[PATCH V2] rtla/Makefile: Properly handle dependencies

[Daniel Bristot de Oliveira]

Linus had a problem compiling RTLA, saying:

"[...] I wish the tracing tools would do a bit more package
checking and helpful error messages too, rather than just
fail with:

    fatal error: tracefs.h: No such file or directory"

Which is indeed not a helpful message. Update the Makefile, adding
proper checks for the dependencies, with useful information about
how to resolve possible problems.

For example, the previous error is now reported as:

    $ make
    ********************************************
    ** NOTICE: libtracefs version 1.3 or higher not found
    **
    ** Consider installing the latest libtracefs from your
    ** distribution, e.g., 'dnf install libtracefs' on Fedora,
    ** or from source:
    **
    **  https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/
    **
    ********************************************

These messages are inspired by the ones used on trace-cmd, as suggested
by Stevel Rostedt.

Link: https://lore.kernel.org/r/CAHk-=whxmA86E=csNv76DuxX_wYsg8mW15oUs3XTabu2Yc80yw@xxxxxxxxxxxxxx/

Changes from V1:
 - Moved the rst2man check to the install phase (when it is used).
 - Removed the procps-ng lib check [1] as it is being removed.

[1] a0f9f8c1030c66305c9b921057c3d483064d5529.1651220820.git.bristot@xxxxxxxxxx

Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Reported-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
---
 Documentation/tools/rtla/Makefile | 14 ++++++++++++-
 tools/tracing/rtla/Makefile       | 35 +++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/Documentation/tools/rtla/Makefile b/Documentation/tools/rtla/Makefile
index 9f2b84af1a6c..093af6d7a0e9 100644
--- a/Documentation/tools/rtla/Makefile
+++ b/Documentation/tools/rtla/Makefile
@@ -17,9 +17,21 @@ DOC_MAN1	= $(addprefix $(OUTPUT),$(_DOC_MAN1))
 RST2MAN_DEP	:= $(shell command -v rst2man 2>/dev/null)
 RST2MAN_OPTS	+= --verbose
 
+TEST_RST2MAN = $(shell sh -c "rst2man --version > /dev/null 2>&1 || echo n")
+
 $(OUTPUT)%.1: %.rst
 ifndef RST2MAN_DEP
-	$(error "rst2man not found, but required to generate man pages")
+	$(info ********************************************)
+	$(info ** NOTICE: rst2man not found)
+	$(info **)
+	$(info ** Consider installing the latest rst2man from your)
+	$(info ** distribution, e.g., 'dnf install python3-docutils' on Fedora,)
+	$(info ** or from source:)
+	$(info **)
+	$(info **  https://docutils.sourceforge.io/docs/dev/repository.html )
+	$(info **)
+	$(info ********************************************)
+	$(error NOTICE: rst2man required to generate man pages)
 endif
 	rst2man $(RST2MAN_OPTS) $< > $@
 
diff --git a/tools/tracing/rtla/Makefile b/tools/tracing/rtla/Makefile
index 523f0a8c38c2..3822f4ea5f49 100644
--- a/tools/tracing/rtla/Makefile
+++ b/tools/tracing/rtla/Makefile
@@ -58,6 +58,41 @@ else
 DOCSRC	=	$(SRCTREE)/../../../Documentation/tools/rtla/
 endif
 
+LIBTRACEEVENT_MIN_VERSION = 1.5
+LIBTRACEFS_MIN_VERSION = 1.3
+
+TEST_LIBTRACEEVENT = $(shell sh -c "$(PKG_CONFIG) --atleast-version $(LIBTRACEEVENT_MIN_VERSION) libtraceevent > /dev/null 2>&1 || echo n")
+ifeq ("$(TEST_LIBTRACEEVENT)", "n")
+.PHONY: warning_traceevent
+warning_traceevent:
+	@echo "********************************************"
+	@echo "** NOTICE: libtraceevent version $(LIBTRACEEVENT_MIN_VERSION) or higher not found"
+	@echo "**"
+	@echo "** Consider installing the latest libtraceevent from your"
+	@echo "** distribution, e.g., 'dnf install libtraceevent' on Fedora,"
+	@echo "** or from source:"
+	@echo "**"
+	@echo "**  https://git.kernel.org/pub/scm/libs/libtrace/libtraceevent.git/ "
+	@echo "**"
+	@echo "********************************************"
+endif
+
+TEST_LIBTRACEFS = $(shell sh -c "$(PKG_CONFIG) --atleast-version $(LIBTRACEFS_MIN_VERSION) libtracefs > /dev/null 2>&1 || echo n")
+ifeq ("$(TEST_LIBTRACEFS)", "n")
+.PHONY: warning_tracefs
+warning_tracefs:
+	@echo "********************************************"
+	@echo "** NOTICE: libtracefs version $(LIBTRACEFS_MIN_VERSION) or higher not found"
+	@echo "**"
+	@echo "** Consider installing the latest libtracefs from your"
+	@echo "** distribution, e.g., 'dnf install libtracefs' on Fedora,"
+	@echo "** or from source:"
+	@echo "**"
+	@echo "**  https://git.kernel.org/pub/scm/libs/libtrace/libtracefs.git/ "
+	@echo "**"
+	@echo "********************************************"
+endif
+
 .PHONY:	all
 all:	rtla
 
-- 
2.32.0