linux-kernel - Re: [PATCH 1/2] platform/x86: wmi: Allow retrieving the number of WMI object instances

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Message-ID: <756215f5-d99c-b172-13f6-1a15e026bf65@redhat.com>
Date:   Sun, 30 Apr 2023 22:41:16 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Armin Wolf <W_Armin@....de>, markgross@...nel.org
Cc:     Mario.Limonciello@....com, prasanth.ksr@...l.com,
        jorgealtxwork@...il.com, james@...iv.tech,
        Dell.Client.Kernel@...l.com, platform-driver-x86@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] platform/x86: wmi: Allow retrieving the number of WMI
 object instances

Hi Armin,

On 4/30/23 22:31, Armin Wolf wrote:
> Currently, the WMI driver core knows how many instances of a given
> WMI object exist, but WMI drivers cannot access this information.
> At the same time, some current and upcoming WMI drivers want to
> have access to this information. Add wmi_instance_count() and
> wmidev_instance_count() to allow WMI drivers to get the number of
> WMI object instances.
> 
> Signed-off-by: Armin Wolf <W_Armin@....de>

Thank you for your work on this.

> ---
>  drivers/platform/x86/wmi.c | 41 ++++++++++++++++++++++++++++++++++++++
>  include/linux/acpi.h       |  2 ++
>  include/linux/wmi.h        |  2 ++
>  3 files changed, 45 insertions(+)
> 
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index c226dd4163a1..5b95d7aa5c2f 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -263,6 +263,47 @@ int set_required_buffer_size(struct wmi_device *wdev, u64 length)
>  }
>  EXPORT_SYMBOL_GPL(set_required_buffer_size);
> 
> +/**
> + * wmi_instance_count - Get number of WMI object instances
> + * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
> + *
> + * Get the number of WMI object instances.
> + *
> + * Returns: Number of WMI object instances or negative error code.
> + */
> +int wmi_instance_count(const char *guid_string)
> +{
> +	struct wmi_block *wblock;
> +	acpi_status status;
> +
> +	status = find_guid(guid_string, &wblock);
> +	if (ACPI_FAILURE(status)) {
> +		if (status == AE_BAD_PARAMETER)
> +			return -EINVAL;
> +
> +		return -ENODEV;

Maybe just return 0 here ?

The GUID not existing at all does not seem like
an error to me, but rather a case of there
being 0 instances.

This will also allow patch 2/2 to completely
drop the get_instance_count() function and
replace its callers with direct calls to
wmi_instance_count() as the code is known
to always pass a valid GUID, so it won't hit
the -EINVAL path.

Regards,

Hans



> +	}
> +
> +	return wmidev_instance_count(&wblock->dev);
> +}
> +EXPORT_SYMBOL_GPL(wmi_instance_count);
> +
> +/**
> + * wmidev_instance_count - Get number of WMI object instances
> + * @wdev: A wmi bus device from a driver
> + *
> + * Get the number of WMI object instances.
> + *
> + * Returns: Number of WMI object instances.
> + */
> +u8 wmidev_instance_count(struct wmi_device *wdev)
> +{
> +	struct wmi_block *wblock = container_of(wdev, struct wmi_block, dev);
> +
> +	return wblock->gblock.instance_count;
> +}
> +EXPORT_SYMBOL_GPL(wmidev_instance_count);
> +
>  /**
>   * wmi_evaluate_method - Evaluate a WMI method (deprecated)
>   * @guid_string: 36 char string of the form fa50ff2b-f2e8-45de-83fa-65417f2f49ba
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index efff750f326d..e52bf2742eaf 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -412,6 +412,8 @@ extern bool acpi_is_pnp_device(struct acpi_device *);
> 
>  typedef void (*wmi_notify_handler) (u32 value, void *context);
> 
> +int wmi_instance_count(const char *guid);
> +
>  extern acpi_status wmi_evaluate_method(const char *guid, u8 instance,
>  					u32 method_id,
>  					const struct acpi_buffer *in,
> diff --git a/include/linux/wmi.h b/include/linux/wmi.h
> index c1a3bd4e4838..763bd382cf2d 100644
> --- a/include/linux/wmi.h
> +++ b/include/linux/wmi.h
> @@ -35,6 +35,8 @@ extern acpi_status wmidev_evaluate_method(struct wmi_device *wdev,
>  extern union acpi_object *wmidev_block_query(struct wmi_device *wdev,
>  					     u8 instance);
> 
> +u8 wmidev_instance_count(struct wmi_device *wdev);
> +
>  extern int set_required_buffer_size(struct wmi_device *wdev, u64 length);
> 
>  /**
> --
> 2.30.2
>