sdk/fidl/fuchsia.sysmem2/constraints.fidl - fuchsia - Git at Google

 // Copyright 2020 The Fuchsia Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.

 library fuchsia.sysmem2;

 const uint32 MAX_COUNT_BUFFER_COLLECTION_CONSTRAINTS_IMAGE_FORMAT_CONSTRAINTS = 64;
 const uint32 MAX_COUNT_BUFFER_MEMORY_CONSTRAINTS_HEAP_PERMITTED = 64;
 const uint32 MAX_COUNT_IMAGE_FORMAT_CONSTRAINTS_COLOR_SPACES = 32;

 // The contents of this file are not final.  Incompatible changes are still
 // being made to this file.  Do not rely on the contents of this file to provide
 // backward compatibility (yet).
 //
 // TODO(fxbug.dev/34192): Sysmem should use llcpp and FIDL tables.  The
 // fuchsia.sysmem2.BufferCollectionConstraints defined here are part of that
 // transition, but the definitions here are not final.  For now, the definition
 // here is only used internally to sysmem (not between processes), and therefore
 // this definition can change for now.  Later after we're happy with this
 // representation, we'll create
 // fuchsia.sysmem2.BufferCollection.SetConstraints() which will accept
 // constraints as defined here.

 /// Constraints on BufferCollection parameters.  These constraints can be
 /// specified per-participant.  The sysmem service implements aggregation of
 /// constraints from multiple participants.
 table BufferCollectionConstraints {
     /// The usage is only meant as a hint to help sysmem choose a more optimal
     /// PixelFormat or similar when multiple compatible options exist.
     ///
     /// When aggregating BufferCollectionConstraints, these values bitwise-OR.
     ///
     /// At least one usage bit must be specified unless the whole
     /// BufferCollectionConstraints is logically null (no fields set).
     1: BufferUsage usage;

     /// Per-participant minimum number of buffers that are needed for camping
     /// purposes.  A participant should specify a number for min_buffer_count
     /// that's >= the maximum number of buffers that the participant may
     /// concurrently camp on for any non-transient period of time.
     ///
     /// For example, a video decoder would specify (at least) the maximum number
     /// of reference frames + 1 frame currently being decoded into.
     ///
     /// A participant must not camp on more buffers than specified here (except
     /// very transiently) else processing may get stuck.
     ///
     /// When aggregating BufferCollectionConstraints, these values add.
     ///
     /// In testing scenarios, camping on more buffers than this for any
     /// significant duration may (ideally will) be flagged as a failure.  In
     /// testing scenarios, the participant may not be provided with more buffers
     /// than this concurrently.
     2: uint32 min_buffer_count_for_camping;

     /// Per-participant minimum number of buffers that are needed for slack
     /// reasons, for better overlap of processing / better performance.
     ///
     /// When aggregating BufferCollectionConstraints, these values add.
     ///
     /// A participant should typically specify 0 or 1 here - typically 0 is
     /// appropriate if min_buffer_count_for_camping is already enough to keep
     /// the participant busy 100% of the time when the participant is slightly
     /// behind, while 1 can be appropriate if 1 more buffer than strictly needed
     /// for min-camping reasons gives enough slack to stay busy 100% of the time
     /// (when slightly behind, vs. lower % without the extra buffer).
     ///
     /// In testing scenarios, this field may be forced to 0, and all
     /// participants are expected to continue to work without getting stuck.  If
     /// a buffer is needed for forward progress reasons, that buffer should be
     /// accounted for in min_buffer_count_for_camping.
     3: uint32 min_buffer_count_for_dedicated_slack;

     /// Similar to min_buffer_count_for_dedicated_slack, except when aggregating
     /// these values max (instead of add).  The value here is not shared with
     /// any participant's min_buffer_count_for_dedicated_slack.
     ///
     /// A participant can specify > 0 here if a participant would like to ensure
     /// there's some slack overall, but doesn't need that slack to be dedicated.
     ///
     /// The choice whether to use min_buffer_count_for_dedicated_slack or
     /// min_buffer_count_for_shared_slack (or both) will typically be about the
     /// degree to which the extra slack improves performance.
     ///
     /// In testing scenarios, this field may be forced to 0, and all
     /// participants are expected to continue to work without getting stuck.  If
     /// a buffer is needed for forward progress reasons, that buffer should be
     /// accounted for in min_buffer_count_for_camping.
     4: uint32 min_buffer_count_for_shared_slack;

