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/driver-api/generic-counter.rst | 573 +++++++++++++++++++++++++++ 1 file changed, 573 insertions(+) create mode 100644 Documentation/driver-api/generic-counter.rst (limited to 'Documentation/driver-api/generic-counter.rst') diff --git a/Documentation/driver-api/generic-counter.rst b/Documentation/driver-api/generic-counter.rst new file mode 100644 index 000000000..71ccc30e5 --- /dev/null +++ b/Documentation/driver-api/generic-counter.rst @@ -0,0 +1,573 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +Generic Counter Interface +========================= + +Introduction +============ + +Counter devices are prevalent among a diverse spectrum of industries. +The ubiquitous presence of these devices necessitates a common interface +and standard of interaction and exposure. This driver API attempts to +resolve the issue of duplicate code found among existing counter device +drivers by introducing a generic counter interface for consumption. The +Generic Counter interface enables drivers to support and expose a common +set of components and functionality present in counter devices. + +Theory +====== + +Counter devices can vary greatly in design, but regardless of whether +some devices are quadrature encoder counters or tally counters, all +counter devices consist of a core set of components. This core set of +components, shared by all counter devices, is what forms the essence of +the Generic Counter interface. + +There are three core components to a counter: + +* Signal: + Stream of data to be evaluated by the counter. + +* Synapse: + Association of a Signal, and evaluation trigger, with a Count. + +* Count: + Accumulation of the effects of connected Synapses. + +SIGNAL +------ +A Signal represents a stream of data. This is the input data that is +evaluated by the counter to determine the count data; e.g. a quadrature +signal output line of a rotary encoder. Not all counter devices provide +user access to the Signal data, so exposure is optional for drivers. + +When the Signal data is available for user access, the Generic Counter +interface provides the following available signal values: + +* SIGNAL_LOW: + Signal line is in a low state. + +* SIGNAL_HIGH: + Signal line is in a high state. + +A Signal may be associated with one or more Counts. + +SYNAPSE +------- +A Synapse represents the association of a Signal with a Count. Signal +data affects respective Count data, and the Synapse represents this +relationship. + +The Synapse action mode specifies the Signal data condition that +triggers the respective Count's count function evaluation to update the +count data. The Generic Counter interface provides the following +available action modes: + +* None: + Signal does not trigger the count function. In Pulse-Direction count + function mode, this Signal is evaluated as Direction. + +* Rising Edge: + Low state transitions to high state. + +* Falling Edge: + High state transitions to low state. + +* Both Edges: + Any state transition. + +A counter is defined as a set of input signals associated with count +data that are generated by the evaluation of the state of the associated +input signals as defined by the respective count functions. Within the +context of the Generic Counter interface, a counter consists of Counts +each associated with a set of Signals, whose respective Synapse +instances represent the count function update conditions for the +associated Counts. + +A Synapse associates one Signal with one Count. + +COUNT +----- +A Count represents the accumulation of the effects of connected +Synapses; i.e. the count data for a set of Signals. The Generic +Counter interface represents the count data as a natural number. + +A Count has a count function mode which represents the update behavior +for the count data. The Generic Counter interface provides the following +available count function modes: + +* Increase: + Accumulated count is incremented. + +* Decrease: + Accumulated count is decremented. + +* Pulse-Direction: + Rising edges on signal A updates the respective count. The input level + of signal B determines direction. + +* Quadrature: + A pair of quadrature encoding signals are evaluated to determine + position and direction. The following Quadrature modes are available: + + - x1 A: + If direction is forward, rising edges on quadrature pair signal A + updates the respective count; if the direction is backward, falling + edges on quadrature pair signal A updates the respective count. + Quadrature encoding determines the direction. + + - x1 B: + If direction is forward, rising edges on quadrature pair signal B + updates the respective count; if the direction is backward, falling + edges on quadrature pair signal B updates the respective count. + Quadrature encoding determines the direction. + + - x2 A: + Any state transition on quadrature pair signal A updates the + respective count. Quadrature encoding determines the direction. + + - x2 B: + Any state transition on quadrature pair signal B updates the + respective count. Quadrature encoding determines the direction. + + - x4: + Any state transition on either quadrature pair signals updates the + respective count. Quadrature encoding determines the direction. + +A Count has a set of one or more associated Synapses. + +Paradigm +======== + +The most basic counter device may be expressed as a single Count +associated with a single Signal via a single Synapse. Take for example +a counter device which simply accumulates a