Date:   Thu, 6 May 2021 09:48:16 +0000
From:   "Yuan, Perry" <Perry.Yuan@...l.com>
To:     Hans de Goede <hdegoede@...hat.com>,
        "pobrn@...tonmail.com" <pobrn@...tonmail.com>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>,
        "oder_chiou@...ltek.com" <oder_chiou@...ltek.com>,
        "perex@...ex.cz" <perex@...ex.cz>,
        "tiwai@...e.com" <tiwai@...e.com>,
        "mgross@...ux.intel.com" <mgross@...ux.intel.com>
CC:     "lgirdwood@...il.com" <lgirdwood@...il.com>,
        "broonie@...nel.org" <broonie@...nel.org>,
        "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "platform-driver-x86@...r.kernel.org" 
        <platform-driver-x86@...r.kernel.org>,
        "mario.limonciello@...look.com" <mario.limonciello@...look.com>,
        Dell Client Kernel <Dell.Client.Kernel@...l.com>
Subject: RE: [PATCH v7 1/2] platform/x86: dell-privacy: Add support for Dell
 hardware privacy

Hi Hans.
I changed the driver in V8 as your comments.
Just one Kconfig change , It will cause some built error .

> -----Original Message-----
> From: Hans de Goede <hdegoede@...hat.com>
> Sent: 2021年4月13日 16:48
> To: Yuan, Perry; pobrn@...tonmail.com; pierre-
> louis.bossart@...ux.intel.com; oder_chiou@...ltek.com; perex@...ex.cz;
> tiwai@...e.com; mgross@...ux.intel.com
> Cc: lgirdwood@...il.com; broonie@...nel.org; alsa-devel@...a-project.org;
> linux-kernel@...r.kernel.org; platform-driver-x86@...r.kernel.org;
> mario.limonciello@...look.com; Dell Client Kernel
> Subject: Re: [PATCH v7 1/2] platform/x86: dell-privacy: Add support for Dell
> hardware privacy
> 
> 
> [EXTERNAL EMAIL]
> 
> Hi,
> 
> On 4/12/21 11:19 AM, Perry Yuan wrote:
> > From: Perry Yuan <perry_yuan@...l.com>
> >
> > add support for Dell privacy driver for the Dell units equipped
> > hardware privacy design, which protect users privacy of audio and
> > camera from hardware level. Once the audio or camera privacy mode
> > activated, any applications will not get any audio or video stream
> > when user pressed ctrl+F4 hotkey, audio privacy mode will be enabled,
> > micmute led will be also changed accordingly The micmute led is fully
> > controlled by hardware & EC(embedded controller) and camera mute
> > hotkey is Ctrl+F9. Currently design only emits SW_CAMERA_LENS_COVER
> > event while the camera lens shutter will be changed by EC &
> > HW(hardware) control
> >
> > *The flow is like this:
> > 1) User presses key. HW does stuff with this key (timeout timer is
> > started)
> > 2) WMI event is emitted from BIOS to kernel
> > 3) WMI event is received by dell-privacy
> > 4) KEY_MICMUTE emitted from dell-privacy
> > 5) Userland picks up key and modifies kcontrol for SW mute
> > 6) Codec kernel driver catches and calls ledtrig_audio_set, like this:
> >    ledtrig_audio_set(LED_AUDIO_MICMUTE, rt715->micmute_led ? LED_ON
> > :LED_OFF);
> > 7) If "LED" is set to on dell-privacy notifies EC, and timeout is cancelled,
> >    HW mic mute activated. If EC not notified, HW mic mute will also be
> >    activated when timeout used up, it is just later than active ack
> >
> > Signed-off-by: Perry Yuan <perry_yuan@...l.com>
> > ---
> > v5 -> v6:
> > * addressed feedback from Hans
> > * addressed feedback from Pierre
> > * optimize some debug format with dev_dbg()
> > * remove platform driver,combined privacy acpi driver into single wmi
> >   driver file
> > * optimize sysfs interface with string added to be more clearly
> > reading
> > * remove unused function and clear header file
> 
> Thank you, almost there. A few small remarks inline.
> 
> > v4 -> v5:
> > * addressed feedback from Randy Dunlap
> > * addressed feedback from Pierre-Louis Bossart
> > * rebase to latest 5.12 rc4 upstream kernel
> > * fix some space alignment problem
> > v3 -> v4:
> > * fix format for Kconfig
> > * add sysfs document
> > * add flow comments to the privacy wmi/acpi driver
> > * addressed feedback from Barnabás Pőcze[Thanks very much]
> > * export privacy_valid to make the global state simpler to query
> > * fix one issue which will block the dell-laptop driver to load when
> >   privacy driver invalid
> > * addressed feedback from Pierre-Louis Bossart,remove the EC ID match
> > v2 -> v3:
> > * add sysfs attributes doc
> > v1 -> v2:
> > * query EC handle from EC driver directly.
> > * fix some code style.
> > * add KEY_END to keymap array.
