diff --git a/2G.deps b/2G.deps
deleted file mode 100644
index c090b6e..0000000
--- a/2G.deps
+++ /dev/null
@@ -1,18 +0,0 @@
-# project	build these first
-libosmocore
-libosmo-abis	libosmocore
-libosmo-netif	libosmo-abis
-libosmo-sccp	libosmo-netif
-libsmpp34
-osmo-ggsn	libosmocore
-osmo-hlr	libosmo-abis
-osmo-mgw	libosmo-netif
-osmo-msc	libosmo-sccp osmo-mgw libsmpp34 osmo-hlr
-osmo-bsc	libosmo-sccp osmo-mgw
-osmo-sgsn	libosmo-sccp osmo-ggsn osmo-hlr
-osmo-sip-connector	libosmocore
-osmo-smlc	libosmo-sccp
-# osmo-trx can build with --enable-sanitize, but then won't work reliably.
-# When omitting --enable-sanitize from osmo-trx only, its 'make check' will fail.
-# So if you want osmo-trx, uncomment and use no sanitize.opts, or use LD_PRELOAD for osmo-trx binaries.
-#osmo-trx	libosmocore
diff --git a/README b/README
index 7e34680..ac77424 100644
--- a/README
+++ b/README
@@ -15,7 +15,7 @@ sudo apt install \
   libdbd-sqlite3 libsqlite3-dev libpcap-dev libc-ares-dev libgnutls28-dev \
   libsctp-dev sqlite3
 
-./gen_makefile.py 3G+2G.deps default.opts iu.opts -I -m make
+./gen_makefile.py default.opts iu.opts -I -m make
 
 cd make
 make
@@ -40,29 +40,39 @@ projects, but works generically.
 The idea is to have all your Osmocom git clones in ./src, while keeping one or
 more separate build trees in ./make-*.
 
-Run ./gen_makefile.py with a choice of projects (2G only or also 3G?)
-and a choice of configure options.
+Run ./gen_makefile.py with a choice of choice of configure options.
 
 
 Examples:
 
-Full 2G and 3G support:
+CN with full 2G and 3G support:
 
-  ./gen_makefile.py 3G+2G.deps default.opts iu.opts  -m make
+  ./gen_makefile.py default.opts iu.opts -m make
   cd make
-  make
+  make cn
 
-2G only, and a custom dir name of 'make-2G':
+Other make targets exist for specific use cases:
 
-  ./gen_makefile.py 2G.deps default.opts -m make-2G
-  cd make-2G
-  make
+  - 'usrp':
+    Build the CN, OsmoBSC, OsmoBTS and OsmoTRX (default, e.g. when connecting
+    to an USRP)
+
+  - 'cn-bsc':
+    Build the CN and OsmoBSC (e.g. when connecting to an external sysmoBTS)
+
+  - 'osmo-msc':
+    Build only the OsmoMSC project and its dependencies (this can be used for
+    any project in all.deps).
+
+  - '.make.osmo-ttcn3-hacks.clone'
+    Clone the osmo-ttcn3-hacks git repository (it cannot be built by osmo-dev,
+    but cloning it is still useful.)
 
 If you make modifications in one of the source trees, this Makefile will pick
-it up, rebuild the project and also rebuild all dependencies (according to the
-*.deps file the Makefile was generated from).
+it up, rebuild the project and also rebuild all dependencies (according to
+all.deps).
 
-If you modify the *.deps or *.opts file, you can easily run 'make regen' in a
+If you modify the all.deps or *.opts file, you can easily run 'make regen' in a
 make-* subdir to regenerate the Makefile from the same files.
 
 In your make-* subdir there are empty status files that are touched for every
@@ -72,7 +82,7 @@ You can manually remove them to force a rebuild of a specific target.
 For example, if you 'rm .make.libosmocore.autoconf', libosmocore and all
 projects depending on libosmocore will be rebuilt from scratch.
 
