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

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Message-ID: <ZXcJr4VS_uGr_6TV@smile.fi.intel.com>
Date:   Mon, 11 Dec 2023 15:07:59 +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 Sat, Dec 09, 2023 at 12:47:47PM +0100, Lino Sanfilippo wrote:
> On 06.12.23 16:42, Lino Sanfilippo wrote:

> >>>> Crescent CY Hsieh (+cc) is in parallel trying to add an RS-422 mode bit
> >>>> to struct serial_rs485:
> >>>>
> >>>> https://lore.kernel.org/all/20231121095122.15948-1-crescentcy.hsieh@moxa.com/
> >>>>
> >>>
> >>> That new flag was suggested by me instead of using SER_RS422_ENABLED, which
> >>> would mostly be redundant to SER_RS485_ENABLED.
> 
> A cleaner solution would probably be to not handle RS422 with the RS485 settings at
> all, but to introduce another set of ioctls to set and read it.
> 
> An own RS422 structure like
> 
> struct serial_rs422 {
> 	__u32	flags;
> #define SER_RS422_ENABLED		(1 << 0)
> #define SER_RS422_TERMINATE_BUS		(1 << 1)
> };
> 
> 
> could be used as the parameter for these new ioctls.
> 
> Any comments on this?

I have (maybe not so constructive) a comment. Please, at all means try to not
extend the existing serial data structures, we have too many ones with too many
fields already. For user space, though, one may use unions and flags, but for
internal ones it might be better ways, I think.

-- 
With Best Regards,
Andy Shevchenko