     /// A particularly-picky participant may unfortunately need to demand a tight
     /// range of buffer_count, or even a specific buffer_count.  This field
     /// should remain 0 unless a participant really must set this field to
     /// constrain the overall BufferCollectionInfo_2.buffer_count.  Any such
     /// participant should still fill out the min_buffer_count_for_* fields.
     ///
     /// If this field is un-set, the logical min_buffer_count is 1.
     5: uint32 min_buffer_count;
     /// A particularly-picky participant may unfortunately need to demand a tight
     /// range of buffer_count, or even a specific buffer_count.  This field
     /// should remain 0 unless a participant really must set this field to
     /// constrain the overall BufferCollectionInfo_2.buffer_count.  Any such
     /// participant should still fill out the min_buffer_count_for_* fields.
     ///
     /// If this field is un-set, the logical max_buffer_count is 0xFFFFFFFF.
     6: uint32 max_buffer_count;

     /// Optional constraints on BufferCollectionSettings.buffer_settings.
     ///
     /// A participant that intends to specify image_format_constraints_count > 1
     /// will typically specify the minimum buffer size implicitly via
     /// image_format_constraints, and possibly specify only the max buffer size
     /// via buffer_memory_constraints.
     ///
     /// If un-set, the client is specifying "don't care" re. any buffer memory
     /// constraints.
     7: BufferMemoryConstraints buffer_memory_constraints;

     /// Optional constraints on the image format parameters of an image stored
     /// in a buffer of the BufferCollection.  This includes pixel format and
     /// image layout.  These constraints are per-pixel-format, so more than one
     /// is permitted. Entries in the list must have unique pixel_formats.
     ///
     /// When aggregating, only pixel formats that are specified by all
     /// particpants with non-zero image_format_constraints_count (and non-Null)
     /// BufferCollectionConstraints) are retained.
     ///
     /// un-set means no image format constraints.  set but zero length is an
     /// error.
     8: vector<ImageFormatConstraints>:MAX_COUNT_BUFFER_COLLECTION_CONSTRAINTS_IMAGE_FORMAT_CONSTRAINTS image_format_constraints;

     /// If true, a secure heap may only be selected if all participants with
     /// BufferMemoryConstraints specify allow_clear_aux_buffers_for_secure.  If
     /// "need" is true, "allow" must also be true.
     ///
     /// If false (or unset), the participant can still work, potentially even
     /// with secure memory (depending on supported heaps), without clear aux
     /// buffers.
     9: bool need_clear_aux_buffers_for_secure;

     /// If true, the participant will use clear aux buffers, if they are
     /// allocated, as appropriate to the participant's role.  If the participant
     /// is a writer, then the participant writer will populate the clear aux
     /// buffers with the clear (not-encrypted, not-DRM-protected) bytes, and
     /// fill protected bytes with data that does not emulate start codes, such
     /// as 0xFF.
     ///
     /// If un-set, then allow_clear_aux_buffers_for_secure is true iff the
     /// participant specifies usage which is read-only.
     ///
     /// If un-set from a participant with write usage, or false, the buffer
     /// collection won't be able to allocate if any participant specifies
     /// need_clear_aux_buffers_for_secure true.
     10: bool allow_clear_aux_buffers_for_secure;
 };

 /// Known heap types.
 /// Device specific types should have bit 60 set. Top order bit is reserved
 /// and should not be set.
 enum HeapType : uint64 {
     SYSTEM_RAM = 0x0000000000000000;

     /// Heap used for amlogic protected memory.
     AMLOGIC_SECURE = 0x1000000000010000;

     /// Heap used for amlogic protected memory between decrypt and video decode.
     AMLOGIC_SECURE_VDEC = 0x1000000000010001;

     /// Heap used by goldfish vulkan for device-local memory.
     GOLDFISH_DEVICE_LOCAL = 0x1000000000020000;

     /// Heap used by goldfish vulkan for host-visible memory.
     GOLDFISH_HOST_VISIBLE = 0x1000000000020001;
 };

 table BufferMemoryConstraints {
     1: uint32 min_size_bytes;
     /// un-set is treated as 0xFFFFFFFF.
     2: uint32 max_size_bytes;

     3: bool physically_contiguous_required;

     /// If true, at least one participant requires secure memory.
     ///
     /// When aggregating BufferCollectionConstraints, these values boolean-OR.
     4: bool secure_required;