count of rising edges on a +source input line:: + + Count Synapse Signal + ----- ------- ------ + +---------------------+ + | Data: Count | Rising Edge ________ + | Function: Increase | <------------- / Source \ + | | ____________ + +---------------------+ + +In this example, the Signal is a source input line with a pulsing +voltage, while the Count is a persistent count value which is repeatedly +incremented. The Signal is associated with the respective Count via a +Synapse. The increase function is triggered by the Signal data condition +specified by the Synapse -- in this case a rising edge condition on the +voltage input line. In summary, the counter device existence and +behavior is aptly represented by respective Count, Signal, and Synapse +components: a rising edge condition triggers an increase function on an +accumulating count datum. + +A counter device is not limited to a single Signal; in fact, in theory +many Signals may be associated with even a single Count. For example, a +quadrature encoder counter device can keep track of position based on +the states of two input lines:: + + Count Synapse Signal + ----- ------- ------ + +-------------------------+ + | Data: Position | Both Edges ___ + | Function: Quadrature x4 | <------------ / A \ + | | _______ + | | + | | Both Edges ___ + | | <------------ / B \ + | | _______ + +-------------------------+ + +In this example, two Signals (quadrature encoder lines A and B) are +associated with a single Count: a rising or falling edge on either A or +B triggers the "Quadrature x4" function which determines the direction +of movement and updates the respective position data. The "Quadrature +x4" function is likely implemented in the hardware of the quadrature +encoder counter device; the Count, Signals, and Synapses simply +represent this hardware behavior and functionality. + +Signals associated with the same Count can have differing Synapse action +mode conditions. For example, a quadrature encoder counter device +operating in a non-quadrature Pulse-Direction mode could have one input +line dedicated for movement and a second input line dedicated for +direction:: + + Count Synapse Signal + ----- ------- ------ + +---------------------------+ + | Data: Position | Rising Edge ___ + | Function: Pulse-Direction | <------------- / A \ (Movement) + | | _______ + | | + | | None ___ + | | <------------- / B \ (Direction) + | | _______ + +---------------------------+ + +Only Signal A triggers the "Pulse-Direction" update function, but the +instantaneous state of Signal B is still required in order to know the +direction so that the position data may be properly updated. Ultimately, +both Signals are associated with the same Count via two respective +Synapses, but only one Synapse has an active action mode condition which +triggers the respective count function while the other is left with a +"None" condition action mode to indicate its respective Signal's +availability for state evaluation despite its non-triggering mode. + +Keep in mind that the Signal, Synapse, and Count are abstract +representations which do not need to be closely married to their +respective physical sources. This allows the user of a counter to +divorce themselves from the nuances of physical components (such as +whether an input line is differential or single-ended) and instead focus +on the core idea of what the data and process represent (e.g. position +as interpreted from quadrature encoding data). + +Driver API +========== + +Driver authors may utilize the Generic Counter interface in their code +by including the include/linux/counter.h header file. This header file +provides several core data structures, function prototypes, and macros +for defining a counter device. + +.. kernel-doc:: include/linux/counter.h + :internal: + +.. kernel-doc:: drivers/counter/counter-core.c + :export: + +.. kernel-doc:: drivers/counter/counter-chrdev.c + :export: + +Driver Implementation +===================== + +To support a counter device, a driver must first allocate the available +Counter Signals via counter_signal structures. These Signals should +be stored as an array and set to the signals array member of an +allocated counter_device structure before the Counter is registered to +the system. + +Counter Counts may be allocated via counter_count structures, and +respective Counter Signal associations (Synapses) made via +counter_synapse structures. Associated counter_synapse structures are +stored as an array and set to the synapses array member of the +respective counter_count structure. These counter_count structures are +set to the counts array member of an allocated counter_device structure +before the Counter is registered to the system. + +Driver callbacks must be provided to the counter_device structure in +order to communicate with the device: to read and write various Signals +and Counts, and to set and get the "action mode" and "function mode" for +various Synapses and Counts respectively. + +A counter_device structure is allocated using counter_alloc() and then +registered to the system by passing it to the counter_add() function, and +unregistered by passing it to the counter_unregister function. There are +device managed variants of these functions: devm_counter_alloc() and +devm_counter_add(). + +The struct counter_comp structure is used to define counter extensions +for Signals, Synapses, and Counts. + +The "type" member specifies the type of high-level data (e.g. BOOL, +COUNT_DIRECTION, etc.) handled