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docs/qapi-code-gen: Beautify formatting

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Mostly, add ``literal`` markers to a lot of things like C types, add
code blocks, and fix the way a few things render.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210720235619.2048797-3-jsnow@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
This commit is contained in:
John Snow 2021-07-20 19:56:18 -04:00 committed by Markus Armbruster
parent f7aa076dbd
commit 55927c5f32
1 changed files with 90 additions and 82 deletions
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docs/devel/qapi-code-gen.rst
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@ -40,7 +40,7 @@ by any commands or events, for the side effect of generated C code
used internally. used internally.
There are several kinds of types: simple types (a number of built-in There are several kinds of types: simple types (a number of built-in
types, such as 'int' and 'str'; as well as enumerations), arrays, types, such as ``int`` and ``str``; as well as enumerations), arrays,
complex types (structs and two flavors of unions), and alternate types complex types (structs and two flavors of unions), and alternate types
(a choice between other types). (a choice between other types).
@ -51,37 +51,37 @@ Schema syntax
Syntax is loosely based on `JSON <http://www.ietf.org/rfc/rfc8259.txt>`_. Syntax is loosely based on `JSON <http://www.ietf.org/rfc/rfc8259.txt>`_.
Differences: Differences:
* Comments: start with a hash character (#) that is not part of a * Comments: start with a hash character (``#``) that is not part of a
string, and extend to the end of the line. string, and extend to the end of the line.
* Strings are enclosed in 'single quotes', not "double quotes". * Strings are enclosed in ``'single quotes'``, not ``"double quotes"``.
* Strings are restricted to printable ASCII, and escape sequences to * Strings are restricted to printable ASCII, and escape sequences to
just '\\'. just ``\\``.
* Numbers and null are not supported. * Numbers and ``null`` are not supported.
A second layer of syntax defines the sequences of JSON texts that are A second layer of syntax defines the sequences of JSON texts that are
a correctly structured QAPI schema. We provide a grammar for this a correctly structured QAPI schema. We provide a grammar for this
syntax in an EBNF-like notation: syntax in an EBNF-like notation:
* Production rules look like non-terminal = expression * Production rules look like ``non-terminal = expression``
* Concatenation: expression A B matches expression A, then B * Concatenation: expression ``A B`` matches expression ``A``, then ``B``
* Alternation: expression A | B matches expression A or B * Alternation: expression ``A | B`` matches expression ``A`` or ``B``
* Repetition: expression A... matches zero or more occurrences of * Repetition: expression ``A...`` matches zero or more occurrences of
expression A expression ``A``
* Repetition: expression A, ... matches zero or more occurrences of * Repetition: expression ``A, ...`` matches zero or more occurrences of
expression A separated by , expression ``A`` separated by ``,``
* Grouping: expression ( A ) matches expression A * Grouping: expression ``( A )`` matches expression ``A``
* JSON's structural characters are terminals: { } [ ] : , * JSON's structural characters are terminals: ``{ } [ ] : ,``
* JSON's literal names are terminals: false true * JSON's literal names are terminals: ``false true``
* String literals enclosed in 'single quotes' are terminal, and match * String literals enclosed in ``'single quotes'`` are terminal, and match
this JSON string, with a leading '*' stripped off this JSON string, with a leading ``*`` stripped off
* When JSON object member's name starts with '*', the member is * When JSON object member's name starts with ``*``, the member is
optional. optional.
* The symbol STRING is a terminal, and matches any JSON string * The symbol ``STRING`` is a terminal, and matches any JSON string
* The symbol BOOL is a terminal, and matches JSON false or true * The symbol ``BOOL`` is a terminal, and matches JSON ``false`` or ``true``
* ALL-CAPS words other than STRING are non-terminals * ALL-CAPS words other than ``STRING`` are non-terminals
The order of members within JSON objects does not matter unless The order of members within JSON objects does not matter unless
explicitly noted. explicitly noted.
@ -109,27 +109,30 @@ These are discussed in detail below.