> > * clean platform device when cleanup called
> > * use hexadecimal format for log print in dev_dbg
> > * remove __set_bit for the report keys from probe.
> > * fix keymap leak
> > * add err_free_keymap in dell_privacy_wmi_probe
> > * wmi driver will be unregistered if privacy_acpi_init() fails
> > * add sysfs attribute files for user space query.
> > * add leds micmute driver to privacy acpi
> > * add more design info the commit info
> > ---
> > ---
> >  .../testing/sysfs-platform-dell-privacy-wmi   |  55 +++
> >  drivers/platform/x86/dell/Kconfig             |  14 +
> >  drivers/platform/x86/dell/Makefile            |   1 +
> >  drivers/platform/x86/dell/dell-laptop.c       |  23 +-
> >  drivers/platform/x86/dell/dell-privacy-wmi.c  | 394
> > ++++++++++++++++++  drivers/platform/x86/dell/dell-privacy-wmi.h  |  23 +
> >  drivers/platform/x86/dell/dell-wmi.c          |   8 +-
> >  7 files changed, 511 insertions(+), 7 deletions(-)  create mode
> > 100644 Documentation/ABI/testing/sysfs-platform-dell-privacy-wmi
> >  create mode 100644 drivers/platform/x86/dell/dell-privacy-wmi.c
> >  create mode 100644 drivers/platform/x86/dell/dell-privacy-wmi.h
> >
> > diff --git a/Documentation/ABI/testing/sysfs-platform-dell-privacy-wmi
> > b/Documentation/ABI/testing/sysfs-platform-dell-privacy-wmi
> > new file mode 100644
> > index 000000000000..7f9e18705861
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-platform-dell-privacy-wmi
> > @@ -0,0 +1,55 @@
> > +What:		/sys/bus/wmi/devices/6932965F-1671-4CEB-B988-
> D3AB0A901919/dell_privacy_supported_type
> > +Date:		Apr 2021
> > +KernelVersion:	5.13
> > +Contact:	"perry.yuan@...l.com>"
> > +Description:
> > +		Display which dell hardware level privacy devices are
> supported
> > +		“Dell Privacy” is a set of HW, FW, and SW features to enhance
> > +		Dell’s commitment to platform privacy for MIC, Camera, and
> > +		ePrivacy screens.
> > +		The supported hardware privacy devices are:
> > +Attributes:
> > +		Microphone Mute:
> > +				Identifies the local microphone can be muted
> by hardware, no applications
> > +				is available to capture system mic sound
> > +
> > +		Camera Shutter:
> > +				Identifies camera shutter controlled by
> hardware, which is a micromechanical
> > +				shutter assembly that is built onto the camera
> module to block capturing images
> > +				from outside the laptop
> > +
> > +		supported:
> > +				The privacy device is supported by this system
> > +
> > +		unsupported:
> > +				The privacy device is not supported on this
> system
> > +
> > +		For example to check which privacy devices are supported:
> > +
> > +		# cat /sys/bus/wmi/drivers/dell-privacy/6932965F-1671-
> 4CEB-B988-D3AB0A901919/dell_privacy_supported_type
> > +		[Microphone Mute] [supported]
> > +		[Camera Shutter] [supported]
> > +		[ePrivacy Screen] [unsupported]
> > +
> > +What:		/sys/bus/wmi/devices/6932965F-1671-4CEB-B988-
> D3AB0A901919/dell_privacy_current_state
> > +Date:		Apr 2021
> > +KernelVersion:	5.13
> > +Contact:	"perry.yuan@...l.com>"
> > +Description:
> > +		Allow user space to check current dell privacy device state.
> > +		Describes the Device State class exposed by BIOS which can
> be
> > +		consumed by various applications interested in knowing the
> Privacy
> > +		feature capabilities
> > +Attributes:
> > +		muted:
> > +			Identifies the privacy device is turned off and cannot
> send stream
> > +to OS applications
> > +
> > +		unmuted:
> > +			Identifies the privacy device is turned on ,audio or
> camera driver can get
> > +			stream from mic and camera module to OS
> applications
> > +
> > +		For example to check all supported current privacy device
> states:
> > +
> > +		# cat /sys/bus/wmi/drivers/dell-privacy/6932965F-1671-
> 4CEB-B988-D3AB0A901919/dell_privacy_current_state
> > +		[Microphone] [unmuted]
> > +		[Camera Shutter] [unmuted]
> > diff --git a/drivers/platform/x86/dell/Kconfig
> > b/drivers/platform/x86/dell/Kconfig
> > index e0a55337f51a..05d124442b25 100644
> > --- a/drivers/platform/x86/dell/Kconfig
> > +++ b/drivers/platform/x86/dell/Kconfig
> > @@ -204,4 +204,18 @@ config DELL_WMI_SYSMAN
> >  	  To compile this driver as a module, choose M here: the module will
> >  	  be called dell-wmi-sysman.
