I bought a M29F040B 4 Mib flash chip for my EPIA-V motherboard today in order to get LinuxBIOS on it, and found that flash_and_burn didn't support it. So, I got the datasheet and modified a copy of the M29F400BT driver to work with it.
I make no guarantees, of course, but it seems to Work For Me (TM), so I thought you might want to include it. I haven't managed to get LinuxBIOS working yet, though, but burning the original BIOS to it works and boots.
I'm attaching the patch as MIME.
Fredrik Tolf