[OE-core] Build Kernel module on target

[Bodke, Kishore K]

>-----Original Message-----
>From: Darren Hart [mailto:dvhart at linux.intel.com]
>Sent: Friday, August 17, 2012 1:42 PM
>To: Bodke, Kishore K
>Cc: linux-yocto at yoctoproject.org
>Subject: Re: Build Kernel module on target
>
>
>
>On 08/17/2012 11:11 AM, Bodke, Kishore K wrote:
>>
>>
>>> -----Original Message-----
>>> From: Darren Hart [mailto:dvhart at linux.intel.com]
>>> Sent: Thursday, August 16, 2012 5:00 PM
>>> To: Bodke, Kishore K
>>> Cc: linux-yocto at yoctoproject.org
>>> Subject: Re: Build Kernel module on target
>>>
>>>
>>>
>>> On 08/16/2012 04:31 PM, Bodke, Kishore K wrote:
>>>> Hi Darren,
>>>
>>> Hi Kishore,
>>>
>>>> I am trying to build the Kernel Module on the target with sdk image.
>>>> I get the below error for all the kernel modules I am building.
>>>>
>>>> == Build lib/librte_eal/linuxapp/igb_uio
>>>>
>>>> make: *** /lib/modules/3.4.6-yocto-standard/build: No such file or
>>>> directory.  Stop.
>>>>
>>>> make[7]: *** [igb_uio.ko] Error 2
>>>>
>>>> Makefile has the kernel source directory  set like below.
>>>>
>>>> RTE_KERNELDIR = /lib/modules/$(shell uname -r)/build
>>>>
>>>> And I see there is no build directory there in
>>>> /lib/modules/3.4.6-yocto-standard .
>>>>
>>>> I changed the RTE_KERNELDIR to
>>>>
>>>> RTE_KERNELDIR =/usr/src/kernel
>>>
>>> Correct.
>>
>> Why Yocto does not have /lib/modules/$(shell uname -r)/build?
>> Generally /lib/modules/$(shell uname -r)/build is where EVERY kernel
>module goes to look for kernel headers to build against.
>
>No reason. That would be a good addition. Please send a patch or open a
>bug with
>the request.
>
>>
>>>
>>>> This time it went further to build the kernel module but failed for the
>>>>
>>>> /usr/src/kernel/scripts/recordmcount: No such file or directory
>>>>
>>>> I saw the ${STAGING_KERNEL_DIR} for the recordmcount.  There is no
>such
>>> file
>>>> I think we need  scripts/recordmcount to be a part of the final image?
>>>
>>> This is an unfortunate result of the kernel building those "scripts" for
>>> the host, which we can't deploy to the target. We intentionally remove
>>> them. To build on the target, you must first build the "scripts":
>>>
>>> $ cd /usr/src/kernel
>>> $ make scripts
>>>
>>> Then try to build your modules.
>>
>> If I had to build the same module using recipe via bitbake, I get the same
>> error.
>
>You shouldn't. If you do, it's a bug either in the module building
>mechanism of oe-core or with your module recipe.
>
>> Unfortunately I cannot inherit module in my recipe.
>
>You really need to.

Moving the discussion to [open embedded core list]

Either I do inherit module or I don't, I need to have the kernel source directory to
point  to  ${STAGING_KERNEL_DIR} in my recipe, since the Makefile has /lib/modules/$(shell uname -r)/build 
for the kernel source, which If I don't override, it will build kernel module for the local host.

Also the Makefile does not have rule for module install, can we have the install rule inside a recipe to make the module 
in to the final image?
Something like 
FILES_${PN}+=  ${base_libdir}/modules/${KERNEL_VERSION}/kernel/drivers"
install -m 640 ${B}/kmod/igb_uio.ko     ${MODULE_DIR} (This being defined in a recipe)

Thanks
Kishore.