> >
> > +config DELL_PRIVACY
> > +	tristate "Dell Hardware Privacy Support"
> > +	depends on ACPI
> > +	depends on ACPI_WMI
> > +	depends on INPUT
> > +	depends on DELL_LAPTOP
> > +	depends on LEDS_TRIGGER_AUDIO
> > +	select DELL_WMI
> 
> DELL_WMI is not a helper library which can be selected, please use depends
> on here.
> 
> More in general I'm a bit worried about the dependencies being added to dell-
> laptop.c and dell-wmi.c on the new dell-privacy-wmi.ko module.
> 
> What if e.g. dell-laptop.c gets builtin while dell-privacy-wmi.c is a module.
> 
> Then we have dell-laptop.c depending on the dell_privacy_present linker-
> symbol, but that symbol is in a module, so the main vmlinuz binary will fail to
> link due to that missing symbol.
> 
> To fix this you need to add:
> 
> 	depends on DELL_PRIVACY || DELL_PRIVACY = n
> 
> To the Kconfig sections for both DELL_WMI and DELL_LAPTOP

If I add "depends on DELL_PRIVACY || DELL_PRIVACY = n" to both DELL_WMI and DELL_LAPTOP
The compile will report error "recursive dependency detected"
I do not think the dell-laptop will be builtin option as we know.

I am confused that why the symbol will be failed to link like that ?
because the compiler can find the dell_privacy_present which is defined in one common header file.



> 
> 
> > +	help
> > +	  This driver provides integration with the "Dell Hardware Privacy"
> feature
> > +	  of Dell laptops.
> > +
> > +	  To compile this driver as a module, choose M here: the module will
> > +	  be called dell_privacy.
> >  endif # X86_PLATFORM_DRIVERS_DELL
> > diff --git a/drivers/platform/x86/dell/Makefile
> > b/drivers/platform/x86/dell/Makefile
> > index d720a3e42ae3..7da0c33dfcca 100644
> > --- a/drivers/platform/x86/dell/Makefile
> > +++ b/drivers/platform/x86/dell/Makefile
> > @@ -19,3 +19,4 @@ obj-$(CONFIG_DELL_WMI_AIO)		+= dell-wmi-
> aio.o
> >  obj-$(CONFIG_DELL_WMI_DESCRIPTOR)	+= dell-wmi-descriptor.o
> >  obj-$(CONFIG_DELL_WMI_LED)		+= dell-wmi-led.o
> >  obj-$(CONFIG_DELL_WMI_SYSMAN)		+= dell-wmi-sysman/
> > +obj-$(CONFIG_DELL_PRIVACY)              += dell-privacy-wmi.o
> > diff --git a/drivers/platform/x86/dell/dell-laptop.c
> > b/drivers/platform/x86/dell/dell-laptop.c
> > index 70edc5bb3a14..e7ffc0b81208 100644
> > --- a/drivers/platform/x86/dell/dell-laptop.c
> > +++ b/drivers/platform/x86/dell/dell-laptop.c
> > @@ -31,6 +31,8 @@
> >  #include "dell-rbtn.h"
> >  #include "dell-smbios.h"
> >
> > +#include "dell-privacy-wmi.h"
> > +
> >  struct quirk_entry {
> >  	bool touchpad_led;
> >  	bool kbd_led_not_present;
> > @@ -90,6 +92,7 @@ static struct rfkill *wifi_rfkill;  static struct
> > rfkill *bluetooth_rfkill;  static struct rfkill *wwan_rfkill;  static
> > bool force_rfkill;
> > +static bool has_privacy;
> 
> There is a problem in the del-laptop.c code with the led_classdev
> unregistering which is not introduced by this patch, but this patch is a good
> opportunity to fix this.
> 
> The problem is that in the dell_init error-exit path as well as in dell_exit
> led_classdev_unregister() gets called unconditionally, while the registering
> has only happened under the following condition:
> 
> 	if (dell_smbios_find_token(GLOBAL_MIC_MUTE_DISABLE) &&
> 	    dell_smbios_find_token(GLOBAL_MIC_MUTE_ENABLE)) {
> 
> So this means that the code may end up unregistering a never registered
> led_classdev which is not good.
> 
> Since you are making the unregistering conditional in this patch, it would be
> good to also fix this issue.
