whatcanGOwrong

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/devfs.go

@@ -0,0 +1,80 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build linux
+// +build linux
+
+package i2c
+
+import (
+	"fmt"
+	"io"
+	"os"
+	"syscall"
+
+	"golang.org/x/exp/io/i2c/driver"
+)
+
+// Devfs is an I2C driver that works against the devfs.
+// You need to load the "i2c-dev" kernel module to use this driver.
+type Devfs struct {
+	// Dev is the I2C bus device, e.g. /dev/i2c-1. Required.
+	Dev string
+}
+
+const (
+	i2c_SLAVE  = 0x0703 // TODO(jbd): Allow users to use I2C_SLAVE_FORCE?
+	i2c_TENBIT = 0x0704
+)
+
+// TODO(jbd): Support I2C_RETRIES and I2C_TIMEOUT at the driver and implementation level.
+
+func (d *Devfs) Open(addr int, tenbit bool) (driver.Conn, error) {
+	f, err := os.OpenFile(d.Dev, os.O_RDWR, os.ModeDevice)
+	if err != nil {
+		return nil, err
+	}
+	conn := &devfsConn{f: f}
+	if tenbit {
+		if err := conn.ioctl(i2c_TENBIT, uintptr(1)); err != nil {
+			conn.Close()
+			return nil, fmt.Errorf("cannot enable the 10-bit address mode on bus %v: %v", d.Dev, err)
+		}
+	}
+	if err := conn.ioctl(i2c_SLAVE, uintptr(addr)); err != nil {
+		conn.Close()
+		return nil, fmt.Errorf("error opening the address (%v) on the bus (%v): %v", addr, d.Dev, err)
+	}
+	return conn, nil
+}
+
+type devfsConn struct {
+	f *os.File
+}
+
+func (c *devfsConn) Tx(w, r []byte) error {
+	if w != nil {
+		if _, err := c.f.Write(w); err != nil {
+			return err
+		}
+		c.f.Sync()
+	}
+	if r != nil {
+		if _, err := io.ReadFull(c.f, r); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (c *devfsConn) Close() error {
+	return c.f.Close()
+}
+
+func (c *devfsConn) ioctl(arg1, arg2 uintptr) error {
+	if _, _, errno := syscall.Syscall(syscall.SYS_IOCTL, c.f.Fd(), arg1, arg2); errno != 0 {
+		return syscall.Errno(errno)
+	}
+	return nil
+}

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/devfs_nonlinux.go

@@ -0,0 +1,25 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build !linux
+// +build !linux
+
+package i2c
+
+import (
+	"errors"
+
+	"golang.org/x/exp/io/i2c/driver"
+)
+
+// Devfs is no-implementation so developers using cross compilation
+// can rely on local tools even though the real implementation isn't
+// available on their platform.
+type Devfs struct {
+	Dev string
+}
+
+func (d *Devfs) Open(addr int, tenbit bool) (driver.Conn, error) {
+	return nil, errors.New("not implemented on this platform")
+}

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/driver/driver.go

@@ -0,0 +1,24 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package driver contains interfaces to be implemented by various I2C implementations.
+package driver // import "golang.org/x/exp/io/i2c/driver"
+
+// Opener opens a connection to an I2C device to communicate with
+// the I2C address given. If the address is an 10-bit I2C address,
+// tenbit is true.
+type Opener interface {
+	Open(addr int, tenbit bool) (Conn, error)
+}
+
+// Conn represents an active connection to an I2C device.
+type Conn interface {
+	// Tx first writes w (if not nil), then reads len(r)
+	// bytes from device into r (if not nil) in a single
+	// I2C transaction.
+	Tx(w, r []byte) error
+
+	// Close closes the connection.
+	Close() error
+}

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/example/displayip/main.go

@@ -0,0 +1,89 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package main contains a program that displays the IPv4 address
+// of the machine on an a Grove-LCD RGB backlight.
+package main
+
+import (
+	"fmt"
+	"net"
+
+	"golang.org/x/exp/io/i2c"
+)
+
+const (
+	DISPLAY_RGB_ADDR  = 0x62
+	DISPLAY_TEXT_ADDR = 0x3e
+)
+
+func main() {
+	d, err := i2c.Open(&i2c.Devfs{Dev: "/dev/i2c-1"}, DISPLAY_RGB_ADDR)
+	if err != nil {
+		panic(err)
+	}
+
+	td, err := i2c.Open(&i2c.Devfs{Dev: "/dev/i2c-1"}, DISPLAY_TEXT_ADDR)
+	if err != nil {
+		panic(err)
+	}
+
+	// Set the backlight color to 100,100,100.
+	write(d, []byte{0, 0})
+	write(d, []byte{1, 0})
+	write(d, []byte{0x08, 0xaa})
+	write(d, []byte{4, 100}) // R value
+	write(d, []byte{3, 100}) // G value
+	write(d, []byte{2, 100}) // B value
+
+	ip, err := resolveIP()
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Printf("host machine IP is %v\n", ip)
+
+	write(td, []byte{0x80, 0x02})        // return home
+	write(td, []byte{0x80, 0x01})        // clean the display
+	write(td, []byte{0x80, 0x08 | 0x04}) // no cursor
+	write(td, []byte{0x80, 0x28})        // two lines
+
+	for _, s := range ip {
+		write(td, []byte{0x40, byte(s)})
+	}
+}
+
+func write(d *i2c.Device, buf []byte) {
+	err := d.Write(buf)
+	if err != nil {
+		panic(err)
+	}
+}
+
+func resolveIP() (string, error) {
+	var ip net.IP
+	ifaces, err := net.Interfaces()
+	if err != nil {
+		panic(err)
+	}
+	for _, i := range ifaces {
+		addrs, err := i.Addrs()
+		if err != nil {
+			panic(err)
+		}
+		for _, addr := range addrs {
+			switch v := addr.(type) {
+			case *net.IPNet:
+				ip = v.IP
+			case *net.IPAddr:
+				ip = v.IP
+			}
+			ip = ip.To4()
+			if ip != nil && ip.String() != "127.0.0.1" {
+				return ip.String(), nil
+			}
+		}
+	}
+	return "", fmt.Errorf("cannot resolve the IP")
+}

