[PATCH] Improved usability of the Makefile in libbpf

[Xin Liu]

Current libbpf Makefile does not contain the help command, which
is inconvenient to use. A help command is provided to list the
commands supported by libbpf make and the functions of the commands.

Signed-off-by: Xin Liu <liuxin350@xxxxxxxxxx>
---
 tools/lib/bpf/Makefile | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 4c904ef0b47e..c86e05df4711 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -286,3 +286,37 @@ tags:
 
 # Delete partially updated (corrupted) files on error
 .DELETE_ON_ERROR:
+
+help:
+	@echo 'Default targets:'
+	@echo '  all               - Run all_cmd'
+	@echo '  all_cmd           - Build library and pkgconfig, check abi and version info'
+	@echo ''
+	@echo 'Cleaning targets:'
+	@echo '  clean             - Remove all generated files'
+	@echo ''
+	@echo 'Build targets:'
+	@echo '  libbpf.so         - Build the dynamic library'
+	@echo '  libbpf.a          - Build the static library'
+	@echo '  libbpf.pc         - Build the pkgconfig file'
+	@echo ''
+	@echo 'Install targets:'
+	@echo '  install           - Install all headers, library and pkgconfig file to'
+	@echo '                      DESTDIR(default: /) with prefix(default: /usr/local)'
+	@echo '  install_lib       - Install only library'
+	@echo '  install_headers   - Install only headers'
+	@echo '  install_pkgconfig - Install only pkgconfig file'
+	@echo ''
+	@echo 'Other generic targets:'
+	@echo '  cscope            - Generate cscope index'
+	@echo '  tags              - Generate tags file for editors'
+	@echo '  check             - Check abi and version info'
+	@echo '  check_abi         - Check versioned symbols'
+	@echo '  check_version     - Check whether the libbpf version defined in libbpf_version.h'
+	@echo '                      is the same as that defined in libbpf.map'
+	@echo ''
+	@echo '  make V=0|1             [targets] 0 => quiet build (default), 1 => verbose build'
+	@echo '  make DESTDIR=/root     [install targets] use DESTDIR for installing'
+	@echo '                                           into a different root directory'
+	@echo '  make prefix=/path      [install targets] use prefix for installing'
+	@echo '                                           into a user defined prefix path'
-- 
2.33.0