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Add comments documenting gousb lifecycle management

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Explain why we use gousb directly instead of antgo/driver/usb
(libusb context leak on error paths), document the defer cleanup
ordering, and note that errors are returned for graceful retry.
This commit is contained in:
Erik Brakkee 2026-06-14 13:03:39 +00:00
parent 9efdfc9b83
commit 8a4457119a
1 changed files with 14 additions and 0 deletions
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14
cmd/bridge/ant.go
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@ -44,6 +44,11 @@ func resetAndWait(drv io.ReadWriter) error {
func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32, func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
events chan<- Event) error { events chan<- Event) error {
// Use gousb directly instead of antgo/driver/usb to manage context
// lifecycle explicitly. The old code created a new gousb.Context on
// every call via libusb_init and leaked it on error paths (device not
// found, interface claim failure, etc.), which triggered a libusb
// assertion after repeated ListenForTrainer calls.
gctx := gousb.NewContext() gctx := gousb.NewContext()
defer gctx.Close() defer gctx.Close()
@ -60,6 +65,9 @@ func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
if err != nil { if err != nil {
return fmt.Errorf("ant: claim interface: %w", err) return fmt.Errorf("ant: claim interface: %w", err)
} }
// Cleanup is ordered by defer stack: done() releases interface,
// dev.Close() closes device, gctx.Close() closes context, cancel()
// cancels the ANT message goroutine.
defer done() defer done()
out, err := intf.OutEndpoint(1) out, err := intf.OutEndpoint(1)
@ -75,6 +83,8 @@ func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
logMsg("ant: device opened") logMsg("ant: device opened")
// Errors are returned (not panicked) so the caller can retry
// gracefully instead of requiring a full process restart.
if err := resetAndWait(drv); err != nil { if err := resetAndWait(drv); err != nil {
return err return err
} }
@ -85,6 +95,8 @@ func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
msgs := make(chan ant.BroadcastMessage, 100) msgs := make(chan ant.BroadcastMessage, 100)
ctx, cancel := context.WithCancel(context.Background()) ctx, cancel := context.WithCancel(context.Background())
// cancel is the final defer in the stack, ensuring the ANT message
// goroutine is torn down after all USB resources are released.
defer cancel() defer cancel()
go func() { go func() {
device.DumpBroadcastMessages(ctx, drv, msgs) device.DumpBroadcastMessages(ctx, drv, msgs)
@ -124,6 +136,8 @@ func ListenForTrainer(vendorId uint16, productId uint16, deviceNumber uint32,
} }
case <-time.After(10 * time.Second): case <-time.After(10 * time.Second):
logMsg("ant: no more messages arrived, restarting") logMsg("ant: no more messages arrived, restarting")
// Return without error so the caller can retry gracefully
// rather than panicking and requiring a full restart.
return nil return nil
} }
} }