> 
> Please change:
> 
> static bool has_privacy;
> 
> To:
> 
> static bool micmute_led_registered;
> 
> 
> 
> >
> >  module_param(force_rfkill, bool, 0444);
> > MODULE_PARM_DESC(force_rfkill, "enable rfkill on non whitelisted
> > models"); @@ -2206,10 +2209,16 @@ static int __init dell_init(void)
> >
> >  	if (dell_smbios_find_token(GLOBAL_MIC_MUTE_DISABLE) &&
> >  	    dell_smbios_find_token(GLOBAL_MIC_MUTE_ENABLE)) {
> > -		micmute_led_cdev.brightness =
> ledtrig_audio_get(LED_AUDIO_MICMUTE);
> > -		ret = led_classdev_register(&platform_device->dev,
> &micmute_led_cdev);
> > -		if (ret < 0)
> > -			goto fail_led;
> > +		if (dell_privacy_present())
> > +			has_privacy = true;
> > +		else
> > +			has_privacy = false;
> > +		if (!has_privacy) {
> > +			micmute_led_cdev.brightness =
> ledtrig_audio_get(LED_AUDIO_MICMUTE);
> > +			ret = led_classdev_register(&platform_device->dev,
> &micmute_led_cdev);
> > +			if (ret < 0)
> > +				goto fail_led;
> > +		}
> >  	}
> 
> And change this block to
> 
> 	if (dell_smbios_find_token(GLOBAL_MIC_MUTE_DISABLE) &&
> 	    dell_smbios_find_token(GLOBAL_MIC_MUTE_ENABLE) &&
> 	    !dell_privacy_present()) {
> 		micmute_led_cdev.brightness =
> ledtrig_audio_get(LED_AUDIO_MICMUTE);
> 		ret = led_classdev_register(&platform_device->dev,
> &micmute_led_cdev);
> 		if (ret < 0)
> 			goto fail_led;
> 		micmute_led_registered = true;
> 	}
> 
> This also looks cleaner/nicer with one less indent level too :)
> 
> 
> >
> >  	if (acpi_video_get_backlight_type() != acpi_backlight_vendor) @@
> > -2257,7 +2266,8 @@ static int __init dell_init(void)
> >  fail_get_brightness:
> >  	backlight_device_unregister(dell_backlight_device);
> >  fail_backlight:
> > -	led_classdev_unregister(&micmute_led_cdev);
> > +	if (!has_privacy)
> 
> Change this to:
> 
> 	if (micmute_led_registered)
> > +		led_classdev_unregister(&micmute_led_cdev);
> 
> This way the if condition also is more logical / easier to see why the if is there.
> 
> >  fail_led:
> >  	dell_cleanup_rfkill();
> >  fail_rfkill:
> > @@ -2278,7 +2288,8 @@ static void __exit dell_exit(void)
> >  		touchpad_led_exit();
> >  	kbd_led_exit();
> >  	backlight_device_unregister(dell_backlight_device);
> > -	led_classdev_unregister(&micmute_led_cdev);
> > +	if (!has_privacy)
> 
> And here too, change this to:
> 
> 	if (micmute_led_registered)
> 
> > +		led_classdev_unregister(&micmute_led_cdev);
> >  	dell_cleanup_rfkill();
> >  	if (platform_device) {
> >  		platform_device_unregister(platform_device);
> > diff --git a/drivers/platform/x86/dell/dell-privacy-wmi.c
> > b/drivers/platform/x86/dell/dell-privacy-wmi.c
> > new file mode 100644
> > index 000000000000..4be7548d1a03
> > --- /dev/null
> > +++ b/drivers/platform/x86/dell/dell-privacy-wmi.c
> > @@ -0,0 +1,394 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Dell privacy notification driver
> > + *
> > + * Copyright (C) 2021 Dell Inc. All Rights Reserved.
> > + */
> > +
> > +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> > +
> > +#include <linux/acpi.h>
> > +#include <linux/bitops.h>
> > +#include <linux/input.h>
> > +#include <linux/input/sparse-keymap.h> #include <linux/list.h>
> > +#include <linux/leds.h> #include <linux/module.h> #include
> > +<linux/wmi.h>
> > +
> > +#include "dell-privacy-wmi.h"
> > +
> > +#define DELL_PRIVACY_GUID "6932965F-1671-4CEB-B988-
> D3AB0A901919"
> > +#define MICROPHONE_STATUS		BIT(0)
> > +#define CAMERA_STATUS		        BIT(1)
> > +#define DELL_PRIVACY_AUDIO_EVENT  0x1 #define
> > +DELL_PRIVACY_CAMERA_EVENT 0x2
> > +#define led_to_priv(c)       container_of(c, struct privacy_wmi_data, cdev)
> > +
> > +/*
> > + * The wmi_list is used to store the privacy_priv struct with mutex
> > +protecting  */ static LIST_HEAD(wmi_list); static
> > +DEFINE_MUTEX(list_mutex);
> > +
> > +struct privacy_wmi_data {
> > +	struct input_dev *input_dev;
> > +	struct wmi_device *wdev;
> > +	struct list_head list;
> > +	struct led_classdev cdev;
> > +	u32 features_present;
> > +	u32 last_status;
> > +};
> > +
> > +/* DELL Privacy Type */
> > +enum dell_hardware_privacy_type {
> > +	DELL_PRIVACY_TYPE_AUDIO = 0,
> > +	DELL_PRIVACY_TYPE_CAMERA,
> > +	DELL_PRIVACY_TYPE_SCREEN,
> > +	DELL_PRIVACY_TYPE_MAX,
> > +};
> > +
> > +static const char * const privacy_types[DELL_PRIVACY_TYPE_MAX] = {
> > +	[DELL_PRIVACY_TYPE_AUDIO] = "Microphone",
> > +	[DELL_PRIVACY_TYPE_CAMERA] = "Camera Shutter",
> > +	[DELL_PRIVACY_TYPE_SCREEN] = "ePrivacy Screen", };
> > +
> > +/*
> > + * Keymap for WMI privacy events of type 0x0012  */ static const
> > +struct key_entry dell_wmi_keymap_type_0012[] = {
> > +	/* privacy mic mute */
> > +	{ KE_KEY, 0x0001, { KEY_MICMUTE } },
> > +	/* privacy camera mute */
> > +	{ KE_SW,  0x0002, { SW_CAMERA_LENS_COVER } },
> > +	{ KE_END, 0},
> > +};
> > +
> > +/*
> > + * global privacy state for other modules to query if the privacy
> > +driver loaded successfully
> > + * or no privacy WMI device was detected at initial probe phase  */
> > +bool dell_privacy_present(void) {
> > +	struct privacy_wmi_data *priv;
> > +
> > +	mutex_lock(&list_mutex);
> > +	priv = list_first_entry_or_null(&wmi_list,
> > +			struct privacy_wmi_data,
> > +			list);
> > +	mutex_unlock(&list_mutex);
> > +
> > +	return priv;
> > +}
> > +EXPORT_SYMBOL_GPL(dell_privacy_present);
> 
> I thought that we had chaned this to dell_privacy_has_mic_mute ?
