The mailing list discussion was started by a user interested in having LM_Sensors support for his ATI hardware. Hans de Goede, an LM_Sensors contributor, then responded that on at least some graphics cards the hardware monitoring IC is on the Radeon multimedia i2c channel. LM_Sensors doesn't yet have a driver supporting the Radeon multimedia i2c channel as with some hardware (the ATI All-In-Wonder was named) this channel is also used by the graphics card.
Kernel mode-setting though will actually come to the rescue now with the mode-setting being in-kernel and eliminating the need for any user-space component to be tapping the registers. The way now to support this i2c channel is by exposing it in the DRM driver and the LM_Sensors should recognize the hardware monitoring adapter.
Following the message from Hans, David Airlie (a Red Hat employee, xf86-video-ati developer, and the kernel's DRM maintainer) chimed in that fellow Red Hat employee Matthew Garrett is currently looking at adding this support.
The LM_Sensors support isn't here yet, but we'll be sure to write about it when it arrives.