From 5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Tue, 21 Feb 2023 18:24:12 -0800 Subject: Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next 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(). ... --- Documentation/i2c/dev-interface.rst | 221 ++++++++++++++++++++++++++++++++++++ 1 file changed, 221 insertions(+) create mode 100644 Documentation/i2c/dev-interface.rst (limited to 'Documentation/i2c/dev-interface.rst') diff --git a/Documentation/i2c/dev-interface.rst b/Documentation/i2c/dev-interface.rst new file mode 100644 index 000000000..c277a8e12 --- /dev/null +++ b/Documentation/i2c/dev-interface.rst @@ -0,0 +1,221 @@ +============================================ +Implementing I2C device drivers in userspace +============================================ + +Usually, I2C devices are controlled by a kernel driver. But it is also +possible to access all devices on an adapter from userspace, through +the /dev interface. You need to load module i2c-dev for this. + +Each registered I2C adapter gets a number, counting from 0. You can +examine /sys/class/i2c-dev/ to see what number corresponds to which adapter. +Alternatively, you can run "i2cdetect -l" to obtain a formatted list of all +I2C adapters present on your system at a given time. i2cdetect is part of +the i2c-tools package. + +I2C device files are character device files with major device number 89 +and a minor device number corresponding to the number assigned as +explained above. They should be called "i2c-%d" (i2c-0, i2c-1, ..., +i2c-10, ...). All 256 minor device numbers are reserved for I2C. + + +C example +========= + +So let's say you want to access an I2C adapter from a C program. +First, you need to include these two headers:: + + #include + #include + +Now, you have to decide which adapter you want to access. You should +inspect /sys/class/i2c-dev/ or run "i2cdetect -l" to decide this. +Adapter numbers are assigned somewhat dynamically, so you can not +assume much about them. They can even change from one boot to the next. + +Next thing, open the device file, as follows:: + + int file; + int adapter_nr = 2; /* probably dynamically determined */ + char filename[20]; + + snprintf(filename, 19, "/dev/i2c-%d", adapter_nr); + file = open(filename, O_RDWR); + if (file < 0) { + /* ERROR HANDLING; you can check errno to see what went wrong */ + exit(1); + } + +When you have opened the device, you must specify with what device +address you want to communicate:: + + int addr = 0x40; /* The I2C address */ + + if (ioctl(file, I2C_SLAVE, addr) < 0) { + /* ERROR HANDLING; you can check errno to see what went wrong */ + exit(1); + } + +Well, you are all set up now. You can now use SMBus commands or plain +I2C to communicate with your device. SMBus commands are preferred if +the device supports them. Both are illustrated below:: + + __u8 reg = 0x10; /* Device register to access */ + __s32 res; + char buf[10]; + + /* Using SMBus commands */ + res = i2c_smbus_read_word_data(file, reg); + if (res < 0) { + /* ERROR HANDLING: I2C transaction failed */ + } else { + /* res contains the read word */ + } + + /* + * Using I2C Write, equivalent of + * i2c_smbus_write_word_data(file, reg, 0x6543) + */ + buf[0] = reg; + buf[1] = 0x43; + buf[2] = 0x65; + if (write(file, buf, 3) != 3) { + /* ERROR HANDLING: I2C transaction failed */ + } + + /* Using I2C Read, equivalent of i2c_smbus_read_byte(file) */ + if (read(file, buf, 1) != 1) { + /* ERROR HANDLING: I2C transaction failed */ + } else { + /* buf[0] contains the read byte */ + } + +Note that only a subset of the I2C and SMBus protocols can be achieved by +the means of read() and write() calls. In particular, so-called combined +transactions (mixing read and write messages in the same transaction) +aren't supported. For this reason, this interface is almost never used by +user-space programs. + +IMPORTANT: because of the use of inline functions, you *have* to use +'-O' or some variation when you compile your program! + + +Full interface description +========================== + +The following IOCTLs are defined: + +``ioctl(file, I2C_SLAVE, long addr)`` + Change slave address. The address is passed in the 7 lower bits of the + argument (except for 10 bit addresses, passed in the 10 lower bits in this + case). + +``ioctl(file, I2C_TENBIT, long select)`` + Selects ten bit addresses if select not equals 0, selects normal 7 bit + addresses if select equals 0. Default 0. This request is only valid + if the adapter has I2C_FUNC_10BIT_ADDR. + +``ioctl(file, I2C_PEC, long select)`` + Selects SMBus PEC (packet error checking) generation and verification + if select not equals 0, disables if select equals 0. Default 0. + Used only for SMBus transactions. This request only has an effect if the + the adapter has