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qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
# -*- Mode: Python -*-
#
# QAPI/QMP introspection
#
# Copyright (C) 2015 Red Hat, Inc.
#
# Authors:
# Markus Armbruster <armbru@redhat.com>
#
# This work is licensed under the terms of the GNU GPL, version 2 or later.
# See the COPYING file in the top-level directory.
##
# @query-qmp-schema
#
# Command query-qmp-schema exposes the QMP wire ABI as an array of
# SchemaInfo. This lets QMP clients figure out what commands and
# events are available in this QEMU, and their parameters and results.
#
# However, the SchemaInfo can't reflect all the rules and restrictions
# that apply to QMP. It's interface introspection (figuring out
# what's there), not interface specification. The specification is in
# the QAPI schema.
#
# Furthermore, while we strive to keep the QMP wire format
# backwards-compatible across qemu versions, the introspection output
# is not guaranteed to have the same stability. For example, one
# version of qemu may list an object member as an optional
# non-variant, while another lists the same member only through the
# object's variants; or the type of a member may change from a generic
# string into a specific enum or from one specific type into an
# alternate that includes the original type alongside something else.
#
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
# Returns: array of @SchemaInfo, where each element describes an
# entity in the ABI: command, event, type, ...
#
qapi-introspect: Document lack of sorting qapi-code-gen.txt already claims that types, commands, and events share a common namespace; set this in stone by further documenting that our introspection output will never have collisions with the same name tied to more than one meta-type. Our largest QMP enum currently has 125 values, our largest object type has 27 members, and the mean for each is less than 10. These sizes are small enough that the per-element overhead of O(log n) binary searching probably outweighs the speed possible with direct O(n) linear searching (a better algorithm with more overhead will only beat a leaner naive algorithm only as you scale to larger input sizes). Arguably, the overall SchemaInfo array could be sorted by name; there, we currently have 531 entities, large enough for a binary search to be faster than linear. However, remember that we have mutually-recursive types, which means there is no topological ordering that will allow clients to learn all information about that type in a single linear pass; thus clients will want to do random access over the data, and they will probably read the introspection output into a hashtable for O(1) lookup rather than O(log n) binary searching, at which point, pre-sorting our introspection output doesn't help the client. It doesn't help that sorting can be subjective if you introduce locales into the mix (I'm not experienced enough with Python to know for sure, but at least it looks like it defaults to sorting in the C locale even when run under a different locale). And while our current introspection output is deterministic (because we visit entities in a sorted order), we may want to change that order in the future (such as using OrderedDict to stick to .json declaration order). For these reasons, we simply document that clients should not rely on any particular order of items in introspection output. And since it is now a documented part of the contract, we have the freedom to later rearrange output if needed, without worrying about breaking well-written clients. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com> [Commit message tweaked] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 07:35:36 +01:00
# The order of the various SchemaInfo is unspecified; however, all
# names are guaranteed to be unique (no name will be duplicated with
# different meta-types).
#
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
# Note: the QAPI schema is also used to help define *internal*
# interfaces, by defining QAPI types. These are not part of the QMP
# wire ABI, and therefore not returned by this command.
#
# Since: 2.5
##
{ 'command': 'query-qmp-schema',
'returns': [ 'SchemaInfo' ],
'gen': false } # just to simplify qmp_query_json()
