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

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Date:   Fri, 8 Dec 2023 15:41:12 +0200 (EET)
From:   Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To:     Armin Wolf <W_Armin@....de>
cc:     Hans de Goede <hdegoede@...hat.com>, corbet@....net,
        Dell.Client.Kernel@...l.com, linux-doc@...r.kernel.org,
        platform-driver-x86@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/5] platform/x86: dell-smbios-wmi: Stop using WMI
 chardev

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@....de>
> ---
>  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?

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

> @@ -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);

-- 
 i.