Add HAL for VR mode.
- Provide HAL for vendors to turn on VR-specific device performance
settings when we enter VR mode in VrManagerService.
Bug: 22855417
Change-Id: I3dee920818eb0988452bf5c25d1a31f11fde7339
diff --git a/include/hardware/vr.h b/include/hardware/vr.h
new file mode 100644
index 0000000..494f016
--- /dev/null
+++ b/include/hardware/vr.h
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ANDROID_INCLUDE_HARDWARE_VR_H
+#define ANDROID_INCLUDE_HARDWARE_VR_H
+
+#include <stdbool.h>
+#include <sys/cdefs.h>
+#include <hardware/hardware.h>
+
+__BEGIN_DECLS
+
+#define VR_HARDWARE_MODULE_ID "vr_module"
+
+#define VR_MODULE_API_VERSION_1_0 HARDWARE_MODULE_API_VERSION(1, 0)
+
+/**
+ * Implement this HAL to receive callbacks when a virtual reality (VR)
+ * application is being used. VR applications characteristically have a number
+ * of special display and performance requirements, including:
+ * - Low sensor latency - Total end-to-end latency from the IMU, accelerometer,
+ * and gyro to an application-visible callback must be extremely low (<5ms
+ * typically). This is required for HIFI sensor support.
+ * - Low display latency - Total end-to-end latency from the GPU draw calls to
+ * the actual display update must be as low as possible. This is typically
+ * achieved by using SurfaceFlinger in a single-buffered mode, and assuring
+ * that draw calls are synchronized with the display scanout correctly. Any
+ * GPU settings required to allow consistent performance of this operation
+ * are required, including the EGL extensions: EGL_IMG_context_priority, and
+ * EGL_XXX_set_render_buffer_mode.
+ * - Low-persistence display - Display persistence settings must be set as low as
+ * possible while still maintaining a reasonable brightness. For a typical
+ * display running at 60Hz, pixels should be illuminated for <4ms to be
+ * considered low-persistence (<2ms is desirable). This avoids ghosting
+ * during movements in a VR setting.
+ * - Consistent performance of the GPU and CPU - When given a mixed GPU/CPU
+ * workload for a VR application with bursts of work at regular intervals
+ * several times a frame. CPU scheduling should ensure that the application
+ * render thread is run consistently within 1ms of when required for the
+ * draw window, and an appropriate clockrate is maintained to ensure the
+ * workload finishes within the time alloted to the draw window. Likewise,
+ * GPU scheduling should ensure that work from the application render thread
+ * is given priority over other GPU work, and that a high enough clockrate can
+ * be maintained to ensure that this completes within the draw window. CTS
+ * tests with example VR workloads will be available to assess performance
+ * tuning.
+ *
+ * Vendors implementing this HAL are expected to use set_vr_mode as a hint to
+ * enable VR-specific performance tuning, and to turn on any device features
+ * optimal for VR display modes (or do nothing if none are available). Devices
+ * that advertise FEATURE_VR_MODE_HIGH_PERFORMANCE are must pass the additional
+ * CTS performance tests required for this feature and follow the additional
+ * guidelines for hardware implementation for "VR Ready" devices.
+ *
+ * No methods in this HAL will be called concurrently from the Android framework.
+ */
+typedef struct vr_module {
+ /**
+ * Common methods of the module. This *must* be the first member of
+ * vr_module as users of * this structure will cast a hw_module_t to a
+ * vr_module pointer in contexts where it's known that the hw_module_t
+ * references a vr_module.
+ */
+ struct hw_module_t common;
+
+ /**
+ * Convenience method for the HAL implementation to set up any state needed
+ * at runtime startup. This is called once from the VrManagerService during
+ * its boot phase. No methods from this HAL will be called before init.
+ */
+ void (*init)(struct vr_module *module);
+
+ /**
+ * Set the VR mode state. Possible states of the enabled parameter are:
+ * false - VR mode is disabled, turn off all VR-specific settings.
+ * true - VR mode is enabled, turn on all VR-specific settings.
+ *
+ * This is called from the VrManagerService whenever the application(s)
+ * currently in use enters or leaves VR mode. This will typically occur
+ * when the user switches or from an application that has indicated to
+ * system_server that it should run in VR mode.
+ */
+ void (*set_vr_mode)(struct vr_module *module, bool enabled);
+
+ /* Reserved for future use. Must be NULL. */
+ void* reserved[8 - 2];
+} vr_module_t;
+
+__END_DECLS
+
+#endif /* ANDROID_INCLUDE_HARDWARE_VR_H */