I check for Slackware updates once a week. Today I noticed a whole bunch of updates available, so I started the update process. Lots of new stuff, and it looks like a whole new build of the X system.
I rebooted after the update and then started X. Ugh. Graphics screen for a few moments, then back to the prompt. First step is to look in the logs for an issue - /var/log/Xorg.0.log.
This showed that X had received a segfault and had stopped.
Not good. This is my work computer, and I needed something running quickly. When this happened before, a rebuild of the config file would fix it. So I used "Xorg -configure" and used the new xorg.conf. Same problem. I tried the Slackware update on two laptops and they worked fine and X would start. This led me to believe that it was a issue with the specific video card I have. This machine is a Dell Optiplex 745 and it uses an ATI Radeon RV516 video card.
I needed something working quickly, so I thought about using framebuffer mode. I still have a Xorg.conf-vesa config file lying around in /etc/X11, although it dates back to 2007. I pulled that in, cleaned out old cruft, and it wouldn't even start grpahic mode. It complained about getting a screen but could find no matching nodes. Okay, that's a failure, so I abandoned framebuffer. Time to use Google.
This was a last resort, because... I had no X and a search of Google would be done in text mode. I fired up links, configured the proxy, and worked with Google. Eventually, I found someone else who had a similar problem, and found some suggestions to resolve it. I can't find that webpage again, because browsing in text mode is a difficult thing.
The main suggestion was that this was a known problem and it was mentioned in the Slackware update file CHANGES_AND_HINTS.TXT. That file said
If you have an ATI/AMD video chipset and are having trouble with Xorg, try enabled KMS to see if it makes a difference - some chipsets run better with it and some work better without it. To enabled KMS, use the following boot parameter as a lilo append: radeon.modeset=1 Alternatively, you can create /etc/modprobe.d/radeon.conf with the following contents: options radeon modeset=1
I have no idea what that means, but it was worth trying. I don't like using anything with lilo, so I chose the second option. I set my original xorg.conf back in place, then created /etc/modprobe.d/radeon.conf with "options radeon modeset=1" and rebooted and started X. Yay. It works. I dropped back out of X to the command line fiddled and then restarted X. This time I got a black and white striped screen with a non-moving mouse and the machine locked. I had to turn it off and on again to get anywhere. I experimented a little, and if I restart X I get a bad result. Never mind. At least now I can run X and get on with work.
I'm sure a newer version of the Radeon driver will come available and this problem will disappear. In the meantime, I have a way of getting on with work. And it doesn't affect my other laptops or computers as they don't have Radeon video.
One note: fonts are very different now. Smaller, slightly cleaner. I don't know if this is better or worse. I've been looking at inadequate fonts for so long they feel familiar now.