makefile

makefile

[David kiarie]

Hi everybody,
I currently started learning how to write Linux drivers.I am following
Linux Device Drivers Third Edition.
I have everything set right but the makefile provided seem not to work.I am
familiar with makefiles but the kernel build system confuses me
Here is the makefile:

# If KERNELRELEASE is defined, we've been invoked from the
# kernel build system and can use its language.
ifneq ($(KERNELRELEASE),)
obj-m := hello.o
# Otherwise we were called directly from the command
# line; invoke the kernel build system.
else
KERNELDIR ?= /lib/modules/$(shell uname -r)/build
PWD := $(shell pwd)
default:
$(MAKE) -C $(KERNELDIR) M=$(PWD) modules
endif
It give the following output when I run make :

make: Nothing to be done for `default'.
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makefile

[Greg Freemyer]

On Tue, Jul 2, 2013 at 9:07 AM, David kiarie <davidkiarie4@gmail.com> wrote:
> Hi everybody,
> I currently started learning how to write Linux drivers.I am following Linux
> Device Drivers Third Edition.
> I have everything set right but the makefile provided seem not to work.I am
> familiar with makefiles but the kernel build system confuses me
> Here is the makefile:
>
> # If KERNELRELEASE is defined, we've been invoked from the
> # kernel build system and can use its language.
> ifneq ($(KERNELRELEASE),)
> obj-m := hello.o
> # Otherwise we were called directly from the command
> # line; invoke the kernel build system.
> else
> KERNELDIR ?= /lib/modules/$(shell uname -r)/build
> PWD := $(shell pwd)
> default:
> $(MAKE) -C $(KERNELDIR) M=$(PWD) modules
> endif
> It give the following output when I run make :
>
> make: Nothing to be done for `default'.

I guess you see ifneq($(KERNELRELEASE),).  And you see that the
"default:" statement is in the else clause of the if.

Thus I am guessing that you are invoking the makefile by hand and you
have the KERNELRELEASE variable set.

The logic used above requires KERNELRELEASE _not_ be defined when
manually invoking the makefile.  It should _only_ be set when invoked
by the kernel's overall build system which will set it internally.

Greg

makefile

[Rajat Sharma]

On Tue, Jul 2, 2013 at 6:37 PM, David kiarie <davidkiarie4@gmail.com> wrote:
> Hi everybody,
> I currently started learning how to write Linux drivers.I am following Linux
> Device Drivers Third Edition.
> I have everything set right but the makefile provided seem not to work.I am
> familiar with makefiles but the kernel build system confuses me
> Here is the makefile:
>
> # If KERNELRELEASE is defined, we've been invoked from the
> # kernel build system and can use its language.
> ifneq ($(KERNELRELEASE),)
> obj-m := hello.o
> # Otherwise we were called directly from the command
> # line; invoke the kernel build system.
> else
> KERNELDIR ?= /lib/modules/$(shell uname -r)/build
> PWD := $(shell pwd)
> default:
> $(MAKE) -C $(KERNELDIR) M=$(PWD) modules

Press a tab here just before $(MAKE) and remember your editor (e.g.
vim) should not have setting to convert tabs into spaces. Makefile
strictly requires a tab. You must be knowing all these already since
you are familiar with Makefiles.

> endif
> It give the following output when I run make :
>
> make: Nothing to be done for `default'.
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>

-Rajat

makefile

[Srinivas Ganji]

Hi David,

As Rajat said, we need to give TAB space before an executable command in
the Makefile. However, here is the simple Makefile, for your reference.

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

obj-m:=hello.o

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

I hope this helps to you.

Regards,
Srinivas



On Tue, Jul 2, 2013 at 6:37 PM, David kiarie <davidkiarie4@gmail.com> wrote:

> Hi everybody,
> I currently started learning how to write Linux drivers.I am following
> Linux Device Drivers Third Edition.
> I have everything set right but the makefile provided seem not to work.I
> am familiar with makefiles but the kernel build system confuses me
> Here is the makefile:
>
> # If KERNELRELEASE is defined, we've been invoked from the
> # kernel build system and can use its language.
> ifneq ($(KERNELRELEASE),)
> obj-m := hello.o
> # Otherwise we were called directly from the command
> # line; invoke the kernel build system.
> else
> KERNELDIR ?= /lib/modules/$(shell uname -r)/build
> PWD := $(shell pwd)
> default:
> $(MAKE) -C $(KERNELDIR) M=$(PWD) modules
> endif
> It give the following output when I run make :
>
> make: Nothing to be done for `default'.
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>
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