     /// By default, participants must ensure the CPU can read or write data to
     /// the buffer without cache operations. If they support using the RAM
     /// domain, data must be available in RAM (with CPU cache state such that
     /// the RAM data won't get corrupted by a dirty CPU cache line writing
     /// incorrect data to RAM), and a consumer reading using the CPU must
     /// invalidate CPU cache before reading (the producer doesn't guarantee
     /// zero stale "clean" cache lines)
     5: bool cpu_domain_supported;
     6: bool ram_domain_supported;
     7: bool inaccessible_domain_supported;

     /// Optional heap constraints. Participants that don't care which heap
     /// memory is allocated on should leave this field un-set.
     8: vector<HeapType>:MAX_COUNT_BUFFER_MEMORY_CONSTRAINTS_HEAP_PERMITTED heap_permitted;
 };

 /// Inaccessible is only for cases where there is no CPU-based access to the
 /// buffers.  A secure_required buffer can still have CoherencyDomain Cpu or
 /// Ram even if the secure_required buffer can only be accessed by the CPU when
 /// the CPU is running in secure mode (or similar).  In contrast, device-local
 /// memory that isn't reachable from the CPU is CoherencyDomain Inaccessible,
 /// even if it's possible to cause a device (physical or virtual) to copy the
 /// data from the Inaccessible buffers to buffers that are visible to the CPU.
 enum CoherencyDomain {
     CPU = 0;
     RAM = 1;
     INACCESSIBLE = 2;
 };

 /// Describes constraints on layout of image data in buffers.
 // TODO(fxbug.dev/32119): change struct to table
 table ImageFormatConstraints {
     /// The PixelFormat for which the following constraints apply.  A
     /// participant may have more than one PixelFormat that's supported, in
     /// which case that participant can use a list of ImageFormatConstraints
     /// with an entry per PixelFormat.  It's not uncommon for the other fields
     /// of ImageFormatConstraints to vary by PixelFormat - for example for a
     /// linear format to support smaller max size than a tiled format.
     1: PixelFormat pixel_format;

     /// Empty is an error.  Redundant entries are an error.  Arbitrary ordering
     /// is not an error.
     2: vector<ColorSpace>:MAX_COUNT_IMAGE_FORMAT_CONSTRAINTS_COLOR_SPACES color_spaces;

     /// Minimum permitted width in pixels.
     ///
     /// For example a video decoder participant may set this field to the
     /// minimum coded_width that might potentially be specified by a stream.  In
     /// contrast, required_min_coded_width would be set to the current
     /// coded_width specified by the stream.  While min_coded_width aggregates
     /// by taking the max, required_min_coded_width aggregates by taking the
     /// min.
     ///
     /// See also required_min_coded_width.
     3: uint32 min_coded_width;
     /// Maximum width in pixels.  For example Scenic may set this field
     /// (directly or via sub-participants) to the maximum width that can be
     /// composited.
     /// un-set is treated as 0xFFFFFFFF.
     4: uint32 max_coded_width;

     /// Minimum height in pixels.  For example a video decoder participant may
     /// set this field to the coded_height specified by a stream.
     5: uint32 min_coded_height;
     /// Maximum height in pixels.  For example Scenic may set this field
     /// (directly or via sub-participants) to the maximum height that can be
     /// composited.
     /// un-set is treated as 0xFFFFFFFF.
     6: uint32 max_coded_height;

     /// Must be >= the value implied by min_coded_width for plane 0.
     7: uint32 min_bytes_per_row;
     /// Must be >= the value implied by max_coded_width for plane 0.
     /// un-set is treated as 0xFFFFFFFF.
     8: uint32 max_bytes_per_row;

     /// The max image area in pixels is limited indirectly via
     /// BufferSettings.size_bytes, and can also be enforced directly via this
     /// field.
     /// un-set is treated as 0xFFFFFFFF.
     9: uint32 max_coded_width_times_coded_height;

     /// coded_width % width_divisor must be 0.
     /// un-set is treated as 1.
     10: uint32 coded_width_divisor;

     /// coded_height % height_divisor must be 0.
     /// un-set is treated as 1.
     11: uint32 coded_height_divisor;

     /// bytes_per_row % bytes_per_row_divisor must be 0.
     /// un-set is treated as 1.
     12: uint32 bytes_per_row_divisor;