-For more details on the *.opts and *.deps syntax, read the docs at the top of
+For more details on the *.opts and all.deps syntax, read the docs at the top of
 ./gen_makefile.py.
 
 It is also easily possible to keep sources and build trees in various
diff --git a/3G+2G.deps b/all.deps
similarity index 75%
rename from 3G+2G.deps
rename to all.deps
index b4372fd..26e0cf4 100644
--- a/3G+2G.deps
+++ b/all.deps
@@ -17,5 +17,10 @@ osmo-bts	libosmo-netif
 osmo-smlc	libosmo-sccp
 # osmo-trx can build with --enable-sanitize, but then won't work reliably.
 # When omitting --enable-sanitize from osmo-trx only, its 'make check' will fail.
-# So if you want osmo-trx, uncomment and use no sanitize.opts, or use LD_PRELOAD for osmo-trx binaries.
-#osmo-trx	libosmocore
+# So if you want osmo-trx, use no sanitize.opts, or use LD_PRELOAD for osmo-trx binaries.
+osmo-trx	libosmocore
+osmo-pcu	libosmocore
+
+# can only clone these
+docker-playground
+osmo-ttcn3-hacks
diff --git a/gen_makefile.py b/gen_makefile.py
index 81d41e7..c08ca4e 100755
--- a/gen_makefile.py
+++ b/gen_makefile.py
@@ -2,20 +2,19 @@
 '''
 Generate a top-level makefile that builds the Osmocom 2G + 3G network components.
 
-  ./gen_makefile.py projects.deps [configure.opts [more.opts]] [-o Makefile.output]
+  ./gen_makefile.py [configure.opts [more.opts]] [-o Makefile.output]
 
 Configured by text files:
 
-  *.deps: whitespace-separated listing of
+  all.deps: whitespace-separated listing of
     project_name depends_on_project_1 depends_on_project_2 ...
 
   *.opts: whitespace-separated listing of
     project_name --config-opt-1 --config-opt-2 ...
 
 Thus it is possible to choose between e.g.
-- 2G+3G or 2G-only by picking a different projects_and_deps.conf,
-- and between building each of those with or without mgcp transcoding support
-  by picking a different configure_opts.conf.
+- building each of those with or without mgcp transcoding support by adding or
+  removing "transcoding.opts" from the command line
 
 From the Makefile nature, the dependencies extend, no need to repeat common deps.
 
@@ -41,7 +40,7 @@ need sudo to install there, you may issue the --sudo-make-install option.
 
 EXAMPLE:
 
-  ./gen_makefile.py 3G+2G.deps default.opts iu.opts -I -m build
+  ./gen_makefile.py default.opts iu.opts -I -m build
   cd build
   make
 
@@ -51,12 +50,10 @@ import sys
 import os
 import argparse
 
+topdir = os.path.dirname(os.path.realpath(__file__))
+all_deps_file = os.path.join(topdir, "all.deps")
 parser = argparse.ArgumentParser(epilog=__doc__, formatter_class=argparse.RawTextHelpFormatter)
 
-parser.add_argument('projects_and_deps_file',
-  help='''Config file containing projects to build and
-dependencies between those''')
-
 parser.add_argument('configure_opts_files',
   help='''Config file containing project name and
 ./configure options''',
@@ -64,7 +61,7 @@ parser.add_argument('configure_opts_files',
 
 parser.add_argument('-m', '--make-dir', dest='make_dir',
   help='''Place Makefile in this dir (default: create
-a new dir named after deps and opts files).''')
+a new dir named after opts files).''')
 
 parser.add_argument('-s', '--src-dir', dest='src_dir', default='./src',
   help='Parent dir for all git clones.')
@@ -242,18 +239,20 @@ def gen_make(proj, deps, configure_opts, jobs, make_dir, src_dir, build_dir, url
     )
 
