linux-kernel - Re: [PATCH V2 1/1] USB: serial: f81232: fix incomplete serial port generation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <aTAZQ2fks4CHtDw1@hovoldconsulting.com>
Date: Wed, 3 Dec 2025 12:04:35 +0100
From: Johan Hovold <johan@...nel.org>
To: Peter Hong <peter_hong@...tek.com.tw>
Cc: gregkh@...uxfoundation.org, linux-usb@...r.kernel.org,
	linux-kernel@...r.kernel.org, tom_tsai@...tek.com.tw,
	yu_chen@...tek.com.tw
Subject: Re: [PATCH V2 1/1] USB: serial: f81232: fix incomplete serial port
 generation

On Tue, Dec 02, 2025 at 01:40:28PM +0800, Peter Hong wrote:
> Hi,
> 
> Johan Hovold 於 2025/12/1 下午 09:38 寫道:
> > On Fri, Nov 28, 2025 at 04:52:44PM +0800, Ji-Ze Hong (Peter Hong) wrote:
> >> The Fintek F81532A/534A/535/536 family relies on the
> >> F81534A_CTRL_CMD_ENABLE_PORT (116h) register during initialization to
> >> both determine serial port status and control port creation. If the
> >> driver experiences fast load/unload cycles, the device state may becomes
> >> unstable, resulting in the incomplete generation of serial ports.
> >>
> >> Performing a dummy read operation on the register prior to the initial
> >> write command resolves the issue. This clears the device's stale internal
> >> state. Subsequent write operations will correctly generate all serial
> >> ports.

> > Did you try removing the retry loop also in the set_register() helper?
> > Perhaps that's no longer needed after the dummy read.
> 
> I will try removing the retry loop in set_register() helper.
> If that worked, could I use the same patch file or series of patches?

I think you can do it in one patch since I assume the existing retry
loop is there to work around the same underlying issue.

Johan