Re: next-20251027: backlight.c:59:39: error: implicit declaration of function 'of_find_node_by_name'; did you mean 'bus_find_device_by_name'?

27 Oct 2025

      On Mon, 27 Oct 2025 at 13:43, Naresh Kamboju naresh.kamboju@linaro.org wrote:
...
The following powerpc ppc6xx_defconfig build regressions noticed on the
Linux next-20251027 tag with gcc-14 and gcc-8.

powerpc, build
gcc-14-ppc6xx_defconfig
gcc-8-ppc6xx_defconfig

First seen on next-20251027
Good: next-20251024
Bad: next-20251027
Regression Analysis:

New regression? yes
Reproducibility? yes

Build regression: next-20251027: backlight.c:59:39: error: implicit
declaration of function 'of_find_node_by_name'; did you mean
'bus_find_device_by_name'?
Build regression: next-20251027: include/linux/math.h:167:43: error:
first argument to '__builtin_choose_expr' not a constant
Build regression: next-20251027: via-pmu-backlight.c:22:20: error:
'FB_BACKLIGHT_LEVELS' undeclared here (not in a function)
Build regression: next-20251027: minmax.h:71:17: error: first argument
to '__builtin_choose_expr' not a constant
Build regression: next-20251027: compiler.h:168:17: error:
'__UNIQUE_ID_x__286' undeclared (first use in this function); did you
mean '__UNIQUE_ID_y__287'?
Anders bisected this down to,
# first bad commit:
   [243ce64b2b371cdf2cbc39c9422cb3047cab6de7]
   backlight: Do not include <linux/fb.h> in header file
...
Reported-by: Linux Kernel Functional Testing lkft@linaro.org
## Build error
arch/powerpc/platforms/powermac/backlight.c: In function
'pmac_has_backlight_type':
arch/powerpc/platforms/powermac/backlight.c:59:39: error: implicit
declaration of function 'of_find_node_by_name'; did you mean
'bus_find_device_by_name'? [-Wimplicit-function-declaration]
   59 |         struct device_node* bk_node =
of_find_node_by_name(NULL, "backlight");
      |                                       ^~~~~~~~~~~~~~~~~~~~
      |                                       bus_find_device_by_name
arch/powerpc/platforms/powermac/backlight.c:59:39: error:
initialization of 'struct device_node *' from 'int' makes pointer from
integer without a cast [-Wint-conversion]
arch/powerpc/platforms/powermac/backlight.c:60:17: error: implicit
declaration of function 'of_property_match_string'
[-Wimplicit-function-declaration]
   60 |         int i = of_property_match_string(bk_node,
"backlight-control", type);
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~
arch/powerpc/platforms/powermac/backlight.c:62:9: error: implicit
declaration of function 'of_node_put'
[-Wimplicit-function-declaration]
   62 |         of_node_put(bk_node);
      |         ^~~~~~~~~~~
drivers/macintosh/via-pmu-backlight.c:22:20: error:
'FB_BACKLIGHT_LEVELS' undeclared here (not in a function)
   22 | static u8 bl_curve[FB_BACKLIGHT_LEVELS];
      |                    ^~~~~~~~~~~~~~~~~~~
In file included from <command-line>:
drivers/macintosh/via-pmu-backlight.c: In function 'pmu_backlight_curve_lookup':
include/linux/compiler.h:168:17: error: '__UNIQUE_ID_x__286'
undeclared (first use in this function); did you mean
'__UNIQUE_ID_y__287'?
  168 |         __PASTE(__UNIQUE_ID_,                                   \
      |                 ^~~~~~~~~~~~
drivers/macintosh/via-pmu-backlight.c:45:23: note: in expansion of macro 'max'
   45 |                 max = max((int)bl_curve[i], max);
      |                       ^~~
include/linux/minmax.h:71:17: error: first argument to
'__builtin_choose_expr' not a constant
   71 |         (typeof(__builtin_choose_expr(sizeof(ux) > 4, 1LL,
1L)))(ux) >= 0)
      |                 ^~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:577:23: note: in definition of macro
'__compiletime_assert'
  577 |                 if (!(condition))
         \
      |                       ^~~~~~~~~
