linux-kernel - [PATCH] coresight: Only register perf symlink for sinks with alloc

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Message-ID: <20250630-etm_perf_sink-v1-1-e4a7211f9ad7@quicinc.com>
Date: Mon, 30 Jun 2025 18:26:19 +0800
From: Yuanfang Zhang <quic_yuanfang@...cinc.com>
To: Suzuki K Poulose <suzuki.poulose@....com>,
        Mike Leach
	<mike.leach@...aro.org>,
        James Clark <james.clark@...aro.org>,
        "Alexander
 Shishkin" <alexander.shishkin@...ux.intel.com>
CC: <kernel@....qualcomm.com>, <coresight@...ts.linaro.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        Yuanfang Zhang <quic_yuanfang@...cinc.com>
Subject: [PATCH] coresight: Only register perf symlink for sinks with
 alloc_buffer

Ensure that etm_perf_add_symlink_sink() is only called for devices
that implement the alloc_buffer operation. This prevents invalid
symlink creation for dummy sinks that do not implement alloc_buffer.

Without this check, perf may attempt to use a dummy sink that lacks
alloc_buffer operationsu to initialise perf's ring buffer, leading
to runtime failures.

Fixes: 9d3ba0b6c0569 ("Coresight: Add coresight dummy driver")
Signed-off-by: Yuanfang Zhang <quic_yuanfang@...cinc.com>
---
 drivers/hwtracing/coresight/coresight-core.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-core.c b/drivers/hwtracing/coresight/coresight-core.c
index fa758cc21827552a5c97b6bdd05d22dec4994b22..fddf04c5ee46eb4d559416296f7e85ce6c5689fa 100644
--- a/drivers/hwtracing/coresight/coresight-core.c
+++ b/drivers/hwtracing/coresight/coresight-core.c
@@ -1374,8 +1374,9 @@ struct coresight_device *coresight_register(struct coresight_desc *desc)
 		goto out_unlock;
 	}
 
-	if (csdev->type == CORESIGHT_DEV_TYPE_SINK ||
-	    csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) {
+	if ((csdev->type == CORESIGHT_DEV_TYPE_SINK ||
+	     csdev->type == CORESIGHT_DEV_TYPE_LINKSINK) &&
+	    sink_ops(csdev)->alloc_buffer) {
 		ret = etm_perf_add_symlink_sink(csdev);
 
 		if (ret) {

---
base-commit: 408c97c4a5e0b634dcd15bf8b8808b382e888164
change-id: 20250630-etm_perf_sink-ee0fcffc6820

Best regards,
-- 
Yuanfang Zhang <quic_yuanfang@...cinc.com>