platform/x86: dell-smbios-wmi: Stop using WMI chardev

The WMI chardev API will be removed in the near future.
Reimplement the necessary bits used by this driver so
that userspace software depending on it does no break.
Signed-off-by: Armin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20231210202443.646427-5-W_Armin@gmx.deReviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

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

@@ -8,11 +8,14 @@
 
 #include <linux/device.h>
 #include <linux/dmi.h>
+#include <linux/fs.h>
 #include <linux/list.h>
+#include <linux/miscdevice.h>
 #include <linux/module.h>
 #include <linux/mutex.h>
 #include <linux/uaccess.h>
 #include <linux/wmi.h>
+#include <uapi/linux/wmi.h>
 #include "dell-smbios.h"
 #include "dell-wmi-descriptor.h"
 
@@ -33,7 +36,8 @@ struct wmi_smbios_priv {
 	struct list_head list;
 	struct wmi_device *wdev;
 	struct device *child;
-	u32 req_buf_size;
+	u64 req_buf_size;
+	struct miscdevice char_dev;
 };
 static LIST_HEAD(wmi_list);
 
@@ -109,48 +113,115 @@ static int dell_smbios_wmi_call(struct calling_interface_buffer *buffer)
 	return ret;
 }
 
-static long dell_smbios_wmi_filter(struct wmi_device *wdev, unsigned int cmd,
-				   struct wmi_ioctl_buffer *arg)
+static int dell_smbios_wmi_open(struct inode *inode, struct file *filp)
 {
 	struct wmi_smbios_priv *priv;
-	int ret = 0;
-
-	switch (cmd) {
-	case DELL_WMI_SMBIOS_CMD:
-		mutex_lock(&call_mutex);
-		priv = dev_get_drvdata(&wdev->dev);
-		if (!priv) {
-			ret = -ENODEV;
-			goto fail_smbios_cmd;
-		}
-		memcpy(priv->buf, arg, priv->req_buf_size);
-		if (dell_smbios_call_filter(&wdev->dev, &priv->buf->std)) {
-			dev_err(&wdev->dev, "Invalid call %d/%d:%8x\n",
-				priv->buf->std.cmd_class,
-				priv->buf->std.cmd_select,
-				priv->buf->std.input[0]);
-			ret = -EFAULT;
-			goto fail_smbios_cmd;
-		}
-		ret = run_smbios_call(priv->wdev);
-		if (ret)
-			goto fail_smbios_cmd;
-		memcpy(arg, priv->buf, priv->req_buf_size);
-fail_smbios_cmd:
-		mutex_unlock(&call_mutex);
-		break;
-	default:
-		ret = -ENOIOCTLCMD;
+
+	priv = container_of(filp->private_data, struct wmi_smbios_priv, char_dev);
+	filp->private_data = priv;
+
+	return nonseekable_open(inode, filp);
+}
+
+static ssize_t dell_smbios_wmi_read(struct file *filp, char __user *buffer, size_t length,
+				    loff_t *offset)
+{
+	struct wmi_smbios_priv *priv = filp->private_data;
+
+	return simple_read_from_buffer(buffer, length, offset, &priv->req_buf_size,
+				       sizeof(priv->req_buf_size));
+}
+
+static long dell_smbios_wmi_do_ioctl(struct wmi_smbios_priv *priv,
+				     struct dell_wmi_smbios_buffer __user *arg)
+{
+	long ret;
+
+	if (get_user(priv->buf->length, &arg->length))
+		return -EFAULT;
+
+	if (priv->buf->length < priv->req_buf_size)
+		return -EINVAL;
+
+	/* if it's too big, warn, driver will only use what is needed */
+	if (priv->buf->length > priv->req_buf_size)
+		dev_err(&priv->wdev->dev, "Buffer %llu is bigger than required %llu\n",
+			priv->buf->length, priv->req_buf_size);
+
+	if (copy_from_user(priv->buf, arg, priv->req_buf_size))
+		return -EFAULT;
+
+	if (dell_smbios_call_filter(&priv->wdev->dev, &priv->buf->std)) {
+		dev_err(&priv->wdev->dev, "Invalid call %d/%d:%8x\n",
+			priv->buf->std.cmd_class,
+			priv->buf->std.cmd_select,
+			priv->buf->std.input[0]);
+
+		return -EINVAL;
 	}
+
+	ret = run_smbios_call(priv->wdev);
+	if (ret)
+		return ret;
+
+	if (copy_to_user(arg, priv->buf, priv->req_buf_size))
+		return -EFAULT;
+
+	return 0;
+}
+
+static long dell_smbios_wmi_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct dell_wmi_smbios_buffer __user *input = (struct dell_wmi_smbios_buffer __user *)arg;
+	struct wmi_smbios_priv *priv = filp->private_data;
+	long ret;
+
+	if (cmd != DELL_WMI_SMBIOS_CMD)
+		return -ENOIOCTLCMD;
+
+	mutex_lock(&call_mutex);
+	ret = dell_smbios_wmi_do_ioctl(priv, input);
+	mutex_unlock(&call_mutex);
+
 	return ret;
 }
 
