linux-kernel - [PATCH 09/17] coresight: Clarify comments around the PID of the sink owner

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Message-Id: <20240429152207.479221-10-james.clark@arm.com>
Date: Mon, 29 Apr 2024 16:21:54 +0100
From: James Clark <james.clark@....com>
To: linux-perf-users@...r.kernel.org,
	gankulkarni@...amperecomputing.com,
	scclevenger@...amperecomputing.com,
	coresight@...ts.linaro.org,
	suzuki.poulose@....com,
	mike.leach@...aro.org
Cc: James Clark <james.clark@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	John Garry <john.g.garry@...cle.com>,
	Will Deacon <will@...nel.org>,
	Leo Yan <leo.yan@...ux.dev>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com
Subject: [PATCH 09/17] coresight: Clarify comments around the PID of the sink owner

"Process being monitored" and "pid of the process to monitor" imply that
this would be the same PID if there were two sessions targeting the same
process. But this is actually the PID of the process that did the Perf
event open call, rather than the target of the session. So update the
comments to make this clearer.

Signed-off-by: James Clark <james.clark@....com>
---
 drivers/hwtracing/coresight/coresight-tmc-etr.c | 5 +++--
 drivers/hwtracing/coresight/coresight-tmc.h     | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c
index e75428fa1592..8962fc27d04f 100644
--- a/drivers/hwtracing/coresight/coresight-tmc-etr.c
+++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c
@@ -36,7 +36,8 @@ struct etr_buf_hw {
  * etr_perf_buffer - Perf buffer used for ETR
  * @drvdata		- The ETR drvdaga this buffer has been allocated for.
  * @etr_buf		- Actual buffer used by the ETR
- * @pid			- The PID this etr_perf_buffer belongs to.
+ * @pid			- The PID of the session owner that etr_perf_buffer
+ *			  belongs to.
  * @snaphost		- Perf session mode
  * @nr_pages		- Number of pages in the ring buffer.
  * @pages		- Array of Pages in the ring buffer.
@@ -1662,7 +1663,7 @@ static int tmc_enable_etr_sink_perf(struct coresight_device *csdev, void *data)
 		goto unlock_out;
 	}
 
-	/* Get a handle on the pid of the process to monitor */
+	/* Get a handle on the pid of the session owner */
 	pid = etr_perf->pid;
 
 	/* Do not proceed if this device is associated with another session */
diff --git a/drivers/hwtracing/coresight/coresight-tmc.h b/drivers/hwtracing/coresight/coresight-tmc.h
index c77763b49de0..2671926be62a 100644
--- a/drivers/hwtracing/coresight/coresight-tmc.h
+++ b/drivers/hwtracing/coresight/coresight-tmc.h
@@ -171,8 +171,9 @@ struct etr_buf {
  * @csdev:	component vitals needed by the framework.
  * @miscdev:	specifics to handle "/dev/xyz.tmc" entry.
  * @spinlock:	only one at a time pls.
- * @pid:	Process ID of the process being monitored by the session
- *		that is using this component.
+ * @pid:	Process ID of the process that owns the session that is using
+ *		this component. For example this would be the pid of the Perf
+ *		process.
  * @buf:	Snapshot of the trace data for ETF/ETB.
  * @etr_buf:	details of buffer used in TMC-ETR
  * @len:	size of the available trace for ETF/ETB.
-- 
2.34.1