Re: [PATCH v4 5/6] console: Introduce ->exit() callback

[Andy Shevchenko]

On Fri, Jan 31, 2020 at 10:31:54AM +0900, Sergey Senozhatsky wrote:
> On (20/01/30 17:25), Andy Shevchenko wrote:
> [..]
> > diff --git a/include/linux/console.h b/include/linux/console.h
> > index f33016b3a401..54759ad0c36b 100644
> > --- a/include/linux/console.h
> > +++ b/include/linux/console.h
> > @@ -148,6 +148,7 @@ struct console {
> >  	struct tty_driver *(*device)(struct console *, int *);
> >  	void	(*unblank)(void);
> >  	int	(*setup)(struct console *, char *);
> > +	void	(*exit)(struct console *);
> 

> Should console ->exit() be able to return an error code?

Let's do it!

> >  	int	(*match)(struct console *, char *name, int idx, char *options);
> >  	short	flags;
> >  	short	index;
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> > index 932345e6cd71..0117d4d92a8e 100644
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -2850,6 +2850,10 @@ int unregister_console(struct console *console)
> >  	console->flags &= ~CON_ENABLED;
> >  	console_unlock();
> >  	console_sysfs_notify();
> > +
> > +	if (!res && console->exit)
> > +		console->exit(console);
> > +
> >  	return res;
> >  }
> 
> I would probably push it a bit further (I posted this snippet in another
> thread). If console is not on the list then there is nothing for us to do
> and sysfs notify is pointless.

I didn't see post in the other thread, but I suppose that this snipped is
for patch 4 in the series, correct?

> 
> ---
> 
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 0117d4d92a8e..7116e421210b 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -2837,7 +2837,13 @@ int unregister_console(struct console *console)
>  		}
>  	}
>  
> -	if (!res && (console->flags & CON_EXTENDED))
> +	if (res) {
> +		console->flags &= ~CON_ENABLED;
> +		console_unlock();
> +		return res;
> +	}
> +
> +	if (console->flags & CON_EXTENDED)
>  		nr_ext_console_drivers--;
>  
>  	/*
> @@ -2851,7 +2857,7 @@ int unregister_console(struct console *console)
>  	console_unlock();
>  	console_sysfs_notify();
>  
> -	if (!res && console->exit)
> +	if (console->exit)

>  		console->exit(console);
>  
>  	return res;

...then something like

		return console->exit(console);

	return 0;

...or...

		res = console->exit(console);

Which one is preferable?

-- 
With Best Regards,
Andy Shevchenko