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Date: Tue, 27 Feb 2024 21:30:58 +0100
From: Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To: Armin Wolf <W_Armin@gmx.de>
Cc: jithu.joseph@intel.com, linux@weissschuh.net, hdegoede@redhat.com,
	ilpo.jarvinen@linux.intel.com, Dell.Client.Kernel@dell.com,
	jdelvare@suse.com, linux@roeck-us.net,
	platform-driver-x86@vger.kernel.org, linux-hwmon@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/3] platform/x86: wmi: Do not instantiate older WMI
 drivers multiple times
Message-ID: <20240227203058.eun4ylvhk4t7uogk@pali>
References: <20240226193557.2888-1-W_Armin@gmx.de>
 <20240226193557.2888-2-W_Armin@gmx.de>
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On Monday 26 February 2024 20:35:56 Armin Wolf wrote:
> Many older WMI drivers cannot be instantiated multiple times for
> two reasons:
> 
> - they are using the legacy GUID-based WMI API
> - they are singletons (with global state)
> 
> Prevent such WMI drivers from binding to WMI devices with a duplicated
> GUID, as this would mean that the WMI driver will be instantiated at
> least two times (one for the original GUID and one for the duplicated
> GUID).
> WMI drivers which can be instantiated multiple times can signal this
> by setting a flag inside struct wmi_driver.

What do you think about opposite direction? Adding ".singleton = true"
into every driver which is not compatible with duplicated initialization
and having the default value that drivers are not singletons.

But if the direction it to not accept new "legacy" drivers and start get
rid of all "legacy" drivers by rewriting them, then it does not matter
if "no_singleton" or "is_singleton" is used...