> 
> Returning:
> 
> 	return priv && (priv->features_present &
> BIT(DELL_PRIVACY_TYPE_AUDIO));
> 
> ?
> 
> What has happened to that change, please change that back, the only user of
> dell_privacy_present() is dell-laptop.c and that wants to know if dell-privacy.c
> will be handling the mute-led or not, so only checking for dell-privacy
> presence is not enough.
> 
> 
> 
> > +
> > +/*
> > + * The flow of privacy event:
> > + * 1) User presses key. HW does stuff with this key (timeout is
> > +started)
> > + * 2) WMI event is emitted from BIOS
> > + * 3) WMI event is received by dell-privacy
> > + * 4) KEY_MICMUTE emitted from dell-privacy
> > + * 5) Userland picks up key and modifies kcontrol for SW mute
> > + * 6) Codec kernel driver catches and calls ledtrig_audio_set defined by
> > + *    dell-privacy-acpi driver. Codec driver will call like this to switch
> micmute led state.
> > + *    ledtrig_audio_set(LED_AUDIO_MICMUTE, micmute_led ?
> LED_ON :LED_OFF);
> > + * 7) If "LED" is set to on dell-privacy notifies EC,and timeout is cancelled,
> > + *	HW mic mute activated.
> > + */
> > +bool dell_privacy_process_event(int type, int code, int status) {
> > +	struct privacy_wmi_data *priv;
> > +	const struct key_entry *key;
> > +	bool ret = false;
> > +
> > +	mutex_lock(&list_mutex);
> > +	priv = list_first_entry_or_null(&wmi_list,
> > +			struct privacy_wmi_data,
> > +			list);
> > +	if (!priv) {
> > +		goto error;
> > +	}
> > +
> > +	key = sparse_keymap_entry_from_scancode(priv->input_dev, (type <<
> 16) | code);
> > +	if (!key) {
> > +		dev_warn(&priv->wdev->dev, "Unknown key with type
> 0x%04x and code 0x%04x pressed\n",
> > +			type, code);
> > +		goto error;
> > +	}
> > +	dev_dbg(&priv->wdev->dev, "Key with type 0x%04x and code 0x%04x
> > +pressed\n", type, code);
> > +
> > +	switch (code) {
> > +	case DELL_PRIVACY_AUDIO_EVENT: /* Mic mute */
> > +	case DELL_PRIVACY_CAMERA_EVENT: /* Camera mute */
> > +		priv->last_status = status;
> > +		sparse_keymap_report_entry(priv->input_dev, key, 1, true);
> > +		ret = true;
> > +		break;
> > +	default:
> > +		dev_dbg(&priv->wdev->dev, "unknown event type 0x%04x
> 0x%04x\n", type, code);
> > +	}
> > +
> > +error:
> > +	mutex_unlock(&list_mutex);
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL_GPL(dell_privacy_process_event);
> > +
> > +static ssize_t dell_privacy_supported_type_show(struct device *dev,
> > +					struct device_attribute *attr,
> > +					char *buf)
> > +{
> > +	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
> > +	enum dell_hardware_privacy_type type;
> > +	u32 privacy_list;
> > +	char *s = buf;
> > +
> > +	privacy_list = priv->features_present;
> > +	for (type = DELL_PRIVACY_TYPE_AUDIO; type <
> DELL_PRIVACY_TYPE_MAX; type++) {
> > +		if (privacy_list & BIT(type))
> > +			s += sprintf(s, "[%s] [supported]\n",
> privacy_types[type]);
> > +		else
> > +			s += sprintf(s, "[%s] [unsupported]\n",
> privacy_types[type]);
> > +	}
> > +
> > +	return (s - buf);
> > +}
> 
> As mentioned before I think (not sure), please use sysfs_emit_at here, like this:
> 
> static ssize_t dell_privacy_supported_type_show(struct device *dev,
> 					struct device_attribute *attr,
> 					char *buf)
> {
> 	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
> 	enum dell_hardware_privacy_type type;
> 	u32 privacy_list;
> 	int len = 0;
> 
> 	privacy_list = priv->features_present;
> 	for (type = DELL_PRIVACY_TYPE_AUDIO; type <
> DELL_PRIVACY_TYPE_MAX; type++) {
> 		if (privacy_list & BIT(type))
> 			len += sysfs_emit_at(buf, len, "[%s] [supported]\n",
> privacy_types[type]);
> 		else
> 			len += sysfs_emit_at(buf, len,  "[%s] [unsupported]\n",
> privacy_types[type]);
> 	}
> 
> 	return len;
> }
> 
> This will ensure that we never overrun the size of the passed in buffer.
