git: 931b121469a9 - stable/12 - MFC r368632: Be bug compatible with other operating systems by allowing non-sequential interface numbering for USB descriptors in userspace. Else certain USB control requests using the interface number, won't be recognized by the USB firmware.

[Hans Petter Selasky]

The branch stable/12 has been updated by hselasky:

URL: https://cgit.FreeBSD.org/src/commit/?id=931b121469a940147e34279783be6ac7343a980c

commit 931b121469a940147e34279783be6ac7343a980c
Author:     Hans Petter Selasky <hselasky at FreeBSD.org>
AuthorDate: 2020-12-14 11:56:16 +0000
Commit:     Hans Petter Selasky <hselasky at FreeBSD.org>
CommitDate: 2020-12-28 12:39:04 +0000

    MFC r368632:
    Be bug compatible with other operating systems by allowing non-sequential
    interface numbering for USB descriptors in userspace. Else certain USB
    control requests using the interface number, won't be recognized by the
    USB firmware.
    
    Refer to section 9.2.3 in the USB 2.0 specification:
    Interfaces are numbered from zero to one less than the number of concurrent interfaces
    supported by the configuration.
    
    PR:             251784
    Sponsored by:   Mellanox Technologies // NVIDIA Networking
---
 lib/libusb/libusb20_desc.c | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/libusb/libusb20_desc.c b/lib/libusb/libusb20_desc.c
index 517a2e5972c3..3052af09e9c2 100644
--- a/lib/libusb/libusb20_desc.c
+++ b/lib/libusb/libusb20_desc.c
@@ -81,9 +81,10 @@ libusb20_parse_config_desc(const void *config_desc)
 	if (ptr[1] != LIBUSB20_DT_CONFIG) {
 		return (NULL);		/* not config descriptor */
 	}
+
 	/*
-	 * The first "bInterfaceNumber" should never have the value 0xff.
-	 * Then it is corrupt.
+	 * The first "bInterfaceNumber" cannot start at 0xFFFF
+	 * because the field is 8-bit.
 	 */
 	niface_no_alt = 0;
 	nendpoint = 0;
@@ -206,12 +207,15 @@ libusb20_parse_config_desc(const void *config_desc)
 			if (libusb20_me_decode(ptr, ptr[0], &last_if->desc)) {
 				/* ignore */
 			}
-			/*
-			 * Sometimes USB devices have corrupt interface
-			 * descriptors and we need to overwrite the provided
-			 * interface number!
-			 */
-			last_if->desc.bInterfaceNumber = niface - 1;
+
+			/* detect broken USB descriptors when USB debugging is enabled */
+			if (last_if->desc.bInterfaceNumber != (uint8_t)(niface - 1)) {
+				const char *str = getenv("LIBUSB_DEBUG");
+				if (str != NULL && str[0] != '\0' && str[0] != '0') {
+					printf("LIBUSB_DEBUG: bInterfaceNumber(%u) is not sequential(%u)\n",
+					    last_if->desc.bInterfaceNumber, niface - 1);
+				}
+			}
 			last_if->extra.ptr = LIBUSB20_ADD_BYTES(ptr, ptr[0]);
 			last_if->extra.len = 0;
 			last_if->extra.type = LIBUSB20_ME_IS_RAW;