Masahiro Yamada e9e81b6343 kbuild: disallow multi-word in M= or KBUILD_EXTMOD
$(firstword ...) in scripts/Makefile.modpost was added by commit
3f3fd3c055 ("[PATCH] kbuild: allow multi-word $M in Makefile.modpost")
to build multiple external module directories.

It was a solution to resolve symbol dependencies when an external
module depends on another external module.

Commit 0d96fb20b7 ("kbuild: Add new Kbuild variable
KBUILD_EXTRA_SYMBOLS") introduced another solution by passing symbol
info via KBUILD_EXTRA_SYMBOLS, then broke the multi-word M= support.

  include $(if $(wildcard $(KBUILD_EXTMOD)/Kbuild), \
               $(KBUILD_EXTMOD)/Kbuild, $(KBUILD_EXTMOD)/Makefile)

... does not work if KBUILD_EXTMOD contains multiple words.

This feature has been broken for more than a decade. Remove the
bitrotten code, and stop parsing if M or KBUILD_EXTMOD contains
multiple words.

As Documentation/kbuild/modules.rst explains, if your module depends
on another one, there are two solutions:
  - add a common top-level Kbuild file
  - use KBUILD_EXTRA_SYMBOLS

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
2020-05-29 03:08:49 +09:00
2020-05-01 09:51:08 +01:00
2020-02-24 22:43:18 -08:00

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.
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