Problem in First-Patch-Tutorial

[Alexander Kapshuk]

On Mon, Mar 13, 2017 at 12:08 PM, SIMRAN SINGHAL
<singhalsimran0 at gmail.com> wrote:
> On Mon, Mar 13, 2017 at 1:05 PM, Greg KH <greg at kroah.com> wrote:
>> On Mon, Mar 13, 2017 at 11:39:36AM +0530, SIMRAN SINGHAL wrote:
>>> On Mon, Mar 13, 2017 at 10:42 AM, Alexander Kapshuk
>>> <alexander.kapshuk at gmail.com> wrote:
>>> > On Mon, Mar 13, 2017 at 6:18 AM, SIMRAN SINGHAL
>>> > <singhalsimran0 at gmail.com> wrote:
>>> >> On Mon, Mar 13, 2017 at 12:05 AM, Alexander Kapshuk
>>> >> <alexander.kapshuk at gmail.com> wrote:
>>> >>> On Sun, Mar 12, 2017 at 8:20 PM, SIMRAN SINGHAL
>>> >>> <singhalsimran0 at gmail.com> wrote:
>>> >>>> On Sun, Mar 12, 2017 at 10:15 PM, Alexander Kapshuk
>>> >>>> <alexander.kapshuk at gmail.com> wrote:
>>> >>>>> On Sun, Mar 12, 2017 at 5:34 PM,  <valdis.kletnieks at vt.edu> wrote:
>>> >>>>>> On Sun, 12 Mar 2017 15:49:31 +0200, Alexander Kapshuk said:
>>> >>>>>>
>>> >>>>>>> Are these drivers, drivers/iio/dummy/{iio_dummy_evgen,iio_dummy}.ko,
>>> >>>>>>> something of your own making, as I'm not seeing them in the kernel
>>> >>>>>>> source tree?
>>> >>>>>>>
>>> >>>>>>> The 'modules_install' make target installs drivers that have been
>>> >>>>>>> compiled as modules as opposed to those compiled into the kernel, into
>>> >>>>>>> /lib/modules/`uname -r`. For your own modules added to the kernel
>>> >>>>>>> source tree, or built out-of-tree, that would involve putting
>>> >>>>>>> appropriate entries into  Kconfig and/or Makefiles.
>>> >>>>>>>
>>> >>>>>>> Modeprobe expects your module to be found in /lib/modules/`uname -r`.
>>> >>>>>>> Otherwise, your module won't get loaded.
>>> >>>>>>
>>> >>>>>> One other thing to remember is that although 'make modules_install' will
>>> >>>>>> take all the .ko files from in-tree modules and put them in their proper
>>> >>>>>> place in /lib/modules/`uname-r`  and then run 'depmod', many out-of-tree
>>> >>>>>> Makefiles manage to forget to do that last step.
>>> >>>>>>
>>> >>>>>> modprobe is a wrapper around insmod - and the file produced by 'depmod'
>>> >>>>>> are what the wrapper uses to find the module.
>>> >>>>>
>>> >>>>> Thanks for elaborating on that.
>>> >>>>
>>> >>>> Still not working
>>> >>>>
>>> >>>> First I executed following commands:-
>>> >>>>
>>> >>>> $ make drivers/iio/dummy/iio_dummy_evgen.ko
>>> >>>> $ make drivers/iio/dummy/iio_dummy.ko
>>> >>>>
>>> >>>> Above commands executed successfully
>>> >>>>
>>> >>>> Then I run following command:
>>> >>>> $ insmod iio_dummy_evgen.ko
>>> >>>>
>>> >>>> Getting following error:
>>> >>>> insmod: ERROR: could not load module iio_dummy_evgen.ko: No such file
>>> >>>> or directory
>>> >>>>
>>> >>>> And, then I try executing them from driver/staging/dummy and then I
>>> >>>> got this error:
>>> >>>> insmod: ERROR: could not insert module iio_dummy_evgen.ko: Operation
>>> >>>> not permitted
>>> >>>
>>> >>> You have to run insmod as user root. Either specify the full path to
>>> >>> your module, or cd into the directory where the module is and run
>>> >>> insmod from there.
>>> >>
>>> >> I tried this before also but as you said I tried it again:
>>> >> # insmod iio_dummy_evgen.ko
>>> >> insmod: ERROR: could not insert module iio_dummy_evgen.ko: Invalid module format
>>> >>
>>> >> Now, I am getting this error.
>>> >
>>> > Sounds like your kernel module has been compiled for kernel sources
>>> > whose version is different to the version of the kernel you are trying
>>> > to load your module into.
>>> >
>>> > See http://www.tldp.org/LDP/lkmpg/2.6/html/x380.html for details.
>>> >
>>> > In other words, the version output by 'uname -r' must match the
>>> > version output by 'modinfo iio_dummy_evgen.ko | grep vermagic'.
>>>
>>> Hi,
>>>
>>> The problem is same you got, I have different versions of uname-r and the
>>> version output I got through vermagic.
>>>
>>> # modinfo iio_dummy_evgen.ko
>>> filename:
>>> /home/simran/git/kernels/staging/drivers/iio/dummy/iio_dummy_evgen.ko
>>> license:        GPL v2
>>> description:    IIO dummy driver
>>> author:         Jonathan Cameron <jic23 at kernel.org>
>>> srcversion:     A8AC238EC07833E018CAF7B
>>> depends:        industrialio
>>> intree:         Y
>>> vermagic:       4.11.0-rc1+ SMP mod_unload modversions
>>>
>>>
>>> $ uname -r
>>> 4.10.0-rc3+
>>>
>>> How to deal with this?
>>
>> You did look in the kernel log when modprobe or insmod failed, right?
>> It should tell you what went wrong.
>>
>> As others pointed out, you need to build your module against the kernel
>> you are running.
>>
> Greg, I got that I have to build the module against the kernel I am using.
> But, How can I do this?
>
>> good luck!
>>
>> greg k-h

Googling for how to configure and build a custom kernel, should return
ample results.
One such resource is the Linux Kernel in a Nutshell available here:
http://www.kroah.com/lkn/