> 
> 
> 
> > +
> > +static ssize_t dell_privacy_current_state_show(struct device *dev,
> > +					struct device_attribute *attr,
> > +					char *buf)
> > +{
> > +	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
> > +	u32 privacy_supported = priv->features_present;
> > +	enum dell_hardware_privacy_type type;
> > +	u32 privacy_state = priv->last_status;
> > +	char *s = buf;
> > +
> > +	for (type = DELL_PRIVACY_TYPE_AUDIO; type <
> DELL_PRIVACY_TYPE_MAX; type++) {
> > +		if (privacy_supported & BIT(type)) {
> > +			if (privacy_state & BIT(type))
> > +				s += sprintf(s, "[%s] [unmuted]\n",
> privacy_types[type]);
> > +			else
> > +				s += sprintf(s, "[%s] [muted]\n",
> privacy_types[type]);
> > +		}
> > +	}
> > +
> > +	return (s - buf);
> > +}
> 
> And the same here.
> 
> 
> > +
> > +static DEVICE_ATTR_RO(dell_privacy_supported_type);
> > +static DEVICE_ATTR_RO(dell_privacy_current_state);
> > +
> > +static struct attribute *privacy_attributes[] = {
> > +	&dev_attr_dell_privacy_supported_type.attr,
> > +	&dev_attr_dell_privacy_current_state.attr,
> > +	NULL,
> > +};
> > +
> > +static const struct attribute_group privacy_attribute_group = {
> > +	.attrs = privacy_attributes
> > +};
> > +
> > +/*
> > + * Describes the Device State class exposed by BIOS which can be
> > +consumed by
> > + * various applications interested in knowing the Privacy feature
> capabilities.
> > + * class DeviceState
> > + * {
> > + *  [key, read] string InstanceName;
> > + *  [read] boolean ReadOnly;
> > + *
> > + *  [WmiDataId(1), read] uint32 DevicesSupported;
> > + *   0 - None; 0x1 - Microphone; 0x2 - Camera; 0x4 - ePrivacy  Screen
> > + *
> > + *  [WmiDataId(2), read] uint32 CurrentState;
> > + *   0 - Off; 1 - On; Bit0 - Microphone; Bit1 - Camera; Bit2 - ePrivacyScreen
> > + * };
> > + */
> > +static int get_current_status(struct wmi_device *wdev) {
> > +	struct privacy_wmi_data *priv = dev_get_drvdata(&wdev->dev);
> > +	union acpi_object *obj_present;
> > +	u32 *buffer;
> > +	int ret = 0;
> > +
> > +	if (!priv) {
> > +		dev_err(&wdev->dev, "dell privacy priv is NULL\n");
> > +		return -EINVAL;
> > +	}
> > +	/* check privacy support features and device states */
> > +	obj_present = wmidev_block_query(wdev, 0);
> > +	if (!obj_present) {
> > +		dev_err(&wdev->dev, "failed to read Binary MOF\n");
> > +		return -EIO;
> > +	}
> > +
> > +	if (obj_present->type != ACPI_TYPE_BUFFER) {
> > +		dev_err(&wdev->dev, "Binary MOF is not a buffer!\n");
> > +		ret = -EIO;
> > +		goto obj_free;
> > +	}
> > +	/*  Although it's not technically a failure, this would lead to
> > +	 *  unexpected behavior
> > +	 */
> > +	if (obj_present->buffer.length != 8) {
> > +		dev_err(&wdev->dev, "Dell privacy buffer has unexpected
> length (%d)!\n",
> > +				obj_present->buffer.length);
> > +		ret = -EINVAL;
> > +		goto obj_free;
> > +	}
> > +	buffer = (u32 *)obj_present->buffer.pointer;
> > +	priv->features_present = buffer[0];
> > +	priv->last_status = buffer[1];
> > +
> > +obj_free:
> > +	kfree(obj_present);
> > +	return ret;
> > +}
> > +
> > +static int dell_privacy_micmute_led_set(struct led_classdev *led_cdev,
> > +					enum led_brightness brightness)
> > +{
> > +	struct privacy_wmi_data *priv = led_to_priv(led_cdev);
> > +	static char *acpi_method = (char *)"ECAK";
> > +	acpi_status status;
> > +	acpi_handle handle;
> > +
> > +	handle = ec_get_handle();
> > +	if (!handle)
> > +		return -EIO;
> > +
> > +	if (!acpi_has_method(handle, acpi_method))
> > +		return -EIO;
> > +
> > +	status = acpi_evaluate_object(handle, acpi_method, NULL, NULL);
> > +	if (ACPI_FAILURE(status)) {
> > +		dev_err(&priv->wdev->dev, "Error setting privacy EC ack
> value: %s\n",
> > +				acpi_format_exception(status));
> > +		return -EIO;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +/*
> > + * Pressing the mute key activates a time delayed circuit to
> > +physically cut
> > + * off the mute. The LED is in the same circuit, so it reflects the
> > +true
> > + * state of the HW mute.  The reason for the EC "ack" is so that
> > +software
> > + * can first invoke a SW mute before the HW circuit is cut off.
