1package drm
2
3import (
4 "context"
5 "errors"
6 "fmt"
7 "sync"
8
9 "github.com/bnema/neferwl/internal/adapters/fdwait"
10 "github.com/bnema/purego"
11 "golang.org/x/sys/unix"
12)
13
14// Hotplug reports connector changes through a udev netlink monitor on the
15// drm subsystem (the kernel sends HOTPLUG=1 on the card). libudev is loaded
16// with purego.
17
18var (
19 udevOnce sync.Once
20 udevErr error
21
22 udevNew func() uintptr
23 udevUnref func(uintptr) uintptr
24 monitorNew func(udev uintptr, name string) uintptr
25 monitorUnref func(uintptr) uintptr
26 monitorFilter func(mon uintptr, subsystem string, devtype uintptr) int32
27 monitorEnable func(uintptr) int32
28 monitorFD func(uintptr) int32
29 monitorReceive func(uintptr) uintptr
30 deviceUnref func(uintptr) uintptr
31 devicePropertyVal func(dev uintptr, key string) string
32)
33
34func loadUdev() error {
35 udevOnce.Do(func() {
36 lib, err := purego.Dlopen("libudev.so.1", purego.RTLD_NOW|purego.RTLD_LOCAL)
37 if err != nil {
38 udevErr = fmt.Errorf("open libudev.so.1: %w", err)
39 return
40 }
41 defer func() {
42 if r := recover(); r != nil {
43 udevErr = fmt.Errorf("libudev: %v", r)
44 }
45 }()
46 reg := func(fn any, name string) { purego.RegisterLibFunc(fn, lib, "udev_"+name) }
47 reg(&udevNew, "new")
48 reg(&udevUnref, "unref")
49 reg(&monitorNew, "monitor_new_from_netlink")
50 reg(&monitorUnref, "monitor_unref")
51 reg(&monitorFilter, "monitor_filter_add_match_subsystem_devtype")
52 reg(&monitorEnable, "monitor_enable_receiving")
53 reg(&monitorFD, "monitor_get_fd")
54 reg(&monitorReceive, "monitor_receive_device")
55 reg(&deviceUnref, "device_unref")
56 reg(&devicePropertyVal, "device_get_property_value")
57 })
58 return udevErr
59}
60
61// WatchHotplug sends on changed after every DRM hotplug event until ctx
62// ends. Events that arrive while a send is pending are merged.
63func WatchHotplug(ctx context.Context, changed chan<- struct{}) error {
64 if err := loadUdev(); err != nil {
65 return err
66 }
67 udev := udevNew()
68 if udev == 0 {
69 return errors.New("udev_new failed")
70 }
71 defer udevUnref(udev)
72 mon := monitorNew(udev, "udev")
73 if mon == 0 {
74 return errors.New("udev_monitor_new_from_netlink failed")
75 }
76 defer monitorUnref(mon)
77 if monitorFilter(mon, "drm", 0) < 0 || monitorEnable(mon) < 0 {
78 return errors.New("udev monitor setup failed")
79 }
80 fd := monitorFD(mon)
81 waiter, err := fdwait.New()
82 if err != nil {
83 return fmt.Errorf("udev waiter: %w", err)
84 }
85 defer waiter.Close()
86 waiter.StopOn(ctx)
87 if err := waiter.Pin(fd); err != nil {
88 return fmt.Errorf("udev waiter: %w", err)
89 }
90 fds := []unix.PollFd{{Fd: fd, Events: unix.POLLIN}}
91 for ctx.Err() == nil {
92 n, err := waiter.Poll(fds, -1)
93 if err != nil && !errors.Is(err, unix.EINTR) {
94 return fmt.Errorf("udev poll: %w", err)
95 }
96 if n <= 0 {
97 continue
98 }
99 dev := monitorReceive(mon)
100 if dev == 0 {
101 continue
102 }
103 hot := devicePropertyVal(dev, "HOTPLUG") == "1"
104 deviceUnref(dev)
105 if !hot {
106 continue
107 }
108 select {
109 case changed <- struct{}{}:
110 default:
111 }
112 }
113 return nil
114}