drivers/macintosh/via-pmu-backlight.c:45:23: note: in expansion of macro 'max'
   45 |                 max = max((int)bl_curve[i], max);
      |                       ^~~
include/linux/minmax.h:71:17: error: first argument to
'__builtin_choose_expr' not a constant
   71 |         (typeof(__builtin_choose_expr(sizeof(ux) > 4, 1LL,
1L)))(ux) >= 0)
      |                 ^~~~~~~~~~~~~~~~~~~~~
include/linux/compiler_types.h:577:23: note: in definition of macro
'__compiletime_assert'
  577 |                 if (!(condition))
         \
      |                       ^~~~~~~~~
include/linux/minmax.h:112:25: note: in expansion of macro '__careful_cmp'
  112 | #define max(x, y)       __careful_cmp(max, x, y)
      |                         ^~~~~~~~~~~~~
drivers/macintosh/via-pmu-backlight.c:45:23: note: in expansion of macro 'max'
   45 |                 max = max((int)bl_curve[i], max);
      |                       ^~~
In file included from include/linux/kernel.h:27,
                 from arch/powerpc/include/asm/page.h:11,
                 from arch/powerpc/include/asm/thread_info.h:13,
                 from include/linux/thread_info.h:60,
                 from arch/powerpc/include/asm/ptrace.h:342,
                 from drivers/macintosh/via-pmu-backlight.c:11:
include/linux/math.h:162:17: error: first argument to
'__builtin_choose_expr' not a constant
  162 |                 __builtin_choose_expr(
         \
      |                 ^~~~~~~~~~~~~~~~~~~~~
drivers/macintosh/via-pmu-backlight.c: In function
'pmu_backlight_get_level_brightness':
drivers/macintosh/via-pmu-backlight.c:63:38: error: 'FB_BACKLIGHT_MAX'
undeclared (first use in this function); did you mean 'BACKLIGHT_RAW'?
   63 |         pmulevel = bl_curve[level] * FB_BACKLIGHT_MAX / MAX_PMU_LEVEL;
      |                                      ^~~~~~~~~~~~~~~~
      |                                      BACKLIGHT_RAW
drivers/macintosh/via-pmu-backlight.c:58:51: warning: parameter
'level' set but not used [-Wunused-but-set-parameter]
   58 | static int pmu_backlight_get_level_brightness(int level)
      |                                               ~~~~^~~~~
drivers/macintosh/via-pmu-backlight.c: In function 'pmu_backlight_init':
drivers/macintosh/via-pmu-backlight.c:144:17: error: implicit
declaration of function 'of_machine_is_compatible'
[-Wimplicit-function-declaration]
  144 |                 of_machine_is_compatible("AAPL,3400/2400") ||
      |                 ^~~~~~~~~~~~~~~~~~~~~~~~
drivers/macintosh/via-pmu-backlight.c: At top level:
drivers/macintosh/via-pmu-backlight.c:22:11: warning: 'bl_curve'
defined but not used [-Wunused-variable]
   22 | static u8 bl_curve[FB_BACKLIGHT_LEVELS];
      |           ^~~~~~~~
make[5]: *** [scripts/Makefile.build:287:
drivers/macintosh/via-pmu-backlight.o] Error 1
make[5]: Target 'drivers/macintosh/' not remade because of errors.
## Source

Kernel version: 6.18.0-rc2-next-20251027
Git tree: https://kernel.googlesource.com/pub/scm/linux/kernel/git/next/linux-next.git
Git describe: next-20251027
Git commit: 8fec172c82c2b5f6f8e47ab837c1dc91ee3d1b87
Architectures: powerpc
Toolchains: gcc-14
Kconfigs: defconfig

## Build

Test log: https://storage.tuxsuite.com/public/linaro/lkft/builds/34dKrlb77LGOQQSoC8FHC...
Test details:

https://regressions.linaro.org/lkft/linux-next-master/next-20251027/build/gc...

Build plan: https://tuxapi.tuxsuite.com/v1/groups/linaro/projects/lkft/builds/34dKrlb77L...
Build link: https://storage.tuxsuite.com/public/linaro/lkft/builds/34dKrlb77LGOQQSoC8FHC...
Kernel config:

https://storage.tuxsuite.com/public/linaro/lkft/builds/34dKrlb77LGOQQSoC8FHC...
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Re: next-20251027: backlight.c:59:39: error: implicit declaration of function 'of_find_node_by_name'; did you mean 'bus_find_device_by_name'?