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/input/input-programming.rst | 348 ++++++++++++++++++++++++++++++ 1 file changed, 348 insertions(+) create mode 100644 Documentation/input/input-programming.rst (limited to 'Documentation/input/input-programming.rst') diff --git a/Documentation/input/input-programming.rst b/Documentation/input/input-programming.rst new file mode 100644 index 000000000..c9264814c --- /dev/null +++ b/Documentation/input/input-programming.rst @@ -0,0 +1,348 @@ +=============================== +Creating an input device driver +=============================== + +The simplest example +~~~~~~~~~~~~~~~~~~~~ + +Here comes a very simple example of an input device driver. The device has +just one button and the button is accessible at i/o port BUTTON_PORT. When +pressed or released a BUTTON_IRQ happens. The driver could look like:: + + #include + #include + #include + + #include + #include + + static struct input_dev *button_dev; + + static irqreturn_t button_interrupt(int irq, void *dummy) + { + input_report_key(button_dev, BTN_0, inb(BUTTON_PORT) & 1); + input_sync(button_dev); + return IRQ_HANDLED; + } + + static int __init button_init(void) + { + int error; + + if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) { + printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq); + return -EBUSY; + } + + button_dev = input_allocate_device(); + if (!button_dev) { + printk(KERN_ERR "button.c: Not enough memory\n"); + error = -ENOMEM; + goto err_free_irq; + } + + button_dev->evbit[0] = BIT_MASK(EV_KEY); + button_dev->keybit[BIT_WORD(BTN_0)] = BIT_MASK(BTN_0); + + error = input_register_device(button_dev); + if (error) { + printk(KERN_ERR "button.c: Failed to register device\n"); + goto err_free_dev; + } + + return 0; + + err_free_dev: + input_free_device(button_dev); + err_free_irq: + free_irq(BUTTON_IRQ, button_interrupt); + return error; + } + + static void __exit button_exit(void) + { + input_unregister_device(button_dev); + free_irq(BUTTON_IRQ, button_interrupt); + } + + module_init(button_init); + module_exit(button_exit); + +What the example does +~~~~~~~~~~~~~~~~~~~~~ + +First it has to include the file, which interfaces to the +input subsystem. This provides all the definitions needed. + +In the _init function, which is called either upon module load or when +booting the kernel, it grabs the required resources (it should also check +for the presence of the device). + +Then it allocates a new input device structure with input_allocate_device() +and sets up input bitfields. This way the device driver tells the other +parts of the input systems what it is - what events can be generated or +accepted by this input device. Our example device can only generate EV_KEY +type events, and from those only BTN_0 event code. Thus we only set these +two bits. We could have used:: + + set_bit(EV_KEY, button_dev->evbit); + set_bit(BTN_0, button_dev->keybit); + +as well, but with more than single bits the first approach tends to be +shorter. + +Then the example driver registers the input device structure by calling:: + + input_register_device(button_dev); + +This adds the button_dev structure to linked lists of the input driver and +calls device handler modules _connect functions to tell them a new input +device has appeared. input_register_device() may sleep and therefore must +not be called from an interrupt or with a spinlock held. + +While in use, the only used function of the driver is:: + + button_interrupt() + +which upon every interrupt from the button checks its state and reports it +via the:: + + input_report_key() + +call to the input system. There is no need to check whether the interrupt +routine isn't reporting two same value events (press, press for example) to +the input system, because the input_report_* functions check that +themselves. + +Then there is the:: + + input_sync() + +call to tell those who receive the events that we've sent a complete report. +This doesn't seem important in the one button case, but is quite important +for example for mouse movement, where you don't want the X and Y values +to be interpreted separately, because that'd result in a different movement. + +dev->open() and dev->close() +~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In case the driver has to repeatedly poll the device, because it doesn't +have an interrupt coming from it and the polling is too expensive to be done +all the time, or if the device uses a valuable resource (e.g. interrupt), it +can use the open and close callback