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/example_test.go

@@ -0,0 +1,24 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package i2c_test
+
+import (
+	"golang.org/x/exp/io/i2c"
+)
+
+func ExampleOpen() {
+	d, err := i2c.Open(&i2c.Devfs{Dev: "/dev/i2c-1"}, 0x39)
+	if err != nil {
+		panic(err)
+	}
+
+	// opens a 10-bit address
+	d, err = i2c.Open(&i2c.Devfs{Dev: "/dev/i2c-1"}, i2c.TenBit(0x78))
+	if err != nil {
+		panic(err)
+	}
+
+	_ = d
+}

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/i2c.go

@@ -0,0 +1,75 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package i2c allows users to read from and write to a slave I2C device.
+//
+// # Deprecated
+//
+// This package is not maintained anymore. An actively supported cross-platform
+// alternative is https://periph.io/.
+package i2c // import "golang.org/x/exp/io/i2c"
+
+import (
+	"golang.org/x/exp/io/i2c/driver"
+)
+
+const tenbitMask = 1 << 12
+
+// Device represents an I2C device. Devices must be closed once
+// they are no longer in use.
+type Device struct {
+	conn driver.Conn
+}
+
+// TenBit marks an I2C address as a 10-bit address.
+func TenBit(addr int) int {
+	return addr | tenbitMask
+}
+
+// Read reads len(buf) bytes from the device.
+func (d *Device) Read(buf []byte) error {
+	return d.conn.Tx(nil, buf)
+}
+
+// ReadReg is similar to Read but it reads from a register.
+func (d *Device) ReadReg(reg byte, buf []byte) error {
+	return d.conn.Tx([]byte{reg}, buf)
+}
+
+// Write writes the buffer to the device. If it is required to write to a
+// specific register, the register should be passed as the first byte in the
+// given buffer.
+func (d *Device) Write(buf []byte) (err error) {
+	return d.conn.Tx(buf, nil)
+}
+
+// WriteReg is similar to Write but writes to a register.
+func (d *Device) WriteReg(reg byte, buf []byte) (err error) {
+	// TODO(jbd): Do not allocate, not optimal.
+	return d.conn.Tx(append([]byte{reg}, buf...), nil)
+}
+
+// Close closes the device and releases the underlying sources.
+func (d *Device) Close() error {
+	return d.conn.Close()
+}
+
+// Open opens a connection to an I2C device.
+// All devices must be closed once they are no longer in use.
+// For devices that use 10-bit I2C addresses, addr can be marked
+// as a 10-bit address with TenBit.
+func Open(o driver.Opener, addr int) (*Device, error) {
+	unmasked, tenbit := resolveAddr(addr)
+	conn, err := o.Open(unmasked, tenbit)
+	if err != nil {
+		return nil, err
+	}
+	return &Device{conn: conn}, nil
+}
+
+// resolveAddr returns whether the addr is 10-bit masked or not.
+// It also returns the unmasked address.
+func resolveAddr(addr int) (unmasked int, tenbit bool) {
+	return addr & (tenbitMask - 1), addr&tenbitMask == tenbitMask
+}

go/pkg/mod/golang.org/x/exp@v0.0.0-20230224173230-c95f2b4c22f2/io/i2c/i2c_test.go

@@ -0,0 +1,31 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package i2c
+
+import (
+	"testing"
+)
+
+func TestTenBit(t *testing.T) {
+	tc := []struct {
+		masked     int
+		addrWant   int
+		tenbitWant bool
+	}{
+		{TenBit(0x5), 0x5, true},
+		{0x5, 0x5, false},
+		{TenBit(0x200), 0x200, true},
+	}
+
+	for _, tt := range tc {
+		unmasked, tenbit := resolveAddr(tt.masked)
+		if want, got := tt.tenbitWant, tenbit; got != want {
+			t.Errorf("want address %x as 10-bit; got non 10-bit", tt.masked)
+		}
+		if want, got := tt.addrWant, unmasked; got != want {
+			t.Errorf("want address %v; got %v", want, got)
+		}
+	}
+}