"dev" is a poor name for something scoped this widely.  One missing "static" and this goes quite horribly wrong when the linker merges all of the "dev"s into the same symbol.  This pattern has caused difficult to debug issues in the past.

I realize this isn't new to this file and that the same issue is in the mpu6000 driver.  Feel free to change this in a subsequent pull request but it really should be changed.