The top-level sysfs hierarchy

sysfs contains:
/sys/block 
all about block devices
should be /sys/class/block
/sys/bus 
bus-oriented view of the system
includes driver information
/sys/cdev
char devices; may be removed
/sys/class
class-oriented system view
/sys/devices
the full device tree
/sys/firmware
for firmware downloads
/sys/power
power management