[PATCH AUTOSEL 6.17-6.1] tools: lib: thermal: use pkg-config to locate libnl3

[Sasha Levin <sashal@kernel.org>]

From: Sascha Hauer <s.hauer@pengutronix.de>

[ Upstream commit b31f7f725cd932e2c2b41f3e4b66273653953687 ]

To make libthermal more cross compile friendly use pkg-config to locate
libnl3. Only if that fails fall back to hardcoded /usr/include/libnl3.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

YES

- `tools/lib/thermal/Makefile:49-52` introduces `NL3_CFLAGS = $(shell
  pkg-config --cflags libnl-3.0 2>/dev/null)` with a fallback to the old
  hard-coded include path. This directly addresses the existing build
  bug where cross-compiling libthermal forced the host’s
  `/usr/include/libnl3`, ignoring the target sysroot supplied via pkg-
  config; without this fix the library fails to build in cross
  environments, so it repairs a user-visible build break.
- `tools/lib/thermal/Makefile:66` now appends `$(NL3_CFLAGS)` into the
  compilation flags, ensuring the pkg-config-provided include directory
  is actually used whenever available. Because the fallback still
  supplies `-I/usr/include/libnl3`, the default on native builds is
  unchanged, keeping risk minimal.
- The change is tightly scoped to the userspace `tools/lib/thermal`
  build logic and mirrors the pattern already used elsewhere (e.g.
  selftests’ Makefiles rely on `pkg-config` for libnl), so it carries
  very low regression risk and no architectural churn while fixing a
  real build issue.

 tools/lib/thermal/Makefile | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/lib/thermal/Makefile b/tools/lib/thermal/Makefile
index ac918e98cd033..41aa7a324ff4d 100644
--- a/tools/lib/thermal/Makefile
+++ b/tools/lib/thermal/Makefile
@@ -46,8 +46,12 @@ else
   CFLAGS := -g -Wall
 endif
 
+NL3_CFLAGS = $(shell pkg-config --cflags libnl-3.0 2>/dev/null)
+ifeq ($(NL3_CFLAGS),)
+NL3_CFLAGS = -I/usr/include/libnl3
+endif
+
 INCLUDES = \
--I/usr/include/libnl3 \
 -I$(srctree)/tools/lib/thermal/include \
 -I$(srctree)/tools/lib/ \
 -I$(srctree)/tools/include \
@@ -59,6 +63,7 @@ INCLUDES = \
 override CFLAGS += $(EXTRA_WARNINGS)
 override CFLAGS += -Werror -Wall
 override CFLAGS += -fPIC
+override CFLAGS += $(NL3_CFLAGS)
 override CFLAGS += $(INCLUDES)
 override CFLAGS += -fvisibility=hidden
 override CFGLAS += -Wl,-L.
-- 
2.51.0