linux-kernel - Re: [PATCH 1/2] dt-bindings: serial: rs485: add rs485-mux-gpios binding

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Message-ID: <ZXG8DI8diij72fBR@smile.fi.intel.com>
Date:   Thu, 7 Dec 2023 14:35:24 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Lino Sanfilippo <LinoSanfilippo@....de>
Cc:     Christoph Niedermaier <cniedermaier@...electronics.com>,
        Lukas Wunner <lukas@...ner.de>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        "brenda.streiff@...com" <brenda.streiff@...com>,
        Crescent CY Hsieh <crescentcy.hsieh@...a.com>,
        Tomas Paukrt <tomaspaukrt@...il.cz>
Subject: Re: [PATCH 1/2] dt-bindings: serial: rs485: add rs485-mux-gpios
 binding

On Wed, Dec 06, 2023 at 04:42:53PM +0100, Lino Sanfilippo wrote:
> On 27.11.23 13:14, Christoph Niedermaier wrote:
> > From: Lino Sanfilippo [mailto:LinoSanfilippo@....de]
> > Sent: Sunday, November 26, 2023 12:40 AM

...

> > RS-485 (2-wire NO RX_DURING_TX): rs485->flags = SER_RS485_ENABLED|SER_RS485_MODE_HALF_DUPLEX
> > RS-485 (2-wire RX_DURING_TX):    rs485->flags = SER_RS485_ENABLED|SER_RS485_MODE_HALF_DUPLEX|SER_RS485_RX_DURING_TX
> 
> I think we can omit the SER_RS485_MODE_HALF_DUPLEX flag if we assume that
> a missing SER_RS485_MODE_FULL_DUPLEX means half duplex (i.e. controlling
> the RTS line).

You should be very careful on these assumptions, i.e. one must to check _all_
existing user space tools (at least that are in use / supplied by main distros)
on how they behave.

-- 
With Best Regards,
Andy Shevchenko