##
# @SchemaMetaType
#
# This is a @SchemaInfo's meta type, i.e. the kind of entity it
# describes.
#
# @builtin: a predefined type such as 'int' or 'bool'.
#
# @enum: an enumeration type
#
# @array: an array type
#
# @object: an object type (struct or union)
#
# @alternate: an alternate type
#
# @command: a QMP command
#
# @event: a QMP event
#
# Since: 2.5
##
{ 'enum': 'SchemaMetaType',
'data': [ 'builtin', 'enum', 'array', 'object', 'alternate',
'command', 'event' ] }
##
# @SchemaInfoBase
#
# Members common to any @SchemaInfo.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoBase',
'data': { 'name': 'str', 'meta-type': 'SchemaMetaType' } }
##
# @SchemaInfo
#
# @name: the entity's name, inherited from @base.
# Commands and events have the name defined in the QAPI schema.
# Unlike command and event names, type names are not part of
# the wire ABI. Consequently, type names are meaningless
qapi-introspect: Document lack of sorting qapi-code-gen.txt already claims that types, commands, and events share a common namespace; set this in stone by further documenting that our introspection output will never have collisions with the same name tied to more than one meta-type. Our largest QMP enum currently has 125 values, our largest object type has 27 members, and the mean for each is less than 10. These sizes are small enough that the per-element overhead of O(log n) binary searching probably outweighs the speed possible with direct O(n) linear searching (a better algorithm with more overhead will only beat a leaner naive algorithm only as you scale to larger input sizes). Arguably, the overall SchemaInfo array could be sorted by name; there, we currently have 531 entities, large enough for a binary search to be faster than linear. However, remember that we have mutually-recursive types, which means there is no topological ordering that will allow clients to learn all information about that type in a single linear pass; thus clients will want to do random access over the data, and they will probably read the introspection output into a hashtable for O(1) lookup rather than O(log n) binary searching, at which point, pre-sorting our introspection output doesn't help the client. It doesn't help that sorting can be subjective if you introduce locales into the mix (I'm not experienced enough with Python to know for sure, but at least it looks like it defaults to sorting in the C locale even when run under a different locale). And while our current introspection output is deterministic (because we visit entities in a sorted order), we may want to change that order in the future (such as using OrderedDict to stick to .json declaration order). For these reasons, we simply document that clients should not rely on any particular order of items in introspection output. And since it is now a documented part of the contract, we have the freedom to later rearrange output if needed, without worrying about breaking well-written clients. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com> [Commit message tweaked] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 07:35:36 +01:00
# strings here, although they are still guaranteed unique
# regardless of @meta-type.
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
#
# All references to other SchemaInfo are by name.
#
# @meta-type: the entity's meta type, inherited from @base.
#
# Additional members depend on the value of @meta-type.
#
# Since: 2.5
##
{ 'union': 'SchemaInfo',
'base': 'SchemaInfoBase',
'discriminator': 'meta-type',
'data': {
'builtin': 'SchemaInfoBuiltin',
'enum': 'SchemaInfoEnum',
'array': 'SchemaInfoArray',
'object': 'SchemaInfoObject',
'alternate': 'SchemaInfoAlternate',
'command': 'SchemaInfoCommand',
'event': 'SchemaInfoEvent' } }
##
# @SchemaInfoBuiltin
#
# Additional SchemaInfo members for meta-type 'builtin'.
#
# @json-type: the JSON type used for this type on the wire.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoBuiltin',
