linux-kernel - [PATCH v2] perf: cs-etm: Improve missing sink warning message

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Message-Id: <20230124110220.460551-1-james.clark@arm.com>
Date:   Tue, 24 Jan 2023 11:02:20 +0000
From:   James Clark <james.clark@....com>
To:     linux-perf-users@...r.kernel.org, acme@...nel.org,
        suzuki.poulose@....com
Cc:     linux-kernel@...r.kernel.org, James Clark <james.clark@....com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Mike Leach <mike.leach@...aro.org>,
        Leo Yan <leo.yan@...aro.org>,
        John Garry <john.g.garry@...cle.com>,
        Will Deacon <will@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>, coresight@...ts.linaro.org,
        linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v2] perf: cs-etm: Improve missing sink warning message

Make the sink error message more similar to the event error message that
reminds about missing kernel support. The available sinks are also
determined by the hardware so mention that too.

Also, usually it's not necessary to specify the sink, so add that as a
hint.

Now the error for a made up sink looks like this:

  $ perf record -e cs_etm/@.../
  Couldn't find sink "abc" on event cs_etm/@.../.
  Missing kernel or device support?

  Hint: An appropriate sink will be picked automatically if one isn't is specified.

For any error other than ENOENT, the same message as before is
displayed.

Signed-off-by: James Clark <james.clark@....com>
---
V1 -> V2: Keep old error message unless it's ENOENT

 tools/perf/arch/arm/util/cs-etm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index 481e170cd3f1..7f71c8a237ff 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -283,9 +283,15 @@ static int cs_etm_set_sink_attr(struct perf_pmu *pmu,
 
 		ret = perf_pmu__scan_file(pmu, path, "%x", &hash);
 		if (ret != 1) {
-			pr_err("failed to set sink \"%s\" on event %s with %d (%s)\n",
-			       sink, evsel__name(evsel), errno,
-			       str_error_r(errno, msg, sizeof(msg)));
+			if (errno == ENOENT)
+				pr_err("Couldn't find sink \"%s\" on event %s\n"
+				       "Missing kernel or device support?\n\n"
+				       "Hint: An appropriate sink will be picked automatically if one isn't specified.\n",
+				       sink, evsel__name(evsel));
+			else
+				pr_err("Failed to set sink \"%s\" on event %s with %d (%s)\n",
+				       sink, evsel__name(evsel), errno,
+				       str_error_r(errno, msg, sizeof(msg)));
 			return ret;
 		}
 

base-commit: 5670ebf54bd26482f57a094c53bdc562c106e0a9
-- 
2.39.1