     /// vmo_usable_start % start_offset_divisor must be 0.
     /// un-set is treated as 1.
     13: uint32 start_offset_divisor;

     /// display_width % display_width_divisor must be 0.
     /// un-set is treated as 1.
     14: uint32 display_width_divisor;

     /// display_height % display_height_divisor must be 0.
     /// un-set is treated as 1.
     15: uint32 display_height_divisor;

     /// required_ dimension bounds.
     ///
     /// In contrast to the corresponding fields without "required_" at the
     /// start, these fields (when set to non-zero values) express a requirement
     /// that the resulting aggregated non-required_ fields specify a space that
     /// fully contain the space expressed by each participant's required_
     /// fields.
     ///
     /// For example, a producer video decoder is perfectly happy for the
     /// consumer to be willing to accept anything, and the video decoder doesn't
     /// really want to constrain the potential space of dimensions that might be
     /// seen in a stream and may be acceptable to the consumer, but the video
     /// decoder needs to ensure that the resulting dimension ranges contain
     /// at least the current dimensions decoded from the stream.
     ///
     /// Similarly, an initiator with a particular dynamic-dimension scenario in
     /// mind may wish to require up front that participants agree to handle at
     /// least the range of dimensions expected by the initiator in that
     /// scenario (else fail earlier rather than later, maybe trying again with
     /// smaller required_ space).
     ///
     /// It's much more common for a producer or initiator to set these fields
     /// than for a consumer to set these fields.
     ///
     /// While the non-required_ fields aggregate by taking the intersection, the
     /// required_ fields aggregate by taking the union.
     ///
     /// If set, the required_max_coded_width and required_max_coded_height will
     /// cause the allocated buffers to be large enough to hold an image that is
     /// required_max_coded_width * required_max_coded_height.
     ///
     /// TODO(fxbug.dev/34192): Make it easier to allocate buffers of minimal size
     /// that can (optionally) also handle 90 degree rotated version of the max
     /// dimensions / alternate required bounds for another main aspect ratio.
     /// un-set is treated as 0xFFFFFFFF.
     16: uint32 required_min_coded_width;
     17: uint32 required_max_coded_width;
     /// un-set is treated as 0xFFFFFFFF.
     18: uint32 required_min_coded_height;
     19: uint32 required_max_coded_height;
     /// un-set is treated as 0xFFFFFFFF.
     20: uint32 required_min_bytes_per_row;
     21: uint32 required_max_bytes_per_row;
 };

 /// Describes how an image is represented.
 // TODO(fxbug.dev/32119): Currently this table is not considered ready for use between
 // processes, but should be fairly soon.
 table ImageFormat {
     /// Pixel format.
     1: PixelFormat pixel_format;

     /// Row width in pixels that exist in the buffer.  Must be >= display_width.
     /// Can be < the width implied by stride_bytes.
     2: uint32 coded_width;

     /// Number of rows.  Must be >= display_height.
     3: uint32 coded_height;

     // Stride in bytes of plane 0.  Planes beyond plane 0 (if any, depending on
     // pixel_format) have a known fixed relationship with plane 0's stride.
     4: uint32 bytes_per_row;

     /// Row width in pixels that are to be displayed.  This can be <=
     /// coded_width.  Any cropping occurs on the right of the image (not left).
     5: uint32 display_width;

     /// Number of rows to be displayed.  This can be <= coded_height, with any
     /// cropping on the bottom (not top).
     6: uint32 display_height;

     /// Color space.
     7: ColorSpace color_space;

     /// The pixel_aspect_ratio_width : pixel_aspect_ratio_height is the pixel
     /// aspect ratio (AKA sample aspect ratio aka SAR) for the luma (AKA Y)
     /// samples. A pixel_aspect_ratio of 1:1 mean square pixels. A
     /// pixel_aspect_ratio of 2:1 would mean pixels that are displayed twice as
     /// wide as they are tall. Codec implementation should ensure these two
     /// values are relatively prime by reducing the fraction (dividing both by
     /// GCF) if necessary.
     ///
     /// A producer should set both these fields, or neither of them.
     ///
     /// A consumer should interpret either of these fields being un-set as an
     /// unknown pixel_aspect_ratio.  A default of 1:1 can be appropriate in some
     /// cases, but a consumer may determine the actual pixel_aspect_ratio by OOB
     /// means.
     8: uint32 pixel_aspect_ratio_width;
     9: uint32 pixel_aspect_ratio_height;
 };
	// Copyright 2020 The Fuchsia Authors. All rights reserved.
	// Use of this source code is governed by a BSD-style license that can be
	// found in the LICENSE file.