'data': { 'json-type': 'JSONType' } }
##
# @JSONType
#
# The four primitive and two structured types according to RFC 7159
# section 1, plus 'int' (split off 'number'), plus the obvious top
# type 'value'.
#
# Since: 2.5
##
{ 'enum': 'JSONType',
'data': [ 'string', 'number', 'int', 'boolean', 'null',
'object', 'array', 'value' ] }
##
# @SchemaInfoEnum
#
# Additional SchemaInfo members for meta-type 'enum'.
#
qapi-introspect: Document lack of sorting qapi-code-gen.txt already claims that types, commands, and events share a common namespace; set this in stone by further documenting that our introspection output will never have collisions with the same name tied to more than one meta-type. Our largest QMP enum currently has 125 values, our largest object type has 27 members, and the mean for each is less than 10. These sizes are small enough that the per-element overhead of O(log n) binary searching probably outweighs the speed possible with direct O(n) linear searching (a better algorithm with more overhead will only beat a leaner naive algorithm only as you scale to larger input sizes). Arguably, the overall SchemaInfo array could be sorted by name; there, we currently have 531 entities, large enough for a binary search to be faster than linear. However, remember that we have mutually-recursive types, which means there is no topological ordering that will allow clients to learn all information about that type in a single linear pass; thus clients will want to do random access over the data, and they will probably read the introspection output into a hashtable for O(1) lookup rather than O(log n) binary searching, at which point, pre-sorting our introspection output doesn't help the client. It doesn't help that sorting can be subjective if you introduce locales into the mix (I'm not experienced enough with Python to know for sure, but at least it looks like it defaults to sorting in the C locale even when run under a different locale). And while our current introspection output is deterministic (because we visit entities in a sorted order), we may want to change that order in the future (such as using OrderedDict to stick to .json declaration order). For these reasons, we simply document that clients should not rely on any particular order of items in introspection output. And since it is now a documented part of the contract, we have the freedom to later rearrange output if needed, without worrying about breaking well-written clients. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com> [Commit message tweaked] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 07:35:36 +01:00
# @values: the enumeration type's values, in no particular order.
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
#
# Values of this type are JSON string on the wire.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoEnum',
'data': { 'values': ['str'] } }
##
# @SchemaInfoArray
#
# Additional SchemaInfo members for meta-type 'array'.
#
# @element-type: the array type's element type.
#
# Values of this type are JSON array on the wire.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoArray',
'data': { 'element-type': 'str' } }
##
# @SchemaInfoObject
#
# Additional SchemaInfo members for meta-type 'object'.
#
qapi-introspect: Document lack of sorting qapi-code-gen.txt already claims that types, commands, and events share a common namespace; set this in stone by further documenting that our introspection output will never have collisions with the same name tied to more than one meta-type. Our largest QMP enum currently has 125 values, our largest object type has 27 members, and the mean for each is less than 10. These sizes are small enough that the per-element overhead of O(log n) binary searching probably outweighs the speed possible with direct O(n) linear searching (a better algorithm with more overhead will only beat a leaner naive algorithm only as you scale to larger input sizes). Arguably, the overall SchemaInfo array could be sorted by name; there, we currently have 531 entities, large enough for a binary search to be faster than linear. However, remember that we have mutually-recursive types, which means there is no topological ordering that will allow clients to learn all information about that type in a single linear pass; thus clients will want to do random access over the data, and they will probably read the introspection output into a hashtable for O(1) lookup rather than O(log n) binary searching, at which point, pre-sorting our introspection output doesn't help the client. It doesn't help that sorting can be subjective if you introduce locales into the mix (I'm not experienced enough with Python to know for sure, but at least it looks like it defaults to sorting in the C locale even when run under a different locale). And while our current introspection output is deterministic (because we visit entities in a sorted order), we may want to change that order in the future (such as using OrderedDict to stick to .json declaration order). For these reasons, we simply document that clients should not rely on any particular order of items in introspection output. And since it is now a documented part of the contract, we have the freedom to later rearrange output if needed, without worrying about breaking well-written clients. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com> [Commit message tweaked] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 07:35:36 +01:00
# @members: the object type's (non-variant) members, in no particular order.
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
#
# @tag: #optional the name of the member serving as type tag.
# An element of @members with this name must exist.
#
# @variants: #optional variant members, i.e. additional members that
# depend on the type tag's value. Present exactly when
qapi-introspect: Document lack of sorting qapi-code-gen.txt already claims that types, commands, and events share a common namespace; set this in stone by further documenting that our introspection output will never have collisions with the same name tied to more than one meta-type. Our largest QMP enum currently has 125 values, our largest object type has 27 members, and the mean for each is less than 10. These sizes are small enough that the per-element overhead of O(log n) binary searching probably outweighs the speed possible with direct O(n) linear searching (a better algorithm with more overhead will only beat a leaner naive algorithm only as you scale to larger input sizes). Arguably, the overall SchemaInfo array could be sorted by name; there, we currently have 531 entities, large enough for a binary search to be faster than linear. However, remember that we have mutually-recursive types, which means there is no topological ordering that will allow clients to learn all information about that type in a single linear pass; thus clients will want to do random access over the data, and they will probably read the introspection output into a hashtable for O(1) lookup rather than O(log n) binary searching, at which point, pre-sorting our introspection output doesn't help the client. It doesn't help that sorting can be subjective if you introduce locales into the mix (I'm not experienced enough with Python to know for sure, but at least it looks like it defaults to sorting in the C locale even when run under a different locale). And while our current introspection output is deterministic (because we visit entities in a sorted order), we may want to change that order in the future (such as using OrderedDict to stick to .json declaration order). For these reasons, we simply document that clients should not rely on any particular order of items in introspection output. And since it is now a documented part of the contract, we have the freedom to later rearrange output if needed, without worrying about breaking well-written clients. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com> [Commit message tweaked] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 07:35:36 +01:00
