I did my weekly system update about 13 hours ago and finally needed to reboot about 2 hours ago. After reboot, I had no X window for almost one hour before I finally found the problem.

At first, I only noticed:
No screens found.
Trying to read forums posts in a 80x24 console using elinks, do you have any idea how hard it is? And it didn't resolve the issue. I tried to downgrade xorg-server, but not xf86-video-ati, which is the actual cause.

I stumbled across the release announcement of version 7.0.0, it says
This is the first KMS only release.  Major changes:
- - Enable 2D tiling by default on r6xx+ asics
  (requires mesa 9.0+).  If you are planning to
  ship xf86-video-ati 7.x with an older version of
  mesa, please disable 2D tiling.
- - xserver 1.13 support including prime
- - glamor support
- - SI support
KMS (Kernel modesetting) only, finally, something makes sense with another message:
[    76.379] (II) [KMS] drm report modesetting isn't supported.
When you put two and two together, it's Eureka! I know my system has no KMS and this must be it, I knew it and I was right.

I re-emerged libdrm with USE flag libkms and rebuilt kernel for necessary changes. Be sure to have framebuffer part done correctly and have firmware installed if you have newer cards, or you will get black console.

After reboot, I can run X again. Somehow, X looks even more beautiful than ever.

You can imagine that I wondered why I didn't get any message from emerging 7.0.0, there should be a small note or an eselect news, but nothing. KMS-only, that's quite a big change.

I guess I am probably a few people who would have encountered this issue, now everyone probably has KMS enabled already. I had been late for many years. Finally, I have KMS, too.

One hour loss, well, not too bad. If anything ever happens again to X Window, I will have 210x65 (1680x1050) console, pretty! But let's hope it won't come to that.

2012-11-21T02:37:36Z: I just noticed that when I booted into X, the memory usage is only 48MB, used to be 72MB. Don't know if that's because of KMS or new X stuff updates.