drm/privacy-screen: Add X86 specific arch init code

Add X86 specific arch init code, which fills the privacy-screen lookup
table by checking for various vendor specific ACPI interfaces for
controlling the privacy-screen.

This initial version only checks for the Lenovo Thinkpad specific ACPI
methods for privacy-screen control.
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211005202322.700909-4-hdegoede@redhat.com

drivers/gpu/drm/Makefile

@@ -32,7 +32,7 @@ drm-$(CONFIG_OF) += drm_of.o
 drm-$(CONFIG_PCI) += drm_pci.o
 drm-$(CONFIG_DEBUG_FS) += drm_debugfs.o drm_debugfs_crc.o
 drm-$(CONFIG_DRM_LOAD_EDID_FIRMWARE) += drm_edid_load.o
-drm-$(CONFIG_DRM_PRIVACY_SCREEN) += drm_privacy_screen.o
+drm-$(CONFIG_DRM_PRIVACY_SCREEN) += drm_privacy_screen.o drm_privacy_screen_x86.o
 
 obj-$(CONFIG_DRM_DP_AUX_BUS) += drm_dp_aux_bus.o
 

drivers/gpu/drm/drm_privacy_screen_x86.c

+// SPDX-License-Identifier: MIT
+/*
+ * Copyright (C) 2020 Red Hat, Inc.
+ *
+ * Authors:
+ * Hans de Goede <hdegoede@redhat.com>
+ */
+
+#include <linux/acpi.h>
+#include <drm/drm_privacy_screen_machine.h>
+
+#ifdef CONFIG_X86
+static struct drm_privacy_screen_lookup arch_lookup;
+
+struct arch_init_data {
+	struct drm_privacy_screen_lookup lookup;
+	bool (*detect)(void);
+};
+
+#if IS_ENABLED(CONFIG_THINKPAD_ACPI)
+static acpi_status __init acpi_set_handle(acpi_handle handle, u32 level,
+					  void *context, void **return_value)
+{
+	*(acpi_handle *)return_value = handle;
+	return AE_CTRL_TERMINATE;
+}
+
+static bool __init detect_thinkpad_privacy_screen(void)
+{
+	union acpi_object obj = { .type = ACPI_TYPE_INTEGER };
+	struct acpi_object_list args = { .count = 1, .pointer = &obj, };
+	acpi_handle ec_handle = NULL;
+	unsigned long long output;
+	acpi_status status;
+
+	/* Get embedded-controller handle */
+	status = acpi_get_devices("PNP0C09", acpi_set_handle, NULL, &ec_handle);
+	if (ACPI_FAILURE(status) || !ec_handle)
+		return false;
+
+	/* And call the privacy-screen get-status method */
+	status = acpi_evaluate_integer(ec_handle, "HKEY.GSSS", &args, &output);
+	if (ACPI_FAILURE(status))
+		return false;
+
+	return (output & 0x10000) ? true : false;
+}
+#endif
+
+static const struct arch_init_data arch_init_data[] __initconst = {
+#if IS_ENABLED(CONFIG_THINKPAD_ACPI)
+	{
+		.lookup = {
+			.dev_id = NULL,
+			.con_id = NULL,
+			.provider = "privacy_screen-thinkpad_acpi",
+		},
+		.detect = detect_thinkpad_privacy_screen,
+	},
+#endif
+};
+
+void __init drm_privacy_screen_lookup_init(void)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(arch_init_data); i++) {
+		if (!arch_init_data[i].detect())
+			continue;
+
+		pr_info("Found '%s' privacy-screen provider\n",
+			arch_init_data[i].lookup.provider);
+
+		/* Make a copy because arch_init_data is __initconst */
+		arch_lookup = arch_init_data[i].lookup;
+		drm_privacy_screen_lookup_add(&arch_lookup);
+		break;
+	}
+}
+
+void drm_privacy_screen_lookup_exit(void)
+{
+	if (arch_lookup.provider)
+		drm_privacy_screen_lookup_remove(&arch_lookup);
+}
+#endif /* ifdef CONFIG_X86 */

include/drm/drm_privacy_screen_machine.h

@@ -31,11 +31,16 @@ struct drm_privacy_screen_lookup {
 void drm_privacy_screen_lookup_add(struct drm_privacy_screen_lookup *lookup);
 void drm_privacy_screen_lookup_remove(struct drm_privacy_screen_lookup *lookup);
 
+#if IS_ENABLED(CONFIG_DRM_PRIVACY_SCREEN) && IS_ENABLED(CONFIG_X86)
+void drm_privacy_screen_lookup_init(void);
+void drm_privacy_screen_lookup_exit(void);
+#else
 static inline void drm_privacy_screen_lookup_init(void)
 {
 }
 static inline void drm_privacy_screen_lookup_exit(void)
 {
 }
+#endif
 
 #endif