Built-in Types Built-in Types
-------------- --------------
The following types are predefined, and map to C as follows:: The following types are predefined, and map to C as follows:
Schema C JSON ============= ============== ============================================
str char * any JSON string, UTF-8 Schema C JSON
number double any JSON number ============= ============== ============================================
int int64_t a JSON number without fractional part ``str`` ``char *`` any JSON string, UTF-8
that fits into the C integer type ``number`` ``double`` any JSON number
int8 int8_t likewise ``int`` ``int64_t`` a JSON number without fractional part
int16 int16_t likewise that fits into the C integer type
int32 int32_t likewise ``int8`` ``int8_t`` likewise
int64 int64_t likewise ``int16`` ``int16_t`` likewise
uint8 uint8_t likewise ``int32`` ``int32_t`` likewise
uint16 uint16_t likewise ``int64`` ``int64_t`` likewise
uint32 uint32_t likewise ``uint8`` ``uint8_t`` likewise
uint64 uint64_t likewise ``uint16`` ``uint16_t`` likewise
size uint64_t like uint64_t, except StringInputVisitor ``uint32`` ``uint32_t`` likewise
accepts size suffixes ``uint64`` ``uint64_t`` likewise
bool bool JSON true or false ``size`` ``uint64_t`` like ``uint64_t``, except
null QNull * JSON null ``StringInputVisitor`` accepts size suffixes
any QObject * any JSON value ``bool`` ``bool`` JSON ``true`` or ``false``
QType QType JSON string matching enum QType values ``null`` ``QNull *`` JSON ``null``
``any`` ``QObject *`` any JSON value
``QType`` ``QType`` JSON string matching enum ``QType`` values
============= ============== ============================================
Include directives Include directives
@ -174,14 +177,14 @@ Pragma 'doc-required' takes a boolean value. If true, documentation
is required. Default is false. is required. Default is false.
Pragma 'command-name-exceptions' takes a list of commands whose names Pragma 'command-name-exceptions' takes a list of commands whose names
may contain '_' instead of '-'. Default is none. may contain ``"_"`` instead of ``"-"``. Default is none.
Pragma 'command-returns-exceptions' takes a list of commands that may Pragma 'command-returns-exceptions' takes a list of commands that may
violate the rules on permitted return types. Default is none. violate the rules on permitted return types. Default is none.
Pragma 'member-name-exceptions' takes a list of types whose member Pragma 'member-name-exceptions' takes a list of types whose member
names may contain uppercase letters, and '_' instead of '-'. Default names may contain uppercase letters, and ``"_"`` instead of ``"-"``.
is none. Default is none.
Enumeration types Enumeration types
@ -200,7 +203,7 @@ Syntax::
Member 'enum' names the enum type. Member 'enum' names the enum type.
Each member of the 'data' array defines a value of the enumeration Each member of the 'data' array defines a value of the enumeration
type. The form STRING is shorthand for { 'name': STRING }. The type. The form STRING is shorthand for :code:`{ 'name': STRING }`. The
'name' values must be be distinct. 'name' values must be be distinct.
Example:: Example::
@ -243,7 +246,7 @@ Syntax::
A string denotes the type named by the string. A string denotes the type named by the string.
A one-element array containing a string denotes an array of the type A one-element array containing a string denotes an array of the type
named by the string. Example: ['int'] denotes an array of 'int'. named by the string. Example: ``['int']`` denotes an array of ``int``.
Struct types Struct types
@ -266,11 +269,11 @@ Member 'struct' names the struct type.
Each MEMBER of the 'data' object defines a member of the struct type. Each MEMBER of the 'data' object defines a member of the struct type.
The MEMBER's STRING name consists of an optional '*' prefix and the The MEMBER's STRING name consists of an optional ``*`` prefix and the
struct member name. If '*' is present, the member is optional. struct member name. If ``*`` is present, the member is optional.
The MEMBER's value defines its properties, in particular its type. The MEMBER's value defines its properties, in particular its type.
The form TYPE-REF is shorthand for { 'type': TYPE-REF }. The form TYPE-REF is shorthand for :code:`{ 'type': TYPE-REF }`.
Example:: Example::
@ -334,7 +337,7 @@ union must have at least one branch.
The BRANCH's STRING name is the branch name. The BRANCH's STRING name is the branch name.
The BRANCH's value defines the branch's properties, in particular its The BRANCH's value defines the branch's properties, in particular its
type. The form TYPE-REF is shorthand for { '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 A simple union type defines a mapping from automatic discriminator
values to data types like in this example:: values to data types like in this example::
@ -381,7 +384,7 @@ struct.
The following example enhances the above simple union example by The following example enhances the above simple union example by
adding an optional common member 'read-only', renaming the adding an optional common member 'read-only', renaming the
discriminator to something more applicable than the simple union's discriminator to something more applicable than the simple union's
default of 'type', and reducing the number of {} required on the wire:: default of 'type', and reducing the number of ``{}`` required on the wire::
{ 'enum': 'BlockdevDriver', 'data': [ 'file', 'qcow2' ] } { 'enum': 'BlockdevDriver', 'data': [ 'file', 'qcow2' ] }
{ 'union': 'BlockdevOptions', { 'union': 'BlockdevOptions',
@ -450,7 +453,7 @@ alternate. An alternate must have at least one branch.
The ALTERNATIVE's STRING name is the branch name. The ALTERNATIVE's STRING name is the branch name.
The ALTERNATIVE's value defines the branch's properties, in particular The ALTERNATIVE's value defines the branch's properties, in particular
its type. The form STRING is shorthand for { 'type': STRING }. its type. The form STRING is shorthand for :code:`{ 'type': STRING }`.
