As stated earlier, the driver is currently under development, and from what I can tell, only recently made it into the base kernel (2.6.14). Mandriva 2005 uses 2.6.11 (almost a year old). Mandriva 2006 (that I recently upgraded to) uses 2.6.12. Upgrading to the latest kernel from kernel.org can be done, but it isn't as trivial as installing one from Mandriva (or RedHat, SUSE, etc). Usually, distribution vendors will add their own patches (like supermount for Mandriva) that either are not currently in the base kernel, or probably will never make it to the main kernel.
If you want to try a newer kernel, the easiest way to configure it is to copy the /boot/config file to the kernel source tree and build based on your current configuration. There will be errors, though, due to changed features. To reduce the build time, you can edit the config file with "make xconfig" and unset the modules you don't need (ham radio support, isa sound cards, etc). Unfortunately, this is one of those area's that Linux hardware support is lacking due to no vender support. If you really need to read SD memory cards (urgent business need, etc), my only recommendation is to pick up an SD card reader that is either usb or pcmcia based. I have both a Sandisk 8 in 1 USB card reader and a pcmcia 4 in 1 card reader, and both work well with Linux (the latest Mandriva now properly detects card removal/insertion from the reader).
I wish I could help more. If I get time after the holiday, I'll experiment with integrating the 2.6.14 kernel with Mandriva's patches. Don't hold your breath, though. I'm still actively looking for a real job (helping on the foorum is very enriching, but not monitarily beneficial).
