ioctl-like function call back is supported. You will seldom
+need this, and its use is deprecated anyway, so newer design should not
+use it.
+
+
+Sending and receiving
+=====================
+
+If you want to communicate with your device, there are several functions
+to do this. You can find all of them in <linux/i2c.h>.
+
+If you can choose between plain I2C communication and SMBus level
+communication, please use the latter. All adapters understand SMBus level
+commands, but only some of them understand plain I2C!
+
+
+Plain I2C communication
+-----------------------
+
+::
+
+	int i2c_master_send(struct i2c_client *client, const char *buf,
+			    int count);
+	int i2c_master_recv(struct i2c_client *client, char *buf, int count);
+
+These routines read and write some bytes from/to a client. The client
+contains the I2C address, so you do not have to include it. The second
+parameter contains the bytes to read/write, the third the number of bytes
+to read/write (must be less than the length of the buffer, also should be
+less than 64k since msg.len is u16.) Returned is the actual number of bytes
+read/written.
+
+::
+
+	int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msg,
+			 int num);
+
+This sends a series of messages. Each message can be a read or write,
+and they can be mixed in any way. The transactions are combined: no
+stop condition is issued between transaction. The i2c_msg structure
+contains for each message the client address, the number of bytes of the
+message and the message data itself.
+
+You can read the file i2c-protocol.rst for more information about the
+actual I2C protocol.
+
+
+SMBus communication
+-------------------
+
+::
+
+	s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr,
+			   unsigned short flags, char read_write, u8 command,
+			   int size, union i2c_smbus_data *data);
+
+This is the generic SMBus function. All functions below are implemented
+in terms of it. Never use this function directly!
+
+::
+
+	s32 i2c_smbus_read_byte(struct i2c_client *client);
+	s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value);
+	s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command);
+	s32 i2c_smbus_write_byte_data(struct i2c_client *client,
+				      u8 command, u8 value);
+	s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command);
+	s32 i2c_smbus_write_word_data(struct i2c_client *client,
+				      u8 command, u16 value);
+	s32 i2c_smbus_read_block_data(struct i2c_client *client,
+				      u8 command, u8 *values);
+	s32 i2c_smbus_write_block_data(struct i2c_client *client,
+				       u8 command, u8 length, const u8 *values);
+	s32 i2c_smbus_read_i2c_block_data(struct i2c_client *client,
+					  u8 command, u8 length, u8 *values);
+	s32 i2c_smbus_write_i2c_block_data(struct i2c_client *client,
+					   u8 command, u8 length,
+					   const u8 *values);
+
+These ones were removed from i2c-core because they had no users, but could
+be added back later if needed::
+
+	s32 i2c_smbus_write_quick(struct i2c_client *client, u8 value);
+	s32 i2c_smbus_process_call(struct i2c_client *client,
+				   u8 command, u16 value);
+	s32 i2c_smbus_block_process_call(struct i2c_client *client,
+					 u8 command, u8 length, u8 *values);
+
+All these transactions return a negative errno value on failure. The 'write'
+transactions return 0 on success; the 'read' transactions return the read
+value, except for block transactions, which return the number of values
+read. The block buffers need not be longer than 32 bytes.
+
+You can read the file smbus-protocol.rst for more information about the
+actual SMBus protocol.
+
+
+General purpose routines
+========================
+
+Below all general purpose routines are listed, that were not mentioned
+before::
+
+	/* Return the adapter number for a specific adapter */
+	int i2c_adapter_id(struct i2c_adapter *adap);