linux-kernel - Re: [PATCH v4] platform/x86: lenovo-wmi-camera: Use SW_CAMERA_LENS_COVER instead of KEY_CAMERA

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Message-ID: <3733c3a7-63ae-4708-8a40-f5e0f1158ab4@gmx.de>
Date: Tue, 31 Dec 2024 16:19:10 +0100
From: Armin Wolf <W_Armin@....de>
To: Ai Chao <aichao@...inos.cn>, hdegoede@...hat.com,
 ilpo.jarvinen@...ux.intel.com, platform-driver-x86@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] platform/x86: lenovo-wmi-camera: Use
 SW_CAMERA_LENS_COVER instead of KEY_CAMERA_ACESS

Am 31.12.24 um 07:13 schrieb Ai Chao:

> Use SW_CAMERA_LENS_COVER instead of KEY_CAMERA_ACESS_ENABLE and
> KEY_CAMERA_ACESS_DISABLE. When the camera toggle switch was hit,
> the lenovo-wmi-camera driver would report an event code.
>
> Signed-off-by: Ai Chao <aichao@...inos.cn>
> ---
> change for v4
> -Add mutex_unlock and report a switch state of 0 if SW_CAMERA_ON.
> change for v3
> -Used input_register_device and input_allocate_device.
> change for v2
> -Only delays the input-device registration and switches to reporting SW_CAMERA_LENS_COVER.
>
>   drivers/platform/x86/lenovo-wmi-camera.c | 61 +++++++++++++++---------
>   1 file changed, 38 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/platform/x86/lenovo-wmi-camera.c b/drivers/platform/x86/lenovo-wmi-camera.c
> index 0c0bedaf7407..2a662b3c78f2 100644
> --- a/drivers/platform/x86/lenovo-wmi-camera.c
> +++ b/drivers/platform/x86/lenovo-wmi-camera.c
> @@ -26,10 +26,34 @@ enum {
>   	SW_CAMERA_ON	= 1,
>   };
>
> +static int camera_shutter_input_setup(struct wmi_device *wdev)
> +{
> +	struct lenovo_wmi_priv *priv = dev_get_drvdata(&wdev->dev);
> +	int err;
> +
> +	priv->idev = input_allocate_device();
> +	if (!priv->idev)
> +		return -ENOMEM;
> +
> +	priv->idev->name = "Lenovo WMI Camera Button";
> +	priv->idev->phys = "wmi/input0";
> +	priv->idev->id.bustype = BUS_HOST;
> +	priv->idev->dev.parent = &wdev->dev;
> +
> +	input_set_capability(priv->idev, EV_SW, SW_CAMERA_LENS_COVER);
> +
> +	err = input_register_device(priv->idev);
> +	if (err) {
> +		input_free_device(priv->idev);
> +		priv->idev = NULL;
> +	}
> +
> +	return err;

Looks good to me, however i just stumbled upon an interesting comment regarding input_event():

	NOTE: input_event() may be safely used right after input device was
allocated with input_allocate_device(), even before it is registered
with input_register_device(), but the event will not reach any of the
input handlers. Such early invocation of input_event() may be used to
'seed' initial state of a switch or initial position of absolute axis,
etc. So maybe it would sense to call input_report_switch() on the input device right before calling
input_device_register(). This would make sure that the initial switch position is correct.

> +}
> +
>   static void lenovo_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
>   {
>   	struct lenovo_wmi_priv *priv = dev_get_drvdata(&wdev->dev);
> -	unsigned int keycode;
>   	u8 camera_mode;
>
>   	if (obj->type != ACPI_TYPE_BUFFER) {
> @@ -55,11 +79,16 @@ static void lenovo_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
>
>   	mutex_lock(&priv->notify_lock);
>
> -	keycode = camera_mode == SW_CAMERA_ON ?
> -		   KEY_CAMERA_ACCESS_ENABLE : KEY_CAMERA_ACCESS_DISABLE;
> -	input_report_key(priv->idev, keycode, 1);
> -	input_sync(priv->idev);
> -	input_report_key(priv->idev, keycode, 0);
> +	if (!priv->idev)
> +		if (camera_shutter_input_setup(wdev)) {
> +			mutex_unlock(&priv->notify_lock);
> +			return;
> +		}

Please add braces to the outer if-statement.

Also if you implement the seeding of the switch position inside camera_shutter_input_setup() when
you can return early if the input device was registered since it would already contain the correct
slider position.

I imagine something like this:

if (!priv->idev) {
	if (camera_shutter_input_setup(wdev, camera_mode))
		dev_warn(&wdev->dev, "Failed to register input device\n");

	mutex_unlock(&priv->notify_lock);
	return;
}

Other than that the patch seems good to me.

Thanks,
Armin Wolf

> +
> +	if (camera_mode == SW_CAMERA_ON)
> +		input_report_switch(priv->idev, SW_CAMERA_LENS_COVER, 0);
> +	else
> +		input_report_switch(priv->idev, SW_CAMERA_LENS_COVER, 1);
>   	input_sync(priv->idev);
>
>   	mutex_unlock(&priv->notify_lock);
> @@ -68,29 +97,12 @@ static void lenovo_wmi_notify(struct wmi_device *wdev, union acpi_object *obj)
>   static int lenovo_wmi_probe(struct wmi_device *wdev, const void *context)
>   {
>   	struct lenovo_wmi_priv *priv;
> -	int ret;
>
>   	priv = devm_kzalloc(&wdev->dev, sizeof(*priv), GFP_KERNEL);
>   	if (!priv)
>   		return -ENOMEM;
>
>   	dev_set_drvdata(&wdev->dev, priv);
> -
> -	priv->idev = devm_input_allocate_device(&wdev->dev);
> -	if (!priv->idev)
> -		return -ENOMEM;
> -
> -	priv->idev->name = "Lenovo WMI Camera Button";
> -	priv->idev->phys = "wmi/input0";
> -	priv->idev->id.bustype = BUS_HOST;
> -	priv->idev->dev.parent = &wdev->dev;
> -	input_set_capability(priv->idev, EV_KEY, KEY_CAMERA_ACCESS_ENABLE);
> -	input_set_capability(priv->idev, EV_KEY, KEY_CAMERA_ACCESS_DISABLE);
> -
> -	ret = input_register_device(priv->idev);
> -	if (ret)
> -		return ret;
> -
>   	mutex_init(&priv->notify_lock);
>
>   	return 0;
> @@ -100,6 +112,9 @@ static void lenovo_wmi_remove(struct wmi_device *wdev)
>   {
>   	struct lenovo_wmi_priv *priv = dev_get_drvdata(&wdev->dev);
>
> +	if (priv->idev)
> +		input_unregister_device(priv->idev);
> +
>   	mutex_destroy(&priv->notify_lock);
>   }
>