cxl/monitor: Make libtracefs dependency optional

Build a stub version of 'cxl monitor' that reports that the facility was
statically disabled at configure / build time. Provide the meson
configuration line to correct the build.

This is in response to the fact that some distros fail to ship
libtracefs-devel even though they ship libtracefs (looking at you CentOS
Stream 8).

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Link: https://lore.kernel.org/r/167718414197.16926.10394415062829848410.stgit@dwillia2-xfh.jf.intel.com
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>

config.h.meson

@@ -19,6 +19,9 @@
 /* ndctl test support */
 #mesondefine ENABLE_TEST
 
+/* cxl monitor support */
+#mesondefine ENABLE_LIBTRACEFS
+
 /* Define to 1 if big-endian-arch */
 #mesondefine HAVE_BIG_ENDIAN
 

cxl/builtin.h

@@ -22,5 +22,14 @@ int cmd_create_region(int argc, const char **argv, struct cxl_ctx *ctx);
 int cmd_enable_region(int argc, const char **argv, struct cxl_ctx *ctx);
 int cmd_disable_region(int argc, const char **argv, struct cxl_ctx *ctx);
 int cmd_destroy_region(int argc, const char **argv, struct cxl_ctx *ctx);
+#ifdef ENABLE_LIBTRACEFS
 int cmd_monitor(int argc, const char **argv, struct cxl_ctx *ctx);
+#else
+static inline int cmd_monitor(int argc, const char **argv, struct cxl_ctx *ctx)
+{
+	fprintf(stderr,
+		"cxl monitor: unavailable, rebuild with '-Dlibtracefs=enabled'\n");
+	return EXIT_FAILURE;
+}
+#endif
 #endif /* _CXL_BUILTIN_H_ */

cxl/meson.build

@@ -7,27 +7,36 @@ cxl_src = [
   'memdev.c',
   'json.c',
   'filter.c',
-  'event_trace.c',
-  'monitor.c',
 ]
 
 if get_option('systemd').enabled()
   install_data('cxl-monitor.service', install_dir : systemdunitdir)
 endif
 
+deps = [
+  cxl_dep,
+  util_dep,
+  uuid,
+  kmod,
+  json,
+  versiondep,
+]
+
+if get_option('libtracefs').enabled()
+  cxl_src += [
+    'event_trace.c',
+    'monitor.c',
+  ]
+  deps += [
+    traceevent,
+    tracefs,
+  ]
+endif
+
 cxl_tool = executable('cxl',
   cxl_src,
   include_directories : root_inc,
-  dependencies : [
-    cxl_dep,
-    util_dep,
-    uuid,
-    kmod,
-    json,
-    versiondep,
-    traceevent,
-    tracefs,
-  ],
+  dependencies : deps,
   install : true,
   install_dir : rootbindir,
 )

meson.build

@@ -143,8 +143,10 @@ kmod = dependency('libkmod')
 libudev = dependency('libudev')
 uuid = dependency('uuid')
 json = dependency('json-c')
-traceevent = dependency('libtraceevent')
-tracefs = dependency('libtracefs')
+if get_option('libtracefs').enabled()
+  traceevent = dependency('libtraceevent')
+  tracefs = dependency('libtracefs')
+endif
 
 if get_option('docs').enabled()
   if get_option('asciidoctor').enabled()
@@ -234,6 +236,7 @@ conf.set('ENABLE_TEST', get_option('test').enabled())
 conf.set('ENABLE_DESTRUCTIVE', get_option('destructive').enabled())
 conf.set('ENABLE_LOGGING', get_option('logging').enabled())
 conf.set('ENABLE_DEBUG', get_option('dbg').enabled())
+conf.set('ENABLE_LIBTRACEFS', get_option('libtracefs').enabled())
 
 typeof_code = '''
   void func() {

meson_options.txt

@@ -2,6 +2,7 @@ option('version-tag', type : 'string',
        description : 'override the git version string')
 option('docs', type : 'feature', value : 'enabled')
 option('asciidoctor', type : 'feature', value : 'enabled')
+option('libtracefs', type : 'feature', value : 'enabled')
 option('systemd', type : 'feature', value : 'enabled')
 option('keyutils', type : 'feature', value : 'enabled',
   description : 'enable nvdimm device passphrase management')

ndctl.spec.in

@@ -13,9 +13,13 @@ BuildRequires:	autoconf
 %if 0%{?rhel} < 9
 BuildRequires:	asciidoc
 %define asciidoctor -Dasciidoctor=disabled
+%define libtracefs -Dlibtracefs=disabled
 %else
 BuildRequires:	rubygem-asciidoctor
+BuildRequires:	libtraceevent-devel
+BuildRequires:	libtracefs-devel
 %define asciidoctor -Dasciidoctor=enabled
+%define libtracefs -Dlibtracefs=enabled
 %endif
 BuildRequires:	xmlto
 BuildRequires:	automake
@@ -31,8 +35,6 @@ BuildRequires:	keyutils-libs-devel
 BuildRequires:	systemd-rpm-macros
 BuildRequires:	iniparser-devel
 BuildRequires:	meson
-BuildRequires:	libtraceevent-devel
-BuildRequires:	libtracefs-devel
 
 %description
 Utility library for managing the "libnvdimm" subsystem.  The "libnvdimm"
@@ -124,7 +126,7 @@ libcxl is a library for enumerating and communicating with CXL devices.
 %setup -q ndctl-%{version}
 
 %build
-%meson %{?asciidoctor} -Dversion-tag=%{version}
+%meson %{?asciidoctor} %{?libtracefs} -Dversion-tag=%{version}
 %meson_build
 
 %install