	library fuchsia.sysmem2;

	const uint32 MAX_COUNT_BUFFER_COLLECTION_CONSTRAINTS_IMAGE_FORMAT_CONSTRAINTS = 64;
	const uint32 MAX_COUNT_BUFFER_MEMORY_CONSTRAINTS_HEAP_PERMITTED = 64;
	const uint32 MAX_COUNT_IMAGE_FORMAT_CONSTRAINTS_COLOR_SPACES = 32;

	// The contents of this file are not final. Incompatible changes are still
	// being made to this file. Do not rely on the contents of this file to provide
	// backward compatibility (yet).
	//
	// TODO(fxbug.dev/34192): Sysmem should use llcpp and FIDL tables. The
	// fuchsia.sysmem2.BufferCollectionConstraints defined here are part of that
	// transition, but the definitions here are not final. For now, the definition
	// here is only used internally to sysmem (not between processes), and therefore
	// this definition can change for now. Later after we're happy with this
	// representation, we'll create
	// fuchsia.sysmem2.BufferCollection.SetConstraints() which will accept
	// constraints as defined here.

	/// Constraints on BufferCollection parameters. These constraints can be
	/// specified per-participant. The sysmem service implements aggregation of
	/// constraints from multiple participants.
	table BufferCollectionConstraints {
	/// The usage is only meant as a hint to help sysmem choose a more optimal
	/// PixelFormat or similar when multiple compatible options exist.
	///
	/// When aggregating BufferCollectionConstraints, these values bitwise-OR.
	///
	/// At least one usage bit must be specified unless the whole
	/// BufferCollectionConstraints is logically null (no fields set).
	1: BufferUsage usage;

	/// Per-participant minimum number of buffers that are needed for camping
	/// purposes. A participant should specify a number for min_buffer_count
	/// that's >= the maximum number of buffers that the participant may
	/// concurrently camp on for any non-transient period of time.
	///
	/// For example, a video decoder would specify (at least) the maximum number
	/// of reference frames + 1 frame currently being decoded into.
	///
	/// A participant must not camp on more buffers than specified here (except
	/// very transiently) else processing may get stuck.
	///
	/// When aggregating BufferCollectionConstraints, these values add.
	///
	/// In testing scenarios, camping on more buffers than this for any
	/// significant duration may (ideally will) be flagged as a failure. In
	/// testing scenarios, the participant may not be provided with more buffers
	/// than this concurrently.
	2: uint32 min_buffer_count_for_camping;

	/// Per-participant minimum number of buffers that are needed for slack
	/// reasons, for better overlap of processing / better performance.
	///
	/// When aggregating BufferCollectionConstraints, these values add.
	///
	/// A participant should typically specify 0 or 1 here - typically 0 is
	/// appropriate if min_buffer_count_for_camping is already enough to keep
	/// the participant busy 100% of the time when the participant is slightly
	/// behind, while 1 can be appropriate if 1 more buffer than strictly needed
	/// for min-camping reasons gives enough slack to stay busy 100% of the time
	/// (when slightly behind, vs. lower % without the extra buffer).
	///
	/// In testing scenarios, this field may be forced to 0, and all
	/// participants are expected to continue to work without getting stuck. If
	/// a buffer is needed for forward progress reasons, that buffer should be
	/// accounted for in min_buffer_count_for_camping.
	3: uint32 min_buffer_count_for_dedicated_slack;

	/// Similar to min_buffer_count_for_dedicated_slack, except when aggregating
	/// these values max (instead of add). The value here is not shared with
	/// any participant's min_buffer_count_for_dedicated_slack.
	///
	/// A participant can specify > 0 here if a participant would like to ensure
	/// there's some slack overall, but doesn't need that slack to be dedicated.
	///
	/// The choice whether to use min_buffer_count_for_dedicated_slack or
	/// min_buffer_count_for_shared_slack (or both) will typically be about the
	/// degree to which the extra slack improves performance.
	///
	/// In testing scenarios, this field may be forced to 0, and all
	/// participants are expected to continue to work without getting stuck. If
	/// a buffer is needed for forward progress reasons, that buffer should be
	/// accounted for in min_buffer_count_for_camping.
	4: uint32 min_buffer_count_for_shared_slack;

