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

[Armin Wolf]

Am 30.04.23 um 22:41 schrieb Hans de Goede:

> 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@xxxxxx>
> 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
Hi,

i would prefer returning -ENODEV instead of 0, so WMI drivers can
distinguish between "not found" and "zero instances". Also i do not
think that relying on the parameter of get_instance_count() always
being a valid GUID is a good idea, just in case wmi_instance_count()
is later modified to be able to encounter runtime errors.

Armin Wolf

> > +	}
> > +
> > +	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