by this extension. The "``*_read``" and +"``*_write``" members can then be set by the counter device driver with +callbacks to handle that data using native C data types (i.e. u8, u64, +etc.). + +Convenience macros such as ``COUNTER_COMP_COUNT_U64`` are provided for +use by driver authors. In particular, driver authors are expected to use +the provided macros for standard Counter subsystem attributes in order +to maintain a consistent interface for userspace. For example, a counter +device driver may define several standard attributes like so:: + + struct counter_comp count_ext[] = { + COUNTER_COMP_DIRECTION(count_direction_read), + COUNTER_COMP_ENABLE(count_enable_read, count_enable_write), + COUNTER_COMP_CEILING(count_ceiling_read, count_ceiling_write), + }; + +This makes it simple to see, add, and modify the attributes that are +supported by this driver ("direction", "enable", and "ceiling") and to +maintain this code without getting lost in a web of struct braces. + +Callbacks must match the function type expected for the respective +component or extension. These function types are defined in the struct +counter_comp structure as the "``*_read``" and "``*_write``" union +members. + +The corresponding callback prototypes for the extensions mentioned in +the previous example above would be:: + + int count_direction_read(struct counter_device *counter, + struct counter_count *count, + enum counter_count_direction *direction); + int count_enable_read(struct counter_device *counter, + struct counter_count *count, u8 *enable); + int count_enable_write(struct counter_device *counter, + struct counter_count *count, u8 enable); + int count_ceiling_read(struct counter_device *counter, + struct counter_count *count, u64 *ceiling); + int count_ceiling_write(struct counter_device *counter, + struct counter_count *count, u64 ceiling); + +Determining the type of extension to create is a matter of scope. + +* Signal extensions are attributes that expose information/control + specific to a Signal. These types of attributes will exist under a + Signal's directory in sysfs. + + For example, if you have an invert feature for a Signal, you can have + a Signal extension called "invert" that toggles that feature: + /sys/bus/counter/devices/counterX/signalY/invert + +* Count extensions are attributes that expose information/control + specific to a Count. These type of attributes will exist under a + Count's directory in sysfs. + + For example, if you want to pause/unpause a Count from updating, you + can have a Count extension called "enable" that toggles such: + /sys/bus/counter/devices/counterX/countY/enable + +* Device extensions are attributes that expose information/control + non-specific to a particular Count or Signal. This is where you would + put your global features or other miscellaneous functionality. + + For example, if your device has an overtemp sensor, you can report the + chip overheated via a device extension called "error_overtemp": + /sys/bus/counter/devices/counterX/error_overtemp + +Subsystem Architecture +====================== + +Counter drivers pass and take data natively (i.e. ``u8``, ``u64``, etc.) +and the shared counter module handles the translation between the sysfs +interface. This guarantees a standard userspace interface for all +counter drivers, and enables a Generic Counter chrdev interface via a +generalized device driver ABI. + +A high-level view of how a count value is passed down from a counter +driver is exemplified by the following. The driver callbacks are first +registered to the Counter core component for use by the Counter +userspace interface components:: + + Driver callbacks registration: + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +----------------------------+ + | Counter device driver | + +----------------------------+ + | Processes data from device | + +----------------------------+ + | + ------------------- + / driver callbacks / + ------------------- + | + V + +----------------------+ + | Counter core | + +----------------------+ + | Routes device driver | + | callbacks to the | + | userspace interfaces | + +----------------------+ + | + ------------------- + / driver callbacks / + ------------------- + | + +---------------+---------------+ + | | + V V + +--------------------+ +---------------------+ + | Counter sysfs | | Counter chrdev | + +--------------------+ +---------------------+ + | Translates to the | | Translates to the | + | standard Counter | | standard Counter | + | sysfs output | | character device | + +--------------------+ +---------------------+ + +Thereafter, data can be transferred directly between the Counter device +driver and Counter userspace interface:: + + Count data request: + ~~~~~~~~~~~~~~~~~~~ + ---------------------- + / Counter device \ + +----------------------+ + | Count register: 0x28 | + +----------------------+ + | + ----------------- + / raw count data / + ----------------- + | + V + +----------------------------+ + | Counter device driver | + +----------------------------+ + | Processes data from device | + |----------------------------| + | Type: u64 | + | Value: 42 | + +----------------------------+ + | + ---------- + / u64 / + ---------- + | + +---------------+---------------+ + | | + V V + +--------------------+ +---------------------+ + | Counter sysfs | | Counter chrdev | + +--------------------+ +---------------------+ + | Translates to the | | Translates to the | + | standard Counter | | standard Counter | + | sysfs output | | character