	/// A particularly-picky participant may unfortunately need to demand a tight
	/// range of buffer_count, or even a specific buffer_count. This field
	/// should remain 0 unless a participant really must set this field to
	/// constrain the overall BufferCollectionInfo_2.buffer_count. Any such
	/// participant should still fill out the min_buffer_count_for_* fields.
	///
	/// If this field is un-set, the logical min_buffer_count is 1.
	5: uint32 min_buffer_count;
	/// A particularly-picky participant may unfortunately need to demand a tight
	/// range of buffer_count, or even a specific buffer_count. This field
	/// should remain 0 unless a participant really must set this field to
	/// constrain the overall BufferCollectionInfo_2.buffer_count. Any such
	/// participant should still fill out the min_buffer_count_for_* fields.
	///
	/// If this field is un-set, the logical max_buffer_count is 0xFFFFFFFF.
	6: uint32 max_buffer_count;

	/// Optional constraints on BufferCollectionSettings.buffer_settings.
	///
	/// A participant that intends to specify image_format_constraints_count > 1
	/// will typically specify the minimum buffer size implicitly via
	/// image_format_constraints, and possibly specify only the max buffer size
	/// via buffer_memory_constraints.
	///
	/// If un-set, the client is specifying "don't care" re. any buffer memory
	/// constraints.
	7: BufferMemoryConstraints buffer_memory_constraints;

	/// Optional constraints on the image format parameters of an image stored
	/// in a buffer of the BufferCollection. This includes pixel format and
	/// image layout. These constraints are per-pixel-format, so more than one
	/// is permitted. Entries in the list must have unique pixel_formats.
	///
	/// When aggregating, only pixel formats that are specified by all
	/// particpants with non-zero image_format_constraints_count (and non-Null)
	/// BufferCollectionConstraints) are retained.
	///
	/// un-set means no image format constraints. set but zero length is an
	/// error.
	8: vector<ImageFormatConstraints>:MAX_COUNT_BUFFER_COLLECTION_CONSTRAINTS_IMAGE_FORMAT_CONSTRAINTS image_format_constraints;

	/// If true, a secure heap may only be selected if all participants with
	/// BufferMemoryConstraints specify allow_clear_aux_buffers_for_secure. If
	/// "need" is true, "allow" must also be true.
	///
	/// If false (or unset), the participant can still work, potentially even
	/// with secure memory (depending on supported heaps), without clear aux
	/// buffers.
	9: bool need_clear_aux_buffers_for_secure;

	/// If true, the participant will use clear aux buffers, if they are
	/// allocated, as appropriate to the participant's role. If the participant
	/// is a writer, then the participant writer will populate the clear aux
	/// buffers with the clear (not-encrypted, not-DRM-protected) bytes, and
	/// fill protected bytes with data that does not emulate start codes, such
	/// as 0xFF.
	///
	/// If un-set, then allow_clear_aux_buffers_for_secure is true iff the
	/// participant specifies usage which is read-only.
	///
	/// If un-set from a participant with write usage, or false, the buffer
	/// collection won't be able to allocate if any participant specifies
	/// need_clear_aux_buffers_for_secure true.
	10: bool allow_clear_aux_buffers_for_secure;
	};

	/// Known heap types.
	/// Device specific types should have bit 60 set. Top order bit is reserved
	/// and should not be set.
	enum HeapType : uint64 {
	SYSTEM_RAM = 0x0000000000000000;

	/// Heap used for amlogic protected memory.
	AMLOGIC_SECURE = 0x1000000000010000;

	/// Heap used for amlogic protected memory between decrypt and video decode.
	AMLOGIC_SECURE_VDEC = 0x1000000000010001;

	/// Heap used by goldfish vulkan for device-local memory.
	GOLDFISH_DEVICE_LOCAL = 0x1000000000020000;

	/// Heap used by goldfish vulkan for host-visible memory.
	GOLDFISH_HOST_VISIBLE = 0x1000000000020001;
	};

	table BufferMemoryConstraints {
	1: uint32 min_size_bytes;
	/// un-set is treated as 0xFFFFFFFF.
	2: uint32 max_size_bytes;

	3: bool physically_contiguous_required;

	/// If true, at least one participant requires secure memory.
	///
	/// When aggregating BufferCollectionConstraints, these values boolean-OR.
	4: bool secure_required;

