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// 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
}
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