to know when it can stop polling or +release the interrupt and when it must resume polling or grab the interrupt +again. To do that, we would add this to our example driver:: + + static int button_open(struct input_dev *dev) + { + if (request_irq(BUTTON_IRQ, button_interrupt, 0, "button", NULL)) { + printk(KERN_ERR "button.c: Can't allocate irq %d\n", button_irq); + return -EBUSY; + } + + return 0; + } + + static void button_close(struct input_dev *dev) + { + free_irq(IRQ_AMIGA_VERTB, button_interrupt); + } + + static int __init button_init(void) + { + ... + button_dev->open = button_open; + button_dev->close = button_close; + ... + } + +Note that input core keeps track of number of users for the device and +makes sure that dev->open() is called only when the first user connects +to the device and that dev->close() is called when the very last user +disconnects. Calls to both callbacks are serialized. + +The open() callback should return a 0 in case of success or any non-zero value +in case of failure. The close() callback (which is void) must always succeed. + +Inhibiting input devices +~~~~~~~~~~~~~~~~~~~~~~~~ + +Inhibiting a device means ignoring input events from it. As such it is about +maintaining relationships with input handlers - either already existing +relationships, or relationships to be established while the device is in +inhibited state. + +If a device is inhibited, no input handler will receive events from it. + +The fact that nobody wants events from the device is exploited further, by +calling device's close() (if there are users) and open() (if there are users) on +inhibit and uninhibit operations, respectively. Indeed, the meaning of close() +is to stop providing events to the input core and that of open() is to start +providing events to the input core. + +Calling the device's close() method on inhibit (if there are users) allows the +driver to save power. Either by directly powering down the device or by +releasing the runtime-PM reference it got in open() when the driver is using +runtime-PM. + +Inhibiting and uninhibiting are orthogonal to opening and closing the device by +input handlers. Userspace might want to inhibit a device in anticipation before +any handler is positively matched against it. + +Inhibiting and uninhibiting are orthogonal to device's being a wakeup source, +too. Being a wakeup source plays a role when the system is sleeping, not when +the system is operating. How drivers should program their interaction between +inhibiting, sleeping and being a wakeup source is driver-specific. + +Taking the analogy with the network devices - bringing a network interface down +doesn't mean that it should be impossible be wake the system up on LAN through +this interface. So, there may be input drivers which should be considered wakeup +sources even when inhibited. Actually, in many I2C input devices their interrupt +is declared a wakeup interrupt and its handling happens in driver's core, which +is not aware of input-specific inhibit (nor should it be). Composite devices +containing several interfaces can be inhibited on a per-interface basis and e.g. +inhibiting one interface shouldn't affect the device's capability of being a +wakeup source. + +If a device is to be considered a wakeup source while inhibited, special care +must be taken when programming its suspend(), as it might need to call device's +open(). Depending on what close() means for the device in question, not +opening() it before going to sleep might make it impossible to provide any +wakeup events. The device is going to sleep anyway. + +Basic event types +~~~~~~~~~~~~~~~~~ + +The most simple event type is EV_KEY, which is used for keys and buttons. +It's reported to the input system via:: + + input_report_key(struct input_dev *dev, int code, int value) + +See uapi/linux/input-event-codes.h for the allowable values of code (from 0 to +KEY_MAX). Value is interpreted as a truth value, i.e. any non-zero value means +key pressed, zero value means key released. The input code generates events only +in case the value is different from before. + +In addition to EV_KEY, there are two more basic event types: EV_REL and +EV_ABS. They are used for relative and absolute values supplied by the +device. A relative value may be for example a mouse movement in the X axis. +The mouse reports it as a relative difference from the last position, +because it doesn't have any absolute coordinate system to work in. Absolute +events are namely for joysticks and digitizers - devices