This code, which is dependent upon the just-proposed TTM memory manager, places the video mode-setting into the Linux kernel and trails the Intel KMS driver, which entered the Linux 2.6.29 kernel. Until things are stabilized, Jerome is looking at tagging the Radeon KMS code as a "staging driver" until Linux 2.6.32 when it has undergone further tests. In his mailing list message, he notes there may be a security issue with the memory management and the ABI may not be stabilized either.
Right now this kernel mode-setting driver supports ATI hardware up through the R500 (X1000 series), while work is currently underway on bringing up this support in the newer R600 and R700 series. In the next few days we will hopefully be able to report that both the TTM and Radeon KMS code has entered the mainline Linux kernel for inclusion in 2.6.31.