Re: [gentoo-user] DRM error: couldn't read SADs

[Jack]

On 2018.02.12 19:57, Peter Humphrey wrote:
> On Sunday, 11 February 2018 05:41:28 GMT 80x24 wrote:
> > On Sun, Feb 11, 2018 at 12:47 AM,
> > Peter Humphrey <peter@××××××××××××.uk> wrote:
> > > [drm:dce_v11_0_afmt_setmode] *ERROR* Couldn't read SADs: 0
> > > [...]
> > > traps: plugin-containe[6833] general protection ip:7f0a2e1711b1
> > > sp:7fff6f64dc30 error:0 in ld-2.25.so[7f0a2e15c000+23000]
> > >
> > > What is a SAD (other than a seasonal affective disorder)? That
> library
> > > comes from glibc, of which I've had 5 versions or revisions in
> that time
> > /**
> >  * drm_edid_to_sad - extracts SADs from EDID
> >  * @edid: EDID to parse
> >  * @sads: pointer that will be set to the extracted SADs
> >  *
> >  * Looks for CEA EDID block and extracts SADs (Short Audio
> Descriptors)
> > fr$
> > *
> >  * Note: The returned pointer needs to be freed using kfree().
> >  *
> >  * Return: The number of found SADs or negative number on error.
> >  */
> >
> > Considering the term ``EDID'' and some audio related words, I think
> > it's reading some info from your monitor.
>
> Hmm. Interesting. Looks like I'll have to revise my screen setup.
> It's a
> Samsung LED device with HDMI input. This box outputs HDMI too, but
> the other
> boxes I use it on output DVI, so by piecemeal development I've ended
> up with
> a four-port DVI switch, all connected with adapter cables.
>
> It seems likely that EDID is getting lost, and I may now also have a
> reason
> for the washed-out appearance of the screen. Modern websites with
> their pale
> colours are hard to read. Even the green of KMail's quoted text is
> hard.
>
> The other boxes I mentioned can also output VGA, and the screen can
> accept
> VGA too and switch between inputs. So I just need a two-port VGA
> switch and
> some cables. I've not long since thrown out all the old VGA stuff -
> damn! I
> knew I should never throw anything away.

It's been a long time since I've needed to do it, and it was also due  
to a (cheap?) KVM switch, but I think there are two things that might  
help.  First, if you boot the PC with that monitor connected, it might  
actually read the EDID data.  Even if not, if you can capture it (one  
time use of a straigt DVI or VGA cable?) you can save it tp a file  
using x11-misc/read-edid, and then there is a way to get kernel/X to  
read that EDID file at startup instead of trying and failing to get it  
directly from the monitor.  If you can't find a reference, I'll dig and  
try to figure out if it's kernel paramater or xorg.conf that you need  
to mess with.

Jack