Commit b5b52979 has split the options "udev" and "udev_kms" for systems
without systemd.
Yet, when building with "-Dudev=false", "udev_kms" still defaults to
true.
That breaks the build because "config_udev_odev_probe()" is not defined:
| config/config.c: In function ‘config_odev_probe’:
| config/config.c:77:5: error: implicit declaration of function
| ‘config_udev_odev_probe’; did you mean
| ‘config_odev_probe’?
| [-Wimplicit-function-declaration]
| 77 | config_udev_odev_probe(probe_callback);
| | ^~~~~~~~~~~~~~~~~~~~~~
| | config_odev_probe
| config/config.c:77:5: warning: nested extern declaration of
| ‘config_udev_odev_probe’ [-Wnested-externs]
Yet, the code of the function "config_udev_odev_probe()" in config/udev.c
is within a "#ifdef udev_kms" conditional, so it is built.
The problem is that the function definition is within an "#ifdef udev"
in the "config_backends.h" header.
So, even though the actual code is compiled, the compiler will fail to
find the function definition, hence the "implicit declaration" error.
To avoid the issue, move the function definition within a separate
"udev_kms" conditional in the "config-backends.h" header file.
Closes: https://gitlab.freedesktop.org/xorg/xserver/-/work_items/1890
Fixes: b5b52979 ("meson: split udev from udev_kms which requires systemd")
Signed-off-by: Olivier Fourdan <ofourdan@redhat.com>
Part-of: <https://gitlab.freedesktop.org/xorg/xserver/-/merge_requests/2203>
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