Re: Post-facto backport request: USB: serial: f81232: fix incomplete serial port generation

[Johan Hovold <johan@kernel.org>]

On Tue, Mar 17, 2026 at 10:21:17AM +0800, PS10 PETER HONG 洪繼澤 wrote:
> Hi Stable Team,
> 
> I would like to request a backport for the following commit to the
> currently supported stable trees 6.1.y, 6.6.y, 6.12.y and 6.18.y
> 
>    cd644b805da8 ("USB: serial: f81232: fix incomplete serial port 
> generation")
> 
> Reason:
>    This patch fixes a stability issue where Fintek F81532A/534A/535/536
>    devices fail to initialize all serial ports during fast load/unload 
> cycles.
>    The fix involves a dummy read to clear the device's stale internal state.
> 
> The patch should apply cleanly to most recent stable branches.

My understanding was that this was only something you'd hit if you
unload and reload the driver which isn't something a user would normally
do. That's why I didn't add a stable tag.

The diff is a bit on the bigger side but it's all straight-forward
enough so I'm fine with backporting if you think it will be useful also
for older kernels.

Johan