linux-kernel - Re: [PATCH v1 31/31] serial: 8250_mxpcie: add RS485-2W auto-adjust sysfs control

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Message-ID: <aTJtEmUycXeGrYPJ@moxa-ThinkCentre-M90t>
Date: Fri, 5 Dec 2025 13:26:42 +0800
From: Crescent Hsieh <crescentcy.hsieh@...a.com>
To: Andy Shevchenko <andy.shevchenko@...il.com>
Cc: gregkh@...uxfoundation.org, jirislaby@...nel.org,
	ilpo.jarvinen@...ux.intel.com, linux-kernel@...r.kernel.org,
	linux-serial@...r.kernel.org
Subject: Re: [PATCH v1 31/31] serial: 8250_mxpcie: add RS485-2W auto-adjust
 sysfs control

On Wed, Dec 03, 2025 at 11:24:58AM +0200, Andy Shevchenko wrote:
> On Wed, Dec 3, 2025 at 4:56 AM Crescent Hsieh <crescentcy.hsieh@...a.com> wrote:
> > On Mon, Dec 01, 2025 at 04:45:58AM +0200, Andy Shevchenko wrote:
> > > On Sun, Nov 30, 2025 at 12:46 PM Crescent Hsieh
> > > <crescentcy.hsieh@...a.com> wrote:
> 
> ...
> 
> > > I'm not going to review this, the patch series is already quite big. I
> > > suggest you to start from the small things in a different series E.g.,
> > > the first series is just converting MOXA from custom to 8250-based
> > > (assuming all features are kept working while ABI is being broken,
> 
> In case you are wondering what I was talking about in the above, I
> meant move from /dev/ttyMIxx to /dev/ttySxx. This will break all the
> current kernel command lines and hence setups with the explicit
> mention of the /dev/ttyMIxx, such as console=.  There might be other
> breakages, but I leave it up to you to research and come up with a
> solution.

Just to clarify my intention: the in-tree UPCI serial driver (mxser) has
been unmaintained for years, and my goal is to replace it with a clean
8250-based implementation that preserves reasonable user expectations
while following the upstream serial framework. This will require some
analysis to reconcile the legacy behavior with what upstream expects.

I’d also like to ask about patch ordering. Since the PCIe serial driver
is much simpler to migrate and has minimal user impact, would it be
acceptable to upstream the PCIe conversion first, before the more
complex UPCI transition? I’m happy to follow whichever order makes
review easiest for you.

---
Sincerely,
Crescent Hsieh