parse error before "Ioff_t"

I am writing a RFID device driver and encounter an compiling error below:

开发者_如何学JAVA[root@localhost kernel]# make modules
  CHK     include/linux/version.h
make[1]: `arch/arm/kernel/asm-offsets.s' is up to date.
make[1]: `include/asm-arm/mach-types.h' is up to date.
  CC [M]  drivers/char/gpio_led.o
  CC [M]  drivers/char/rf531_drv.o
drivers/char/rf531_drv.c:35: error: parse error before "Ioff_t"
drivers/char/rf531_drv.c:35: warning: function declaration isn't a prototype
drivers/char/rf531_drv.c:36: error: parse error before "Ioff_t"
drivers/char/rf531_drv.c:36: warning: function declaration isn't a prototype

Then I find the type Ioff_t is defined in $(srctree)/include/linux/types.h,so I added the #include header to the source code rf531_drv.c,but the error still there.Anyone had encountered this kind of problem? Could you give some suggestions and help?

That's loff_t with a lowercase "L", not Ioff_t.