linux-kernel - Re: [PATCH] serial: core: Add sysfs links for serial core port instances for ttys

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Message-ID: <ZLd1uCKoGMBruwiN@smile.fi.intel.com>
Date:   Wed, 19 Jul 2023 08:33:44 +0300
From:   Andy Shevchenko <andriy.shevchenko@...el.com>
To:     Tony Lindgren <tony@...mide.com>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jirislaby@...nel.org>, Dhruva Gole <d-gole@...com>,
        Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
        John Ogness <john.ogness@...utronix.de>,
        Johan Hovold <johan@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-omap@...r.kernel.org, linux-serial@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serial: core: Add sysfs links for serial core port
 instances for ttys

On Wed, Jul 19, 2023 at 08:16:11AM +0300, Tony Lindgren wrote:
> Let's allow the userspace to find out the tty name for a serial core
> controller id if a tty exists. This can be done with:
> 
> $ grep DEVNAME /sys/bus/serial-base/devices/port*/tty/uevent
> /sys/bus/serial-base/devices/port.00:04.0/tty/uevent:DEVNAME=ttyS0
> /sys/bus/serial-base/devices/port.serial8250.1/tty/uevent:DEVNAME=ttyS1
> /sys/bus/serial-base/devices/port.serial8250.2/tty/uevent:DEVNAME=ttyS2
> /sys/bus/serial-base/devices/port.serial8250.3/tty/uevent:DEVNAME=ttyS3

What part is the controller ID here?

We also have something in procfs (I don't remember what info exactly is there).

> And with this, we can add /dev/serial/by-id symlinks to the serial port
> device instances so we can start using serial core port addressing in
> addition to the legacy ttyS naming.
> 
> The naming we can use is dev_name:0.0 where 0.0 are the serial core
> controller id and port id, so for the ttyS0 example above the naming
> would be 00:04.0:0.0.

This is interesting idea. But any hint why it can be useful?

-- 
With Best Regards,
Andy Shevchenko