linux-kernel - Re: [PATCH 20/29] tty: srmcons: fix retval from srmcons

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Message-ID: <6e5ee9a3-f3fa-413e-b8cc-2fdfa8537590@kernel.org>
Date: Fri, 21 Feb 2025 08:53:34 +0100
From: Jiri Slaby <jirislaby@...nel.org>
To: Magnus Lindholm <linmag7@...il.com>
Cc: gregkh@...uxfoundation.org, linux-serial@...r.kernel.org,
 linux-kernel@...r.kernel.org,
 Richard Henderson <richard.henderson@...aro.org>,
 Matt Turner <mattst88@...il.com>, linux-alpha@...r.kernel.org
Subject: Re: [PATCH 20/29] tty: srmcons: fix retval from srmcons_init()

On 20. 02. 25, 22:48, Magnus Lindholm wrote:
> I've applied and verified this patch on an Alphaserver ES40 with
> serial console.
> 
> Regarding the future use of label err_free_drv, is the intention to
> use it to break out early if tty_alloc_driver() fails?

...

>> +       if (!srm_is_registered_console)
>> +               return -ENODEV;
>> +
>> +       driver = tty_alloc_driver(MAX_SRM_CONSOLE_DEVICES, 0);
>> +       if (IS_ERR(driver))
>> +               return PTR_ERR(driver);
>> +
>> +       tty_port_init(&srmcons_singleton.port);
>> +
>> +       driver->driver_name = "srm";
>> +       driver->name = "srm";
>> +       driver->major = 0;      /* dynamic */
>> +       driver->minor_start = 0;
>> +       driver->type = TTY_DRIVER_TYPE_SYSTEM;
>> +       driver->subtype = SYSTEM_TYPE_SYSCONS;
>> +       driver->init_termios = tty_std_termios;
>> +       tty_set_operations(driver, &srmcons_ops);
>> +       tty_port_link_device(&srmcons_singleton.port, driver, 0);

I plan on removing tty_port_link_device() as it was a temporary aid. 
Yay, for 13 years! (commit 2cb4ca0208722).

>> +       err = tty_register_driver(driver);
>> +       if (err)
>> +               goto err_free_drv;

Instead, the idea is to properly tty_port_register_device() after 
tty_register_driver() instead. And that can fail. So is fail path reuses 
err_free_drv (and adds tty_unregister_driver() on top).

>> +
>> +       srmcons_driver = driver;
>> +
>> +       return 0;
>> +err_free_drv:
>> +       tty_driver_kref_put(driver);
>> +       tty_port_destroy(&srmcons_singleton.port);
>> +
>> +       return err;

thanks,
-- 
js
suse labs