linux-kernel - Re: [PATCH v3 4/5] console: Avoid positive return code from unregister

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Date:   Tue, 28 Jan 2020 11:22:35 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.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 v3 4/5] console: Avoid positive return code from
 unregister_console()

On Tue, Jan 28, 2020 at 01:43:32PM +0900, Sergey Senozhatsky wrote:
> On (20/01/27 13:47), Andy Shevchenko wrote:
> [..]
> >  	res = _braille_unregister_console(console);
> > -	if (res)
> > +	if (res < 0)
> >  		return res;
> > +	if (res > 0)
> > +		return 0;
> >  
> > -	res = 1;
> > +	res = -ENODEV;
> >  	console_lock();
> >  	if (console_drivers == console) {
> >  		console_drivers=console->next;
> > @@ -2838,6 +2840,9 @@ int unregister_console(struct console *console)
> >  	if (!res && (console->flags & CON_EXTENDED))
> >  		nr_ext_console_drivers--;
> >  
> > +	if (res && !(console->flags & CON_ENABLED))
> > +		res = 0;
> 
> Console is not on the console_drivers list. Why does !ENABLED case
> require extra handling?

It's mirroring (to some extend) the register_console() abort conditions.

> What about the case when console is ENABLED
> but still not registered?

What about when console is ENABLED and we call register_console()?
I think you can tell me what to do in these corner cases (however,
that's not the point of this series).

> I think that if the console is not on the list (was never registered)
> then we can just bail out, without console_sysfs_notify(), etc. IOW,
> 
> 	if (res) {
> 		console->flags &= ~CON_ENABLED; /* just in case */
> 		console_unlock();
> 		return res;
> 	}

Perhaps. But see above. I would rather drop this condition for now
for sake of this series being to the point.

-- 
With Best Regards,
Andy Shevchenko