Golang ioctl sample

00_ioctl_golang

Golang ioctl sample

i2c.go

package i2c

import (
    "os"
    "syscall"
    "unsafe"
)

type I2c_client struct {
    f *os.File
}

func Open(devname string) (c *I2c_client, err error) {
    f, err := os.OpenFile(devname, syscall.O_RDWR, 0666)
    if err != nil {
        return nil, err
    }
    return &I2c_client{f: f}, nil
}

func (c *I2c_client) Close() (err error) {
    return c.f.Close()
}

func (c *I2c_client) ReadByte(slave uint8, offset uint8) (b uint8, err error) {
    buf := []uint8{0}
    msg := []i2c_msg{
        {
            addr:  uint16(slave),
            flags: 0,
            len:   1,
            buf:   uintptr(unsafe.Pointer(&offset)),
        },
        {
            addr:  uint16(slave),
            flags: uint16(_I2C_M_RD),
            len:   uint16(len(buf)),
            buf:   uintptr(unsafe.Pointer(&buf[0])),
        },
    }
    err = transfer(c.f, &msg[0], len(msg))
    if err != nil {
        return 0, err
    }
    return buf[0], nil
}

func (c *I2c_client) ReadWord(slave uint8, offset uint8) (w uint16, err error) {
    buf := []uint8{0,0}
    msg := []i2c_msg{
        {
            addr:  uint16(slave),
            flags: 0,
            len:   1,
            buf:   uintptr(unsafe.Pointer(&offset)),
        },
        {
            addr:  uint16(slave),
            flags: uint16(_I2C_M_RD),
            len:   uint16(len(buf)),
            buf:   uintptr(unsafe.Pointer(&buf[0])),
        },
    }
    err = transfer(c.f, &msg[0], len(msg))
    if err != nil {
        return 0, err
    }
    w = (uint16(buf[0]) << 8) | uint16(buf[1])
    return
}

func (c *I2c_client) WriteByte(slave uint8, offset uint8, b uint8) (err error) {
    buf := []uint8{offset, b}
    msg := []i2c_msg{
        {
            addr:  uint16(slave),
            flags: 0,
            len:   uint16(len(buf)),
            buf:   uintptr(unsafe.Pointer(&buf[0])),
        },
    }
    return transfer(c.f, &msg[0], len(msg))
}

const (
    _I2C_RDWR                = 0x0707
    _I2C_RDRW_IOCTL_MAX_MSGS = 42
    _I2C_M_RD                = 0x0001
)

type i2c_msg struct {
    addr      uint16
    flags     uint16
    len       uint16
    __padding uint16
    buf       uintptr
}

type i2c_rdwr_ioctl_data struct {
    msgs  uintptr
    nmsgs uint32
}

func transfer(f *os.File, msgs *i2c_msg, n int) (err error) {
    data := i2c_rdwr_ioctl_data{
        msgs:  uintptr(unsafe.Pointer(msgs)),
        nmsgs: uint32(n),
    }
    err = nil
    _, _, errno := syscall.Syscall(
        syscall.SYS_IOCTL,
        uintptr(f.Fd()),
        uintptr(_I2C_RDWR),
        uintptr(unsafe.Pointer(&data)),
    )
    if (errno != 0) {
        err = errno
    }
    return
}