platform/x86: dell-smbios-wmi: Disable userspace interface if missing hotfix

The Dell SMBIOS WMI interface will fail for some more complex calls unless
a WMI hotfix has been included.  Most platforms have this fix available in
a maintenance BIOS release.  In the case the driver is loaded on a
platform without this fix, disable the userspace interface.

A hotfix indicator is present in the dell-wmi-descriptor that represents
whether or not more complex calls will work properly.

"Simple" calls such as those used by dell-laptop and dell-wmi will continue
to work properly so dell-smbios-wmi should not be blocked from binding and
being used as the dell-smbios dispatcher.

Suggested-by: Girish Prakash <girish.prakash@dell.com>
Signed-off-by: Mario Limonciello <mario.limonciello@dell.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/dell-smbios-wmi.c

@@ -147,7 +147,10 @@ fail_smbios_cmd:
 
 static int dell_smbios_wmi_probe(struct wmi_device *wdev)
 {
+	struct wmi_driver *wdriver =
+		container_of(wdev->dev.driver, struct wmi_driver, driver);
 	struct wmi_smbios_priv *priv;
+	u32 hotfix;
 	int count;
 	int ret;
 
@@ -164,6 +167,16 @@ static int dell_smbios_wmi_probe(struct wmi_device *wdev)
 	if (!dell_wmi_get_size(&priv->req_buf_size))
 		return -EPROBE_DEFER;
 
+	/* some SMBIOS calls fail unless BIOS contains hotfix */
+	if (!dell_wmi_get_hotfix(&hotfix))
+		return -EPROBE_DEFER;
+	if (!hotfix) {
+		dev_warn(&wdev->dev,
+			"WMI SMBIOS userspace interface not supported(%u), try upgrading to a newer BIOS\n",
+			hotfix);
+		wdriver->filter_callback = NULL;
+	}
+
 	/* add in the length object we will use internally with ioctl */
 	priv->req_buf_size += sizeof(u64);
 	ret = set_required_buffer_size(wdev, priv->req_buf_size);

drivers/platform/x86/dell-wmi-descriptor.c

@@ -27,6 +27,7 @@ struct descriptor_priv {
 	struct list_head list;
 	u32 interface_version;
 	u32 size;
+	u32 hotfix;
 };
 static int descriptor_valid = -EPROBE_DEFER;
 static LIST_HEAD(wmi_list);
@@ -77,6 +78,24 @@ bool dell_wmi_get_size(u32 *size)
 }
 EXPORT_SYMBOL_GPL(dell_wmi_get_size);
 
+bool dell_wmi_get_hotfix(u32 *hotfix)
+{
+	struct descriptor_priv *priv;
+	bool ret = false;
+
+	mutex_lock(&list_mutex);
+	priv = list_first_entry_or_null(&wmi_list,
+					struct descriptor_priv,
+					list);
+	if (priv) {
+		*hotfix = priv->hotfix;
+		ret = true;
+	}
+	mutex_unlock(&list_mutex);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(dell_wmi_get_hotfix);
+
 /*
  * Descriptor buffer is 128 byte long and contains:
  *
@@ -85,6 +104,7 @@ EXPORT_SYMBOL_GPL(dell_wmi_get_size);
  * Object Signature          4       4    " WMI"
  * WMI Interface Version     8       4    <version>
  * WMI buffer length        12       4    <length>
+ * WMI hotfix number        16       4    <hotfix>
  */
 static int dell_wmi_descriptor_probe(struct wmi_device *wdev)
 {
@@ -144,15 +164,17 @@ static int dell_wmi_descriptor_probe(struct wmi_device *wdev)
 
 	priv->interface_version = buffer[2];
 	priv->size = buffer[3];
+	priv->hotfix = buffer[4];
 	ret = 0;
 	dev_set_drvdata(&wdev->dev, priv);
 	mutex_lock(&list_mutex);
 	list_add_tail(&priv->list, &wmi_list);
 	mutex_unlock(&list_mutex);
 
-	dev_dbg(&wdev->dev, "Detected Dell WMI interface version %lu and buffer size %lu\n",
+	dev_dbg(&wdev->dev, "Detected Dell WMI interface version %lu, buffer size %lu, hotfix %lu\n",
 		(unsigned long) priv->interface_version,
-		(unsigned long) priv->size);
+		(unsigned long) priv->size,
+		(unsigned long) priv->hotfix);
 
 out:
 	kfree(obj);

drivers/platform/x86/dell-wmi-descriptor.h

@@ -23,5 +23,6 @@ int dell_wmi_get_descriptor_valid(void);
 
 bool dell_wmi_get_interface_version(u32 *version);
 bool dell_wmi_get_size(u32 *size);
+bool dell_wmi_get_hotfix(u32 *hotfix);
 
 #endif