> Tested on a ASUS Prime B650-Plus.
> 
> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
> ---
>  drivers/hwmon/dell-smm-hwmon.c                 |  1 +
>  drivers/platform/x86/dell/dell-wmi-ddv.c       |  1 +
>  drivers/platform/x86/intel/wmi/sbl-fw-update.c |  1 +
>  drivers/platform/x86/intel/wmi/thunderbolt.c   |  1 +
>  drivers/platform/x86/wmi-bmof.c                |  1 +
>  drivers/platform/x86/wmi.c                     | 12 ++++++++++++
>  include/linux/wmi.h                            |  2 ++
>  7 files changed, 19 insertions(+)
> 
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 6d8c0f328b7b..168d669c4eca 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -1587,6 +1587,7 @@ static struct wmi_driver dell_smm_wmi_driver = {
>  	},
>  	.id_table = dell_smm_wmi_id_table,
>  	.probe = dell_smm_wmi_probe,
> +	.no_singleton = true,
>  };
> 
>  /*
> diff --git a/drivers/platform/x86/dell/dell-wmi-ddv.c b/drivers/platform/x86/dell/dell-wmi-ddv.c
> index db1e9240dd02..0b2299f7a2de 100644
> --- a/drivers/platform/x86/dell/dell-wmi-ddv.c
> +++ b/drivers/platform/x86/dell/dell-wmi-ddv.c
> @@ -882,6 +882,7 @@ static struct wmi_driver dell_wmi_ddv_driver = {
>  	},
>  	.id_table = dell_wmi_ddv_id_table,
>  	.probe = dell_wmi_ddv_probe,
> +	.no_singleton = true,
>  };
>  module_wmi_driver(dell_wmi_ddv_driver);
> 
> diff --git a/drivers/platform/x86/intel/wmi/sbl-fw-update.c b/drivers/platform/x86/intel/wmi/sbl-fw-update.c
> index 040153ad67c1..75c82c08117f 100644
> --- a/drivers/platform/x86/intel/wmi/sbl-fw-update.c
> +++ b/drivers/platform/x86/intel/wmi/sbl-fw-update.c
> @@ -131,6 +131,7 @@ static struct wmi_driver intel_wmi_sbl_fw_update_driver = {
>  	.probe = intel_wmi_sbl_fw_update_probe,
>  	.remove = intel_wmi_sbl_fw_update_remove,
>  	.id_table = intel_wmi_sbl_id_table,
> +	.no_singleton = true,
>  };
>  module_wmi_driver(intel_wmi_sbl_fw_update_driver);
> 
> diff --git a/drivers/platform/x86/intel/wmi/thunderbolt.c b/drivers/platform/x86/intel/wmi/thunderbolt.c
> index e2ad3f46f356..08df560a2c7a 100644
> --- a/drivers/platform/x86/intel/wmi/thunderbolt.c
> +++ b/drivers/platform/x86/intel/wmi/thunderbolt.c
> @@ -63,6 +63,7 @@ static struct wmi_driver intel_wmi_thunderbolt_driver = {
>  		.dev_groups = tbt_groups,
>  	},
>  	.id_table = intel_wmi_thunderbolt_id_table,
> +	.no_singleton = true,
>  };
> 
>  module_wmi_driver(intel_wmi_thunderbolt_driver);
> diff --git a/drivers/platform/x86/wmi-bmof.c b/drivers/platform/x86/wmi-bmof.c
> index 644d2fd889c0..df6f0ae6e6c7 100644
> --- a/drivers/platform/x86/wmi-bmof.c
> +++ b/drivers/platform/x86/wmi-bmof.c
> @@ -94,6 +94,7 @@ static struct wmi_driver wmi_bmof_driver = {
>  	.probe = wmi_bmof_probe,
>  	.remove = wmi_bmof_remove,
>  	.id_table = wmi_bmof_id_table,
> +	.no_singleton = true,
>  };
> 
>  module_wmi_driver(wmi_bmof_driver);
> diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
> index 29dfe52eb802..349deced87e8 100644
> --- a/drivers/platform/x86/wmi.c
> +++ b/drivers/platform/x86/wmi.c
> @@ -883,6 +883,18 @@ static int wmi_dev_probe(struct device *dev)
>  	struct wmi_driver *wdriver = drv_to_wdrv(dev->driver);
>  	int ret = 0;
> 
> +	/* Some older WMI drivers will break if instantiated multiple times,
> +	 * so they are blocked from probing WMI devices with a duplicated GUID.
> +	 *
> +	 * New WMI drivers should support being instantiated multiple times.
> +	 */
> +	if (test_bit(WMI_GUID_DUPLICATED, &wblock->flags) && !wdriver->no_singleton) {
> +		dev_warn(dev, "Legacy driver %s cannot be instantiated multiple times\n",
> +			 dev->driver->name);
> +
> +		return -ENODEV;
> +	}
> +
>  	if (wdriver->notify) {
>  		if (test_bit(WMI_NO_EVENT_DATA, &wblock->flags) && !wdriver->no_notify_data)
>  			return -ENODEV;
> diff --git a/include/linux/wmi.h b/include/linux/wmi.h
> index 781958310bfb..63cca3b58d6d 100644
> --- a/include/linux/wmi.h
> +++ b/include/linux/wmi.h
> @@ -49,6 +49,7 @@ u8 wmidev_instance_count(struct wmi_device *wdev);
>   * @driver: Driver model structure
>   * @id_table: List of WMI GUIDs supported by this driver
>   * @no_notify_data: Driver supports WMI events which provide no event data
> + * @no_singleton: Driver can be instantiated multiple times
>   * @probe: Callback for device binding
>   * @remove: Callback for device unbinding
>   * @notify: Callback for receiving WMI events
> @@ -59,6 +60,7 @@ struct wmi_driver {
>  	struct device_driver driver;
>  	const struct wmi_device_id *id_table;
>  	bool no_notify_data;
> +	bool no_singleton;
> 
>  	int (*probe)(struct wmi_device *wdev, const void *context);
>  	void (*remove)(struct wmi_device *wdev);
> --
> 2.39.2
>