Lasse Collin [off-list ref] writes:

XZ_EXTERN was used to make internal functions static in the preboot code.
However, in other decompressors this hasn't been done. On x86-64, this
makes no difference to the kernel image size.

Omit XZ_EXTERN and let some of the internal functions be extern in the
preboot code. Omitting XZ_EXTERN from include/linux/xz.h fixes warnings
in "make htmldocs" and makes the intradocument links to xz_dec functions
work in Documentation/staging/xz.rst. The alternative would have been to
add "XZ_EXTERN" to c_id_attributes in Documentation/conf.py but omitting
XZ_EXTERN seemed cleaner.

Link: https://lore.kernel.org/lkml/20240723205437.3c0664b0@kaneli/ (local)
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-doc@vger.kernel.org
Signed-off-by: Lasse Collin <lasse.collin@tukaani.org>
---

Notes:
    This touches xz_config.h in PowerPC boot code. I haven't tested it but
    zlib's functions are extern in the same context, thus this should be
    a safe change on PowerPC.

     
I gave it a quick build and boot, seems fine.

Tested-by: Michael Ellerman <mpe@ellerman.id.au> (powerpc)

cheers