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Date: Fri, 15 Mar 2024 18:26:23 +0100
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Subject: Re: [PATCH v8] platform/x86: add lenovo wmi camera button driver
To: =?UTF-8?Q?Ilpo_J=C3=A4rvinen?= <ilpo.jarvinen@linux.intel.com>,
 Ai Chao <aichao@kylinos.cn>
Cc: Hans de Goede <hdegoede@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
 platform-driver-x86@vger.kernel.org
References: <20240314050319.171816-1-aichao@kylinos.cn>
 <d7c2de21-50f9-4602-abd0-b83ecbc3f42f@gmx.de>
 <62b54638-92eb-52e1-d4ad-074963771157@linux.intel.com>
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From: Armin Wolf <W_Armin@gmx.de>
In-Reply-To: <62b54638-92eb-52e1-d4ad-074963771157@linux.intel.com>
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Am 15.03.24 um 12:51 schrieb Ilpo J=C3=A4rvinen:

> On Thu, 14 Mar 2024, Armin Wolf wrote:
>
>> Am 14.03.24 um 06:03 schrieb Ai Chao:
>>
>>> Add lenovo generic wmi driver to support camera button.
>>> The Camera button is a GPIO device. This driver receives ACPI notifyi
>>> when the camera button is switched on/off. This driver is used in
>>> Lenovo A70, it is a Computer integrated machine.
>>>
>>> Signed-off-by: Ai Chao <aichao@kylinos.cn>
>>> ---
>>> v8: Dev_deb convert to dev_err.
>>> v7: Add dev_dbg and remove unused dev in struct.
>>> v6: Modify SW_CAMERA_LENS_COVER to
>>> KEY_CAMERA_ACCESS_ENABLE/KEY_CAMERA_ACCESS_DISABLE.
>>> v5: Remove camera button groups, modify KEY_CAMERA to SW_CAMERA_LENS_C=
OVER.
>>> v4: Remove lenovo_wmi_input_setup, move camera_mode into struct
>>> lenovo_wmi_priv.
>>> v3: Remove lenovo_wmi_remove function.
>>> v2: Adjust GPL v2 to GPL, adjust sprintf to sysfs_emit.
>>>
>>>    drivers/platform/x86/Kconfig             |  12 +++
>>>    drivers/platform/x86/Makefile            |   1 +
>>>    drivers/platform/x86/lenovo-wmi-camera.c | 108 ++++++++++++++++++++=
+++
>>>    3 files changed, 121 insertions(+)
>>>    create mode 100644 drivers/platform/x86/lenovo-wmi-camera.c
>>>
>>> diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconf=
ig
>>> index bdd302274b9a..9506a455b547 100644
>>> --- a/drivers/platform/x86/Kconfig
>>> +++ b/drivers/platform/x86/Kconfig
>>> @@ -1001,6 +1001,18 @@ config INSPUR_PLATFORM_PROFILE
>>>    	To compile this driver as a module, choose M here: the module
>>>    	will be called inspur-platform-profile.
>>>
>>> +config LENOVO_WMI_CAMERA
>>> +	tristate "Lenovo WMI Camera Button driver"
>>> +	depends on ACPI_WMI
>>> +	depends on INPUT
>>> +	help
>>> +	  This driver provides support for Lenovo camera button. The Camera
>>> +	  button is a GPIO device. This driver receives ACPI notify when the
>>> +	  camera button is switched on/off.
>>> +
>>> +	  To compile this driver as a module, choose M here: the module
>>> +	  will be called lenovo-wmi-camera.
>>> +
>>>    source "drivers/platform/x86/x86-android-tablets/Kconfig"
>>>
>>>    config FW_ATTR_CLASS
>>> diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Make=
file
>>> index 1de432e8861e..217e94d7c877 100644
>>> --- a/drivers/platform/x86/Makefile
>>> +++ b/drivers/platform/x86/Makefile
>>> @@ -66,6 +66,7 @@ obj-$(CONFIG_SENSORS_HDAPS)	+=3D hdaps.o
