libusb: don't treat EINVAL from USB_FS_COMPLETE as device detach

ugen20_process() treats any non-EBUSY errno returned by USB_FS_COMPLETE
as device detach and returns LIBUSB20_ERROR_OTHER. This causes libusb10
to set device_is_gone and fail all subsequent transfer with
LIBUSB_ERROR_NO_DEVICE.

However, USB_FS_COMPLETE can also return EINVAL when a completion
references an endpoint that no longer exists, for example after
SET_INTERFACE or SET_CONFIG removes and recreates endpoints. This is a
transient condition and does not indicate device detach.

Treat EINVAL the same as EBUSY and stop draining completions. This
prevents a guest selecting an isochronous streaming altsetting from
permanently breaking the passed-through device.

Reviewed by:    bapt
Event:          Halifax Hackathon 202606
Location:       Peggy's Cove Rock
Sponsored by:   The FreeBSD Foundation
Differential Revision:  https://reviews.freebsd.org/D57542

1 files changed, 10 insertions, 1 deletions

diff --git a/lib/libusb/libusb20_ugen20.c b/lib/libusb/libusb20_ugen20.c
index 6c838814a45d..32c8d53cd611 100644
--- a/lib/libusb/libusb20_ugen20.c
+++ b/lib/libusb/libusb20_ugen20.c
@@ -765,7 +765,16 @@ ugen20_process(struct libusb20_device *pdev)
 	while (1) {
 
 	  if (ioctl(pdev->file, IOUSB(USB_FS_COMPLETE), &temp)) {
-			if (errno == EBUSY) {
+			if (errno == EBUSY || errno == EINVAL) {
+				/*
+				 * EBUSY: no completion is pending.
+				 * EINVAL: a dequeued completion referenced an
+				 * endpoint that no longer exists, e.g. a stale
+				 * completion left over after a SET_INTERFACE /
+				 * SET_CONFIG tore the endpoints down. This is not
+				 * a device detach, so stop draining rather than
+				 * declaring the device gone.
+				 */
 				break;
 			} else {
 				/* device detached */