I was setting up a machine which has a MegaRAID SAS 8208ELP SATA/SAS raid controller. The stock gentoo-sources-2.6.34-r1 did not seem to recognize this chip.
I found a patch  which enables support for the chipset in the kernel. After applying this patch, the raid controller was recognized and seems to work. I've only tested one hard-drive in the bay so far, but it is recognized, mounts and checksum verifies on the existing files, and hot-swap works. A cursory test of suspend-to-ram suggests that works, too.
It seems next logical step is inclusion of this patch in gentoo-sources. Hence this bug.
Created attachment 236695 [details, diff]
Patch for gentoo-sources-2.6.34-r1 and probably others
Created attachment 236697 [details]
ebuild that applies patch to gentoo-sources-2.6.34-r1
patch has been rejected repeatedly by eric moore for inclusion in the kernel, since device id 0x59 is in use by megasr (megaraid driver) which is not included in the kernel. megasr supports "hardware" raid arrays created within controller bios, but no direct access to sata drives.
Created attachment 236721 [details, diff]
updated, more complete patch for 2.6.33 and newer
We ( as kernel team ) don't accept patches outside the Linux kernel tree. I will leave this bug open just for reference
Let us know if this or a similar patch gets accepted into the upstream kernel tree