	/// By default, participants must ensure the CPU can read or write data to
	/// the buffer without cache operations. If they support using the RAM
	/// domain, data must be available in RAM (with CPU cache state such that
	/// the RAM data won't get corrupted by a dirty CPU cache line writing
	/// incorrect data to RAM), and a consumer reading using the CPU must
	/// invalidate CPU cache before reading (the producer doesn't guarantee
	/// zero stale "clean" cache lines)
	5: bool cpu_domain_supported;
	6: bool ram_domain_supported;
	7: bool inaccessible_domain_supported;

	/// Optional heap constraints. Participants that don't care which heap
	/// memory is allocated on should leave this field un-set.
	8: vector<HeapType>:MAX_COUNT_BUFFER_MEMORY_CONSTRAINTS_HEAP_PERMITTED heap_permitted;
	};

	/// Inaccessible is only for cases where there is no CPU-based access to the
	/// buffers. A secure_required buffer can still have CoherencyDomain Cpu or
	/// Ram even if the secure_required buffer can only be accessed by the CPU when
	/// the CPU is running in secure mode (or similar). In contrast, device-local
	/// memory that isn't reachable from the CPU is CoherencyDomain Inaccessible,
	/// even if it's possible to cause a device (physical or virtual) to copy the
	/// data from the Inaccessible buffers to buffers that are visible to the CPU.
	enum CoherencyDomain {
	CPU = 0;
	RAM = 1;
	INACCESSIBLE = 2;
	};

	/// Describes constraints on layout of image data in buffers.
	// TODO(fxbug.dev/32119): change struct to table
	table ImageFormatConstraints {
	/// The PixelFormat for which the following constraints apply. A
	/// participant may have more than one PixelFormat that's supported, in
	/// which case that participant can use a list of ImageFormatConstraints
	/// with an entry per PixelFormat. It's not uncommon for the other fields
	/// of ImageFormatConstraints to vary by PixelFormat - for example for a
	/// linear format to support smaller max size than a tiled format.
	1: PixelFormat pixel_format;

	/// Empty is an error. Redundant entries are an error. Arbitrary ordering
	/// is not an error.
	2: vector<ColorSpace>:MAX_COUNT_IMAGE_FORMAT_CONSTRAINTS_COLOR_SPACES color_spaces;

	/// Minimum permitted width in pixels.
	///
	/// For example a video decoder participant may set this field to the
	/// minimum coded_width that might potentially be specified by a stream. In
	/// contrast, required_min_coded_width would be set to the current
	/// coded_width specified by the stream. While min_coded_width aggregates
	/// by taking the max, required_min_coded_width aggregates by taking the
	/// min.
	///
	/// See also required_min_coded_width.
	3: uint32 min_coded_width;
	/// Maximum width in pixels. For example Scenic may set this field
	/// (directly or via sub-participants) to the maximum width that can be
	/// composited.
	/// un-set is treated as 0xFFFFFFFF.
	4: uint32 max_coded_width;

	/// Minimum height in pixels. For example a video decoder participant may
	/// set this field to the coded_height specified by a stream.
	5: uint32 min_coded_height;
	/// Maximum height in pixels. For example Scenic may set this field
	/// (directly or via sub-participants) to the maximum height that can be
	/// composited.
	/// un-set is treated as 0xFFFFFFFF.
	6: uint32 max_coded_height;

	/// Must be >= the value implied by min_coded_width for plane 0.
	7: uint32 min_bytes_per_row;
	/// Must be >= the value implied by max_coded_width for plane 0.
	/// un-set is treated as 0xFFFFFFFF.
	8: uint32 max_bytes_per_row;

	/// The max image area in pixels is limited indirectly via
	/// BufferSettings.size_bytes, and can also be enforced directly via this
	/// field.
	/// un-set is treated as 0xFFFFFFFF.
	9: uint32 max_coded_width_times_coded_height;

	/// coded_width % width_divisor must be 0.
	/// un-set is treated as 1.
	10: uint32 coded_width_divisor;

	/// coded_height % height_divisor must be 0.
	/// un-set is treated as 1.
	11: uint32 coded_height_divisor;

	/// bytes_per_row % bytes_per_row_divisor must be 0.
	/// un-set is treated as 1.
	12: uint32 bytes_per_row_divisor;

