[PATCH net-next 2/2] tools/ynl: add check-deps target to verify Makefile.deps completeness

[Stanislav Fomichev <sdf.kernel@gmail.com>]

Add two make rules that detect missing entries in Makefile.deps:

check-existing-deps-<family>: for families that already have CFLAGS,
  parse each force-included header for #include directives and verify
  that every included uapi header is either already listed in CFLAGS
  or findable by the compiler without -idirafter.

check-new-deps-<family>: for families without CFLAGS, check whether
  their default uapi header (linux/<family>.h) exists in the kernel
  tree but is not findable by the compiler -- meaning it needs a new
  CFLAGS entry.

(this is slop but I added extensive comments on how it works)

Signed-off-by: Stanislav Fomichev <sdf@fomichev.me>
---
 tools/net/ynl/Makefile.deps      | 35 ++++++++++++++++++++++++++++++++
 tools/net/ynl/generated/Makefile |  6 +++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/tools/net/ynl/Makefile.deps b/tools/net/ynl/Makefile.deps
index cc53b2f21c44..f2c24097a2c8 100644
--- a/tools/net/ynl/Makefile.deps
+++ b/tools/net/ynl/Makefile.deps
@@ -52,3 +52,38 @@ CFLAGS_tc:= $(call get_hdr_inc,__LINUX_RTNETLINK_H,rtnetlink.h) \
 	$(call get_hdr_inc,_TC_TUNNEL_KEY_H,tc_act/tc_tunnel_key.h)
 CFLAGS_tcp_metrics:=$(call get_hdr_inc,_LINUX_TCP_METRICS_H,tcp_metrics.h)
 CFLAGS_wireguard:=$(call get_hdr_inc2,_LINUX_WIREGUARD_H,_WG_UAPI_WIREGUARD_H,wireguard.h)
+
+# For families that already have CFLAGS, verify that every #include in
+# their force-included headers is accounted for.
+#
+# How it works:
+#   1. Extract -include paths from CFLAGS_<family>      (grep + sed)
+#   2. Parse each header for #include <...> directives  (sed)
+#   3. Skip if the included file is not a uapi header   (test against UAPI_PATH)
+#   4. Skip if it is already listed in CFLAGS_<family>  (grep)
+#   5. Skip if the compiler can find it without help    (try $(CC))
+#   6. Otherwise error -- the header needs to be added
+check-existing-deps-%:
+	@for inc in $$(sed -n 's/.*#include <\([^>]*\)>.*/\1/p' \
+		$$(echo "$(CFLAGS_$*)" | grep -o '\-include [^ ]*' | sed 's/-include //')); do \
+	  test -f $(UAPI_PATH)/$$inc || continue; \
+	  echo "$(CFLAGS_$*)" | grep -qF "$$inc" && continue; \
+	  echo "#include <$$inc>" | $(CC) -x c -fsyntax-only - 2>/dev/null && continue; \
+	  echo "ERROR: $* missing $$inc"; exit 1; \
+	done; true
+
+# For families without CFLAGS, check whether their default uapi header
+# (linux/<family>.h) exists in the kernel tree but is not findable by
+# the compiler -- meaning it needs a new CFLAGS entry.
+#
+# How it works (short-circuit chain, all four must fail to error):
+#   1. Skip if CFLAGS_<family> is already defined          (test -n)
+#   2. Skip if the default uapi header does not exist      (test -f)
+#   3. Skip if the compiler can find it without help       (try $(CC))
+#   4. Otherwise error -- a new CFLAGS entry is needed
+check-new-deps-%:
+	@test -n "$(CFLAGS_$*)" \
+	  || ! test -f $(UAPI_PATH)/linux/$(subst -,_,$*).h \
+	  || echo "#include <linux/$(subst -,_,$*).h>" | \
+	     $(CC) -x c -fsyntax-only - 2>/dev/null \
+	  || { echo "ERROR: $* needs CFLAGS entry for linux/$(subst -,_,$*).h"; exit 1; }
diff --git a/tools/net/ynl/generated/Makefile b/tools/net/ynl/generated/Makefile
index 86e1e4a959a7..0f1d2c70b6a5 100644
--- a/tools/net/ynl/generated/Makefile
+++ b/tools/net/ynl/generated/Makefile
@@ -83,5 +83,9 @@ install-rsts: $(RSTS)
 
 install: install-headers install-rsts install-specs
 
-.PHONY: all clean distclean regen install install-headers install-rsts install-specs
+check-deps: $(patsubst %,check-existing-deps-%,$(GENS)) \
+	    $(patsubst %,check-new-deps-%,$(GENS))
+	@echo "All Makefile.deps OK"
+
+.PHONY: all clean distclean regen install install-headers install-rsts install-specs check-deps
 .DEFAULT_GOAL: all
-- 
2.53.0-Meta