linux-kernel - Re: [PATCH v9 5/6] serial: Support for RS-485 multipoint addresses

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Message-ID: <20220920112011.GA7187@wunner.de>
Date:   Tue, 20 Sep 2022 13:20:11 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
Cc:     linux-serial@...r.kernel.org, Greg KH <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>,
        Jonathan Corbet <corbet@....net>,
        Arnd Bergmann <arnd@...db.de>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>,
        Lino Sanfilippo <LinoSanfilippo@....de>,
        linux-api@...r.kernel.org
Subject: Re: [PATCH v9 5/6] serial: Support for RS-485 multipoint addresses

On Fri, Jun 24, 2022 at 11:42:09PM +0300, Ilpo Järvinen wrote:
> ADDRB in termios indicates 9th bit addressing mode is enabled. In this
> mode, 9th bit is used to indicate an address (byte) within the
> communication line. ADDRB can only be enabled/disabled through
> ->rs485_config() that is also responsible for setting the destination and
> receiver (filter) addresses.
[...]
> --- a/include/uapi/asm-generic/termbits-common.h
> +++ b/include/uapi/asm-generic/termbits-common.h
> @@ -46,6 +46,7 @@ typedef unsigned int	speed_t;
>  #define EXTA		B19200
>  #define EXTB		B38400
>  
> +#define ADDRB		0x20000000	/* address bit */
>  #define CMSPAR		0x40000000	/* mark or space (stick) parity */
>  #define CRTSCTS		0x80000000	/* flow control */
>

You may want to consider submitting a patch to the Linux man-pages
project to document the newly introduced bit:

https://www.kernel.org/doc/man-pages/patches.html
https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/man3/termios.3

Thanks,

Lukas