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Linux module "Hello world" Makefile is missing something

Hi!

I'm trying to run a "make" on a basic Makefile I created for a "Hello world" linux module, however if I run "make" or "make clean" it fails to work. I have to write more stuff in order to make it work (redundant stuff cause I define that stuff in the Makefile).

First, the Makefile:

Code:

obj-m := helloworld.o



KDIR=/lib/modules/$(shell uname -r)/build

PWD=$(shell pwd)



all:

    make -C $(KDIR) M=$(PWD) modules



clean:

    make -C $(KDIR) M=$(PWD) clean

Now, see what happens when I call make directly:

Code:

$ make

make: Nothing to be done for `all'.

$ make clean

make: Nothing to be done for `clean'.

I have to duplicate what's in the Makefile for it to work:

Code:

$ make -C /lib/modules/$( uname -r )/build M=$PWD

make: Entering directory `/usr/src/linux-headers-2.6.35-22-generic'

  LD      /home/antoranz/projects/modexp/module/built-in.o

  CC [M]  /home/antoranz/projects/modexp/module/helloworld.o

  Building modules, stage 2.

  MODPOST 1 modules

  CC      /home/antoranz/projects/modexp/module/helloworld.mod.o

  LD [M]  /home/antoranz/projects/modexp/module/helloworld.ko

make: Leaving directory `/usr/src/linux-headers-2.6.35-22-generic'

$ make -C /lib/modules/$( uname -r )/build M=$PWD clean

make: Entering directory `/usr/src/linux-headers-2.6.35-22-generic'

  CLEAN  /home/antoranz/projects/modexp/module/.tmp_versions

  CLEAN  /home/antoranz/projects/modexp/module/Module.symvers /home/antoranz/projects/modexp/module/modules.order

make: Leaving directory `/usr/src/linux-headers-2.6.35-22-generic'

What am I doing wrong?

would you be invoking make from within a makefile? i would imagine you'de be invoking the compiler
here's an example makefile from Xcplay (i didn't write the makefile i just happened to have it on hand)

Code:

SHELL := /bin/sh



.SUFFIXES:

.SUFFIXES: .c .o



DESTDIR = 



prefix = /usr/local

bindir = $(prefix)/bin

srcdir = .



INSTALL = install

INSTALL_PROGRAM = $(INSTALL)



PROGRAM := xcplay

VERSION := 0.3.6

DISTFILES := $(PROGRAM).c Changelog COPYING INSTALL Makefile mkinstalldirs

DISTFILES += README TODO

DISTNAME := $(PROGRAM)-$(VERSION)



CFLAGS = -Wall -O2

XCPLAY_CFLAGS := $(shell xmms-config --cflags)

XCPLAY_LDFLAGS := $(shell xmms-config --libs) -lncurses -lpthread



all: $(PROGRAM)



$(PROGRAM).o: $(PROGRAM).c

        $(CC) -o $@ -c $< $(CFLAGS) $(XCPLAY_CFLAGS)



$(PROGRAM): $(PROGRAM).o

        $(CC) -o $@ $(LDFLAGS) $(XCPLAY_LDFLAGS) $<



installdirs: mkinstalldirs

        $(srcdir)/mkinstalldirs $(DESTDIR)$(bindir)



install: all installdirs

        $(INSTALL_PROGRAM) xcplay $(DESTDIR)$(bindir)



dist: clean

        mkdir dist

        mkdir dist/$(DISTNAME)

        $(foreach file, $(DISTFILES), cp -pR $(file) dist/$(DISTNAME)/;)

        tar -czf $(DISTNAME).tar.gz -C dist $(DISTNAME)

        chmod 644 $(PROGRAM)-$(VERSION).tar.gz

        rm -rf dist



clean:

        rm -rf $(PROGRAM) dist *.o *.tar.gz

Here is an example of a Makefile for a kernel module.

Now the important thing here to note is that the red dots shown below must be replaced by a TAB, replacing them by spaces will cause Makefile to malfunction.

Code:

obj-m += hello.o



all:

.......make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules



clean:

.......make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

With no file helloworld.c , the make command will reply :
" make: Nothing to be done for `all'. "

Example hello.c
http://www.cyberciti.biz/tips/compil...el-module.html

Code:

#include <linux/module.h>      /* Needed by all modules */

#include <linux/kernel.h>      /* Needed for KERN_INFO */

#include <linux/init.h>        /* Needed for the macros */



static int __init hello_start(void)

{

printk(KERN_INFO "Loading hello module...\n");

printk(KERN_INFO "Hello world\n");

return 0;

}



static void __exit hello_end(void)

{

printk(KERN_INFO "Goodbye Mr.\n");

}



module_init(hello_start);

module_exit(hello_end);

And the simple Makefile

Code:

 

obj-m    := hello.o



KDIR    := /lib/modules/$(shell uname -r)/build

PWD    := $(shell pwd)



default:

        $(MAKE) -C $(KDIR) SUBDIRS=$(PWD) modules

Now you will get a hello.ko created with 'make'.
http://www.captain.at/programming/kernel-2.6/
..

@anishakaul: The tabs made it work. Thanks!

Also replacing make for $(MAKE) looks very elegant:

Code:

obj-m := helloworld.o



KDIR=/lib/modules/$(shell uname -r)/build

PWD=$(shell pwd)



all:

        $(MAKE) -C $(KDIR) M=$(PWD) modules



clean:

        $(MAKE) -C $(KDIR) M=$(PWD) clean

Quote:

Originally Posted by eantoranz (Post 4170740)

@anishakaul: The tabs made it work. Thanks!

I am happy that I could help you :)