diff options
Diffstat (limited to 'docs')
-rw-r--r-- | docs/devel/qapi-code-gen.rst | 107 |
1 files changed, 58 insertions, 49 deletions
diff --git a/docs/devel/qapi-code-gen.rst b/docs/devel/qapi-code-gen.rst index 07b11e2a40..26c62b0e7b 100644 --- a/docs/devel/qapi-code-gen.rst +++ b/docs/devel/qapi-code-gen.rst @@ -156,6 +156,7 @@ from making a forward reference to a type that is only introduced by an outer file. The parser may be made stricter in the future to prevent incomplete include files. +.. _pragma: Pragma directives ----------------- @@ -186,6 +187,7 @@ Pragma 'member-name-exceptions' takes a list of types whose member names may contain uppercase letters, and ``"_"`` instead of ``"-"``. Default is none. +.. _ENUM-VALUE: Enumeration types ----------------- @@ -228,13 +230,15 @@ additional enumeration constant PREFIX__MAX with value N. Do not use string or an integer type when an enumeration type can do the job satisfactorily. -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring the +schema`_ below for more on this. -The optional 'features' member specifies features. See "Features" +The optional 'features' member specifies features. See Features_ below for more on this. +.. _TYPE-REF: + Type references and array types ------------------------------- @@ -269,11 +273,13 @@ Member 'struct' names the struct type. Each MEMBER of the 'data' object defines a member of the struct type. +.. _MEMBERS: + The MEMBER's STRING name consists of an optional ``*`` prefix and the struct member name. If ``*`` is present, the member is optional. The MEMBER's value defines its properties, in particular its type. -The form TYPE-REF is shorthand for :code:`{ 'type': TYPE-REF }`. +The form TYPE-REF_ is shorthand for :code:`{ 'type': TYPE-REF }`. Example:: @@ -300,10 +306,10 @@ both members like this:: { "file": "/some/place/my-image", "backing": "/some/place/my-backing-file" } -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring +the schema`_ below for more on this. -The optional 'features' member specifies features. See "Features" +The optional 'features' member specifies features. See Features_ below for more on this. @@ -337,7 +343,7 @@ union must have at least one branch. The BRANCH's STRING name is the branch name. The BRANCH's value defines the branch's properties, in particular its -type. The form TYPE-REF is shorthand for :code:`{ 'type': TYPE-REF }`. +type. The form TYPE-REF_ is shorthand for :code:`{ 'type': TYPE-REF }`. A simple union type defines a mapping from automatic discriminator values to data types like in this example:: @@ -368,12 +374,12 @@ Flat unions permit arbitrary common members that occur in all variants of the union, not just a discriminator. Their discriminators need not be named 'type'. They also avoid nesting on the wire. -The 'base' member defines the common members. If it is a MEMBERS +The 'base' member defines the common members. If it is a MEMBERS_ object, it defines common members just like a struct type's 'data' member defines struct type members. If it is a STRING, it names a struct type whose members are the common members. -All flat union branches must be of struct type. +All flat union branches must be `Struct types`_. In the Client JSON Protocol, a flat union is represented by an object with the common members (from the base type) and the selected branch's @@ -425,10 +431,10 @@ is identical on the wire to:: { 'union': 'Flat', 'base': { 'type': 'Enum' }, 'discriminator': 'type', 'data': { 'one': 'Branch1', 'two': 'Branch2' } } -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring +the schema`_ below for more on this. -The optional 'features' member specifies features. See "Features" +The optional 'features' member specifies features. See Features_ below for more on this. @@ -481,10 +487,10 @@ following example objects:: "read-only": false, "filename": "/tmp/mydisk.qcow2" } } -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring +the schema`_ below for more on this. -The optional 'features' member specifies features. See "Features" +The optional 'features' member specifies features. See Features_ below for more on this. @@ -511,10 +517,10 @@ Syntax:: Member 'command' names the command. -Member 'data' defines the arguments. It defaults to an empty MEMBERS +Member 'data' defines the arguments. It defaults to an empty MEMBERS_ object. -If 'data' is a MEMBERS object, then MEMBERS defines arguments just +If 'data' is a MEMBERS_ object, then MEMBERS defines arguments just like a struct type's 'data' defines struct type members. If 'data' is