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

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Date:   Fri, 8 Dec 2023 19:00:15 +0100
From:   Armin Wolf <W_Armin@....de>
To:     Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
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

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@....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?

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);