linux-kernel - [PATCH v5 04/13] coresight: Hide unused ETMv3 format attributes

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Message-Id: <20251118-james-cs-syncfreq-v5-4-82efd7b1a751@linaro.org>
Date: Tue, 18 Nov 2025 16:27:54 +0000
From: James Clark <james.clark@...aro.org>
To: Suzuki K Poulose <suzuki.poulose@....com>, 
 Mike Leach <mike.leach@...aro.org>, 
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
 Jonathan Corbet <corbet@....net>, Leo Yan <leo.yan@....com>, 
 Randy Dunlap <rdunlap@...radead.org>
Cc: coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org, 
 James Clark <james.clark@...aro.org>
Subject: [PATCH v5 04/13] coresight: Hide unused ETMv3 format attributes

ETMv3 only has a few attributes, and setting unused ones results in an
error, so hide them to begin with.

Signed-off-by: James Clark <james.clark@...aro.org>
---
 drivers/hwtracing/coresight/coresight-etm-perf.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/drivers/hwtracing/coresight/coresight-etm-perf.c b/drivers/hwtracing/coresight/coresight-etm-perf.c
index 17afa0f4cdee..faebd7822a77 100644
--- a/drivers/hwtracing/coresight/coresight-etm-perf.c
+++ b/drivers/hwtracing/coresight/coresight-etm-perf.c
@@ -106,8 +106,30 @@ static struct attribute *etm_config_formats_attr[] = {
 	NULL,
 };
 
+static umode_t etm_format_attr_is_visible(struct kobject *kobj,
+					  struct attribute *attr, int unused)
+{
+	/* ETM4 has all attributes */
+	if (IS_ENABLED(CONFIG_CORESIGHT_SOURCE_ETM4X))
+		return attr->mode;
+
+	/*
+	 * ETM3 only uses these attributes for programming itself (see
+	 * ETM3X_SUPPORTED_OPTIONS). Sink ID is also supported for selecting a
+	 * sink, but not used for configuring the ETM.
+	 */
+	if (attr == &format_attr_cycacc.attr ||
+	    attr == &format_attr_timestamp.attr ||
+	    attr == &format_attr_retstack.attr ||
+	    attr == &format_attr_sinkid.attr)
+		return attr->mode;
+
+	return 0;
+}
+
 static const struct attribute_group etm_pmu_format_group = {
 	.name   = "format",
+	.is_visible = etm_format_attr_is_visible,
 	.attrs  = etm_config_formats_attr,
 };
 

-- 
2.34.1