device | + |--------------------| |---------------------| + | Type: const char * | | Type: u64 | + | Value: "42" | | Value: 42 | + +--------------------+ +---------------------+ + | | + --------------- ----------------------- + / const char * / / struct counter_event / + --------------- ----------------------- + | | + | V + | +-----------+ + | | read | + | +-----------+ + | \ Count: 42 / + | ----------- + | + V + +--------------------------------------------------+ + | `/sys/bus/counter/devices/counterX/countY/count` | + +--------------------------------------------------+ + \ Count: "42" / + -------------------------------------------------- + +There are four primary components involved: + +Counter device driver +--------------------- +Communicates with the hardware device to read/write data; e.g. counter +drivers for quadrature encoders, timers, etc. + +Counter core +------------ +Registers the counter device driver to the system so that the respective +callbacks are called during userspace interaction. + +Counter sysfs +------------- +Translates counter data to the standard Counter sysfs interface format +and vice versa. + +Please refer to the ``Documentation/ABI/testing/sysfs-bus-counter`` file +for a detailed breakdown of the available Generic Counter interface +sysfs attributes. + +Counter chrdev +-------------- +Translates Counter events to the standard Counter character device; data +is transferred via standard character device read calls, while Counter +events are configured via ioctl calls. + +Sysfs Interface +=============== + +Several sysfs attributes are generated by the Generic Counter interface, +and reside under the ``/sys/bus/counter/devices/counterX`` directory, +where ``X`` is to the respective counter device id. Please see +``Documentation/ABI/testing/sysfs-bus-counter`` for detailed information +on each Generic Counter interface sysfs attribute. + +Through these sysfs attributes, programs and scripts may interact with +the Generic Counter paradigm Counts, Signals, and Synapses of respective +counter devices. + +Counter Character Device +======================== + +Counter character device nodes are created under the ``/dev`` directory +as ``counterX``, where ``X`` is the respective counter device id. +Defines for the standard Counter data types are exposed via the +userspace ``include/uapi/linux/counter.h`` file. + +Counter events +-------------- +Counter device drivers can support Counter events by utilizing the +``counter_push_event`` function:: + + void counter_push_event(struct counter_device *const counter, const u8 event, + const u8 channel); + +The event id is specified by the ``event`` parameter; the event channel +id is specified by the ``channel`` parameter. When this function is +called, the Counter data associated with the respective event is +gathered, and a ``struct counter_event`` is generated for each datum and +pushed to userspace. + +Counter events can be configured by users to report various Counter +data of interest. This can be conceptualized as a list of Counter +component read calls to perform. For example: + + +------------------------+------------------------+ + | COUNTER_EVENT_OVERFLOW | COUNTER_EVENT_INDEX | + +========================+========================+ + | Channel 0 | Channel 0 | + +------------------------+------------------------+ + | * Count 0 | * Signal 0 | + | * Count 1 | * Signal 0 Extension 0 | + | * Signal 3 | * Extension 4 | + | * Count 4 Extension 2 +------------------------+ + | * Signal 5 Extension 0 | Channel 1 | + | +------------------------+ + | | * Signal 4 | + | | * Signal 4 Extension 0 | + | | * Count 7 | + +------------------------+------------------------+ + +When ``counter_push_event(counter, COUNTER_EVENT_INDEX, 1)`` is called +for example, it will go down the list for the ``COUNTER_EVENT_INDEX`` +event channel 1 and execute the read callbacks for Signal 4, Signal 4 +Extension 0, and Count 7 -- the data returned for each is pushed to a +kfifo as a ``struct counter_event``, which userspace can retrieve via a +standard read operation on the respective character device node. + +Userspace +--------- +Userspace applications can configure Counter events via ioctl operations +on the Counter character device node. There following ioctl codes are +supported and provided by the ``linux/counter.h`` userspace header file: + +* :c:macro:`COUNTER_ADD_WATCH_IOCTL` + +* :c:macro:`COUNTER_ENABLE_EVENTS_IOCTL` + +* :c:macro:`COUNTER_DISABLE_EVENTS_IOCTL` + +To configure events to gather Counter data, users first populate a +``struct counter_watch`` with the relevant event id, event channel id, +and the information for the desired Counter component from which to +read, and then pass it via the ``COUNTER_ADD_WATCH_IOCTL`` ioctl +command. + +Note that an event can be watched without gathering Counter data by +setting the ``component.type`` member equal to +``COUNTER_COMPONENT_NONE``. With this configuration the Counter +character device will simply populate the event timestamps for those +respective ``struct counter_event`` elements and ignore the component +value. + +The ``COUNTER_ADD_WATCH_IOCTL`` command will buffer these Counter +watches. When ready, the ``COUNTER_ENABLE_EVENTS_IOCTL`` ioctl command +may be used to activate these Counter watches. + +Userspace applications can then execute a ``read`` operation (optionally +calling ``poll`` first) on the Counter character device node to retrieve +``struct counter_event`` elements with the desired data. -- cgit v1.2.3