+static const struct file_operations dell_smbios_wmi_fops = {
+	.owner		= THIS_MODULE,
+	.open		= dell_smbios_wmi_open,
+	.read		= dell_smbios_wmi_read,
+	.unlocked_ioctl	= dell_smbios_wmi_ioctl,
+	.compat_ioctl	= compat_ptr_ioctl,
+};
+
+static void dell_smbios_wmi_unregister_chardev(void *data)
+{
+	struct miscdevice *char_dev = data;
+
+	misc_deregister(char_dev);
+}
+
+static int dell_smbios_wmi_register_chardev(struct wmi_smbios_priv *priv)
+{
+	int ret;
+
+	priv->char_dev.minor = MISC_DYNAMIC_MINOR;
+	priv->char_dev.name = "wmi/dell-smbios";
+	priv->char_dev.fops = &dell_smbios_wmi_fops;
+	priv->char_dev.mode = 0444;
+
+	ret = misc_register(&priv->char_dev);
+	if (ret < 0)
+		return ret;
+
+	return devm_add_action_or_reset(&priv->wdev->dev, dell_smbios_wmi_unregister_chardev,
+					&priv->char_dev);
+}
+
 static int dell_smbios_wmi_probe(struct wmi_device *wdev, const void *context)
 {
-	struct wmi_driver *wdriver =
-		container_of(wdev->dev.driver, struct wmi_driver, driver);
 	struct wmi_smbios_priv *priv;
-	u32 hotfix;
+	u32 buffer_size, hotfix;
 	int count;
 	int ret;
 
@@ -163,39 +234,42 @@ static int dell_smbios_wmi_probe(struct wmi_device *wdev, const void *context)
 	if (!priv)
 		return -ENOMEM;
 
+	priv->wdev = wdev;
+	dev_set_drvdata(&wdev->dev, priv);
+
 	/* WMI buffer size will be either 4k or 32k depending on machine */
-	if (!dell_wmi_get_size(&priv->req_buf_size))
+	if (!dell_wmi_get_size(&buffer_size))
 		return -EPROBE_DEFER;
 
+	priv->req_buf_size = buffer_size;
+
 	/* some SMBIOS calls fail unless BIOS contains hotfix */
 	if (!dell_wmi_get_hotfix(&hotfix))
 		return -EPROBE_DEFER;
-	if (!hotfix) {
+
+	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);
-	if (ret)
-		return ret;
 
 	count = get_order(priv->req_buf_size);
 	priv->buf = (void *)devm_get_free_pages(&wdev->dev, GFP_KERNEL, count);
 	if (!priv->buf)
 		return -ENOMEM;
 
+	ret = dell_smbios_wmi_register_chardev(priv);
+	if (ret)
+		return ret;
+
 	/* ID is used by dell-smbios to set priority of drivers */
 	wdev->dev.id = 1;
 	ret = dell_smbios_register_device(&wdev->dev, &dell_smbios_wmi_call);
 	if (ret)
 		return ret;
 
-	priv->wdev = wdev;
-	dev_set_drvdata(&wdev->dev, priv);
 	mutex_lock(&list_mutex);
 	list_add_tail(&priv->list, &wmi_list);
 	mutex_unlock(&list_mutex);
@@ -250,7 +324,6 @@ static struct wmi_driver dell_smbios_wmi_driver = {
 	.probe = dell_smbios_wmi_probe,
 	.remove = dell_smbios_wmi_remove,
 	.id_table = dell_smbios_wmi_id_table,
-	.filter_callback = dell_smbios_wmi_filter,
 };
 
 int init_dell_smbios_wmi(void)