platform/x86: thinkpad_acpi: Register a privacy-screen device

Register a privacy-screen device on laptops with a privacy-screen,
this exports the PrivacyGuard features to user-space using a
standardized vendor-agnostic sysfs interface. Note the sysfs interface
is read-only.

Registering a privacy-screen device with the new privacy-screen class
code will also allow the GPU driver to get a handle to it and export
the privacy-screen setting as a property on the DRM connector object
for the LCD panel. This DRM connector property is a new standardized
interface which all user-space code should use to query and control
the privacy-screen.
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Mark Pearson <markpearson@lenovo.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005202322.700909-9-hdegoede@redhat.com

drivers/platform/x86/Kconfig

@@ -501,7 +501,9 @@ config THINKPAD_ACPI
 	depends on ACPI_VIDEO || ACPI_VIDEO = n
 	depends on BACKLIGHT_CLASS_DEVICE
 	depends on I2C
+	depends on DRM
 	select ACPI_PLATFORM_PROFILE
+	select DRM_PRIVACY_SCREEN
 	select HWMON
 	select NVRAM
 	select NEW_LEDS

drivers/platform/x86/thinkpad_acpi.c

@@ -73,6 +73,7 @@
 #include <linux/uaccess.h>
 #include <acpi/battery.h>
 #include <acpi/video.h>
+#include <drm/drm_privacy_screen_driver.h>
 #include "dual_accel_detect.h"
 
 /* ThinkPad CMOS commands */
@@ -157,6 +158,7 @@ enum tpacpi_hkey_event_t {
 	TP_HKEY_EV_VOL_UP		= 0x1015, /* Volume up or unmute */
 	TP_HKEY_EV_VOL_DOWN		= 0x1016, /* Volume down or unmute */
 	TP_HKEY_EV_VOL_MUTE		= 0x1017, /* Mixer output mute */
+	TP_HKEY_EV_PRIVACYGUARD_TOGGLE	= 0x130f, /* Toggle priv.guard on/off */
 
 	/* Reasons for waking up from S3/S4 */
 	TP_HKEY_EV_WKUP_S3_UNDOCK	= 0x2304, /* undock requested, S3 */
@@ -3889,6 +3891,12 @@ static bool hotkey_notify_extended_hotkey(const u32 hkey)
 {
 	unsigned int scancode;
 
+	switch (hkey) {
+	case TP_HKEY_EV_PRIVACYGUARD_TOGGLE:
+		tpacpi_driver_event(hkey);
+		return true;
+	}
+
 	/* Extended keycodes start at 0x300 and our offset into the map
 	 * TP_ACPI_HOTKEYSCAN_EXTENDED_START. The calculated scancode
 	 * will be positive, but might not be in the correct range.
@@ -9819,30 +9827,40 @@ static struct ibm_struct battery_driver_data = {
  * LCD Shadow subdriver, for the Lenovo PrivacyGuard feature
  */
 
+static struct drm_privacy_screen *lcdshadow_dev;
 static acpi_handle lcdshadow_get_handle;
 static acpi_handle lcdshadow_set_handle;
-static int lcdshadow_state;
 
-static int lcdshadow_on_off(bool state)
+static int lcdshadow_set_sw_state(struct drm_privacy_screen *priv,
+				  enum drm_privacy_screen_status state)
 {
 	int output;
 
+	if (WARN_ON(!mutex_is_locked(&priv->lock)))
+		return -EIO;
+
 	if (!acpi_evalf(lcdshadow_set_handle, &output, NULL, "dd", (int)state))
 		return -EIO;
 
-	lcdshadow_state = state;
+	priv->hw_state = priv->sw_state = state;
 	return 0;
 }
 
-static int lcdshadow_set(bool on)
+static void lcdshadow_get_hw_state(struct drm_privacy_screen *priv)
 {
-	if (lcdshadow_state < 0)
-		return lcdshadow_state;
-	if (lcdshadow_state == on)
-		return 0;
-	return lcdshadow_on_off(on);
+	int output;
+
+	if (!acpi_evalf(lcdshadow_get_handle, &output, NULL, "dd", 0))
+		return;
+
+	priv->hw_state = priv->sw_state = output & 0x1;
 }
 
