linux-kernel - Re: [PATCH 06/21] fbcon: delete delayed loading code

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Message-ID: <YgJzQboE3VVj6OL7@phenom.ffwll.local>
Date:   Tue, 8 Feb 2022 14:42:25 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Sam Ravnborg <sam@...nborg.org>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        linux-fbdev@...r.kernel.org, Du Cheng <ducheng2@...il.com>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Claudio Suarez <cssk@...-c.es>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Helge Deller <deller@....de>
Subject: Re: [PATCH 06/21] fbcon: delete delayed loading code

On Thu, Feb 03, 2022 at 09:45:29PM +0100, Sam Ravnborg wrote:
> Hi Daniel,
> 
> On Mon, Jan 31, 2022 at 10:05:37PM +0100, Daniel Vetter wrote:
> > Before
> > 
> > commit 6104c37094e729f3d4ce65797002112735d49cd1
> > Author: Daniel Vetter <daniel.vetter@...ll.ch>
> > Date:   Tue Aug 1 17:32:07 2017 +0200
> > 
> >     fbcon: Make fbcon a built-time depency for fbdev
> > 
> > it was possible to load fbcon and fbdev drivers in any order, which
> > means that fbcon init had to handle the case where fbdev drivers where
> > already registered.
> > 
> > This is no longer possible, hence delete that code.
> > 
> > Note that the exit case is a bit more complex and will be done in a
> > separate patch.
> > 
> > Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> > Cc: Helge Deller <deller@....de>
> > Cc: Daniel Vetter <daniel@...ll.ch>
> > Cc: Claudio Suarez <cssk@...-c.es>
> > Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
> > Cc: Du Cheng <ducheng2@...il.com>
> > ---
> >  drivers/video/fbdev/core/fbcon.c | 13 +------------
> >  1 file changed, 1 insertion(+), 12 deletions(-)
> > 
> > diff --git a/drivers/video/fbdev/core/fbcon.c b/drivers/video/fbdev/core/fbcon.c
> > index 8f971de35885..814b648e8f09 100644
> > --- a/drivers/video/fbdev/core/fbcon.c
> > +++ b/drivers/video/fbdev/core/fbcon.c
> > @@ -942,7 +942,7 @@ static const char *fbcon_startup(void)
> >  		return display_desc;
> >  	/*
> >  	 * Instead of blindly using registered_fb[0], we use info_idx, set by
> > -	 * fb_console_init();
> > +	 * fbcon_fb_registered();
> >  	 */
> This comment change looks like it does not belong in this patch.
> Also, the comment is wrong as info_idx is set in several places.
> Like set_con2fb_map(), fbcon_remap_all(), and more.

Yeah I can split this out into a separate patch, but I spotted this wrong
comment as part of reviewing this code change here - essentially you have
to check how fb_info for fbcon are registered and fbcon init happens to
validate that deleting the below code is correct.

Ok if I put this explainer into the commit message, or do you want me to
split this out fully?
-Daniel

> 
> Though it is not set by fb_console_init - so partly OK.
> 
> With the comment adjustment dropped.
> Acked-by: Sam Ravnborg <sam@...nborg.org>
> 
> at least the code deletion looked OK, I failed to follow all the logic.
> So would be good if someone else could ack it too.
> 
> 	Sam
> 
> 
> 
> >  	info = registered_fb[info_idx];
> >  	if (!info)
> > @@ -3316,17 +3316,6 @@ static void fbcon_start(void)
> >  		return;
> >  	}
> >  #endif
> > -
> > -	if (num_registered_fb) {
> > -		int i;
> > -
> > -		for_each_registered_fb(i) {
> > -			info_idx = i;
> > -			break;
> > -		}
> > -
> > -		do_fbcon_takeover(0);
> > -	}
> >  }
> >  
> >  static void fbcon_exit(void)
> > -- 
> > 2.33.0

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch