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This is a fresh install of F7t4 updated to latest development packages. The hardware is an IBM Thinkpad T30. Using both the F7t4 kernel-2.6.20-1.3104.fc7 and current kernel-2.6.21-1.3116.fc7, the system doesn't "see" my battery. It did under F6, so after a short investigation I confirmed, that downgrading the kernel to kernel-2.6.20-1.2948.fc6 (latest from F6 updates) fixes the issue. Other laptop-centric functions like panel backlight control, suspending and hibernating, work. But the battery is totally absent, it doesn't even report the presence of a battery bay (I've seen a bug in Bugzilla about a battery bay present, but reported empty). This issue is critical for my work habits with this laptop. I guess majority of laptop users need battery state report (and this laptop doesn't have any external indicator of battery charge level, so I'm left with the OS telling me that). I'll attach dmesg from latest F6 and development kernels, you'll see different ACPI subsystem version and much more errors in the F7 one.
Created attachment 154384 [details] dmesg from the latest development kernel
Created attachment 154385 [details] dmesg from F6 kernel - battery detected and working
In case someone else searches for this, I'll set the summary to include the magic word :) The workaround, as I stated earlier, is to downgrade the kernel to the one from Fedora 6 updates. I have IDE devices, but things work anyhow thanks to labeled swap and all the magic.
Does the system have the latest BIOS installed? There is a problem with it. IBM usually provides two separate updates, one for the system BIOS and one for the Embedded Controller.
The BIOS is 2.01 (latest on ibm.com is 2.10) and the Embedded Controller Program is 1.02 (latest is 1.07). I don't have Windows nor FDD, so I guess there isn't a safe way to upgrade my BIOS. ThinkWiki recommends creating bootable CD-s from floppy images, which is unsupported, but I could do it, if only... not the dependency hell of the BIOS and ECP (BIOS 2.10 requires ECP 1.05, ECP 1.07 requires BIOS 2.08, so I can't upgrade to any of them and I don't know, which version is safe with my current version). Please, don't make me do it :) Even if the BIOS is buggy, please notice that under FC6 and under F7 with FC6 kernel, everything is perfectly working. So it is a regression, even if it's caused by some workaround or even a bug removed from the kernel (just a guess).
I've managed to get the BIOS updated with a professional help. You were right - it helped! Now there are no ACPI errors in dmesg and no problems with the battery (at least it seems), even on a 2.6.21 kernel. I still think some change in the kernel was for worse and should be fixed, but you can reject this as not being a bug, as now I'm not even able to check if it's fixed (because my new BIOS can't hit it).