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

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Message-ID: <CA+=Fv5RadC05i29h_geUq3Moyn3hGydoRu335T-q9vnfcwZqew@mail.gmail.com>
Date: Thu, 20 Feb 2025 22:48:59 +0100
From: Magnus Lindholm <linmag7@...il.com>
To: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
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()

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?


Tested-by: Magnus Lindholm <linmag7@...il.com>




On Thu, Feb 20, 2025 at 12:22 PM Jiri Slaby (SUSE) <jirislaby@...nel.org> wrote:
>
> The value returned from srmcons_init() was -ENODEV for over 2 decades.
> But it does not matter, given device_initcall() ignores retvals.
>
> But to be honest, return 0 in case the tty driver was registered
> properly.
>
> To do that, the condition is inverted and a short path taken in case of
> error.
>
> err_free_drv is introduced as it will be used from more places later.
>
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
> Cc: Richard Henderson <richard.henderson@...aro.org>
> Cc: Matt Turner <mattst88@...il.com>
> Cc: linux-alpha@...r.kernel.org
> ---
>  arch/alpha/kernel/srmcons.c | 62 ++++++++++++++++++++-----------------
>  1 file changed, 33 insertions(+), 29 deletions(-)
>
> diff --git a/arch/alpha/kernel/srmcons.c b/arch/alpha/kernel/srmcons.c
> index 3e61073f4b30..b9cd364e814e 100644
> --- a/arch/alpha/kernel/srmcons.c
> +++ b/arch/alpha/kernel/srmcons.c
> @@ -196,40 +196,44 @@ static const struct tty_operations srmcons_ops = {
>  static int __init
>  srmcons_init(void)
>  {
> +       struct tty_driver *driver;
> +       int err;
> +
>         timer_setup(&srmcons_singleton.timer, srmcons_receive_chars, 0);
> -       if (srm_is_registered_console) {
> -               struct tty_driver *driver;
> -               int err;
> -
> -               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);
> -               err = tty_register_driver(driver);
> -               if (err) {
> -                       tty_driver_kref_put(driver);
> -                       tty_port_destroy(&srmcons_singleton.port);
> -                       return err;
> -               }
> -               srmcons_driver = driver;
> -       }
>
> -       return -ENODEV;
> +       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);
> +       err = tty_register_driver(driver);
> +       if (err)
> +               goto err_free_drv;
> +
> +       srmcons_driver = driver;
> +
> +       return 0;
> +err_free_drv:
> +       tty_driver_kref_put(driver);
> +       tty_port_destroy(&srmcons_singleton.port);
> +
> +       return err;
>  }
>  device_initcall(srmcons_init);
>
> -
>  /*
>   * The console driver
>   */
> --
> 2.48.1
>
>