Re: [9front] displayport thinkpad x230 external monitor black screen

[qwx@sciops.net]

On Thu Mar 30 19:37:16 +0200 2023, unobe@cpan.org wrote:
> I have a TP x230 that has a displayport and vga socket.  I have an
> adapter from vga-to-hdmi (wиth а USB dongle for power) that works with
> an ultrawide LG, but the largest mode via VGA is 1920x1080.  Using the
> displayport to connect to the monitor shows a 2560x1080 mode, along
> with the same modes that are shown with the VGA adapter.  However,
> when trying to use any mode with the displayport directly, I just get
> a black screen.

Displayport not working is unfortunately a frequent issue for
sandybridge (x220) and above, possibly even from earlier generations.
I don't know what the issue is, it could be a lot of things, but
checking for a regression is a very good idea.  iirc x230 is among the
first models that were worked on.

> I reviewed the log for changes to igfx to see if I could pin down the commit
> that might be related, and the best I could come up with is 
>   6f63752d84254b470322fc028dce1c79f7443e3b
> back in May 2017 (almost 6 years ago). I reverted
> /sys/src/9/pc/vgaigfx.c to that commit to see
> if it would build, but unsurprisingly, it does not:
> 
> vgaigfx.c:18 structure not fully declared Pcidev
> vgaigfx.c:68 structure not fully declared Pcidev
> warning: vgaigfx.c:61 used and not set: gtt 
> vgaigfx.c:92 structure not fully declared Pcidev
> vgaigfx.c:92 structure not fully declared Pcidev
> vgaigfx.c:95 structure not fully declared Pcidev
> vgaigfx.c:95 structure not fully declared Pcidev
> vgaigfx.c:161 structure not fully declared Pcidev
> vgaigfx.c:214 name not declared: arrow

You won't get far by reverting just this one file, a lot of
system-wide changes have happened since; you'll have to also revert
the rest of the changes elsewhere.  I'd also go earlier and revert to
21570a47195d90b1dc2a3634d8042929543599d3.  Perhaps just use a separate
tree or something.

Hope this helps,
qwx