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