Re: [PATCH 3/5] platform/x86: dell-smbios-wmi: Stop using WMI chardev

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Am 08.12.23 um 14:41 schrieb Ilpo Järvinen:

On Thu, 7 Dec 2023, Armin Wolf wrote:

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@xxxxxx>
---
  drivers/platform/x86/dell/dell-smbios-wmi.c | 163 ++++++++++++++------
  1 file changed, 117 insertions(+), 46 deletions(-)

diff --git a/drivers/platform/x86/dell/dell-smbios-wmi.c b/drivers/platform/x86/dell/dell-smbios-wmi.c
index 931cc50136de..61f40f462eca 100644
--- a/drivers/platform/x86/dell/dell-smbios-wmi.c
+++ b/drivers/platform/x86/dell/dell-smbios-wmi.c
@@ -32,7 +35,9 @@ struct wmi_smbios_priv {
  	struct list_head list;
  	struct wmi_device *wdev;
  	struct device *child;
-	u32 req_buf_size;
+	u64 req_buf_size;
+	u32 hotfix;
+	struct miscdevice char_dev;
  };
  static LIST_HEAD(wmi_list);

  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;
  	int count;
  	int ret;

@@ -162,39 +225,44 @@ 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))
+	if (!dell_wmi_get_hotfix(&priv->hotfix))
  		return -EPROBE_DEFER;
-	if (!hotfix) {
+
+	if (!priv->hotfix)
  		dev_warn(&wdev->dev,
  			"WMI SMBIOS userspace interface not supported(%u), try upgrading to a newer BIOS\n",
-			hotfix);
-		wdriver->filter_callback = NULL;
-	}
+			priv->hotfix);

  	/* 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 *)__get_free_pages(GFP_KERNEL, count);
  	if (!priv->buf)
  		return -ENOMEM;

+	if (priv->hotfix) {
+		ret = dell_smbios_wmi_register_chardev(priv);
+		if (ret)
+			goto fail_chardev;
+	}
+
  	/* 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)
  		goto fail_register;

-	priv->wdev = wdev;
-	dev_set_drvdata(&wdev->dev, priv);
  	mutex_lock(&list_mutex);
  	list_add_tail(&priv->list, &wmi_list);
  	mutex_unlock(&list_mutex);
@@ -202,6 +270,9 @@ static int dell_smbios_wmi_probe(struct wmi_device *wdev, const void *context)
  	return 0;

  fail_register:
+	if (priv->hotfix)
+               dell_smbios_wmi_unregister_chardev(priv);
I don't understand how hotfix -> priv->hotfix is related to this patch nor
why it's necessary?

Or did you mean to use it also in dell_smbios_wmi_remove() but forgot to
add the if (priv->hotfix) there?

I indeed forgot to add the "if (priv->hotfix)" here, good catch.

In any case, it would be better to put that conversion into own patch
before this one.

I could also drop the priv->hotfix related changes and instead modify the driver
to use devres (devm_get_free_pages() for example). This would also simplify the
error handling code.

I will send a v2 soon containing the necessary patches.

@@ -211,6 +282,7 @@ static void dell_smbios_wmi_remove(struct wmi_device *wdev)
        struct wmi_smbios_priv *priv = dev_get_drvdata(&wdev->dev);
        int count;

+      dell_smbios_wmi_unregister_chardev(priv);
        mutex_lock(&call_mutex);
        mutex_lock(&list_mutex);
        list_del(&priv->list);





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