that do work in an +absolute coordinate systems. + +Having the device report EV_REL buttons is as simple as with EV_KEY; simply +set the corresponding bits and call the:: + + input_report_rel(struct input_dev *dev, int code, int value) + +function. Events are generated only for non-zero values. + +However EV_ABS requires a little special care. Before calling +input_register_device, you have to fill additional fields in the input_dev +struct for each absolute axis your device has. If our button device had also +the ABS_X axis:: + + button_dev.absmin[ABS_X] = 0; + button_dev.absmax[ABS_X] = 255; + button_dev.absfuzz[ABS_X] = 4; + button_dev.absflat[ABS_X] = 8; + +Or, you can just say:: + + input_set_abs_params(button_dev, ABS_X, 0, 255, 4, 8); + +This setting would be appropriate for a joystick X axis, with the minimum of +0, maximum of 255 (which the joystick *must* be able to reach, no problem if +it sometimes reports more, but it must be able to always reach the min and +max values), with noise in the data up to +- 4, and with a center flat +position of size 8. + +If you don't need absfuzz and absflat, you can set them to zero, which mean +that the thing is precise and always returns to exactly the center position +(if it has any). + +BITS_TO_LONGS(), BIT_WORD(), BIT_MASK() +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +These three macros from bitops.h help some bitfield computations:: + + BITS_TO_LONGS(x) - returns the length of a bitfield array in longs for + x bits + BIT_WORD(x) - returns the index in the array in longs for bit x + BIT_MASK(x) - returns the index in a long for bit x + +The id* and name fields +~~~~~~~~~~~~~~~~~~~~~~~ + +The dev->name should be set before registering the input device by the input +device driver. It's a string like 'Generic button device' containing a +user friendly name of the device. + +The id* fields contain the bus ID (PCI, USB, ...), vendor ID and device ID +of the device. The bus IDs are defined in input.h. The vendor and device IDs +are defined in pci_ids.h, usb_ids.h and similar include files. These fields +should be set by the input device driver before registering it. + +The idtype field can be used for specific information for the input device +driver. + +The id and name fields can be passed to userland via the evdev interface. + +The keycode, keycodemax, keycodesize fields +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +These three fields should be used by input devices that have dense keymaps. +The keycode is an array used to map from scancodes to input system keycodes. +The keycode max should contain the size of the array and keycodesize the +size of each entry in it (in bytes). + +Userspace can query and alter current scancode to keycode mappings using +EVIOCGKEYCODE and EVIOCSKEYCODE ioctls on corresponding evdev interface. +When a device has all 3 aforementioned fields filled in, the driver may +rely on kernel's default implementation of setting and querying keycode +mappings. + +dev->getkeycode() and dev->setkeycode() +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +getkeycode() and setkeycode() callbacks allow drivers to override default +keycode/keycodesize/keycodemax mapping mechanism provided by input core +and implement sparse keycode maps. + +Key autorepeat +~~~~~~~~~~~~~~ + +... is simple. It is handled by the input.c module. Hardware autorepeat is +not used, because it's not present in many devices and even where it is +present, it is broken sometimes (at keyboards: Toshiba notebooks). To enable +autorepeat for your device, just set EV_REP in dev->evbit. All will be +handled by the input system. + +Other event types, handling output events +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The other event types up to now are: + +- EV_LED - used for the keyboard LEDs. +- EV_SND - used for keyboard beeps. + +They are very similar to for example key events, but they go in the other +direction - from the system to the input device driver. If your input device +driver can handle these events, it has to set the respective bits in evbit, +*and* also the callback routine:: + + button_dev->event = button_event; + + int button_event(struct input_dev *dev, unsigned int type, + unsigned int code, int value) + { + if (type == EV_SND && code == SND_BELL) { + outb(value, BUTTON_BELL); + return 0; + } + return -1; + } + +This callback routine can be called from an interrupt or a BH (although that +isn't a rule), and thus must not sleep, and must not take too long to finish. -- cgit v1.2.3