linux-kernel - [PATCH v7 08/28] tracing: Add init callback to trace remotes

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Message-ID: <20251003133825.2068970-9-vdonnefort@google.com>
Date: Fri,  3 Oct 2025 14:38:05 +0100
From: Vincent Donnefort <vdonnefort@...gle.com>
To: rostedt@...dmis.org, mhiramat@...nel.org, mathieu.desnoyers@...icios.com, 
	linux-trace-kernel@...r.kernel.org, maz@...nel.org, oliver.upton@...ux.dev, 
	joey.gouly@....com, suzuki.poulose@....com, yuzenghui@...wei.com
Cc: kvmarm@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	jstultz@...gle.com, qperret@...gle.com, will@...nel.org, 
	aneesh.kumar@...nel.org, kernel-team@...roid.com, 
	linux-kernel@...r.kernel.org, Vincent Donnefort <vdonnefort@...gle.com>
Subject: [PATCH v7 08/28] tracing: Add init callback to trace remotes

Add a .init call back so the trace remote callers can add entries to the
tracefs directory.

Signed-off-by: Vincent Donnefort <vdonnefort@...gle.com>

diff --git a/include/linux/trace_remote.h b/include/linux/trace_remote.h
index 55754ef78104..15a579633123 100644
--- a/include/linux/trace_remote.h
+++ b/include/linux/trace_remote.h
@@ -3,11 +3,14 @@
 #ifndef _LINUX_TRACE_REMOTE_H
 #define _LINUX_TRACE_REMOTE_H
 
+#include <linux/dcache.h>
 #include <linux/ring_buffer.h>
 
 /**
  * struct trace_remote_callbacks - Callbacks used by Tracefs to control the remote
  *
+ * @init:		Called once the remote has been registered. Allows the
+ *			caller to extend the Tracefs remote directory
  * @load_trace_buffer:  Called before Tracefs accesses the trace buffer for the first
  *			time. Must return a &trace_buffer_desc
  *			(most likely filled with trace_remote_alloc_buffer())
@@ -23,6 +26,7 @@
  *			new reader-page from the @cpu ring-buffer.
  */
 struct trace_remote_callbacks {
+	int	(*init)(struct dentry *d, void *priv);
 	struct trace_buffer_desc *(*load_trace_buffer)(unsigned long size, void *priv);
 	void	(*unload_trace_buffer)(struct trace_buffer_desc *desc, void *priv);
 	int	(*enable_tracing)(bool enable, void *priv);
diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c
index c011df20df95..55ba3fd9e002 100644
--- a/kernel/trace/trace_remote.c
+++ b/kernel/trace/trace_remote.c
@@ -837,6 +837,7 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo
 int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs, void *priv)
 {
 	struct trace_remote *remote;
+	int ret;
 
 	remote = kzalloc(sizeof(*remote), GFP_KERNEL);
 	if (!remote)
@@ -854,7 +855,11 @@ int trace_remote_register(const char *name, struct trace_remote_callbacks *cbs,
 		return -ENOMEM;
 	}
 
-	return 0;
+	ret = cbs->init ? cbs->init(remote->dentry, priv) : 0;
+	if (ret)
+		pr_err("Init failed for trace remote '%s' (%d)\n", name, ret);
+
+	return ret;
 }
 
 void trace_remote_free_buffer(struct trace_buffer_desc *desc)
-- 
2.51.0.618.g983fd99d29-goog