I2C_FUNC_SMBUS_PEC; it is still safe if not, it just + doesn't have any effect. + +``ioctl(file, I2C_FUNCS, unsigned long *funcs)`` + Gets the adapter functionality and puts it in ``*funcs``. + +``ioctl(file, I2C_RDWR, struct i2c_rdwr_ioctl_data *msgset)`` + Do combined read/write transaction without stop in between. + Only valid if the adapter has I2C_FUNC_I2C. The argument is + a pointer to a:: + + struct i2c_rdwr_ioctl_data { + struct i2c_msg *msgs; /* ptr to array of simple messages */ + int nmsgs; /* number of messages to exchange */ + } + + The msgs[] themselves contain further pointers into data buffers. + The function will write or read data to or from that buffers depending + on whether the I2C_M_RD flag is set in a particular message or not. + The slave address and whether to use ten bit address mode has to be + set in each message, overriding the values set with the above ioctl's. + +``ioctl(file, I2C_SMBUS, struct i2c_smbus_ioctl_data *args)`` + If possible, use the provided ``i2c_smbus_*`` methods described below instead + of issuing direct ioctls. + +You can do plain I2C transactions by using read(2) and write(2) calls. +You do not need to pass the address byte; instead, set it through +ioctl I2C_SLAVE before you try to access the device. + +You can do SMBus level transactions (see documentation file smbus-protocol.rst +for details) through the following functions:: + + __s32 i2c_smbus_write_quick(int file, __u8 value); + __s32 i2c_smbus_read_byte(int file); + __s32 i2c_smbus_write_byte(int file, __u8 value); + __s32 i2c_smbus_read_byte_data(int file, __u8 command); + __s32 i2c_smbus_write_byte_data(int file, __u8 command, __u8 value); + __s32 i2c_smbus_read_word_data(int file, __u8 command); + __s32 i2c_smbus_write_word_data(int file, __u8 command, __u16 value); + __s32 i2c_smbus_process_call(int file, __u8 command, __u16 value); + __s32 i2c_smbus_block_process_call(int file, __u8 command, __u8 length, + __u8 *values); + __s32 i2c_smbus_read_block_data(int file, __u8 command, __u8 *values); + __s32 i2c_smbus_write_block_data(int file, __u8 command, __u8 length, + __u8 *values); + +All these transactions return -1 on failure; you can read errno to see +what happened. The 'write' transactions return 0 on success; the +'read' transactions return the read value, except for read_block, which +returns the number of values read. The block buffers need not be longer +than 32 bytes. + +The above functions are made available by linking against the libi2c library, +which is provided by the i2c-tools project. See: +https://git.kernel.org/pub/scm/utils/i2c-tools/i2c-tools.git/. + + +Implementation details +====================== + +For the interested, here's the code flow which happens inside the kernel +when you use the /dev interface to I2C: + +1) Your program opens /dev/i2c-N and calls ioctl() on it, as described in + section "C example" above. + +2) These open() and ioctl() calls are handled by the i2c-dev kernel + driver: see i2c-dev.c:i2cdev_open() and i2c-dev.c:i2cdev_ioctl(), + respectively. You can think of i2c-dev as a generic I2C chip driver + that can be programmed from user-space. + +3) Some ioctl() calls are for administrative tasks and are handled by + i2c-dev directly. Examples include I2C_SLAVE (set the address of the + device you want to access) and I2C_PEC (enable or disable SMBus error + checking on future transactions.) + +4) Other ioctl() calls are converted to in-kernel function calls by + i2c-dev. Examples include I2C_FUNCS, which queries the I2C adapter + functionality using i2c.h:i2c_get_functionality(), and I2C_SMBUS, which + performs an SMBus transaction using i2c-core-smbus.c:i2c_smbus_xfer(). + + The i2c-dev driver is responsible for checking all the parameters that + come from user-space for validity. After this point, there is no + difference between these calls that came from user-space through i2c-dev + and calls that would have been performed by kernel I2C chip drivers + directly. This means that I2C bus drivers don't need to implement + anything special to support access from user-space. + +5) These i2c.h functions are wrappers to the actual implementation of + your I2C bus driver. Each adapter must declare callback functions + implementing these standard calls. i2c.h:i2c_get_functionality() calls + i2c_adapter.algo->functionality(), while + i2c-core-smbus.c:i2c_smbus_xfer() calls either + adapter.algo->smbus_xfer() if it is implemented, or if not, + i2c-core-smbus.c:i2c_smbus_xfer_emulated() which in turn calls + i2c_adapter.algo->master_xfer(). + +After your I2C bus driver has processed these requests, execution runs +up the call chain, with almost no processing done, except by i2c-dev to +package the returned data, if any, in suitable format for the ioctl. -- cgit v1.2.3