linux-kernel - Re: [PATCH v2 1/5] console: Don't perform test for CON

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Message-ID: <20200127024114.GC100275@google.com>
Date:   Mon, 27 Jan 2020 11:41:14 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Petr Mladek <pmladek@...e.com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] console: Don't perform test for CON_BRL flag twice

On (20/01/24 17:57), Andy Shevchenko wrote:
[..]
> +++ b/drivers/accessibility/braille/braille_console.c
> @@ -369,10 +369,10 @@ int braille_register_console(struct console *console, int index,
>  
>  int braille_unregister_console(struct console *console)
>  {
> -	if (braille_co != console)
> -		return -EINVAL;
>  	if (!(console->flags & CON_BRL))
>  		return 0;
> +	if (braille_co != console)
> +		return -EINVAL;
>  	unregister_keyboard_notifier(&keyboard_notifier_block);
>  	unregister_vt_notifier(&vt_notifier_block);
>  	braille_co = NULL;
> diff --git a/kernel/printk/braille.c b/kernel/printk/braille.c
> index 17a9591e54ff..2ec42173890f 100644
> --- a/kernel/printk/braille.c
> +++ b/kernel/printk/braille.c
> @@ -51,8 +51,5 @@ _braille_register_console(struct console *console, struct console_cmdline *c)
>  int
>  _braille_unregister_console(struct console *console)
>  {
> -	if (console->flags & CON_BRL)
> -		return braille_unregister_console(console);
> -
> -	return 0;
> +	return braille_unregister_console(console);
>  }

Hmm, I don't know. This moves sort of important code from common upper
layer down to particular driver implementation. Should there be another
driver/super-braille.c it must test CON_BRL flag as well.
Because printk invokes _braille_unregister_console() unconditionally,
and _braille_unregister_console() unconditionally calls into the driver.

I guess we can remove CON_BRL from braille_unregister_console() instead,
because printk tests it.

	-ss