Getting a block from a block device?

Hallo everyone, could someone please give me a hint on how to get a block (e.g. 512 bytes) from a block device from a kernel module? What .txt should I consult? Which headerfiles must I include? Where can I find the required function's definitions? In userspace I used fopen() with the device path as filename, I bet it isn't that easy in kernel mode. I am using kernel sources from gentoo: 3.0.6-gentoo, but I can use vanilla if it really helps. thanks, Dan -- Dan Luedtke http://www.danrl.de