The branch main has been updated by aokblast: URL: https://cgit.FreeBSD.org/src/commit/?id=d84b639a684e7e0640e7c24a1a6dbc09da4bc3d4
commit d84b639a684e7e0640e7c24a1a6dbc09da4bc3d4 Author: ShengYi Hung <[email protected]> AuthorDate: 2025-08-06 12:48:05 +0000 Commit: ShengYi Hung <[email protected]> CommitDate: 2026-06-22 13:36:48 +0000 libusb: implement zlp flag in libusb transfer The USB protocol defines a Zero-Length Packet (ZLP) to signal the end of a transfer when the data size is an exact multiple of the Maximum Packet Size (MPS). Without a ZLP in such cases, the device may not be able to determine that the transfer has completed. This flag is added to libusb to allow the user send a ZLP in the end of libusb_xfer. Reviewed by: adrian Sponsored by: The FreeBSD Foundataion Differential Revision: https://reviews.freebsd.org/D51759 --- lib/libusb/libusb.h | 1 + lib/libusb/libusb10.c | 29 ++++++++++++++++++++++++++++- 2 files changed, 29 insertions(+), 1 deletion(-) diff --git a/lib/libusb/libusb.h b/lib/libusb/libusb.h index b6853879412c..95f7faf900f8 100644 --- a/lib/libusb/libusb.h +++ b/lib/libusb/libusb.h @@ -264,6 +264,7 @@ enum libusb_transfer_flags { LIBUSB_TRANSFER_SHORT_NOT_OK = 1 << 0, LIBUSB_TRANSFER_FREE_BUFFER = 1 << 1, LIBUSB_TRANSFER_FREE_TRANSFER = 1 << 2, + LIBUSB_TRANSFER_ADD_ZERO_PACKET = 1 << 3, }; enum libusb_log_level { diff --git a/lib/libusb/libusb10.c b/lib/libusb/libusb10.c index ab92c219409a..bd3c25c0f052 100644 --- a/lib/libusb/libusb10.c +++ b/lib/libusb/libusb10.c @@ -1419,6 +1419,7 @@ libusb10_bulk_intr_proxy(struct libusb20_transfer *pxfer) uint32_t actlen; uint8_t status; uint8_t flags; + uint8_t tr_flags; status = libusb20_tr_get_status(pxfer); sxfer = libusb20_tr_get_priv_sc1(pxfer); @@ -1471,6 +1472,20 @@ libusb10_bulk_intr_proxy(struct libusb20_transfer *pxfer) sxfer->curr_data += max_bulk; sxfer->rem_len -= max_bulk; + /* + * When a zero length packet (ZLP) is requested, ask the + * kernel to terminate the last frame of the transfer with + * a short packet. This appends a ZLP when the data length + * is an exact multiple of the maximum packet size. + */ + tr_flags = libusb20_tr_get_flags(pxfer); + if (sxfer->rem_len == 0 && + (flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET)) + tr_flags |= LIBUSB20_TRANSFER_FORCE_SHORT; + else + tr_flags &= ~LIBUSB20_TRANSFER_FORCE_SHORT; + libusb20_tr_set_flags(pxfer, tr_flags); + libusb20_tr_submit(pxfer); /* check if we can fork another USB transfer */ @@ -1710,7 +1725,7 @@ libusb_submit_transfer(struct libusb_transfer *uxfer) struct libusb_super_transfer *sxfer; struct libusb_device *dev; uint8_t endpoint; - int err; + int err, mps; if (uxfer == NULL) return (LIBUSB_ERROR_INVALID_PARAM); @@ -1731,6 +1746,18 @@ libusb_submit_transfer(struct libusb_transfer *uxfer) pxfer0 = libusb10_get_transfer(uxfer->dev_handle, endpoint, 0); pxfer1 = libusb10_get_transfer(uxfer->dev_handle, endpoint, 1); + mps = libusb_get_max_packet_size(dev, endpoint); + + /* + * The ADD_ZERO_PACKET flag only has an effect on host-to-device + * (OUT) transfers whose length is an exact multiple of the maximum + * packet size. Clear it otherwise so the kernel is not asked to + * terminate the transfer with a short packet, see + * libusb10_bulk_intr_proxy(). + */ + if ((uxfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) && + ((endpoint & LIBUSB_ENDPOINT_IN) || uxfer->length % mps != 0)) + uxfer->flags &= ~LIBUSB_TRANSFER_ADD_ZERO_PACKET; if (pxfer0 == NULL || pxfer1 == NULL) { err = LIBUSB_ERROR_OTHER;
