linux-kernel - Re: [PATCH v2] drm/bochs: add edid present check

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Message-ID: <20181220083027.GF21184@phenom.ffwll.local>
Date:   Thu, 20 Dec 2018 09:30:27 +0100
From:   Daniel Vetter <daniel@...ll.ch>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, andr2000@...il.com,
        David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR BOCHS VIRTUAL GPU" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v2] drm/bochs: add edid present check

On Thu, Dec 20, 2018 at 09:28:26AM +0100, Daniel Vetter wrote:
> On Thu, Dec 20, 2018 at 07:50:01AM +0100, Gerd Hoffmann wrote:
> > Check first two header bytes before trying to read the edid blob,
> > to avoid the log being spammed in case qemu has no edid support (old
> > qemu or edid turned off).
> > 
> > Fixes: 01f23459cf drm/bochs: add edid support.
> > Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> 
> It's a bit a hack, but makes sense.

On 2nd thought, maybe make it less of a hack by reading all 8 bytes of the
header and checking it with drm_edit_is_valid().
-Daniel

> 
> Acked-by: Daniel Vetter <daniel.vetter@...ll.ch>
> > ---
> >  drivers/gpu/drm/bochs/bochs_hw.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/bochs/bochs_hw.c b/drivers/gpu/drm/bochs/bochs_hw.c
> > index c90a0d492f..e1f8ffce00 100644
> > --- a/drivers/gpu/drm/bochs/bochs_hw.c
> > +++ b/drivers/gpu/drm/bochs/bochs_hw.c
> > @@ -89,6 +89,14 @@ int bochs_hw_load_edid(struct bochs_device *bochs)
> >  	if (!bochs->mmio)
> >  		return -1;
> >  
> > +	/*
> > +	 * Check first two EDID blob header bytes to figure whenever
> > +	 * edid support is enabled in qemu.
> > +	 */
> > +	if (readb(bochs->mmio + 0) != 0x00 ||
> > +	    readb(bochs->mmio + 1) != 0xff)
> > +		return -1;
> > +
> >  	kfree(bochs->edid);
> >  	bochs->edid = drm_do_get_edid(&bochs->connector,
> >  				      bochs_get_edid_block, bochs);
> > -- 
> > 2.9.3
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@...ts.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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

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