 
-projects_deps = read_projects_deps(args.projects_and_deps_file)
+projects_deps = read_projects_deps(all_deps_file)
 configure_opts = listdict()
 configure_opts_files = sorted(args.configure_opts_files or [])
 for configure_opts_file in configure_opts_files:
+  if configure_opts_file.endswith(".deps"):
+    print(f"WARNING: using {all_deps_file} instead of {configure_opts_file}")
+    continue
   r = read_configure_opts(configure_opts_file)
   configure_opts.extend_dict(read_configure_opts(configure_opts_file))
 
 make_dir = args.make_dir
 if not make_dir:
-  deps_name = args.projects_and_deps_file.replace('.deps', '')
   opts_names = '+'.join([f.replace('.opts', '') for f in configure_opts_files])
-  make_dir = 'make-%s-%s' % (deps_name, opts_names)
+  make_dir = 'make-%s' % opts_names
 
 if not os.path.isdir(make_dir):
   os.makedirs(make_dir)
@@ -268,9 +267,36 @@ print('Writing to %r' % output)
 with open(output, 'w') as out:
   out.write('# This Makefile was generated by %s\n' % os.path.basename(sys.argv[0]))
 
+  configure_opts_args = ""
+  for f in configure_opts_files:
+    if not f.endswith(".deps"):
+      configure_opts_args += f' \\\n\t\t{os.path.relpath(f, make_dir)}'
+
   # convenience: add a regen target that updates the generated makefile itself
   out.write(r'''
-default: all
+default: usrp
+
+cn: \
+	osmo-ggsn \
+	osmo-hlr \
+	osmo-iuh \
+	osmo-mgw \
+	osmo-msc \
+	osmo-sgsn \
+	osmo-sip-connector \
+	osmo-smlc \
+	$(NULL)
+
+cn-bsc: \
+	cn \
+	osmo-bsc \
+	$(NULL)
+
+usrp: \
+	cn-bsc \
+	osmo-bts \
+	osmo-trx \
+	$(NULL)
 
 .PHONY: all_debug
 all_debug:
@@ -281,7 +307,6 @@ all_debug:
 .PHONY: regen
 regen:
 	{script} \
-		{projects_and_deps} \
 		{configure_opts} \
 		-m {make_dir} \
 		-o {makefile} \
@@ -291,8 +316,7 @@ regen:
 
 '''.format(
     script=os.path.relpath(sys.argv[0], make_dir),
-    projects_and_deps=os.path.relpath(args.projects_and_deps_file, make_dir),
-    configure_opts=' \\\n\t\t'.join([os.path.relpath(f, make_dir) for f in configure_opts_files]),
+    configure_opts=configure_opts_args,
     make_dir='.',
     makefile=args.output,
     src_dir=os.path.relpath(args.src_dir, make_dir),
diff --git a/ttcn3/ttcn3.sh b/ttcn3/ttcn3.sh
index 826fb40..2cb4b3a 100755
--- a/ttcn3/ttcn3.sh
+++ b/ttcn3/ttcn3.sh
@@ -95,20 +95,10 @@ check_ttcn3_install() {
 setup_dir_make() {
 	cd "$DIR_OSMODEV"
 
-	( echo "# Generated by ttcn3.sh, do not edit"
-	  cat ./3G+2G.deps
-	  echo
-	  echo "osmo-bts	libosmocore libosmo-abis"
-	  echo "osmo-pcu	libosmocore"
-	  # just clone these, building is handled by ttcn3.sh
-	  echo "docker-playground"
-	  echo "osmo-ttcn3-hacks" ) > ttcn3/3G+2G_ttcn3.deps
-
 	local docker_cmd="$DIR_OSMODEV/ttcn3/scripts/docker_configure_make.sh"
 	docker_cmd="$docker_cmd $USER/$DOCKER_IMG_BUILD"
 
 	./gen_makefile.py \
-		ttcn3/3G+2G_ttcn3.deps \
 		default.opts \
 		iu.opts \
 		no_systemd.opts \