workqueue: __WORK_INITIALIZER compiler warning - linux-kernel

Question

Just to learn, I try to compile an old device driver example on Ubuntu 14, and I get a warning.
I guess this warning is triggered because some inconsistency between the type returned from __WORK_INITIALIZER and the work_struct structure. What I don't understand is how that can happen. :)
This happens at row 19 in my file shortprint.c, at an include line that includes module.h according to the call stack shown below. So I guess that my code is irrelevant, this seems to be inside the linux include files. Am I right?
I'm running Ubuntu 14.04.
fredrik#fredrik-VirtualBox:~/Documents/lab8_3/shortprint$ make
make -C /lib/modules/3.13.0-45-generic/build M=/home/fredrik/Documents/lab8_3/shortprint modules
make[1]: Entering directory `/usr/src/linux-headers-3.13.0-45-generic'
CC [M] /home/fredrik/Documents/lab8_3/shortprint/shortprint.o
In file included from include/linux/srcu.h:34:0,
from include/linux/notifier.h:15,
from include/linux/memory_hotplug.h:6,
from include/linux/mmzone.h:801,
from include/linux/gfp.h:4,
from include/linux/kmod.h:22,
from include/linux/module.h:13,
from /home/fredrik/Documents/lab8_3/shortprint/shortprint.c:19:
include/linux/workqueue.h:172:9: warning: initialization from incompatible pointer type [enabled by default]
struct work_struct n = __WORK_INITIALIZER(n, f)
FWIW I also include my makefile:
# Comment/uncomment the following line to disable/enable debugging
#DEBUG = y
EXTRA_CFLAGS += -O2 -I..
ifneq ($(KERNELRELEASE),)
# call from kernel build system
obj-m := shortprint.o
else
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
endif
clean:
rm -rf *.o *~ core .depend .*.cmd *.ko *.mod.c .tmp_versions
depend .depend dep:
$(CC) $(CFLAGS) -M *.c > .depend
ifeq (.depend,$(wildcard .depend))
include .depend
endif
The corrected code. The function was of void short_do_work(void*) before the correction:
static void shortp_do_work(struct work_struct *work);
static DECLARE_WORK(shortp_work, shortp_do_work);

Answer 1

Your code is certainly relevant. The entire kernel uses these macros and somehow works, so I'd suspect the problem is in the way you call them. It would be an incompatible function pointer type passed to __WORK_INITIALIZER().
By the way, please use DECLARE_WORK() or INIT_WORK() if possible.
The function prototype for workers is
typedef void (*work_func_t)(struct work_struct *work);
Defined in include/linux/workqueue.h