Re: [PATCH v3] fbcon: Silence fbcon logo on 'quiet' boots

[Petr Mladek <pmladek@suse.com>]

On Thu 2018-12-20 17:31:57, Bartlomiej Zolnierkiewicz wrote:
> 
> [ added Petr & Sergey to Cc: ]
> 
> Hi,
> 
> On 10/30/2018 04:44 PM, Prarit Bhargava wrote:
> > On text-based systems the 'quiet' boot option will show printk levels
> > higher than CONSOLE_LOGLEVEL_QUIET.  The displaying of the Tux logo
> > during boot can cause some consoles to lose display data and as a result
> > confuse the end user.
> > 
> > Do not display the Tux logo on systems that are in 'quiet' boot.
> > 
> > v2: It helps to commit all my changes before sending them.  Remove extra
> > bracket.
> > v3: buildbot error fix: fbcon can be built as part of a module so export console_printk
> > 
> > Signed-off-by: Prarit Bhargava <prarit@redhat.com>
> > Cc: Hans de Goede <hdegoede@redhat.com>
> > Cc: Marko Myllynen <myllynen@redhat.com>
> > Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
> > Cc: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> > Cc: Kees Cook <keescook@chromium.org>
> > Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> > Cc: Thierry Reding <treding@nvidia.com>
> > Cc: Yisheng Xie <ysxie@foxmail.com>
> > Cc: dri-devel@lists.freedesktop.org
> > ---
> >  drivers/video/fbdev/core/fbcon.c | 13 ++++++++-----
> >  kernel/printk/printk.c           |  1 +
> >  2 files changed, 9 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > index 8958ccc8b1ac..08e092eaf45c 100644
> > --- a/drivers/video/fbdev/core/fbcon.c
> > +++ b/drivers/video/fbdev/core/fbcon.c
> > @@ -649,11 +649,14 @@ static void fbcon_prepare_logo(struct vc_data *vc, struct fb_info *info,
> >  		kfree(save);
> >  	}
> >  
> > +	if (logo_shown = FBCON_LOGO_DONTSHOW)
> > +		return;
> > +
> >  	if (logo_lines > vc->vc_bottom) {
> >  		logo_shown = FBCON_LOGO_CANSHOW;
> >  		printk(KERN_INFO
> >  		       "fbcon_init: disable boot-logo (boot-logo bigger than screen).\n");
> > -	} else if (logo_shown != FBCON_LOGO_DONTSHOW) {
> > +	} else {
> >  		logo_shown = FBCON_LOGO_DRAW;
> >  		vc->vc_top = logo_lines;
> >  	}
> > @@ -1051,7 +1054,7 @@ static void fbcon_init(struct vc_data *vc, int init)
> >  	struct vc_data **default_mode = vc->vc_display_fg;
> >  	struct vc_data *svc = *default_mode;
> >  	struct display *t, *p = &fb_display[vc->vc_num];
> > -	int logo = 1, new_rows, new_cols, rows, cols, charcnt = 256;
> > +	int new_rows, new_cols, rows, cols, charcnt = 256;
> >  	int cap, ret;
> >  
> >  	if (info_idx = -1 || info = NULL)
> > @@ -1059,9 +1062,9 @@ static void fbcon_init(struct vc_data *vc, int init)
> >  
> >  	cap = info->flags;
> >  
> > -	if (vc != svc || logo_shown = FBCON_LOGO_DONTSHOW ||
> > +	if (vc != svc || console_loglevel <= CONSOLE_LOGLEVEL_QUIET ||
> >  	    (info->fix.type = FB_TYPE_TEXT))
> > -		logo = 0;
> > +		logo_shown = FBCON_LOGO_DONTSHOW;
> 
> "logo" variable removal is an unrelated change which actually
> changes the code behavior ("logo_shown" will be now modified
> also for "vc != svc" and "info->fix.type = FB_TYPE_TEXT" cases).
> 
> Please either drop it or explain in the patch description why
> it is a safe thing to do.

Good question! I am not familiar with fbcon code but it seems
that there might be more instances and they share the behavior
via this variable.

Note that console_loglevel might get modified at anytime. What if
the first fbcon was initialized with a different loglevel?


> >  	if (var_to_display(p, &info->var, info))
> >  		return;
> > @@ -1176,7 +1179,7 @@ static void fbcon_init(struct vc_data *vc, int init)
> >  	} else
> >  		vc_resize(vc, new_cols, new_rows);
> >  
> > -	if (logo)
> > +	if (logo_shown != FBCON_LOGO_DONTSHOW)
> >  		fbcon_prepare_logo(vc, info, cols, rows, new_cols, new_rows);
> >  
> >  	if (vc = svc && softback_buf)
> > diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> > index b77150ad1965..391e390feac9 100644
> > --- a/kernel/printk/printk.c
> > +++ b/kernel/printk/printk.c
> > @@ -66,6 +66,7 @@ int console_printk[4] = {
> >  	CONSOLE_LOGLEVEL_MIN,		/* minimum_console_loglevel */
> >  	CONSOLE_LOGLEVEL_DEFAULT,	/* default_console_loglevel */
> >  };
> > +EXPORT_SYMBOL(console_printk);
> 
> You need printk Maintainers Ack on it.

I am fine with the added export (as a printk maintainer).

Best Regards,
Petr