[poky] How to export kernel specific headers to userspace

[Bas Mevissen]

On 2018-06-19 15:55, Bruce Ashfield wrote:
> On 06/19/2018 09:44 AM, Bas Mevissen wrote:
>> On 2018-06-19 07:16, Ankit Rastogi wrote:
>>> Hi,
>>> 
>>> Can someone provide any pointers on how to export kernel specific
>>> headers to userspace?
>>> 
>>> I am getting below error while building our one of the component 
>>> which
>>> requires kernel uapi headers.
>>> 
>>> Error Received:
>>>  /hdmi-capture/main.c:16:10: fatal error: linux/hdmi_info.h: No such
>>> file or directory
>>>> |  #include <linux/hdmi_info.h>
>>>> |           ^~~~~~~~~~~~~~~~~~~
>>>> | compilation terminated.
>>> 
>>> In yocto 2.5, userspace is boot strapped with linux-libc-headers
>>> package which uses a set of uapi headers from Linux kernel 4.15. Can
>>> someone suggest for custom kernels, how to expose uapi headers to
>>> userspace? Thus create a separate linux-apl-headers package with 
>>> those
>>> files.
>>> 
>> 
>> You might want to (re)move the linux-libc-headers package (header 
>> files) and install kernel-devsrc package. Then link the include 
>> directories from /usr/src/kernel/include/{asm*,linux} to /usr/include 
>> or modify your Makefile to get the linux include files from 
>> /usr/src/kernel/include/linux instead of /usr/include/linux.
>> 
>> Please note that the kernel-devsrc package is not without problems. 
>> Building it and manually installing it with --nodeps (for rpm) will do 
>> the trick. The package is due for replacement, see a thread on this 
>> started by me a few weeks ago.
>> 
>> Please also note that linux-libc-headers are cleaned-up versions of 
>> the 4.15 kernel headers, so expect some rough edges.
> 
> They aren't actually cleaned up at all. They are the standard uapi
> installed headers from the latest kernel in a given yocto release.
> 

Oh, maybe I'm confused with the ones installed by Centos and Fedora. 
There the #ifdef __KERNEL__ (..) #endif stuff is removed from the uapi 
headers package.

> They will be updated to 4.18 shortly, since I'm preparing the next
> round of kernel updates


> (and devsrc resubmission).
> 

That would be really nice as it is not really usable at the moment.

> Bruce
> 
> 
> 
>>