Re: [PATCH v2 2/2] platform/x86: dell-*wmi*: Relay failed initial probe to dependent drivers

[sathyanarayanan kuppuswamy]

Hi,


On 11/09/2017 09:49 AM, Mario Limonciello wrote:
> dell-wmi and dell-smbios-wmi are dependent upon dell-wmi-descriptor
> finishing probe successfully to probe themselves.
if they are dependent, then why not control the device creation of 
dell-wmi and dell-smbios-wmi drivers in del-wmi-descriptor probe ?

> Currently if dell-wmi-descriptor fails probing in a non-recoverable way
> (such as invalid header) dell-wmi and dell-smbios-wmi will continue to
> try to redo probing due to deferred probing.
>
> To solve this have the dependent drivers query the dell-wmi-descriptor
> driver whether the descriptor has been determined valid. The possible
> results are:
> -ENODEV: Descriptor GUID missing from WMI bus
> -EPROBE_DEFER: Descriptor not yet probed, dependent driver should wait
>   and use deferred probing
> < 0: Descriptor probed, invalid.  Dependent driver should return an
>   error.
> 0: Successful descriptor probe, dependent driver can continue
>
> Successful descriptor probe still doesn't mean that the descriptor driver
> is necessarily bound at the time of initialization of dependent driver.
> Userspace can unbind the driver, so all methods used from driver
> should still be verified to return success values otherwise deferred
> probing be used.
>
> Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxxx>
> ---
>   drivers/platform/x86/dell-smbios-wmi.c     |  5 +++--
>   drivers/platform/x86/dell-wmi-descriptor.c | 16 ++++++++++++++++
>   drivers/platform/x86/dell-wmi-descriptor.h |  8 +++++++-
>   drivers/platform/x86/dell-wmi.c            |  6 ++++--
>   4 files changed, 30 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/platform/x86/dell-smbios-wmi.c b/drivers/platform/x86/dell-smbios-wmi.c
> index 35c13815b24c..ca556803c8c9 100644
> --- a/drivers/platform/x86/dell-smbios-wmi.c
> +++ b/drivers/platform/x86/dell-smbios-wmi.c
> @@ -148,8 +148,9 @@ static int dell_smbios_wmi_probe(struct wmi_device *wdev)
>   	int count;
>   	int ret;
>   
> -	if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
> -		return -ENODEV;
> +	ret = dell_wmi_get_descriptor_valid();
> +	if (ret)
> +		return ret;
>   
>   	priv = devm_kzalloc(&wdev->dev, sizeof(struct wmi_smbios_priv),
>   			    GFP_KERNEL);
> diff --git a/drivers/platform/x86/dell-wmi-descriptor.c b/drivers/platform/x86/dell-wmi-descriptor.c
> index 28ef5f37cfbf..4dfef1f53481 100644
> --- a/drivers/platform/x86/dell-wmi-descriptor.c
> +++ b/drivers/platform/x86/dell-wmi-descriptor.c
> @@ -21,14 +21,26 @@
>   #include <linux/wmi.h>
>   #include "dell-wmi-descriptor.h"
>   
> +#define DELL_WMI_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"
> +
>   struct descriptor_priv {
>   	struct list_head list;
>   	u32 interface_version;
>   	u32 size;
>   };
> +static int descriptor_valid = -EPROBE_DEFER;
>   static LIST_HEAD(wmi_list);
>   static DEFINE_MUTEX(list_mutex);
>   
> +int dell_wmi_get_descriptor_valid(void)
> +{
> +	if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
> +		return -ENODEV;
> +
> +	return descriptor_valid;
> +}
> +EXPORT_SYMBOL_GPL(dell_wmi_get_descriptor_valid);
> +
>   bool dell_wmi_get_interface_version(u32 *version)
>   {
>   	struct descriptor_priv *priv;
> @@ -91,6 +103,7 @@ static int dell_wmi_descriptor_probe(struct wmi_device *wdev)
>   	if (obj->type != ACPI_TYPE_BUFFER) {
>   		dev_err(&wdev->dev, "Dell descriptor has wrong type\n");
>   		ret = -EINVAL;
> +		descriptor_valid = ret;
>   		goto out;
>   	}
>   
> @@ -102,6 +115,7 @@ static int dell_wmi_descriptor_probe(struct wmi_device *wdev)
>   			"Dell descriptor buffer has unexpected length (%d)\n",
>   			obj->buffer.length);
>   		ret = -EINVAL;
> +		descriptor_valid = ret;
>   		goto out;
>   	}
>   
> @@ -111,8 +125,10 @@ static int dell_wmi_descriptor_probe(struct wmi_device *wdev)
>   		dev_err(&wdev->dev, "Dell descriptor buffer has invalid signature (%8ph)\n",
>   			buffer);
>   		ret = -EINVAL;
> +		descriptor_valid = ret;
>   		goto out;
>   	}
> +	descriptor_valid = 0;
>   
>   	if (buffer[2] != 0 && buffer[2] != 1)
>   		dev_warn(&wdev->dev, "Dell descriptor buffer has unknown version (%lu)\n",
> diff --git a/drivers/platform/x86/dell-wmi-descriptor.h b/drivers/platform/x86/dell-wmi-descriptor.h
> index 5f7b69c2c83a..1e8cb96ffd78 100644
> --- a/drivers/platform/x86/dell-wmi-descriptor.h
> +++ b/drivers/platform/x86/dell-wmi-descriptor.h
> @@ -13,7 +13,13 @@
>   
>   #include <linux/wmi.h>
>   
> -#define DELL_WMI_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"
> +/* possible return values:
> + *  -ENODEV: Descriptor GUID missing from WMI bus
> + *  -EPROBE_DEFER: probing for dell-wmi-descriptor not yet run
> + *  0: valid descriptor, successfully probed
> + *  < 0: invalid descriptor, don't probe dependent devices
> + */
> +int dell_wmi_get_descriptor_valid(void);
>   
>   bool dell_wmi_get_interface_version(u32 *version);
>   bool dell_wmi_get_size(u32 *size);
> diff --git a/drivers/platform/x86/dell-wmi.c b/drivers/platform/x86/dell-wmi.c
> index 54321080a30d..39d2f4518483 100644
> --- a/drivers/platform/x86/dell-wmi.c
> +++ b/drivers/platform/x86/dell-wmi.c
> @@ -655,9 +655,11 @@ static int dell_wmi_events_set_enabled(bool enable)
>   static int dell_wmi_probe(struct wmi_device *wdev)
>   {
>   	struct dell_wmi_priv *priv;
> +	int ret;
>   
> -	if (!wmi_has_guid(DELL_WMI_DESCRIPTOR_GUID))
> -		return -ENODEV;
> +	ret = dell_wmi_get_descriptor_valid();
> +	if (ret)
> +		return ret;
>   
>   	priv = devm_kzalloc(
>   		&wdev->dev, sizeof(struct dell_wmi_priv), GFP_KERNEL);

--
Sathyanarayanan Kuppuswamy
Linux kernel developer