> > +Without SW
> > + * cutting this off first does not affect the time delayed muting or
> > +status
> > + * of the LED but there is a possibility of a "popping" noise.
> > + *
> > + * If the EC receives the SW ack, the circuit will be activated
> > +before the
> > + * delay completed.
> > + *
> > + * Exposing as an LED device allows the codec drivers notification
> > +path to
> > + * EC ACK to work
> > + */
> > +static int dell_privacy_leds_setup(struct device *dev) {
> > +	struct privacy_wmi_data *priv = dev_get_drvdata(dev);
> > +
> > +	priv->cdev.name = "dell-privacy::micmute";
> > +	priv->cdev.max_brightness = 1;
> > +	priv->cdev.brightness_set_blocking = dell_privacy_micmute_led_set;
> > +	priv->cdev.default_trigger = "audio-micmute";
> > +	priv->cdev.brightness = ledtrig_audio_get(LED_AUDIO_MICMUTE);
> > +	return devm_led_classdev_register(dev, &priv->cdev); }
> > +
> > +static int dell_privacy_wmi_probe(struct wmi_device *wdev, const void
> > +*context) {
> > +	struct privacy_wmi_data *priv;
> > +	struct key_entry *keymap;
> > +	int ret, i;
> > +
> > +	ret = wmi_has_guid(DELL_PRIVACY_GUID);
> > +	if (!ret)
> > +		pr_debug("Unable to detect available Dell privacy
> devices!\n");
> > +
> > +	priv = devm_kzalloc(&wdev->dev, sizeof(*priv), GFP_KERNEL);
> > +	if (!priv)
> > +		return -ENOMEM;
> > +
> > +	dev_set_drvdata(&wdev->dev, priv);
> > +	priv->wdev = wdev;
> > +	/* create evdev passing interface */
> > +	priv->input_dev = devm_input_allocate_device(&wdev->dev);
> > +	if (!priv->input_dev)
> > +		return -ENOMEM;
> > +
> > +	/* remap the wmi keymap event to new keymap */
> > +	keymap = kcalloc(ARRAY_SIZE(dell_wmi_keymap_type_0012),
> > +			sizeof(struct key_entry), GFP_KERNEL);
> > +	if (!keymap)
> > +		return -ENOMEM;
> > +
> > +	/* remap the keymap code with Dell privacy key type 0x12 as prefix
> > +	 * KEY_MICMUTE scancode will be reported as 0x120001
> > +	 */
> > +	for (i = 0; i < ARRAY_SIZE(dell_wmi_keymap_type_0012); i++) {
> > +		keymap[i] = dell_wmi_keymap_type_0012[i];
> > +		keymap[i].code |= (0x0012 << 16);
> > +	}
> > +	ret = sparse_keymap_setup(priv->input_dev, keymap, NULL);
> > +	kfree(keymap);
> > +	if (ret)
> > +		return ret;
> > +
> > +	priv->input_dev->dev.parent = &wdev->dev;
> > +	priv->input_dev->name = "Dell Privacy Driver";
> > +	priv->input_dev->id.bustype = BUS_HOST;
> > +
> > +	ret = input_register_device(priv->input_dev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = get_current_status(priv->wdev);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = devm_device_add_group(&wdev->dev,
> &privacy_attribute_group);
> > +	if (ret)
> > +		return ret;
> > +
> > +	ret = dell_privacy_leds_setup(&priv->wdev->dev);
> > +	if (ret)
> > +		return ret;
> 
> This should be conditional on the audio privacy feature being supported:
> 
> 	if (priv->features_present & BIT(DELL_PRIVACY_TYPE_AUDIO)) {
> 		ret = dell_privacy_leds_setup(&priv->wdev->dev);
> 		if (ret)
> 			return ret;
> 	}
> 
> 
> > +
> > +	mutex_lock(&list_mutex);
> > +	list_add_tail(&priv->list, &wmi_list);
> > +	mutex_unlock(&list_mutex);
> > +	return 0;
> > +}
> > +
> > +static int dell_privacy_wmi_remove(struct wmi_device *wdev) {
> > +	struct privacy_wmi_data *priv = dev_get_drvdata(&wdev->dev);
> > +
> > +	mutex_lock(&list_mutex);
> > +	list_del(&priv->list);