# @tag is present. The variants are in no particular order,
# and may even differ from the order of the values of the
# enum type of the @tag.
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
#
# Values of this type are JSON object on the wire.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoObject',
'data': { 'members': [ 'SchemaInfoObjectMember' ],
'*tag': 'str',
'*variants': [ 'SchemaInfoObjectVariant' ] } }
##
# @SchemaInfoObjectMember
#
# An object member.
#
# @name: the member's name, as defined in the QAPI schema.
#
# @type: the name of the member's type.
#
# @default: #optional default when used as command parameter.
# If absent, the parameter is mandatory.
# If present, the value must be null. The parameter is
# optional, and behavior when it's missing is not specified
# here.
# Future extension: if present and non-null, the parameter
# is optional, and defaults to this value.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoObjectMember',
'data': { 'name': 'str', 'type': 'str', '*default': 'any' } }
# @default's type must be null or match @type
##
# @SchemaInfoObjectVariant
#
# The variant members for a value of the type tag.
#
# @case: a value of the type tag.
#
# @type: the name of the object type that provides the variant members
# when the type tag has value @case.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoObjectVariant',
'data': { 'case': 'str', 'type': 'str' } }
##
# @SchemaInfoAlternate
#
# Additional SchemaInfo members for meta-type 'alternate'.
#
qapi-introspect: Document lack of sorting qapi-code-gen.txt already claims that types, commands, and events share a common namespace; set this in stone by further documenting that our introspection output will never have collisions with the same name tied to more than one meta-type. Our largest QMP enum currently has 125 values, our largest object type has 27 members, and the mean for each is less than 10. These sizes are small enough that the per-element overhead of O(log n) binary searching probably outweighs the speed possible with direct O(n) linear searching (a better algorithm with more overhead will only beat a leaner naive algorithm only as you scale to larger input sizes). Arguably, the overall SchemaInfo array could be sorted by name; there, we currently have 531 entities, large enough for a binary search to be faster than linear. However, remember that we have mutually-recursive types, which means there is no topological ordering that will allow clients to learn all information about that type in a single linear pass; thus clients will want to do random access over the data, and they will probably read the introspection output into a hashtable for O(1) lookup rather than O(log n) binary searching, at which point, pre-sorting our introspection output doesn't help the client. It doesn't help that sorting can be subjective if you introduce locales into the mix (I'm not experienced enough with Python to know for sure, but at least it looks like it defaults to sorting in the C locale even when run under a different locale). And while our current introspection output is deterministic (because we visit entities in a sorted order), we may want to change that order in the future (such as using OrderedDict to stick to .json declaration order). For these reasons, we simply document that clients should not rely on any particular order of items in introspection output. And since it is now a documented part of the contract, we have the freedom to later rearrange output if needed, without worrying about breaking well-written clients. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1446791754-23823-13-git-send-email-eblake@redhat.com> [Commit message tweaked] Signed-off-by: Markus Armbruster <armbru@redhat.com>