Example:: Example::
@ -515,7 +518,7 @@ If 'data' is a MEMBERS object, then MEMBERS defines arguments just
like a struct type's 'data' defines struct type members. like a struct type's 'data' defines struct type members.
If 'data' is a STRING, then STRING names a complex type whose members If 'data' is a STRING, then STRING names a complex type whose members
are the arguments. A union type requires 'boxed': true. are the arguments. A union type requires ``'boxed': true``.
Member 'returns' defines the command's return type. It defaults to an Member 'returns' defines the command's return type. It defaults to an
empty struct type. It must normally be a complex type or an array of empty struct type. It must normally be a complex type or an array of
@ -555,7 +558,7 @@ section "Code generated for commands" for examples.
The function returns the return type. When member 'boxed' is absent, The function returns the return type. When member 'boxed' is absent,
it takes the command arguments as arguments one by one, in QAPI schema it takes the command arguments as arguments one by one, in QAPI schema
order. Else it takes them wrapped in the C struct generated for the order. Else it takes them wrapped in the C struct generated for the
complex argument type. It takes an additional Error ** argument in complex argument type. It takes an additional ``Error **`` argument in
either case. either case.
The generator also emits a marshalling function that extracts The generator also emits a marshalling function that extracts
@ -638,11 +641,11 @@ blocking the guest and other background operations.
Coroutine safety can be hard to prove, similar to thread safety. Common Coroutine safety can be hard to prove, similar to thread safety. Common
pitfalls are: pitfalls are:
- The global mutex isn't held across qemu_coroutine_yield(), so - The global mutex isn't held across ``qemu_coroutine_yield()``, so
operations that used to assume that they execute atomically may have operations that used to assume that they execute atomically may have
to be more careful to protect against changes in the global state. to be more careful to protect against changes in the global state.
- Nested event loops (AIO_WAIT_WHILE() etc.) are problematic in - Nested event loops (``AIO_WAIT_WHILE()`` etc.) are problematic in
coroutine context and can easily lead to deadlocks. They should be coroutine context and can easily lead to deadlocks. They should be
replaced by yielding and reentering the coroutine when the condition replaced by yielding and reentering the coroutine when the condition
becomes false. becomes false.
@ -650,9 +653,9 @@ pitfalls are:
Since the command handler may assume coroutine context, any callers Since the command handler may assume coroutine context, any callers
other than the QMP dispatcher must also call it in coroutine context. other than the QMP dispatcher must also call it in coroutine context.
In particular, HMP commands calling such a QMP command handler must be In particular, HMP commands calling such a QMP command handler must be
marked .coroutine = true in hmp-commands.hx. marked ``.coroutine = true`` in hmp-commands.hx.
It is an error to specify both 'coroutine': true and 'allow-oob': true It is an error to specify both ``'coroutine': true`` and ``'allow-oob': true``
for a command. We don't currently have a use case for both together and 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 without a use case, it's not entirely clear what the semantics should
be. be.
@ -689,7 +692,7 @@ If 'data' is a MEMBERS object, then MEMBERS defines event-specific
data just like a struct type's 'data' defines struct type members. data just like a struct type's 'data' defines struct type members.
If 'data' is a STRING, then STRING names a complex type whose members If 'data' is a STRING, then STRING names a complex type whose members
are the event-specific data. A union type requires 'boxed': true. are the event-specific data. A union type requires ``'boxed': true``.
An example event is:: An example event is::
@ -763,16 +766,16 @@ digits, hyphen, and underscore. There are two exceptions: enum values
may start with a digit, and names that are downstream extensions (see 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 Names beginning with ``q_`` are reserved for the generator, which uses
them for munging QMP names that resemble C keywords or other them for munging QMP names that resemble C keywords or other
problematic strings. For example, a member named "default" in qapi problematic strings. For example, a member named ``default`` in qapi
becomes "q_default" in the generated C code. becomes ``q_default`` in the generated C code.
Types, commands, and events share a common namespace. Therefore, Types, commands, and events share a common namespace. Therefore,
generally speaking, type definitions should always use CamelCase for generally speaking, type definitions should always use CamelCase for
user-defined type names, while built-in types are lowercase. user-defined type names, while built-in types are lowercase.
Type names ending with 'Kind' or 'List' are reserved for the Type names ending with ``Kind`` or ``List`` are reserved for the
generator, which uses them for implicit union enums and array types, generator, which uses them for implicit union enums and array types,
respectively. respectively.
@ -783,15 +786,15 @@ consistency is preferred over blindly avoiding underscore.
Event names should be ALL_CAPS with words separated by underscore. Event names should be ALL_CAPS with words separated by underscore.
Member name 'u' and names starting with 'has-' or 'has\_' are reserved Member name ``u`` and names starting with ``has-`` or ``has_`` are reserved
for the generator, which uses them for unions and for tracking for the generator, which uses them for unions and for tracking
optional members. optional members.
