-first thing to do is `#include <linux/i2c.h>" and "#include <linux/i2c-dev.h>.
-Yes, I know, you should never include kernel header files, but until glibc
-knows about i2c, there is not much choice.
+first thing to do is "#include <linux/i2c-dev.h>". Please note that
+there are two files named "i2c-dev.h" out there, one is distributed
+with the Linux kernel and is meant to be included from kernel
+driver code, the other one is distributed with lm_sensors and is
+meant to be included from user-space programs. You obviously want
+the second one here.