linux-kernel - [PATCH v4] tpm: Replace scnprintf() with sysfs_emit() and sysfs_emit

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Message-ID: <20250625050346.11500-1-chelsyratnawat2001@gmail.com>
Date: Tue, 24 Jun 2025 22:03:46 -0700
From: Chelsy Ratnawat <chelsyratnawat2001@...il.com>
To: peterhuewe@....de,
	jarkko@...nel.org
Cc: jgg@...pe.ca,
	linux-integrity@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Chelsy Ratnawat <chelsyratnawat2001@...il.com>
Subject: [PATCH v4] tpm: Replace scnprintf() with sysfs_emit() and sysfs_emit_at() in sysfs show functions

Documentation/filesystems/sysfs.rst mentions that show() should only
use sysfs_emit() or sysfs_emit_at() when formating the value to be
returned to user space. So replace scnprintf() with sysfs_emit().

Signed-off-by: Chelsy Ratnawat <chelsyratnawat2001@...il.com>
---
Changes in v4: 
- updated the commit message.
 
 drivers/char/tpm/tpm_ppi.c | 48 ++++++++++++++++++--------------------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/drivers/char/tpm/tpm_ppi.c b/drivers/char/tpm/tpm_ppi.c
index bc7b1b4501b3..50f64d9b53c8 100644
--- a/drivers/char/tpm/tpm_ppi.c
+++ b/drivers/char/tpm/tpm_ppi.c
@@ -52,7 +52,7 @@ static ssize_t tpm_show_ppi_version(struct device *dev,
 {
 	struct tpm_chip *chip = to_tpm_chip(dev);
 
-	return scnprintf(buf, PAGE_SIZE, "%s\n", chip->ppi_version);
+	return sysfs_emit(buf, "%s\n", chip->ppi_version);
 }
 
 static ssize_t tpm_show_ppi_request(struct device *dev,
@@ -87,12 +87,10 @@ static ssize_t tpm_show_ppi_request(struct device *dev,
 		else {
 			req = obj->package.elements[1].integer.value;
 			if (tpm_ppi_req_has_parameter(req))
-				size = scnprintf(buf, PAGE_SIZE,
-				    "%llu %llu\n", req,
+				size = sysfs_emit(buf, "%llu %llu\n", req,
 				    obj->package.elements[2].integer.value);
 			else
-				size = scnprintf(buf, PAGE_SIZE,
-						"%llu\n", req);
+				size = sysfs_emit(buf, "%llu\n", req);
 		}
 	} else if (obj->package.count == 2 &&
 	    obj->package.elements[0].type == ACPI_TYPE_INTEGER &&
@@ -100,7 +98,7 @@ static ssize_t tpm_show_ppi_request(struct device *dev,
 		if (obj->package.elements[0].integer.value)
 			size = -EFAULT;
 		else
-			size = scnprintf(buf, PAGE_SIZE, "%llu\n",
+			size = sysfs_emit(buf, "%llu\n",
 				 obj->package.elements[1].integer.value);
 	}
 
@@ -211,10 +209,10 @@ static ssize_t tpm_show_ppi_transition_action(struct device *dev,
 	}
 
 	if (ret < ARRAY_SIZE(info) - 1)
-		status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret, info[ret]);
+		status = sysfs_emit(buf, "%d: %s\n", ret, info[ret]);
 	else
-		status = scnprintf(buf, PAGE_SIZE, "%d: %s\n", ret,
-				   info[ARRAY_SIZE(info)-1]);
+		status = sysfs_emit(buf, "%d: %s\n", ret,
+				    info[ARRAY_SIZE(info)-1]);
 	return status;
 }
 
@@ -255,23 +253,23 @@ static ssize_t tpm_show_ppi_response(struct device *dev,
 	res = ret_obj[2].integer.value;
 	if (req) {
 		if (res == 0)
-			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
-					   "0: Success");
+			status = sysfs_emit(buf, "%llu %s\n", req,
+					    "0: Success");
 		else if (res == 0xFFFFFFF0)
-			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
-					   "0xFFFFFFF0: User Abort");
+			status = sysfs_emit(buf, "%llu %s\n", req,
+					    "0xFFFFFFF0: User Abort");
 		else if (res == 0xFFFFFFF1)
-			status = scnprintf(buf, PAGE_SIZE, "%llu %s\n", req,
-					   "0xFFFFFFF1: BIOS Failure");
+			status = sysfs_emit(buf, "%llu %s\n", req,
+					    "0xFFFFFFF1: BIOS Failure");
 		else if (res >= 1 && res <= 0x00000FFF)
-			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
-					   req, res, "Corresponding TPM error");
+			status = sysfs_emit(buf, "%llu %llu: %s\n",
+					    req, res, "Corresponding TPM error");
 		else
-			status = scnprintf(buf, PAGE_SIZE, "%llu %llu: %s\n",
-					   req, res, "Error");
+			status = sysfs_emit(buf, "%llu %llu: %s\n",
+					    req, res, "Error");
 	} else {
-		status = scnprintf(buf, PAGE_SIZE, "%llu: %s\n",
-				   req, "No Recent Request");
+		status = sysfs_emit(buf, "%llu: %s\n",
+				    req, "No Recent Request");
 	}
 
 cleanup:
@@ -284,7 +282,7 @@ static ssize_t show_ppi_operations(acpi_handle dev_handle, char *buf, u32 start,
 {
 	int i;
 	u32 ret;
-	char *str = buf;
+	int len = 0;
 	union acpi_object *obj, tmp;
 	union acpi_object argv = ACPI_INIT_DSM_ARGV4(1, &tmp);
 
@@ -314,11 +312,11 @@ static ssize_t show_ppi_operations(acpi_handle dev_handle, char *buf, u32 start,
 		}
 
 		if (ret > 0 && ret < ARRAY_SIZE(info))
-			str += scnprintf(str, PAGE_SIZE, "%d %d: %s\n",
-					 i, ret, info[ret]);
+			len += sysfs_emit_at(buf, len, "%d %d: %s\n",
+					     i, ret, info[ret]);
 	}
 
-	return str - buf;
+	return len;
 }
 
 static ssize_t tpm_show_ppi_tcg_operations(struct device *dev,
-- 
2.47.1