	/// vmo_usable_start % start_offset_divisor must be 0.
	/// un-set is treated as 1.
	13: uint32 start_offset_divisor;

	/// display_width % display_width_divisor must be 0.
	/// un-set is treated as 1.
	14: uint32 display_width_divisor;

	/// display_height % display_height_divisor must be 0.
	/// un-set is treated as 1.
	15: uint32 display_height_divisor;

	/// required_ dimension bounds.
	///
	/// In contrast to the corresponding fields without "required_" at the
	/// start, these fields (when set to non-zero values) express a requirement
	/// that the resulting aggregated non-required_ fields specify a space that
	/// fully contain the space expressed by each participant's required_
	/// fields.
	///
	/// For example, a producer video decoder is perfectly happy for the
	/// consumer to be willing to accept anything, and the video decoder doesn't
	/// really want to constrain the potential space of dimensions that might be
	/// seen in a stream and may be acceptable to the consumer, but the video
	/// decoder needs to ensure that the resulting dimension ranges contain
	/// at least the current dimensions decoded from the stream.
	///
	/// Similarly, an initiator with a particular dynamic-dimension scenario in
	/// mind may wish to require up front that participants agree to handle at
	/// least the range of dimensions expected by the initiator in that
	/// scenario (else fail earlier rather than later, maybe trying again with
	/// smaller required_ space).
	///
	/// It's much more common for a producer or initiator to set these fields
	/// than for a consumer to set these fields.
	///
	/// While the non-required_ fields aggregate by taking the intersection, the
	/// required_ fields aggregate by taking the union.
	///
	/// If set, the required_max_coded_width and required_max_coded_height will
	/// cause the allocated buffers to be large enough to hold an image that is
	/// required_max_coded_width * required_max_coded_height.
	///
	/// TODO(fxbug.dev/34192): Make it easier to allocate buffers of minimal size
	/// that can (optionally) also handle 90 degree rotated version of the max
	/// dimensions / alternate required bounds for another main aspect ratio.
	/// un-set is treated as 0xFFFFFFFF.
	16: uint32 required_min_coded_width;
	17: uint32 required_max_coded_width;
	/// un-set is treated as 0xFFFFFFFF.
	18: uint32 required_min_coded_height;
	19: uint32 required_max_coded_height;
	/// un-set is treated as 0xFFFFFFFF.
	20: uint32 required_min_bytes_per_row;
	21: uint32 required_max_bytes_per_row;
	};

	/// Describes how an image is represented.
	// TODO(fxbug.dev/32119): Currently this table is not considered ready for use between
	// processes, but should be fairly soon.
	table ImageFormat {
	/// Pixel format.
	1: PixelFormat pixel_format;

	/// Row width in pixels that exist in the buffer. Must be >= display_width.
	/// Can be < the width implied by stride_bytes.
	2: uint32 coded_width;

	/// Number of rows. Must be >= display_height.
	3: uint32 coded_height;

	// Stride in bytes of plane 0. Planes beyond plane 0 (if any, depending on
	// pixel_format) have a known fixed relationship with plane 0's stride.
	4: uint32 bytes_per_row;

	/// Row width in pixels that are to be displayed. This can be <=
	/// coded_width. Any cropping occurs on the right of the image (not left).
	5: uint32 display_width;

	/// Number of rows to be displayed. This can be <= coded_height, with any
	/// cropping on the bottom (not top).
	6: uint32 display_height;

	/// Color space.
	7: ColorSpace color_space;

	/// The pixel_aspect_ratio_width : pixel_aspect_ratio_height is the pixel
	/// aspect ratio (AKA sample aspect ratio aka SAR) for the luma (AKA Y)
	/// samples. A pixel_aspect_ratio of 1:1 mean square pixels. A
	/// pixel_aspect_ratio of 2:1 would mean pixels that are displayed twice as
	/// wide as they are tall. Codec implementation should ensure these two
	/// values are relatively prime by reducing the fraction (dividing both by
	/// GCF) if necessary.
	///
	/// A producer should set both these fields, or neither of them.
	///
	/// A consumer should interpret either of these fields being un-set as an
	/// unknown pixel_aspect_ratio. A default of 1:1 can be appropriate in some
	/// cases, but a consumer may determine the actual pixel_aspect_ratio by OOB
	/// means.
	8: uint32 pixel_aspect_ratio_width;
	9: uint32 pixel_aspect_ratio_height;
	};