> > +	mutex_unlock(&list_mutex);
> > +	return 0;
> > +}
> > +
> > +static const struct wmi_device_id dell_wmi_privacy_wmi_id_table[] = {
> > +	{ .guid_string = DELL_PRIVACY_GUID },
> > +	{ },
> > +};
> > +
> > +static struct wmi_driver dell_privacy_wmi_driver = {
> > +	.driver = {
> > +		.name = "dell-privacy",
> > +	},
> > +	.probe = dell_privacy_wmi_probe,
> > +	.remove = dell_privacy_wmi_remove,
> > +	.id_table = dell_wmi_privacy_wmi_id_table, };
> > +
> > +module_wmi_driver(dell_privacy_wmi_driver);
> > +
> > +MODULE_DEVICE_TABLE(wmi, dell_wmi_privacy_wmi_id_table);
> > +MODULE_AUTHOR("Perry Yuan <perry_yuan@...l.com>");
> > +MODULE_DESCRIPTION("Dell Privacy WMI Driver");
> MODULE_LICENSE("GPL");
> > diff --git a/drivers/platform/x86/dell/dell-privacy-wmi.h
> > b/drivers/platform/x86/dell/dell-privacy-wmi.h
> > new file mode 100644
> > index 000000000000..04c49d2fa924
> > --- /dev/null
> > +++ b/drivers/platform/x86/dell/dell-privacy-wmi.h
> > @@ -0,0 +1,23 @@
> > +/* SPDX-License-Identifier: GPL-2.0-only */
> > +/*
> > + * Dell privacy notification driver
> > + *
> > + * Copyright (C) 2021 Dell Inc. All Rights Reserved.
> > + */
> > +
> > +#ifndef _DELL_PRIVACY_WMI_H_
> > +#define _DELL_PRIVACY_WMI_H_
> > +
> > +#if IS_ENABLED(CONFIG_DELL_PRIVACY)
> > +bool dell_privacy_present(void);
> > +bool dell_privacy_process_event(int type, int code, int status);
> > +#else /* CONFIG_DELL_PRIVACY */ static inline bool
> > +dell_privacy_present(void) {
> > +	return -ENODEV;
> > +}
> > +
> > +static inline bool dell_privacy_process_event(int type, int code, int
> > +status) {}
> 
> This is missing a return false; between the {}.
> 
> > +#endif /* CONFIG_DELL_PRIVACY */
> > +#endif
> > diff --git a/drivers/platform/x86/dell/dell-wmi.c
> > b/drivers/platform/x86/dell/dell-wmi.c
> > index bbdb3e860892..228e85a427f5 100644
> > --- a/drivers/platform/x86/dell/dell-wmi.c
> > +++ b/drivers/platform/x86/dell/dell-wmi.c
> > @@ -27,6 +27,7 @@
> >  #include <acpi/video.h>
> >  #include "dell-smbios.h"
> >  #include "dell-wmi-descriptor.h"
> > +#include "dell-privacy-wmi.h"
> >
> >  MODULE_AUTHOR("Matthew Garrett <mjg@...hat.com>");
> > MODULE_AUTHOR("Pali Rohár <pali@...nel.org>"); @@ -427,7 +428,6
> @@
> > static void dell_wmi_notify(struct wmi_device *wdev,
> >
> >  		switch (buffer_entry[1]) {
> >  		case 0x0000: /* One key pressed or event occurred */
> > -		case 0x0012: /* Event with extended data occurred */
> >  			if (len > 2)
> >  				dell_wmi_process_key(wdev, buffer_entry[1],
> >  						     buffer_entry[2]);
> > @@ -439,6 +439,12 @@ static void dell_wmi_notify(struct wmi_device
> *wdev,
> >  				dell_wmi_process_key(wdev, buffer_entry[1],
> >  						     buffer_entry[i]);
> >  			break;
> > +		case 0x0012:
> > +			if ((len > 4) &&
> dell_privacy_process_event(buffer_entry[1], buffer_entry[3], buffer_entry[4]))
> > +				/* privacy hotkey handle */;
> 
> Please change this comment to:
> 
> 				/* dell_privacy_process_event() has handled
> the event */ ;
> 
> 
> > +			else if (len > 2)
> > +				dell_wmi_process_key(wdev, buffer_entry[1],
> buffer_entry[2]);
> > +			break;
> >  		default: /* Unknown event */
> >  			pr_info("Unknown WMI event type 0x%x\n",
> >  				(int)buffer_entry[1]);
> >
> 
> 
> 
> Regards,
> 
> Hans

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