[PATCH v1 01/10] platform/x86: msi-wmi-platform: Use input buffer for returning result

[Antheas Kapenekakis <lkml@antheas.dev>]

From: Armin Wolf <W_Armin@gmx.de>

Modify msi_wmi_platform_query() to reuse the input buffer for
returning the result of a WMI method call. Using a separate output
buffer to return the result is unnecessary because the WMI interface
requires both buffers to have the same length anyway.

Co-developed-by: Antheas Kapenekakis <lkml@antheas.dev>
Signed-off-by: Antheas Kapenekakis <lkml@antheas.dev>
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
---
 drivers/platform/x86/msi-wmi-platform.c | 53 ++++++++++++-------------
 1 file changed, 26 insertions(+), 27 deletions(-)

diff --git a/drivers/platform/x86/msi-wmi-platform.c b/drivers/platform/x86/msi-wmi-platform.c
index dc5e9878cb682..41218a9d6e35d 100644
--- a/drivers/platform/x86/msi-wmi-platform.c
+++ b/drivers/platform/x86/msi-wmi-platform.c
@@ -21,6 +21,7 @@
 #include <linux/mutex.h>
 #include <linux/printk.h>
 #include <linux/rwsem.h>
+#include <linux/string.h>
 #include <linux/types.h>
 #include <linux/wmi.h>
 
@@ -140,19 +141,19 @@ static int msi_wmi_platform_parse_buffer(union acpi_object *obj, u8 *output, siz
 }
 
 static int msi_wmi_platform_query(struct msi_wmi_platform_data *data,
-				  enum msi_wmi_platform_method method, u8 *input,
-				  size_t input_length, u8 *output, size_t output_length)
+				  enum msi_wmi_platform_method method, u8 *buffer,
+				  size_t length)
 {
 	struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
 	struct acpi_buffer in = {
-		.length = input_length,
-		.pointer = input
+		.length = length,
+		.pointer = buffer
 	};
 	union acpi_object *obj;
 	acpi_status status;
 	int ret;
 
-	if (!input_length || !output_length)
+	if (!length)
 		return -EINVAL;
 
 	/*
@@ -169,7 +170,7 @@ static int msi_wmi_platform_query(struct msi_wmi_platform_data *data,
 	if (!obj)
 		return -ENODATA;
 
-	ret = msi_wmi_platform_parse_buffer(obj, output, output_length);
+	ret = msi_wmi_platform_parse_buffer(obj, buffer, length);
 	kfree(obj);
 
 	return ret;
@@ -185,17 +186,15 @@ static int msi_wmi_platform_read(struct device *dev, enum hwmon_sensor_types typ
 				 int channel, long *val)
 {
 	struct msi_wmi_platform_data *data = dev_get_drvdata(dev);
-	u8 input[32] = { 0 };
-	u8 output[32];
+	u8 buffer[32] = { 0 };
 	u16 value;
 	int ret;
 
-	ret = msi_wmi_platform_query(data, MSI_PLATFORM_GET_FAN, input, sizeof(input), output,
-				     sizeof(output));
+	ret = msi_wmi_platform_query(data, MSI_PLATFORM_GET_FAN, buf, sizeof(buf));
 	if (ret < 0)
 		return ret;
 
-	value = get_unaligned_be16(&output[channel * 2 + 1]);
+	value = get_unaligned_be16(&buffer[channel * 2 + 1]);
 	if (!value)
 		*val = 0;
 	else
@@ -245,13 +244,17 @@ static ssize_t msi_wmi_platform_write(struct file *fp, const char __user *input,
 		return ret;
 
 	down_write(&data->buffer_lock);
-	ret = msi_wmi_platform_query(data->data, data->method, payload, data->length, data->buffer,
+	ret = msi_wmi_platform_query(data->data, data->method, data->buffer,
 				     data->length);
 	up_write(&data->buffer_lock);
 
 	if (ret < 0)
 		return ret;
 
+	down_write(&data->buffer_lock);
+	memcpy(data->buffer, payload, data->length);
+	up_write(&data->buffer_lock);
+
 	return length;
 }
 
@@ -348,23 +351,21 @@ static int msi_wmi_platform_hwmon_init(struct msi_wmi_platform_data *data)
 
 static int msi_wmi_platform_ec_init(struct msi_wmi_platform_data *data)
 {
-	u8 input[32] = { 0 };
-	u8 output[32];
+	u8 buffer[32] = { 0 };
 	u8 flags;
 	int ret;
 
-	ret = msi_wmi_platform_query(data, MSI_PLATFORM_GET_EC, input, sizeof(input), output,
-				     sizeof(output));
+	ret = msi_wmi_platform_query(data, MSI_PLATFORM_GET_EC, buffer, sizeof(buffer));
 	if (ret < 0)
 		return ret;
 
-	flags = output[MSI_PLATFORM_EC_FLAGS_OFFSET];
+	flags = buffer[MSI_PLATFORM_EC_FLAGS_OFFSET];
 
 	dev_dbg(&data->wdev->dev, "EC RAM version %lu.%lu\n",
 		FIELD_GET(MSI_PLATFORM_EC_MAJOR_MASK, flags),
 		FIELD_GET(MSI_PLATFORM_EC_MINOR_MASK, flags));
 	dev_dbg(&data->wdev->dev, "EC firmware version %.28s\n",
-		&output[MSI_PLATFORM_EC_VERSION_OFFSET]);
+		&buffer[MSI_PLATFORM_EC_VERSION_OFFSET]);
 
 	if (!(flags & MSI_PLATFORM_EC_IS_TIGERLAKE)) {
 		if (!force)
@@ -378,27 +379,25 @@ static int msi_wmi_platform_ec_init(struct msi_wmi_platform_data *data)
 
 static int msi_wmi_platform_init(struct msi_wmi_platform_data *data)
 {
-	u8 input[32] = { 0 };
-	u8 output[32];
+	u8 buffer[32] = { 0 };
 	int ret;
 
-	ret = msi_wmi_platform_query(data, MSI_PLATFORM_GET_WMI, input, sizeof(input), output,
-				     sizeof(output));
+	ret = msi_wmi_platform_query(data, MSI_PLATFORM_GET_WMI, buffer, sizeof(buffer));
 	if (ret < 0)
 		return ret;
 
 	dev_dbg(&data->wdev->dev, "WMI interface version %u.%u\n",
-		output[MSI_PLATFORM_WMI_MAJOR_OFFSET],
-		output[MSI_PLATFORM_WMI_MINOR_OFFSET]);
+		buffer[MSI_PLATFORM_WMI_MAJOR_OFFSET],
+		buffer[MSI_PLATFORM_WMI_MINOR_OFFSET]);
 
-	if (output[MSI_PLATFORM_WMI_MAJOR_OFFSET] != MSI_WMI_PLATFORM_INTERFACE_VERSION) {
+	if (buffer[MSI_PLATFORM_WMI_MAJOR_OFFSET] != MSI_WMI_PLATFORM_INTERFACE_VERSION) {
 		if (!force)
 			return -ENODEV;
 
 		dev_warn(&data->wdev->dev,
 			 "Loading despite unsupported WMI interface version (%u.%u)\n",
-			 output[MSI_PLATFORM_WMI_MAJOR_OFFSET],
-			 output[MSI_PLATFORM_WMI_MINOR_OFFSET]);
+			 buffer[MSI_PLATFORM_WMI_MAJOR_OFFSET],
+			 buffer[MSI_PLATFORM_WMI_MINOR_OFFSET]);
 	}
 
 	return 0;
-- 
2.49.0