a STRING, then STRING names a complex type whose members @@ -553,7 +559,7 @@ which would validate this Client JSON Protocol transaction:: The generator emits a prototype for the C function implementing the command. The function itself needs to be written by hand. See -section "Code generated for commands" for examples. +section `Code generated for commands`_ for examples. The function returns the return type. When member 'boxed' is absent, it takes the command arguments as arguments one by one, in QAPI schema @@ -660,10 +666,10 @@ for a command. We don't currently have a use case for both together and without a use case, it's not entirely clear what the semantics should be. -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring +the schema`_ below for more on this. -The optional 'features' member specifies features. See "Features" +The optional 'features' member specifies features. See Features_ below for more on this. @@ -708,15 +714,17 @@ Resulting in this JSON object:: The generator emits a function to send the event. When member 'boxed' is absent, it takes event-specific data one by one, in QAPI schema order. Else it takes them wrapped in the C struct generated for the -complex type. See section "Code generated for events" for examples. +complex type. See section `Code generated for events`_ for examples. -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring +the schema`_ below for more on this. -The optional 'features' member specifies features. See "Features" +The optional 'features' member specifies features. See Features_ below for more on this. +.. _FEATURE: + Features -------- @@ -735,8 +743,8 @@ For this purpose, a list of features can be specified for a command or struct type. Each list member can either be ``{ 'name': STRING, '*if': COND }``, or STRING, which is shorthand for ``{ 'name': STRING }``. -The optional 'if' member specifies a conditional. See "Configuring -the schema" below for more on this. +The optional 'if' member specifies a conditional. See `Configuring +the schema`_ below for more on this. Example:: @@ -745,7 +753,7 @@ Example:: 'features': [ 'allow-negative-numbers' ] } The feature strings are exposed to clients in introspection, as -explained in section "Client JSON Protocol introspection". +explained in section `Client JSON Protocol introspection`_. Intended use is to have each feature string signal that this build of QEMU shows a certain behaviour. @@ -764,7 +772,7 @@ Naming rules and reserved names All names must begin with a letter, and contain only ASCII letters, digits, hyphen, and underscore. There are two exceptions: enum values may start with a digit, and names that are downstream extensions (see -section Downstream extensions) start with underscore. +section `Downstream extensions`_) start with underscore. Names beginning with ``q_`` are reserved for the generator, which uses them for munging QMP names that resemble C keywords or other @@ -794,8 +802,9 @@ Any name (command, event, type, member, or enum value) beginning with ``x-`` is marked experimental, and may be withdrawn or changed incompatibly in a future release. -Pragmas ``command-name-exceptions`` and ``member-name-exceptions`` let you -violate naming rules. Use for new code is strongly discouraged. +Pragmas ``command-name-exceptions`` and ``member-name-exceptions`` let +you violate naming rules. Use for new code is strongly discouraged. See +`Pragma directives`_ for details. Downstream extensions @@ -851,7 +860,7 @@ member 'bar' :: A union's discriminator may not be conditional. Likewise, individual enumeration values be conditional. This requires -the longhand form of ENUM-VALUE. +the longhand form of ENUM-VALUE_. Example: an enum type with unconditional value 'foo' and conditional value 'bar' :: @@ -861,7 +870,7 @@ value 'bar' :: { 'name' : 'bar', 'if': 'defined(IFCOND)' } ] } Likewise, features can be conditional. This requires the longhand -form of FEATURE. +form of FEATURE_. Example: a struct with conditional feature 'allow-negative-numbers' :: @@ -893,7 +902,7 @@ If the documentation comment starts like :: it documents the definition of SYMBOL, else it's free-form documentation. -See below for more on definition documentation. +See below for more on `Definition documentation`_. Free-form documentation may be used to provide additional text and structuring content. @@ -984,7 +993,7 @@ Definition documentation Definition documentation, if present, must immediately precede the definition it documents. -When documentation is required (see pragma 'doc-required'), every +When documentation is required (see pragma_ 'doc-required'), every definition must have documentation. Definition documentation starts with a line naming the definition, @@ -1181,7 +1190,7 @@ the wire then. Each command or event defined with 'data' as MEMBERS object in the QAPI schema implicitly defines an object type. -Example: the SchemaInfo for EVENT_C from section Events :: +Example: the SchemaInfo for EVENT_C from section Events_ :: { "name": "EVENT_C", "meta-type": "event", "arg-type": "q_obj-EVENT_C-arg" } @@ -1205,7 +1214,7 @@ extensions. The "members" array is in no particular order; clients must search the entire object when learning whether a particular member is supported. -Example: the SchemaInfo for MyType from section Struct types :: +Example: the SchemaInfo for MyType from section `Struct types`_ :: { "name": "MyType", "meta-type": "object", "members": [ @@ -1216,7 +1225,7 @@ Example: the SchemaInfo for MyType from section Struct types :: "features" exposes the command's feature strings as a JSON array of strings. -Example: the SchemaInfo for TestType from section Features:: +Example: the SchemaInfo for TestType from section Features_:: { "name": "TestType", "meta-type": "object", "members": [ @@ -1232,7 +1241,7 @@ that provides the variant members for this type tag value). The list cases in the same order as the corresponding "tag" enum type. Example: the SchemaInfo for flat union BlockdevOptions from section -Union types :: +`Union types`_ :: { "name": "BlockdevOptions", "meta-type": "object", "members": [ @@ -1247,13 +1256,13 @@ Note that base types are "flattened": its members are included in the "members" array. A simple union implicitly defines an enumeration type for its implicit -discriminator (called "type" on the wire, see section Union types). +discriminator (called "type" on the wire, see section `Union types`_). A simple union implicitly defines an object type for each of its variants. Example: the SchemaInfo for simple union BlockdevOptionsSimple from section -Union types :: +`Union types`_ :: { "name": "BlockdevOptionsSimple", "meta-type": "object", "members": [ @@ -1273,7 +1282,7 @@ a JSON object with member "type", which names a type. Values of the alternate type conform to exactly one of its member types. There is no guarantee on the order in which "members" will be listed. -Example: the SchemaInfo for BlockdevRef from section Alternate types :: +Example: the SchemaInfo for BlockdevRef from section `Alternate types`_ :: { "name": "BlockdevRef", "meta-type": "alternate", "members": [ @@ -1297,13 +1306,13 @@ variant member "values". The values are listed in no particular order; clients must search the entire enum when learning whether a particular value is supported. -Example: the SchemaInfo for MyEnum from section Enumeration types :: +Example: the SchemaInfo for MyEnum from section `Enumeration types`_ :: { "name": "MyEnum", "meta-type": "enum", "values": [ "value1", "value2", "value3" ] } The SchemaInfo for a built-in type has the same name as the type in -the QAPI schema (see section Built-in Types), with one exception +the QAPI schema (see section `Built-in Types`_), with one exception detailed below. It has variant member "json-type" that shows how values of this type are encoded on the wire. @@ -1505,7 +1514,7 @@ Example:: [Uninteresting stuff omitted...] -For a modular QAPI schema (see section Include directives), code for +For a modular QAPI schema (see section `Include directives`_), code for each sub-module SUBDIR/SUBMODULE.json is actually generated into :: SUBDIR/$(prefix)qapi-types-SUBMODULE.h @@ -1643,7 +1652,7 @@ Example:: [Uninteresting stuff omitted...] -For a modular QAPI schema (see section Include directives), code for +For a modular QAPI schema (see section `Include directives`_), code for each sub-module SUBDIR/SUBMODULE.json is actually generated into :: SUBDIR/$(prefix)qapi-visit-SUBMODULE.h @@ -1773,7 +1782,7 @@ Example:: } [Uninteresting stuff omitted...] -For a modular QAPI schema (see section Include directives), code for +For a modular QAPI schema (see section `Include directives`_), code for each sub-module SUBDIR/SUBMODULE.json is actually generated into:: SUBDIR/$(prefix)qapi-commands-SUBMODULE.h @@ -1862,7 +1871,7 @@ Example:: [Uninteresting stuff omitted...] -For a modular QAPI schema (see section Include directives), code for +For a modular QAPI schema (see section `Include directives`_), code for each sub-module SUBDIR/SUBMODULE.json is actually generated into :: SUBDIR/$(prefix)qapi-events-SUBMODULE.h |