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

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Message-ID: <20250813175313.2585-1-zenmchen@gmail.com>
Date: Thu, 14 Aug 2025 01:53:12 +0800
From: Zenm Chen <zenmchen@...il.com>
To: stern@...land.harvard.edu
Cc: gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org,
	pkshih@...ltek.com,
	rtl8821cerfe2@...il.com,
	stable@...r.kernel.org,
	usb-storage@...ts.one-eyed-alien.net,
	usbwifi2024@...il.com,
	zenmchen@...il.com
Subject: Re: [PATCH] USB: storage: Ignore driver CD mode for Realtek multi-mode Wi-Fi dongles

Alan Stern <stern@...land.harvard.edu> 於 2025年8月14日 週四 上午12:58寫道：
>
> On Thu, Aug 14, 2025 at 12:24:15AM +0800, Zenm Chen wrote:
> > 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.
>
> There are several other entries like this already in the unusual_devs.h
> file.  But I wonder if we really still need them.  Shouldn't the
> usb_modeswitch program be smart enough by now to know how to handle
> these things?

Hi Alan,

Thanks for your review and reply.

Without this patch applied, usb_modeswitch cannot switch my Mercury MW310UH
into Wi-Fi mode [1]. I also ran into a similar problem like [2] with D-Link
AX9U, so I believe this patch is needed.

>
> In theory, someone might want to access the Windows driver on the
> emulated CD.  With this quirk, they wouldn't be able to.
>

Actually an emulated CD doesn't appear when I insert these 2 Wi-Fi dongles into
my Linux PC, so users cannot access that Windows driver even if this patch is not 
applied.

> Alan Stern

[1] https://drive.google.com/file/d/1YfWUTxKnvSeu1egMSwcF-memu3Kis8Mg/view?usp=drive_link

[2] https://github.com/morrownr/rtw89/issues/10