Use the new buffer-based WMI API to also support ACPI firmware
implementations that do not use ACPI buffers for returning the
results of a SMBIOS call.

Signed-off-by: Armin Wolf <W_Armin@gmx.de>
---
 drivers/platform/x86/dell/dell-smbios-wmi.c | 46 +++++++++++----------
 1 file changed, 25 insertions(+), 21 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-smbios-wmi.c b/drivers/platform/x86/dell/dell-smbios-wmi.c
index a7dca8c59d60..3c05b48354b3 100644
--- a/drivers/platform/x86/dell/dell-smbios-wmi.c
+++ b/drivers/platform/x86/dell/dell-smbios-wmi.c
@@ -50,38 +50,42 @@ static inline struct wmi_smbios_priv *get_first_smbios_priv(void)
 
 static int run_smbios_call(struct wmi_device *wdev)
 {
-	struct acpi_buffer output = {ACPI_ALLOCATE_BUFFER, NULL};
-	struct wmi_smbios_priv *priv;
-	struct acpi_buffer input;
-	union acpi_object *obj;
-	acpi_status status;
-
-	priv = dev_get_drvdata(&wdev->dev);
-	input.length = priv->req_buf_size - sizeof(u64);
-	input.pointer = &priv->buf->std;
+	struct wmi_smbios_priv *priv = dev_get_drvdata(&wdev->dev);
+	const struct wmi_buffer input = {
+		.length = priv->req_buf_size - sizeof(u64),
+		.data = &priv->buf->std,
+	};
+	struct wmi_buffer output;
+	int ret;
 
 	dev_dbg(&wdev->dev, "evaluating: %u/%u [%x,%x,%x,%x]\n",
 		priv->buf->std.cmd_class, priv->buf->std.cmd_select,
 		priv->buf->std.input[0], priv->buf->std.input[1],
 		priv->buf->std.input[2], priv->buf->std.input[3]);
 
-	status = wmidev_evaluate_method(wdev, 0, 1, &input, &output);
-	if (ACPI_FAILURE(status))
-		return -EIO;
-	obj = (union acpi_object *)output.pointer;
-	if (obj->type != ACPI_TYPE_BUFFER) {
-		dev_dbg(&wdev->dev, "received type: %d\n", obj->type);
-		if (obj->type == ACPI_TYPE_INTEGER)
-			dev_dbg(&wdev->dev, "SMBIOS call failed: %llu\n",
-				obj->integer.value);
-		kfree(output.pointer);
+	ret = wmidev_invoke_method(wdev, 0, 1, &input, &output);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * The output buffer returned by the WMI method should have at least the size
+	 * of the input buffer. Because the Windows WMI implementation ignores any surplus
+	 * data returned by a WMI method call we emulate this behavior here.
+	 *
+	 * Additionally the ACPI firmware might return buffers with not enough data to
+	 * signal an error, so we only print a debug message here.
+	 */
+	if (output.length < input.length) {
+		dev_dbg(&wdev->dev, "SMBIOS call returned not enough data (%zu)\n", output.length);
+		kfree(output.data);
 		return -EIO;
 	}
-	memcpy(input.pointer, obj->buffer.pointer, obj->buffer.length);
+
+	memcpy(input.data, output.data, input.length);
 	dev_dbg(&wdev->dev, "result: [%08x,%08x,%08x,%08x]\n",
 		priv->buf->std.output[0], priv->buf->std.output[1],
 		priv->buf->std.output[2], priv->buf->std.output[3]);
-	kfree(output.pointer);
+	kfree(output.data);
 
 	return 0;
 }
-- 
2.39.5