Any name (command, event, type, member, or enum value) beginning with Any name (command, event, type, member, or enum value) beginning with
"x-" is marked experimental, and may be withdrawn or changed ``x-`` is marked experimental, and may be withdrawn or changed
incompatibly in a future release. incompatibly in a future release.
Pragmas 'command-name-exceptions' and 'member-name-exceptions' let you Pragmas ``command-name-exceptions`` and ``member-name-exceptions`` let you
violate naming rules. Use for new code is strongly discouraged. violate naming rules. Use for new code is strongly discouraged.
@ -805,7 +808,7 @@ who controls the valid, reverse fully qualified domain name RFQDN.
RFQDN may only contain ASCII letters, digits, hyphen and period. RFQDN may only contain ASCII letters, digits, hyphen and period.
Example: Red Hat, Inc. controls redhat.com, and may therefore add a Example: Red Hat, Inc. controls redhat.com, and may therefore add a
downstream command __com.redhat_drive-mirror. downstream command ``__com.redhat_drive-mirror``.
Configuring the schema Configuring the schema
@ -879,7 +882,7 @@ this particular build.
Documentation comments Documentation comments
---------------------- ----------------------
A multi-line comment that starts and ends with a '##' line is a A multi-line comment that starts and ends with a ``##`` line is a
documentation comment. documentation comment.
If the documentation comment starts like :: If the documentation comment starts like ::
@ -887,7 +890,7 @@ If the documentation comment starts like ::
## ##
# @SYMBOL: # @SYMBOL:
it documents the definition if SYMBOL, else it's free-form it documents the definition of SYMBOL, else it's free-form
documentation. documentation.
See below for more on definition documentation. See below for more on definition documentation.
@ -900,7 +903,7 @@ Headings and subheadings
~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~
A free-form documentation comment containing a line which starts with A free-form documentation comment containing a line which starts with
some '=' symbols and then a space defines a section heading:: some ``=`` symbols and then a space defines a section heading::
## ##
# = This is a top level heading # = This is a top level heading
@ -924,22 +927,22 @@ Documentation markup
~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~
Documentation comments can use most rST markup. In particular, Documentation comments can use most rST markup. In particular,
a '::' literal block can be used for examples:: a ``::`` literal block can be used for examples::
# :: # ::
# #
# Text of the example, may span # Text of the example, may span
# multiple lines # multiple lines
'*' starts an itemized list:: ``*`` starts an itemized list::
# * First item, may span # * First item, may span
# multiple lines # multiple lines
# * Second item # * Second item
You can also use '-' instead of '*'. You can also use ``-`` instead of ``*``.
A decimal number followed by '.' starts a numbered list:: A decimal number followed by ``.`` starts a numbered list::
# 1. First item, may span # 1. First item, may span
# multiple lines # multiple lines
@ -952,11 +955,11 @@ If a list item's text spans multiple lines, then the second and
subsequent lines must be correctly indented to line up with the subsequent lines must be correctly indented to line up with the
first character of the first line. first character of the first line.
The usual '**strong**', '*emphasised*' and '``literal``' markup should The usual ****strong****, *\*emphasized\** and ````literal```` markup
be used. If you need a single literal '*' you will need to should be used. If you need a single literal ``*``, you will need to
backslash-escape it. As an extension beyond the usual rST syntax, you backslash-escape it. As an extension beyond the usual rST syntax, you
can also use '@foo' to reference a name in the schema; this is can also use ``@foo`` to reference a name in the schema; this is rendered
rendered the same way as '``foo``'. the same way as ````foo````.
Example:: Example::
@ -991,9 +994,9 @@ alternates), or value (for enums), and finally optional tagged
sections. sections.
Descriptions of arguments can span multiple lines. The description Descriptions of arguments can span multiple lines. The description
text can start on the line following the '@argname:', in which case it text can start on the line following the '\@argname:', in which case it
must not be indented at all. It can also start on the same line as must not be indented at all. It can also start on the same line as
the '@argname:'. In this case if it spans multiple lines then second the '\@argname:'. In this case if it spans multiple lines then second
and subsequent lines must be indented to line up with the first and subsequent lines must be indented to line up with the first
character of the first line of the description:: character of the first line of the description::
@ -1006,8 +1009,13 @@ character of the first line of the description::
The number of spaces between the ':' and the text is not significant. The number of spaces between the ':' and the text is not significant.
FIXME: the parser accepts these things in almost any order. .. admonition:: FIXME
FIXME: union branches should be described, too.
The parser accepts these things in almost any order.
.. admonition:: FIXME
union branches should be described, too.
Extensions added after the definition was first released carry a Extensions added after the definition was first released carry a
'(since x.y.z)' comment. '(since x.y.z)' comment.