2015-11-06 07:35:36 +01:00
# @members: the alternate type's members, in no particular order.
qapi: New QMP command query-qmp-schema for QMP introspection qapi/introspect.json defines the introspection schema. It's designed for QMP introspection, but should do for similar uses, such as QGA. The introspection schema does not reflect all the rules and restrictions that apply to QAPI schemata. A valid QAPI schema has an introspection value conforming to the introspection schema, but the converse is not true. Introspection lowers away a number of schema details, and makes implicit things explicit: * The built-in types are declared with their JSON type. All integer types are mapped to 'int', because how many bits we use internally is an implementation detail. It could be pressed into external interface service as very approximate range information, but that's a bad idea. If we need range information, we better do it properly. * Implicit type definitions are made explicit, and given auto-generated names: - Array types, named by appending "List" to the name of their element type, like in generated C. - The enumeration types implicitly defined by simple union types, named by appending "Kind" to the name of their simple union type, like in generated C. - Types that don't occur in generated C. Their names start with ':' so they don't clash with the user's names. * All type references are by name. * The struct and union types are generalized into an object type. * Base types are flattened. * Commands take a single argument and return a single result. Dictionary argument or list result is an implicit type definition. The empty object type is used when a command takes no arguments or produces no results. The argument is always of object type, but the introspection schema doesn't reflect that. The 'gen': false directive is omitted as implementation detail. The 'success-response' directive is omitted as well for now, even though it's not an implementation detail, because it's not used by QMP. * Events carry a single data value. Implicit type definition and empty object type use, just like for commands. The value is of object type, but the introspection schema doesn't reflect that. * Types not used by commands or events are omitted. Indirect use counts as use. * Optional members have a default, which can only be null right now Instead of a mandatory "optional" flag, we have an optional default. No default means mandatory, default null means optional without default value. Non-null is available for optional with default (possible future extension). * Clients should *not* look up types by name, because type names are not ABI. Look up the command or event you're interested in, then follow the references. TODO Should we hide the type names to eliminate the temptation? New generator scripts/qapi-introspect.py computes an introspection value for its input, and generates a C variable holding it. It can generate awfully long lines. Marked TODO. A new test-qmp-input-visitor test case feeds its result for both tests/qapi-schema/qapi-schema-test.json and qapi-schema.json to a QmpInputVisitor to verify it actually conforms to the schema. New QMP command query-qmp-schema takes its return value from that variable. Its reply is some 85KiBytes for me right now. If this turns out to be too much, we have a couple of options: * We can use shorter names in the JSON. Not the QMP style. * Optionally return the sub-schema for commands and events given as arguments. Right now qmp_query_schema() sends the string literal computed by qmp-introspect.py. To compute sub-schema at run time, we'd have to duplicate parts of qapi-introspect.py in C. Unattractive. * Let clients cache the output of query-qmp-schema. It changes only on QEMU upgrades, i.e. rarely. Provide a command query-qmp-schema-hash. Clients can have a cache indexed by hash, and re-query the schema only when they don't have it cached. Even simpler: put the hash in the QMP greeting. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com>
2015-09-16 13:06:28 +02:00
# The members' wire encoding is distinct, see
# docs/qapi-code-gen.txt section Alternate types.
#
# On the wire, this can be any of the members.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoAlternate',
'data': { 'members': [ 'SchemaInfoAlternateMember' ] } }
##
# @SchemaInfoAlternateMember
#
# An alternate member.
#
# @type: the name of the member's type.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoAlternateMember',
'data': { 'type': 'str' } }
##
# @SchemaInfoCommand
#
# Additional SchemaInfo members for meta-type 'command'.
#
# @arg-type: the name of the object type that provides the command's
# parameters.
#
# @ret-type: the name of the command's result type.
#
# TODO @success-response (currently irrelevant, because it's QGA, not QMP)
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoCommand',
'data': { 'arg-type': 'str', 'ret-type': 'str' } }
##
# @SchemaInfoEvent
#
# Additional SchemaInfo members for meta-type 'event'.
#
# @arg-type: the name of the object type that provides the event's
# parameters.
#
# Since: 2.5
##
{ 'struct': 'SchemaInfoEvent',
'data': { 'arg-type': 'str' } }