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gpioioctl:Implement ioctl access to Linux GPIO chips/lines. (#59)
Includes new unit test that are conditionally compiled on linux. Mock in case of no chip available.
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‎gpioioctl/README.md

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# GPIO IOCTL
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This directory contains an implementation for Linux GPIO manipulation
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using the ioctl v2 interface.
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Basic test is provided, but a much more complete smoke test is provided
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in periph.io/x/cmd/periph-smoketest/gpiosmoketest

‎gpioioctl/basic_test.go

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// Copyright 2024 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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// Basic tests. More complete test is contained in the
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// periph.io/x/cmd/periph-smoketest/gpiosmoketest
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// folder.
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//go:build linux
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package gpioioctl
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import (
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"log"
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"testing"
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"periph.io/x/conn/v3/gpio"
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"periph.io/x/conn/v3/gpio/gpioreg"
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)
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var testLine *GPIOLine
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func init() {
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var err error
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if len(Chips) == 0 {
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/*
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During pipeline builds, GPIOChips may not be available, or
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it may build on another OS. In that case, mock in enough
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for a test to pass.
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*/
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line := GPIOLine{
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number: 0,
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name: "DummyGPIOLine",
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consumer: "",
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edge: gpio.NoEdge,
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pull: gpio.PullNoChange,
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direction: LineDirNotSet,
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}
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chip := GPIOChip{name: "DummyGPIOChip",
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path: "/dev/gpiochipdummy",
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label: "Dummy GPIOChip for Testing Purposes",
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lineCount: 1,
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lines: []*GPIOLine{&line},
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}
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Chips = append(Chips, &chip)
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if err = gpioreg.Register(&line); err != nil {
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nameStr := chip.Name()
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lineStr := line.String()
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log.Println("chip", nameStr, " gpioreg.Register(line) ", lineStr, " returned ", err)
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}
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}
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}
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func TestChips(t *testing.T) {
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chip := Chips[0]
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t.Log(chip.String())
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if len(chip.Name()) == 0 {
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t.Error("chip.Name() is 0 length")
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}
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if len(chip.Path()) == 0 {
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t.Error("chip path is 0 length")
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}
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if len(chip.Label()) == 0 {
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t.Error("chip label is 0 length!")
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}
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if len(chip.Lines()) != chip.LineCount() {
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t.Errorf("Incorrect line count. Found: %d for LineCount, Returned Lines length=%d", chip.LineCount(), len(chip.Lines()))
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}
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for _, line := range chip.Lines() {
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if len(line.Consumer()) == 0 && len(line.Name()) > 0 {
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testLine = line
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break
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}
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}
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if testLine == nil {
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t.Error("Error finding unused line for testing!")
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}
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for _, c := range Chips {
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s := c.String()
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if len(s) == 0 {
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t.Error("Error calling chip.String(). No output returned!")
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} else {
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t.Log(s)
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}
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}
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}
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func TestGPIORegistryByName(t *testing.T) {
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if testLine == nil {
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return
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}
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outLine := gpioreg.ByName(testLine.Name())
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if outLine == nil {
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t.Fatalf("Error retrieving GPIO Line %s", testLine.Name())
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}
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if outLine.Name() != testLine.Name() {
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t.Errorf("Error checking name. Expected %s, received %s", testLine.Name(), outLine.Name())
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}
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if outLine.Number() < 0 || outLine.Number() >= len(Chips[0].Lines()) {
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t.Errorf("Invalid chip number %d received for %s", outLine.Number(), testLine.Name())
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}
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}
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func TestNumber(t *testing.T) {
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chip := Chips[0]
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if testLine == nil {
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return
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}
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l := chip.ByName(testLine.Name())
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if l == nil {
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t.Fatalf("Error retrieving GPIO Line %s", testLine.Name())
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}
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if l.Number() < 0 || l.Number() >= chip.LineCount() {
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t.Errorf("line.Number() returned value (%d) out of range", l.Number())
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}
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l2 := chip.ByNumber(l.Number())
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if l2 == nil {
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t.Errorf("retrieve Line from chip by number %d failed.", l.Number())
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}
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}
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func TestString(t *testing.T) {
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if testLine == nil {
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return
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}
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line := gpioreg.ByName(testLine.Name())
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if line == nil {
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t.Fatalf("Error retrieving GPIO Line %s", testLine.Name())
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}
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s := line.String()
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if len(s) == 0 {
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t.Errorf("GPIOLine.String() failed.")
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}
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}

