linux-kernel - [PATCH 1/2] firmware: cs_dsp: Factor out common debugfs string read

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Message-ID: <20251120130640.1169780-2-rf@opensource.cirrus.com>
Date: Thu, 20 Nov 2025 13:06:39 +0000
From: Richard Fitzgerald <rf@...nsource.cirrus.com>
To: broonie@...nel.org
Cc: linux-sound@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...nsource.cirrus.com
Subject: [PATCH 1/2] firmware: cs_dsp: Factor out common debugfs string read

cs_dsp_debugfs_wmfw_read() and cs_dsp_debugfs_bin_read() were identical
except for which struct member they printed. Move all this duplicated
code into a common function cs_dsp_debugfs_string_read().

The check for dsp->booted has been removed because this is redundant.
The two strings are set when the DSP is booted and cleared when the
DSP is powered-down.

Access to the string char * must be protected by the pwr_lock mutex. The
string is passed into cs_dsp_debugfs_string_read() as a pointer to the
char * so that the mutex lock can also be factored out into
cs_dsp_debugfs_string_read().

wmfw_file_name and bin_file_name members of struct cs_dsp have been
changed to const char *. It makes for a better API to pass a const
pointer into cs_dsp_debugfs_string_read().

Signed-off-by: Richard Fitzgerald <rf@...nsource.cirrus.com>
---
 drivers/firmware/cirrus/cs_dsp.c       | 45 ++++++++++++--------------
 include/linux/firmware/cirrus/cs_dsp.h |  4 +--
 2 files changed, 23 insertions(+), 26 deletions(-)

diff --git a/drivers/firmware/cirrus/cs_dsp.c b/drivers/firmware/cirrus/cs_dsp.c
index f51047d8ea64..58e41751dbc1 100644
--- a/drivers/firmware/cirrus/cs_dsp.c
+++ b/drivers/firmware/cirrus/cs_dsp.c
@@ -9,6 +9,7 @@
  *                         Cirrus Logic International Semiconductor Ltd.
  */
 
+#include <linux/cleanup.h>
 #include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
@@ -410,24 +411,30 @@ static void cs_dsp_debugfs_clear(struct cs_dsp *dsp)
 	dsp->bin_file_name = NULL;
 }
 
+static ssize_t cs_dsp_debugfs_string_read(struct cs_dsp *dsp,
+					  char __user *user_buf,
+					  size_t count, loff_t *ppos,
+					  const char **pstr)
+{
+	const char *str;
+
+	scoped_guard(mutex, &dsp->pwr_lock) {
+		str = *pstr;
+		if (!str)
+			return 0;
+
+		return simple_read_from_buffer(user_buf, count, ppos, str, strlen(str));
+	}
+}
+
 static ssize_t cs_dsp_debugfs_wmfw_read(struct file *file,
 					char __user *user_buf,
 					size_t count, loff_t *ppos)
 {
 	struct cs_dsp *dsp = file->private_data;
-	ssize_t ret;
 
-	mutex_lock(&dsp->pwr_lock);
-
-	if (!dsp->wmfw_file_name || !dsp->booted)
-		ret = 0;
-	else
-		ret = simple_read_from_buffer(user_buf, count, ppos,
-					      dsp->wmfw_file_name,
-					      strlen(dsp->wmfw_file_name));
-
-	mutex_unlock(&dsp->pwr_lock);
-	return ret;
+	return cs_dsp_debugfs_string_read(dsp, user_buf, count, ppos,
+					  &dsp->wmfw_file_name);
 }
 
 static ssize_t cs_dsp_debugfs_bin_read(struct file *file,
@@ -435,19 +442,9 @@ static ssize_t cs_dsp_debugfs_bin_read(struct file *file,
 				       size_t count, loff_t *ppos)
 {
 	struct cs_dsp *dsp = file->private_data;
-	ssize_t ret;
 
-	mutex_lock(&dsp->pwr_lock);
-
-	if (!dsp->bin_file_name || !dsp->booted)
-		ret = 0;
-	else
-		ret = simple_read_from_buffer(user_buf, count, ppos,
-					      dsp->bin_file_name,
-					      strlen(dsp->bin_file_name));
-
-	mutex_unlock(&dsp->pwr_lock);
-	return ret;
+	return cs_dsp_debugfs_string_read(dsp, user_buf, count, ppos,
+					  &dsp->bin_file_name);
 }
 
 static const struct {
diff --git a/include/linux/firmware/cirrus/cs_dsp.h b/include/linux/firmware/cirrus/cs_dsp.h
index a66eb7624730..69959032f8f5 100644
--- a/include/linux/firmware/cirrus/cs_dsp.h
+++ b/include/linux/firmware/cirrus/cs_dsp.h
@@ -188,8 +188,8 @@ struct cs_dsp {
 
 #ifdef CONFIG_DEBUG_FS
 	struct dentry *debugfs_root;
-	char *wmfw_file_name;
-	char *bin_file_name;
+	const char *wmfw_file_name;
+	const char *bin_file_name;
 #endif
 };
 
-- 
2.47.3