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From: Mehrdad Afshari <mehrdad@signeen.com>
To: Oliver Neukum <oliver@neukum.org>, netdev@vger.kernel.org
Cc: Andrew Lunn <andrew+netdev@lunn.ch>,
	"David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	linux-usb@vger.kernel.org, Mehrdad Afshari <mehrdad@signeen.com>
Subject: [PATCH] net: usb: cdc_ncm: add Apple MacBook Pro USB product ID 0x1902
Date: Sat, 15 Aug 2026 21:04:26 -0700	[thread overview]
Message-ID: <20260816040426.57132-1-mehrdad@signeen.com> (raw)

The cdc_devs[] quirk table special-cases the Mac CDC-NCM private
interface personality only for USB product ID 0x1905.
Some MacBook Pro models (e.g. M1 Max) connected over a
USB4/Thunderbolt 3/4 cable to a host whose Thunderbolt controller
lacks PCIe tunneling support (no NHI function, USB4-only mode)
present themselves with product ID 0x1902 instead,
using the same descriptor layout as 0x1905: a Communications
control interface with zero endpoints (no interrupt/status endpoint)
paired with a CDC Data interface, at
interface numbers 0 and 2.

Because 0x1902 is unmatched, these devices fall through to the
generic cdc_ncm_info driver_info, which sets FLAG_LINK_INTR and
therefore requires an interrupt endpoint on the control interface.
Apple's private NCM interface never provides one, so cdc_ncm_bind()
fails outright:

  cdc_ncm 2-1:1.0: bind() failure
  cdc_ncm 2-1:1.2: bind() failure

and no network device is created, breaking Ethernet-over-USB4
between the Mac and any USB4 host lacking Thunderbolt PCIe
tunneling.

Add matching entries for 0x1902 alongside the existing 0x1905
ones, reusing apple_private_interface_info as with the other Mac
ID.

Signed-off-by: Mehrdad Afshari <mehrdad@signeen.com>
---
 drivers/net/usb/cdc_ncm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 0223a17..35db38c 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -2013,6 +2013,12 @@ static const struct usb_device_id cdc_devs[] = {
 	},
 
 	/* Mac */
+	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x1902, 0),
+		.driver_info = (unsigned long)&apple_private_interface_info,
+	},
+	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x1902, 2),
+		.driver_info = (unsigned long)&apple_private_interface_info,
+	},
 	{ USB_DEVICE_INTERFACE_NUMBER(0x05ac, 0x1905, 0),
 		.driver_info = (unsigned long)&apple_private_interface_info,
 	},
-- 
2.55.0


             reply	other threads:[~2026-08-16  4:04 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-08-16  4:04 Mehrdad Afshari [this message]
2026-08-18 17:12 ` [PATCH] net: usb: cdc_ncm: add Apple MacBook Pro USB product ID 0x1902 Jakub Kicinski
2026-08-21  0:10 ` patchwork-bot+netdevbpf

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