perf tools: Fix 'make help' message error

Currently 'make help' message has such hint:

   use "make prefix=<path> <install target>" to install to a particular
       path like make prefix=/usr/local install install-doc

But this is misleading, when I specify "prefix=/usr/local", it has got no
respect at all.

This is because that, "DESTDIR" is considered first. In this case, "DESTDIR"
has an empty value, so "prefix" is honored. However, "prefix" is unconditionally
assigned to $HOME, regardless of what it is set to from command line. So our
"prefix" setting got no respect and the actual destination falls back to $HOME.

This patch fixes this issue and corrects the help message.

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: http://lkml.kernel.org/r/1401727474-19370-1-git-send-email-nasa4836@gmail.com
Signed-off-by: Jiri Olsa <jolsa@kernel.org>

2 files changed, 3 insertions, 3 deletions

diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 6286e13adc2e..ae20edfcc3f7 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -789,8 +789,8 @@ help:
         @echo ''
         @echo 'Perf install targets:'
         @echo '  NOTE: documentation build requires asciidoc, xmlto packages to be installed'
-        @echo '  HINT: use "make prefix=<path> <install target>" to install to a particular'
-        @echo '        path like make prefix=/usr/local install install-doc'
+        @echo '  HINT: use "prefix" or "DESTDIR" to install to a particular'
+        @echo '        path like "make prefix=/usr/local install install-doc"'
         @echo '  install        - install compiled binaries'
         @echo '  install-doc    - install *all* documentation'
         @echo '  install-man    - install manpage documentation'
diff --git a/tools/perf/config/Makefile b/tools/perf/config/Makefile
index 319426f632fc..4f100b54ba8b 100644
--- a/tools/perf/config/Makefile
+++ b/tools/perf/config/Makefile
@@ -600,7 +600,7 @@ endif
 
 # Make the path relative to DESTDIR, not to prefix
 ifndef DESTDIR
-prefix = $(HOME)
+prefix ?= $(HOME)
 endif
 bindir_relative = bin
 bindir = $(prefix)/$(bindir_relative)