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interrupt.go
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interrupt.go
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// Generic Interrupt Pins.
package generic
import (
"errors"
"fmt"
"sync"
"syscall"
"github.com/zlowred/embd"
)
const (
MaxGPIOInterrupt = 64
)
var ErrorPinAlreadyRegistered = errors.New("pin interrupt already registered")
type interrupt struct {
pin embd.DigitalPin
initialTrigger bool
handler func(embd.DigitalPin)
}
func (i *interrupt) Signal() {
if !i.initialTrigger {
i.initialTrigger = true
return
}
i.handler(i.pin)
}
type epollListener struct {
mu sync.Mutex // Guards the following.
fd int
interruptablePins map[int]*interrupt
}
var epollListenerInstance *epollListener
func getEpollListenerInstance() *epollListener {
if epollListenerInstance == nil {
epollListenerInstance = initEpollListener()
}
return epollListenerInstance
}
func initEpollListener() *epollListener {
fd, err := syscall.EpollCreate1(0)
if err != nil {
panic(fmt.Sprintf("Unable to create epoll: %v", err))
}
listener := &epollListener{fd: fd, interruptablePins: make(map[int]*interrupt)}
go func() {
var epollEvents [MaxGPIOInterrupt]syscall.EpollEvent
for {
n, err := syscall.EpollWait(listener.fd, epollEvents[:], -1)
if err != nil {
panic(fmt.Sprintf("EpollWait error: %v", err))
}
for i := 0; i < n; i++ {
if irq, ok := listener.interruptablePins[int(epollEvents[i].Fd)]; ok {
irq.Signal()
}
}
}
}()
return listener
}
func registerInterrupt(pin *digitalPin, handler func(embd.DigitalPin)) error {
l := getEpollListenerInstance()
pinFd := int(pin.val.Fd())
l.mu.Lock()
defer l.mu.Unlock()
if _, ok := l.interruptablePins[pinFd]; ok {
return ErrorPinAlreadyRegistered
}
var event syscall.EpollEvent
event.Events = syscall.EPOLLIN | (syscall.EPOLLET & 0xffffffff) | syscall.EPOLLPRI
if err := syscall.SetNonblock(pinFd, true); err != nil {
return err
}
event.Fd = int32(pinFd)
if err := syscall.EpollCtl(l.fd, syscall.EPOLL_CTL_ADD, pinFd, &event); err != nil {
return err
}
l.interruptablePins[pinFd] = &interrupt{pin: pin, handler: handler}
return nil
}
func unregisterInterrupt(pin *digitalPin) error {
l := getEpollListenerInstance()
pinFd := int(pin.val.Fd())
l.mu.Lock()
defer l.mu.Unlock()
if _, ok := l.interruptablePins[pinFd]; !ok {
return nil
}
if err := syscall.EpollCtl(l.fd, syscall.EPOLL_CTL_DEL, pinFd, nil); err != nil {
return err
}
if err := syscall.SetNonblock(pinFd, false); err != nil {
return err
}
delete(l.interruptablePins, pinFd)
return nil
}