kernel-headers: platform/target patches are not applied

[Felix Fietkau]

Hi Martin,

On 27.07.23 13:23, Martin Schiller wrote:
> When preparing the kernel sources to build the kernel headers, currently
> only the patches from the generic folder are applied, but not from the
> actual selected target.
> 
> This is basically understandable if one assumes that one wants to use a
> toolchain for different targets with the same architecture.
> 
> But if a target has a kernel patch which also changes the uapi, then
> this is not considered in the toolchain/kernel-headers and thus when
> compiling Userspace applications at the moment.
> 
> This is currently already the case for the following targets:
> * ath79
> * bcm27xx
> * bcm63xx
> * ipq40xx
> * lantiq
> * realtek
> 
> I am currently working on a new target, have now stumbled across this
> problem and would now like to start a discussion here on how best to
> solve this now.
> 
> I am looking forward to your ideas.

Packages that depend on target specific UAPI changes can always include 
kernel.mk in the package Makefile, make themselves non-shared and pull 
include files from $(LINUX_DIR)/user_headers

The default for all other packages should be to not rely on target 
specific UAPI changes.

- Felix