brightness: more aggressive ddc rescans on device changes

core/internal/server/brightness/ddc.go

@@ -40,6 +40,10 @@ func (b *DDCBackend) scanI2CDevices() error {
 	return b.scanI2CDevicesInternal(false)
 }
 
+func (b *DDCBackend) ForceRescan() error {
+	return b.scanI2CDevicesInternal(true)
+}
+
 func (b *DDCBackend) scanI2CDevicesInternal(force bool) error {
 	b.scanMutex.Lock()
 	defer b.scanMutex.Unlock()
@@ -261,8 +265,16 @@ func (b *DDCBackend) setBrightnessImmediateWithExponent(id string, value int) er
 
 	busPath := fmt.Sprintf("/dev/i2c-%d", dev.bus)
 
+	if _, err := os.Stat(busPath); os.IsNotExist(err) {
+		b.devices.Delete(id)
+		log.Debugf("removed stale DDC device %s (bus no longer exists)", id)
+		return fmt.Errorf("device disconnected: %s", id)
+	}
+
 	fd, err := syscall.Open(busPath, syscall.O_RDWR, 0)
 	if err != nil {
+		b.devices.Delete(id)
+		log.Debugf("removed DDC device %s (open failed: %v)", id, err)
 		return fmt.Errorf("open i2c device: %w", err)
 	}
 	defer syscall.Close(fd)

core/internal/server/brightness/manager.go

@@ -89,6 +89,13 @@ func (m *Manager) initDDC() {
 
 func (m *Manager) Rescan() {
 	log.Debug("Rescanning brightness devices...")
+
+	if m.ddcReady && m.ddcBackend != nil {
+		if err := m.ddcBackend.ForceRescan(); err != nil {
+			log.Debugf("DDC force rescan failed: %v", err)
+		}
+	}
+
 	m.updateState()
 }
 

core/internal/server/brightness/udev.go

@@ -5,13 +5,18 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
+	"time"
 
 	"github.com/AvengeMedia/DankMaterialShell/core/internal/log"
 	"github.com/pilebones/go-udev/netlink"
 )
 
 type UdevMonitor struct {
-	stop chan struct{}
+	stop          chan struct{}
+	rescanMutex   sync.Mutex
+	rescanTimer   *time.Timer
+	rescanPending bool
 }
 
 func NewUdevMonitor(manager *Manager) *UdevMonitor {
@@ -34,10 +39,8 @@ func (m *UdevMonitor) run(manager *Manager) {
 	matcher := &netlink.RuleDefinitions{
 		Rules: []netlink.RuleDefinition{
 			{Env: map[string]string{"SUBSYSTEM": "backlight"}},
-			// ! TODO: most drivers dont emit this for leds?
-			// ! inotify brightness_hw_changed works, but thn some devices dont do that...
-			// ! So for now the GUI just shows OSDs for leds, without reflecting actual HW value
-			// {Env: map[string]string{"SUBSYSTEM": "leds"}},
+			{Env: map[string]string{"SUBSYSTEM": "drm"}},
+			{Env: map[string]string{"SUBSYSTEM": "i2c"}},
 		},
 	}
 	if err := matcher.Compile(); err != nil {
@@ -49,7 +52,7 @@ func (m *UdevMonitor) run(manager *Manager) {
 	errs := make(chan error)
 	conn.Monitor(events, errs, matcher)
 
-	log.Info("Udev monitor started for backlight/leds events")
+	log.Info("Udev monitor started for backlight/drm/i2c events")
 
 	for {
 		select {
@@ -75,11 +78,54 @@ func (m *UdevMonitor) handleEvent(manager *Manager, event netlink.UEvent) {
 	sysname := filepath.Base(devpath)
 	action := string(event.Action)
 
+	switch subsystem {
+	case "drm", "i2c":
+		m.handleDisplayEvent(manager, action, subsystem, sysname)
+	case "backlight":
+		m.handleBacklightEvent(manager, action, sysname)
+	}
+}
+
+func (m *UdevMonitor) handleDisplayEvent(manager *Manager, action, subsystem, sysname string) {
+	switch action {
+	case "add", "remove", "change":
+		log.Debugf("Udev %s event: %s:%s - queueing DDC rescan", action, subsystem, sysname)
+		m.debouncedRescan(manager)
+	}
+}
+
+func (m *UdevMonitor) debouncedRescan(manager *Manager) {
+	m.rescanMutex.Lock()
+	defer m.rescanMutex.Unlock()
+
+	m.rescanPending = true
+
+	if m.rescanTimer != nil {
+		m.rescanTimer.Reset(2 * time.Second)
+		return
+	}
+
+	m.rescanTimer = time.AfterFunc(2*time.Second, func() {
+		m.rescanMutex.Lock()
+		pending := m.rescanPending
+		m.rescanPending = false
+		m.rescanMutex.Unlock()
+
+		if !pending {
+			return
+		}
+
+		log.Debug("Executing debounced DDC rescan")
+		manager.Rescan()
+	})
+}
+
+func (m *UdevMonitor) handleBacklightEvent(manager *Manager, action, sysname string) {
 	switch action {
 	case "change":
-		m.handleChange(manager, subsystem, sysname)
+		m.handleChange(manager, "backlight", sysname)
 	case "add", "remove":
-		log.Debugf("Udev %s event: %s:%s - triggering rescan", action, subsystem, sysname)
+		log.Debugf("Udev %s event: backlight:%s - triggering rescan", action, sysname)
 		manager.Rescan()
 	}
 }