linux-kernel - Re: [PATCH 05/11] video/aperture: Only kick vgacon when the pdev is decoding vga

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Date:   Wed, 11 Jan 2023 17:55:18 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Thomas Zimmermann <tzimmermann@...e.de>
Cc:     Daniel Vetter <daniel.vetter@...ll.ch>,
        DRI Development <dri-devel@...ts.freedesktop.org>,
        linux-fbdev@...r.kernel.org,
        Intel Graphics Development <intel-gfx@...ts.freedesktop.org>,
        Javier Martinez Canillas <javierm@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Helge Deller <deller@....de>
Subject: Re: [PATCH 05/11] video/aperture: Only kick vgacon when the pdev is
 decoding vga

On Wed, Jan 11, 2023 at 05:03:02PM +0100, Thomas Zimmermann wrote:
> Hi
> 
> Am 11.01.23 um 16:41 schrieb Daniel Vetter:
> > Otherwise it's bit silly, and we might throw out the driver for the
> > screen the user is actually looking at. I haven't found a bug report
> > for this case yet, but we did get bug reports for the analog case
> > where we're throwing out the efifb driver.
> > 
> > References: https://bugzilla.kernel.org/show_bug.cgi?id=216303
> > Signed-off-by: Daniel Vetter <daniel.vetter@...el.com>
> > Cc: Thomas Zimmermann <tzimmermann@...e.de>
> > Cc: Javier Martinez Canillas <javierm@...hat.com>
> > Cc: Helge Deller <deller@....de>
> > Cc: linux-fbdev@...r.kernel.org
> > ---
> >   drivers/video/aperture.c | 3 +++
> >   1 file changed, 3 insertions(+)
> > 
> > diff --git a/drivers/video/aperture.c b/drivers/video/aperture.c
> > index 3d8c925c7365..6f351a58f6c6 100644
> > --- a/drivers/video/aperture.c
> > +++ b/drivers/video/aperture.c
> > @@ -341,6 +341,9 @@ int aperture_remove_conflicting_pci_devices(struct pci_dev *pdev, const char *na
> >   			return ret;
> >   	}
> > +	if (!primary)
> > +		return 0;
> > +
> 
> The original code from fbdev didn't do this, so this code didn't either.
> 
> It appears more to be a special case than an early-out branch. So can we
> write it as

Yeah I think this was a mistake going way back to when I added this to
i915 originally. It is a real change, but also I guess the people who have
machines without efifb or vesafb are ... really not many :-) Iirc you had
some very funny kernels going way back when vgacon was considered the only
safe choice to even hit this stuff.

> if (primary) {
>   // kick_vgacon
> }

Yeah, but next patch adds the vga aperture, and then I think it makes a
bit more sense.
-Daniel

> 
> ?
> 
> Best regards
> Thomas
> 
> >   	/*
> >   	 * WARNING: Apparently we must kick fbdev drivers before vgacon,
> >   	 * otherwise the vga fbdev driver falls over.
> 
> -- 
> Thomas Zimmermann
> Graphics Driver Developer
> SUSE Software Solutions Germany GmbH
> Maxfeldstr. 5, 90409 Nürnberg, Germany
> (HRB 36809, AG Nürnberg)
> Geschäftsführer: Ivo Totev




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