gpioioctl:Implement ioctl access to Linux GPIO chips/lines.

gpioioctl/Testing.md

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+# Testing
+
+The tests implemented perform *functional* tests of the library. This means that 
+the tests performed interact with a GPIO chipset, and perform actual read/write 
+operations. Using this test set, it's possible to quickly and accurately check 
+if the library is working as expected on a specific hardware/kernel combination.
+
+## Requirements
+
+Although the library is not Raspberry Pi specific, the GPIO pin names used for 
+tests are.
+
+As written, the tests must be executed on a Raspberry Pi SBC running Linux. Tested 
+models are:
+
+* Raspberry Pi 3B
+* Raspberry Pi Zero W
+* Raspberry Pi 4
+* Raspberry Pi 5
+
+You must also have the golang SDK installed.
+
+## Setting Up
+
+In order to execute the functional tests, you must jumper the sets of pins shown 
+below together.
+
+For example, the single line tests require GPIO5 and GPIO13 to be connected to 
+each other, so a jumper is required between pins 29 and 33. For the multi-line 
+tests to work, you must connect the following GPIO pins together with jumpers.
+
+| GPIO Output | Output Pin # | GPIO Input | Input Pin # |
+| ----------- | ------------ | ---------- | ----------- |
+| GPIO2       |            3 | GPIO10     |          19 |
+| GPIO3       |            5 | GPIO11     |          23 |
+| GPIO4       |            7 | GPIO12     |          32 |
+| GPIO5       |           29 | GPIO13     |          33 |
+| GPIO6       |           31 | GPIO14     |           8 |
+| GPIO7       |           26 | GPIO15     |          10 |
+| GPIO8       |           24 | GPIO16     |          36 |
+| GPIO9       |           21 | GPIO17     |          11 |
+
+## Cross-Compiling
+If you don't have a working go installation on the target machine, you can cross
+compile from one machine and then copy the test binary to the target machine.
+
+To cross compile for Raspberry Pi, execute the command:
+
+```bash
+$periph.io/x/host/gpioctl> GOOS=linux GOARCH=arm64 go test -c
+$periph.io/x/host/gpioctl> scp gpioioctl.test [email protected]:~
+$periph.io/x/host/gpioctl> ssh [email protected]
+$user> ./gpioioctl.test -test.v
+```
+for Pi Zero W, use:
+
+```bash
+$periph.io/x/host/gpioctl> GOOS=linux GOARCH=arm GOARM=6 go test -c
+$periph.io/x/host/gpioctl> scp gpioioctl.test [email protected]:~
+$periph.io/x/host/gpioctl> ssh [email protected]
+$user> ./gpioioctl.test -test.v
+
+```
+
+## Executing the Tests
+
+After connecting the jumper wires as shown above, and you have golang installed 
+and the go/bin directory in the path, change to this directory and execute the 
+command:
+
+```bash
+$> go test -v -cover
+```

gpioioctl/example_test.go

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