‎gpioioctl/doc.go

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// Copyright 2024 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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//
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// Package gpioioctl provides access to Linux GPIO lines using the ioctl interface.
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//
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// https://docs.kernel.org/userspace-api/gpio/index.html
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//
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// GPIO Pins can be accessed via periph.io/x/conn/v3/gpio/gpioreg,
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// or using the Chips collection to access the specific GPIO chip
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// and using it's ByName()/ByNumber methods.
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//
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// GPIOChip provides a LineSet feature that allows you to atomically
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// read/write to multiple GPIO pins as a single operation.
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package gpioioctl

‎gpioioctl/example_test.go

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//go:build linux
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package gpioioctl_test
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// Copyright 2024 The Periph Authors. All rights reserved.
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// Use of this source code is governed under the Apache License, Version 2.0
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// that can be found in the LICENSE file.
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import (
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"fmt"
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"log"
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"time"
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"periph.io/x/conn/v3/driver/driverreg"
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"periph.io/x/conn/v3/gpio"
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"periph.io/x/conn/v3/gpio/gpioreg"
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"periph.io/x/host/v3"
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"periph.io/x/host/v3/gpioioctl"
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)
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func Example() {
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_, _ = host.Init()
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_, _ = driverreg.Init()
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fmt.Println("GPIO Test Program")
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chip := gpioioctl.Chips[0]
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defer chip.Close()
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fmt.Println(chip.String())
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// Test by flashing an LED.
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led := gpioreg.ByName("GPIO5")
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fmt.Println("Flashing LED ", led.Name())
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for i := range 20 {
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_ = led.Out((i % 2) == 0)
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time.Sleep(500 * time.Millisecond)
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}
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_ = led.Out(true)
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testRotary(chip, "GPIO20", "GPIO21", "GPIO19")
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}
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// Test the LineSet functionality by using it to read a Rotary Encoder w/ Button.
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func testRotary(chip *gpioioctl.GPIOChip, stateLine, dataLine, buttonLine string) {
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config := gpioioctl.LineSetConfig{DefaultDirection: gpioioctl.LineInput, DefaultEdge: gpio.RisingEdge, DefaultPull: gpio.PullUp}
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config.Lines = []string{stateLine, dataLine, buttonLine}
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// The Data Pin of the Rotary Encoder should NOT have an edge.
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_ = config.AddOverrides(gpioioctl.LineInput, gpio.NoEdge, gpio.PullUp, dataLine)
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ls, err := chip.LineSetFromConfig(&config)
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if err != nil {
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log.Fatal(err)
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}
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defer ls.Close()
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statePinNumber := uint32(ls.ByOffset(0).Number())
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buttonPinNumber := uint32(ls.ByOffset(2).Number())
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var tLast = time.Now().Add(-1 * time.Second)
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var halting bool
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go func() {
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time.Sleep(60 * time.Second)
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halting = true
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fmt.Println("Sending halt!")
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_ = ls.Halt()
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}()
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fmt.Println("Test Rotary Switch - Turn dial to test rotary encoder, press button to test it.")
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for {
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lineNumber, _, err := ls.WaitForEdge(0)
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if err == nil {
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tNow := time.Now()
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if (tNow.UnixMilli() - tLast.UnixMilli()) < 100 {
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continue
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}
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tLast = tNow
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if lineNumber == statePinNumber {
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var bits uint64
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tDeadline := tNow.UnixNano() + 20_000_000
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var consecutive uint64
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for time.Now().UnixNano() < tDeadline {
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// Spin on reading the pins until we get some number
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// of consecutive readings that are the same.
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bits, _ = ls.Read(0x03)
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if bits&0x01 == 0x00 {
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// We're bouncing.
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consecutive = 0
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} else {
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consecutive += 1
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if consecutive > 25 {
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if bits == 0x01 {
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fmt.Printf("Clockwise bits=%d\n", bits)
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} else if bits == 0x03 {
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fmt.Printf("CounterClockwise bits=%d\n", bits)
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}
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break
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}
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}
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}
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} else if lineNumber == buttonPinNumber {
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fmt.Println("Button Pressed!")
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}
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} else {
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fmt.Println("Timeout detected")
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if halting {
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break
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}
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}
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}
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}

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