linux-kernel - [PATCH] USB: storage: Ignore driver CD mode for Realtek multi-mode Wi-Fi dongles

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Message-ID: <20250813162415.2630-1-zenmchen@gmail.com>
Date: Thu, 14 Aug 2025 00:24:15 +0800
From: Zenm Chen <zenmchen@...il.com>
To: stern@...land.harvard.edu,
	gregkh@...uxfoundation.org,
	linux-usb@...r.kernel.org,
	usb-storage@...ts.one-eyed-alien.net,
	linux-kernel@...r.kernel.org
Cc: pkshih@...ltek.com,
	rtl8821cerfe2@...il.com,
	usbwifi2024@...il.com,
	zenmchen@...il.com,
	stable@...r.kernel.org
Subject: [PATCH] USB: storage: Ignore driver CD mode for Realtek multi-mode Wi-Fi dongles

Many Realtek USB Wi-Fi dongles released in recent years have two modes: 
one is driver CD mode which has Windows driver onboard, another one is
Wi-Fi mode. Add the US_FL_IGNORE_DEVICE quirk for these multi-mode devices.
Otherwise, usb_modeswitch may fail to switch them to Wi-Fi mode.

Currently there are only two USB IDs known to be used by these multi-mode
Wi-Fi dongles: 0bda:1a2b and 0bda:a192.

Information about Mercury MW310UH in /sys/kernel/debug/usb/devices.
T:  Bus=02 Lev=01 Prnt=01 Port=01 Cnt=01 Dev#= 12 Spd=480  MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=0bda ProdID=a192 Rev= 2.00
S:  Manufacturer=Realtek
S:  Product=DISK
C:* #Ifs= 1 Cfg#= 1 Atr=80 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=(none)
E:  Ad=8a(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=0b(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms

Information about D-Link AX9U rev. A1 in /sys/kernel/debug/usb/devices.
T:  Bus=03 Lev=01 Prnt=01 Port=02 Cnt=01 Dev#= 55 Spd=480  MxCh= 0
D:  Ver= 2.00 Cls=00(>ifc ) Sub=00 Prot=00 MxPS=64 #Cfgs=  1
P:  Vendor=0bda ProdID=1a2b Rev= 0.00
S:  Manufacturer=Realtek
S:  Product=DISK
C:* #Ifs= 1 Cfg#= 1 Atr=e0 MxPwr=500mA
I:* If#= 0 Alt= 0 #EPs= 2 Cls=08(stor.) Sub=06 Prot=50 Driver=(none)
E:  Ad=84(I) Atr=02(Bulk) MxPS= 512 Ivl=0ms
E:  Ad=05(O) Atr=02(Bulk) MxPS= 512 Ivl=0ms

Cc: stable@...r.kernel.org # 5.4.x
Signed-off-by: Zenm Chen <zenmchen@...il.com>
---
 drivers/usb/storage/unusual_devs.h | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/usb/storage/unusual_devs.h b/drivers/usb/storage/unusual_devs.h
index 54f0b1c83..5a6577a57 100644
--- a/drivers/usb/storage/unusual_devs.h
+++ b/drivers/usb/storage/unusual_devs.h
@@ -1494,6 +1494,28 @@ UNUSUAL_DEV( 0x0bc2, 0x3332, 0x0000, 0x9999,
 		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
 		US_FL_NO_WP_DETECT ),
 
+/*
+ * Reported by Zenm Chen <zenmchen@...il.com>
+ * Ignore driver CD mode, otherwise usb_modeswitch may fail to switch
+ * the device into Wi-Fi mode.
+ */
+UNUSUAL_DEV( 0x0bda, 0x1a2b, 0x0000, 0xffff,
+		"Realtek",
+		"DISK",
+		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
+		US_FL_IGNORE_DEVICE ),
+
+/*
+ * Reported by Zenm Chen <zenmchen@...il.com>
+ * Ignore driver CD mode, otherwise usb_modeswitch may fail to switch
+ * the device into Wi-Fi mode.
+ */
+UNUSUAL_DEV( 0x0bda, 0xa192, 0x0000, 0xffff,
+		"Realtek",
+		"DISK",
+		USB_SC_DEVICE, USB_PR_DEVICE, NULL,
+		US_FL_IGNORE_DEVICE ),
+
 UNUSUAL_DEV(  0x0d49, 0x7310, 0x0000, 0x9999,
 		"Maxtor",
 		"USB to SATA",
-- 
2.50.1