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Date:   Sat, 9 Dec 2023 12:24:48 +0100
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Subject: Re: [PATCH 1/2] dt-bindings: serial: rs485: add rs485-mux-gpios
 binding
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To:     Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc:     Christoph Niedermaier <cniedermaier@dh-electronics.com>,
        Lukas Wunner <lukas@wunner.de>,
        Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-serial@vger.kernel.org" <linux-serial@vger.kernel.org>,
        =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
        "brenda.streiff@ni.com" <brenda.streiff@ni.com>,
        Crescent CY Hsieh <crescentcy.hsieh@moxa.com>,
        Tomas Paukrt <tomaspaukrt@email.cz>
References: <20231120151056.148450-1-linux@rasmusvillemoes.dk>
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 <20231122145344.GA18949@wunner.de>
 <3b8548b1-b8a9-0c9e-4040-5cfda06a85c6@gmx.de>
 <ec66d25162de4cbc92720df1e7008fe8@dh-electronics.com>
 <5c140498-69e3-4187-8703-db0c41e7ca89@gmx.de>
 <ZXG8DI8diij72fBR@smile.fi.intel.com>
From:   Lino Sanfilippo <LinoSanfilippo@gmx.de>
In-Reply-To: <ZXG8DI8diij72fBR@smile.fi.intel.com>
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Precedence: bulk

Hi Andy,

On 07.12.23 13:35, Andy Shevchenko wrote:
> 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@gmx.de]
>>> Sent: Sunday, November 26, 2023 12:40 AM
>
> ...
>
>>> RS-485 (2-wire NO RX_DURING_TX): rs485->flags =3D SER_RS485_ENABLED|SE=
R_RS485_MODE_HALF_DUPLEX
>>> RS-485 (2-wire RX_DURING_TX):    rs485->flags =3D SER_RS485_ENABLED|SE=
R_RS485_MODE_HALF_DUPLEX|SER_RS485_RX_DURING_TX
>>
>> I think we can omit the SER_RS485_MODE_HALF_DUPLEX flag if we assume th=
at
>> a missing SER_RS485_MODE_FULL_DUPLEX means half duplex (i.e. controllin=
g
>> 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 d=
istros)
> on how they behave.
>

Until now the DUPLEX flags do not yet exist, so existing userspace applica=
tions are not
concerned. Christoph suggested to introduce two flags to distinguish betwe=
en
a FULL duplex and a half duplex RS485 mode. My point was that we  do not n=
eed the flag
for half duplex, since this would be the default.

BR,
Lino