+static const struct drm_privacy_screen_ops lcdshadow_ops = {
+	.set_sw_state = lcdshadow_set_sw_state,
+	.get_hw_state = lcdshadow_get_hw_state,
+};
+
 static int tpacpi_lcdshadow_init(struct ibm_init_struct *iibm)
 {
 	acpi_status status1, status2;
@@ -9850,36 +9868,44 @@ static int tpacpi_lcdshadow_init(struct ibm_init_struct *iibm)
 
 	status1 = acpi_get_handle(hkey_handle, "GSSS", &lcdshadow_get_handle);
 	status2 = acpi_get_handle(hkey_handle, "SSSS", &lcdshadow_set_handle);
-	if (ACPI_FAILURE(status1) || ACPI_FAILURE(status2)) {
-		lcdshadow_state = -ENODEV;
+	if (ACPI_FAILURE(status1) || ACPI_FAILURE(status2))
 		return 0;
-	}
 
-	if (!acpi_evalf(lcdshadow_get_handle, &output, NULL, "dd", 0)) {
-		lcdshadow_state = -EIO;
+	if (!acpi_evalf(lcdshadow_get_handle, &output, NULL, "dd", 0))
 		return -EIO;
-	}
-	if (!(output & 0x10000)) {
-		lcdshadow_state = -ENODEV;
+
+	if (!(output & 0x10000))
 		return 0;
-	}
-	lcdshadow_state = output & 0x1;
+
+	lcdshadow_dev = drm_privacy_screen_register(&tpacpi_pdev->dev,
+						    &lcdshadow_ops);
+	if (IS_ERR(lcdshadow_dev))
+		return PTR_ERR(lcdshadow_dev);
 
 	return 0;
 }
 
+static void lcdshadow_exit(void)
+{
+	drm_privacy_screen_unregister(lcdshadow_dev);
+}
+
 static void lcdshadow_resume(void)
 {
-	if (lcdshadow_state >= 0)
-		lcdshadow_on_off(lcdshadow_state);
+	if (!lcdshadow_dev)
+		return;
+
+	mutex_lock(&lcdshadow_dev->lock);
+	lcdshadow_set_sw_state(lcdshadow_dev, lcdshadow_dev->sw_state);
+	mutex_unlock(&lcdshadow_dev->lock);
 }
 
 static int lcdshadow_read(struct seq_file *m)
 {
-	if (lcdshadow_state < 0) {
+	if (!lcdshadow_dev) {
 		seq_puts(m, "status:\t\tnot supported\n");
 	} else {
-		seq_printf(m, "status:\t\t%d\n", lcdshadow_state);
+		seq_printf(m, "status:\t\t%d\n", lcdshadow_dev->hw_state);
 		seq_puts(m, "commands:\t0, 1\n");
 	}
 
@@ -9891,7 +9917,7 @@ static int lcdshadow_write(char *buf)
 	char *cmd;
 	int res, state = -EINVAL;
 
-	if (lcdshadow_state < 0)
+	if (!lcdshadow_dev)
 		return -ENODEV;
 
 	while ((cmd = strsep(&buf, ","))) {
@@ -9903,11 +9929,18 @@ static int lcdshadow_write(char *buf)
 	if (state >= 2 || state < 0)
 		return -EINVAL;
 
-	return lcdshadow_set(state);
+	mutex_lock(&lcdshadow_dev->lock);
+	res = lcdshadow_set_sw_state(lcdshadow_dev, state);
+	mutex_unlock(&lcdshadow_dev->lock);
+
+	drm_privacy_screen_call_notifier_chain(lcdshadow_dev);
+
+	return res;
 }
 
 static struct ibm_struct lcdshadow_driver_data = {
 	.name = "lcdshadow",
+	.exit = lcdshadow_exit,
 	.resume = lcdshadow_resume,
 	.read = lcdshadow_read,
 	.write = lcdshadow_write,
@@ -10717,6 +10750,20 @@ static void tpacpi_driver_event(const unsigned int hkey_event)
 		if (!atomic_add_unless(&dytc_ignore_event, -1, 0))
 			dytc_profile_refresh();
 	}
+
+	if (lcdshadow_dev && hkey_event == TP_HKEY_EV_PRIVACYGUARD_TOGGLE) {
+		enum drm_privacy_screen_status old_hw_state;
+		bool changed;
+
+		mutex_lock(&lcdshadow_dev->lock);
+		old_hw_state = lcdshadow_dev->hw_state;
+		lcdshadow_get_hw_state(lcdshadow_dev);
+		changed = lcdshadow_dev->hw_state != old_hw_state;
+		mutex_unlock(&lcdshadow_dev->lock);
+
+		if (changed)
+			drm_privacy_screen_call_notifier_chain(lcdshadow_dev);
+	}
 }
 
 static void hotkey_driver_event(const unsigned int scancode)