[tip:perf/core] perf util: Add const modifier to buf in "writen" function

From: tip-bot for David Carrillo-Cisneros
Date: Thu Jul 20 2017 - 05:04:13 EST


Commit-ID: 7c72440506e2108494bab3b68a4118fa61a9dbf4
Gitweb: http://git.kernel.org/tip/7c72440506e2108494bab3b68a4118fa61a9dbf4
Author: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
AuthorDate: Mon, 17 Jul 2017 21:25:37 -0700
Committer: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Tue, 18 Jul 2017 23:14:29 -0300

perf util: Add const modifier to buf in "writen" function

Make buf in helper function "writen" constant to simplify the life of
its callers.

This requires to hack a cast of buf prior to passing it to "ion" which
is simpler than the alternative of reworking the "ion" function to
provide a read and a write paths, the latter with constant buf argument.

Signed-off-by: David Carrillo-Cisneros <davidcc@xxxxxxxxxx>
Acked-by: David Ahern <dsahern@xxxxxxxxx>
Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: He Kuang <hekuang@xxxxxxxxxx>
Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Simon Que <sque@xxxxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Wang Nan <wangnan0@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170718042549.145161-5-davidcc@xxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
tools/perf/util/util.c | 6 ++++--
tools/perf/util/util.h | 2 +-
2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 9e4ea85..4c360da 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -281,6 +281,7 @@ static ssize_t ion(bool is_read, int fd, void *buf, size_t n)
size_t left = n;

while (left) {
+ /* buf must be treated as const if !is_read. */
ssize_t ret = is_read ? read(fd, buf, left) :
write(fd, buf, left);

@@ -308,9 +309,10 @@ ssize_t readn(int fd, void *buf, size_t n)
/*
* Write exactly 'n' bytes or return an error.
*/
-ssize_t writen(int fd, void *buf, size_t n)
+ssize_t writen(int fd, const void *buf, size_t n)
{
- return ion(false, fd, buf, n);
+ /* ion does not modify buf. */
+ return ion(false, fd, (void *)buf, n);
}

size_t hex_width(u64 v)
diff --git a/tools/perf/util/util.h b/tools/perf/util/util.h
index 062dd20..b136c27 100644
--- a/tools/perf/util/util.h
+++ b/tools/perf/util/util.h
@@ -38,7 +38,7 @@ int copyfile_ns(const char *from, const char *to, struct nsinfo *nsi);
int copyfile_offset(int fromfd, loff_t from_ofs, int tofd, loff_t to_ofs, u64 size);

ssize_t readn(int fd, void *buf, size_t n);
-ssize_t writen(int fd, void *buf, size_t n);
+ssize_t writen(int fd, const void *buf, size_t n);

size_t hex_width(u64 v);
int hex2u64(const char *ptr, u64 *val);