ConfigStore

In Android, system properties are stored in the ConfigStore class. ConfigStore uses build flags to store config values in the vendor partition, and a service in the system partition accesses those values using HIDL.

System properties use PRODUCT_DEFAULT_PROPERTY_OVERRIDES to store system properties in default.prop in the vendor partition, and the service uses sysprop to read those properties.

The ConfigStore HAL remains in AOSP to support legacy vendor partitions. On devices running Android 10, surfaceflinger reads system properties first; if no system property is defined for a config item in SurfaceFlingerProperties.sysprop, surfaceflinger falls back to the ConfigStore HAL.

Build flags and system properties

Each build flag in ConfigStore has a matching system property, as shown in the following table.

Build flags	System properties
`TARGET_FORCE_HWC_FOR_VIRTUAL_DISPLAYS`	`ro.surface_flinger.force_hwc_copy_for_virtual_displays`
`TARGET_HAS_HDR_DISPLAY`	`ro.surface_flinger.has_HDR_display`
`TARGET_HAS_WIDE_COLOR_DISPLAY`	`ro.surface_flinger.has_wide_color_display`
`NUM_FRAMEBUFFER_SURFACE_BUFFERS`	`ro.surface_flinger.max_frame_buffer_acquired_buffers`
`MAX_VIRTUAL_DISPLAY_DIMENSION`	`ro.surface_flinger.max_virtual_display_dimension`
`PRIMARY_DISPLAY_ORIENTATION`	`ro.surface_flinger.primary_display_orientation`
`PRESENT_TIME_OFFSET_FROM_VSYNC_NS`	`ro.surface_flinger.present_time_offset_from_vsync_ns`
`TARGET_RUNNING_WITHOUT_SYNC_FRAMEWORK`	`ro.surface_flinger.running_without_sync_framework`
`SF_START_GRAPHICS_ALLOCATOR_SERVICE`	`ro.surface_flinger.start_graphics_allocator_service`
`TARGET_USE_CONTEXT_PRIORITY`	`ro.surface_flinger.use_context_priority`
`USE_VR_FLINGER`	`ro.surface_flinger.use_vr_flinger`
`VSYNC_EVENT_PHASE_OFFSET_NS`	`ro.surface_flinger.vsync_event_phase_offset_ns`
`SF_VSYNC_EVENT_PHASE_OFFSET_NS`	`ro.surface_flinger.vsync_sf_event_phase_offset_ns`

New system properties

Android 10 includes the following new system properties:

ro.surface_flinger.default_composition_dataspace
ro.surface_flinger.default_composition_pixel_format
ro.surface_flinger.use_color_management
ro.surface_flinger.wcg_composition_dataspace
ro.surface_flinger.wcg_composition_pixel_format
ro.surface_flinger.display_primary_red
ro.surface_flinger.display_primary_green
ro.surface_flinger.display_primary_blue
ro.surface_flinger.display_primary_white
ro.surface_flinger.protected_contents
ro.surface_flinger.set_idle_timer_ms
ro.surface_flinger.set_touch_timer_ms
ro.surface_flinger.use_smart_90_for_video
ro.surface_flinger.protected_contents
ro.surface_flinger.support_kernel_idle_timer

For details on these properties, refer to frameworks/native/services/surfaceflinger/sysprop/SurfaceFlingerProperties.sysprop.

Use SurfaceFlingerProperties

In the following examples for the SurfaceFlingerProperties library, the function name is api_name in SurfaceFlingerProperties.sysprop.

cc_binary {
    name: "cc_client",
    srcs: ["baz.cpp"],
    shared_libs: ["SurfaceFlingerProperties"],
}
java_library {
    name: "JavaClient",
    srcs: ["foo/bar.java"],
    libs: ["SurfaceFlingerProperties"],
}

import android.sysprop.SurfaceFlingerProperties;
...

static void foo() {
    ...
    boolean temp = SurfaceFlingerProperties.vsync_event_phase_offset_ns().orElse(true);
    ...
}
...

#include <SurfaceFlingerProperties.sysprop.h>
using namespace android::sysprop;

...

void bar() {
    ...
    bool temp = SurfaceFlingerProperties::vsync_event_phase_offset_ns(true);
    ...
}
...