Re: [dpdk-dev] Impossible to build external application if user build DPDK with "make config"

[Tom Barbette <barbette@kth.se>]

Le 27/03/2020 à 11:35, Thomas Monjalon a écrit :
> 27/03/2020 10:14, Tom Barbette:
>> CC'ing original participants as I don't see a way out of this.
>>
>> Le 12/03/2020 à 13:04, Tom Barbette a écrit :
>>> Hi all,
>>>
>>> If the user follows the quick guide
>>> (http://core.dpdk.org/doc/quick-start/) DPDK will be compiled in the
>>> "build" folder.
>>>
>>> However, external applications will always fail to build because
>>> RTE_SDK_BIN is strictly defined as $RTE_SDK/$RTE_TARGET, and
>>> mk/internal/rte.extvars.mk needs to find .config in $RTE_SDK_BIN.
>>>
>>> Therefore please apply the patch at:
>>> http://patchwork.dpdk.org/patch/9991/ that allows external apps to
>>> override $RTE_SDK_BIN.
>>>
>>> Or (less preferable) modify the quick start guide to use something more
>>> standard that allows to build with external apps (eg use the menu or
>>> propose "make config T=x86_64-native-linuxapp-gcc
>>> O=x86_64-native-linuxapp-gcc" instead). It's much easier for external
>>> apps maintainer to refer to the DPDK tutorial for DPDK installation.
> 
> I don't understand the issue.
> First of all, the external application should link an installed DPDK.
> Then you should be able to set $RTE_SDK and $RTE_TARGET to fit
> the installation directories.
> 
> Just checked doc/guides/linux_gsg/build_dpdk.rst
> I see the whole build process with make is not correctly documented.
> It should be:
> 
> 1/
> 	make defconfig
> 	or
> 	make config T=x86_64-native-linux-gcc O=mybuild
> 
> 2/	make -j4 O=mybuild
> 
> 3/	make install O=mybuild DESTDIR=myinstall prefix=
> 
> 4/	RTE_SDK=$(pwd)/myinstall/share/dpdk RTE_TARGET=x86_64-native-linux-gcc make -C myapp
> 
> Please can you confirm it works?
> 
> 

I don't think it is usual to link against an "installed" DPDK, actually. 
I've only seen people explaining "build DPDK with 1 & 2", which is 
probably why the quick start also use only that and the usertools menu 
also only builds in the usual folder SDK/TARGET.

Then also using the install method you propose, I'm missing a few 
libraries, eg -lethdev which I would have to find using 
-L$RTE_SDK/../../lib which does not sound great. But adding a link to 
../../lib under share fixes the problem, and the install script could do it.

Making RTE_SDK_BIN a ?= instead of a := would allow us to fix the 
non-installed, but built-in-a-funny-folder installation path easily.

So I would recommend doing the lib link, but still the change proposed 
because I'm really not sure people "install" DPDK...


Thanks,
Tom