embd/host/generic/linux/gpio/gpio.go

150 lines
2.4 KiB
Go

package gpio
import (
"fmt"
"os"
"strconv"
"github.com/golang/glog"
"github.com/kidoman/embd/gpio"
)
const (
Normal int = 1 << iota
I2C
UART
SPI
)
type PinDesc struct {
N int
IDs []string
Caps int
}
type PinMap []*PinDesc
func (m PinMap) Lookup(k interface{}) (*PinDesc, bool) {
switch key := k.(type) {
case int:
for i := range m {
if m[i].N == key {
return m[i], true
}
}
case string:
for i := range m {
for j := range m[i].IDs {
if m[i].IDs[j] == key {
return m[i], true
}
}
}
}
return nil, false
}
type GPIO struct {
exporter, unexporter *os.File
initialized bool
pinMap PinMap
initializedPins map[int]*digitalPin
}
func New(pinMap PinMap) *GPIO {
return &GPIO{
pinMap: pinMap,
initializedPins: map[int]*digitalPin{},
}
}
func (io *GPIO) init() (err error) {
if io.initialized {
return
}
if io.exporter, err = os.OpenFile("/sys/class/gpio/export", os.O_WRONLY, os.ModeExclusive); err != nil {
return
}
if io.unexporter, err = os.OpenFile("/sys/class/gpio/unexport", os.O_WRONLY, os.ModeExclusive); err != nil {
return
}
io.initialized = true
return
}
func (io *GPIO) lookupKey(key interface{}) (*PinDesc, bool) {
return io.pinMap.Lookup(key)
}
func (io *GPIO) export(n int) (err error) {
_, err = io.exporter.WriteString(strconv.Itoa(n))
return
}
func (io *GPIO) unexport(n int) (err error) {
_, err = io.unexporter.WriteString(strconv.Itoa(n))
return
}
func (io *GPIO) digitalPin(key interface{}) (p *digitalPin, err error) {
pd, found := io.lookupKey(key)
if !found {
err = fmt.Errorf("gpio: could not find pin matching %q", key)
return
}
n := pd.N
var ok bool
if p, ok = io.initializedPins[n]; ok {
return
}
if pd.Caps&Normal == 0 {
err = fmt.Errorf("gpio: sorry, pin %q cannot be used for GPIO", key)
return
}
if pd.Caps != Normal {
glog.Infof("gpio: pin %q is not a dedicated GPIO pin. please refer to the system reference manual for more details", key)
}
if err = io.export(n); err != nil {
return
}
if p, err = newDigitalPin(n); err != nil {
io.unexport(n)
return
}
io.initializedPins[n] = p
return
}
func (io *GPIO) DigitalPin(key interface{}) (gpio.DigitalPin, error) {
if err := io.init(); err != nil {
return nil, err
}
return io.digitalPin(key)
}
func (io *GPIO) Close() error {
for n := range io.initializedPins {
io.unexport(n)
}
io.exporter.Close()
io.unexporter.Close()
return nil
}