linux-kernel - Re: [PATCH v11 05/15] platform/x86: dell-wmi-descriptor: split WMI descriptor into it's own driver

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Date:   Mon, 30 Oct 2017 12:46:52 +0100
From:   Pali Rohár <pali.rohar@...il.com>
To:     Mario Limonciello <mario.limonciello@...l.com>
Cc:     dvhart@...radead.org, Andy Shevchenko <andy.shevchenko@...il.com>,
        LKML <linux-kernel@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Andy Lutomirski <luto@...nel.org>, quasisec@...gle.com,
        rjw@...ysocki.net, mjg59@...gle.com, hch@....de,
        Greg KH <greg@...ah.com>, Alan Cox <gnomes@...rguk.ukuu.org.uk>
Subject: Re: [PATCH v11 05/15] platform/x86: dell-wmi-descriptor: split WMI
 descriptor into it's own driver

On Friday 20 October 2017 12:40:20 Mario Limonciello wrote:
> diff --git a/drivers/platform/x86/dell-wmi-descriptor.c b/drivers/platform/x86/dell-wmi-descriptor.c
> new file mode 100644
> index 000000000000..3204c408e261
> --- /dev/null
> +++ b/drivers/platform/x86/dell-wmi-descriptor.c

This dell-wmi-descriptor.c looks good now!

> diff --git a/drivers/platform/x86/dell-wmi-descriptor.h b/drivers/platform/x86/dell-wmi-descriptor.h
> new file mode 100644
> index 000000000000..5f7b69c2c83a
> --- /dev/null
> +++ b/drivers/platform/x86/dell-wmi-descriptor.h
> @@ -721,7 +652,9 @@ static int dell_wmi_events_set_enabled(bool enable)
>  static int dell_wmi_probe(struct wmi_device *wdev)
>  {
>  	struct dell_wmi_priv *priv;
> -	int err;
> +
> +	if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
> +		return -ENODEV;
>  
>  	priv = devm_kzalloc(
>  		&wdev->dev, sizeof(struct dell_wmi_priv), GFP_KERNEL);
> @@ -729,9 +662,8 @@ static int dell_wmi_probe(struct wmi_device *wdev)
>  		return -ENOMEM;
>  	dev_set_drvdata(&wdev->dev, priv);
>  
> -	err = dell_wmi_check_descriptor_buffer(wdev);
> -	if (err)
> -		return err;
> +	if (!dell_wmi_get_interface_version(&priv->interface_version))
> +		return -EPROBE_DEFER;

But here is still a problem. You added check that
DELL_WMI_DESCRIPTOR_GUID exists in APCI table, but it does not mean that
probe method of dell-wmi-descriptor cannot fail.

With PROBE_DEFER, dell_wmi_probe function would be called later again
and again, even when probing dell-wmi-descriptor failed and so dell-wmi
in this case cannot work.

>  	return dell_wmi_input_setup(wdev);
>  }

-- 
Pali Rohár
pali.rohar@...il.com