>>>    obj-$(CONFIG_THINKPAD_ACPI)	+=3D thinkpad_acpi.o
>>>    obj-$(CONFIG_THINKPAD_LMI)	+=3D think-lmi.o
>>>    obj-$(CONFIG_YOGABOOK)		+=3D lenovo-yogabook.o
>>> +obj-$(CONFIG_LENOVO_WMI_CAMERA)	+=3D lenovo-wmi-camera.o
>>>
>>>    # Intel
>>>    obj-y				+=3D intel/
>>> diff --git a/drivers/platform/x86/lenovo-wmi-camera.c
>>> b/drivers/platform/x86/lenovo-wmi-camera.c
>>> new file mode 100644
>>> index 000000000000..f83e3ccd9189
>>> --- /dev/null
>>> +++ b/drivers/platform/x86/lenovo-wmi-camera.c
>>> @@ -0,0 +1,108 @@
>>> +// SPDX-License-Identifier: GPL-2.0
>>> +/*
>>> + * Lenovo WMI Camera Button Driver
>>> + *
>>> + * Author: Ai Chao <aichao@kylinos.cn>
>>> + * Copyright (C) 2024 KylinSoft Corporation.
>>> + */
>>> +
>>> +#include <linux/acpi.h>
>>> +#include <linux/device.h>
>>> +#include <linux/input.h>
>>> +#include <linux/module.h>
>>> +#include <linux/wmi.h>
>>> +
>>> +#define WMI_LENOVO_CAMERABUTTON_EVENT_GUID
>>> "50C76F1F-D8E4-D895-0A3D-62F4EA400013"
>>> +
>>> +struct lenovo_wmi_priv {
>>> +	struct input_dev *idev;
>>> +};
>>> +
>>> +enum {
>>> +	SW_CAMERA_OFF	=3D 0,
>>> +	SW_CAMERA_ON	=3D 1,
>>> +};
>>> +
>>> +static void lenovo_wmi_notify(struct wmi_device *wdev, union acpi_obj=
ect
>>> *obj)
>>> +{
>>> +	struct lenovo_wmi_priv *priv =3D dev_get_drvdata(&wdev->dev);
>>> +	u8 camera_mode;
>>> +
>>> +	if (obj->type !=3D ACPI_TYPE_BUFFER) {
>>> +		dev_err(&wdev->dev, "Bad response type %u\n", obj->type);
>>> +		return;
>>> +	}
>>> +
>>> +	if (obj->buffer.length !=3D 1) {
>>> +		dev_err(&wdev->dev, "Invalid buffer length %u\n",
>>> obj->buffer.length);
>>> +		return;
>>> +	}
>>> +
>>> +	/* obj->buffer.pointer[0] is camera mode:
>>> +	 *      0 camera close
>>> +	 *      1 camera open
>>> +	 */
>>> +	camera_mode =3D obj->buffer.pointer[0];
>>> +	if (camera_mode > SW_CAMERA_ON) {
>>> +		dev_err(&wdev->dev, "Unknown camera mode %u\n", camera_mode);
>>> +		return;
>>> +	}
>>> +
>>> +	if (camera_mode =3D=3D SW_CAMERA_ON) {
>>> +		input_report_key(priv->idev, KEY_CAMERA_ACCESS_ENABLE, 1);
>>> +		input_sync(priv->idev);
>>> +		input_report_key(priv->idev, KEY_CAMERA_ACCESS_ENABLE, 0);
>>> +	} else {
>>> +		input_report_key(priv->idev, KEY_CAMERA_ACCESS_DISABLE, 1);
>>> +		input_sync(priv->idev);
>>> +		input_report_key(priv->idev, KEY_CAMERA_ACCESS_DISABLE, 0);
>>> +	}
> While not exactly wrong the if seems unnecessary, you could do:
>
> 	unsigned int keycode;
>
> 	...
>
> 	keycode =3D camera_mode =3D=3D 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);
>>> +	input_sync(priv->idev);
>>> +}
> Armin,
>
> I tried to figure out the concurrency rules for the WMI notify handler b=
ut
> came up basically nothing. I suppose it boils down on ACPI notify handli=
ng
> and I couldn't find useful documentation about that either. :-/
>
> Could you perhaps add this information into WMI documentation?

As far as i know, the ACPI notify handlers can be scheduled concurrently o=
n all CPUs,
see https://lore.kernel.org/all/7617703.EvYhyI6sBW@kreacher/ for details.

I will add a short note about this to the WMI driver guide which i plan to=
 upstream
soon (after the EC handler stuff is finished).

Thanks,
Armin Wolf