Re: [PATCH 8/9] docs/devel: mention the spacing requirement for QOM

[Mark Cave-Ayland]

On 20/04/2023 16:57, Alex Bennée wrote:

> We have a more complete document on QOM but we should at least mention
> the style requirements in the style guide.
>
> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
> Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> ---
>   docs/devel/qom.rst   |  2 ++
>   docs/devel/style.rst | 29 +++++++++++++++++++++++++++++
>   2 files changed, 31 insertions(+)
>
> diff --git a/docs/devel/qom.rst b/docs/devel/qom.rst
> index 3e34b07c98..c9237950d0 100644
> --- a/docs/devel/qom.rst
> +++ b/docs/devel/qom.rst
> @@ -1,3 +1,5 @@
> +.. _qom:
> +
>   ===========================
>   The QEMU Object Model (QOM)
>   ===========================
> diff --git a/docs/devel/style.rst b/docs/devel/style.rst
> index 5bc6f2f095..0bd01f3fca 100644
> --- a/docs/devel/style.rst
> +++ b/docs/devel/style.rst
> @@ -628,6 +628,35 @@ are still some caveats to beware of
>   QEMU Specific Idioms
>   ********************
>   
> +QEMU Object Model Declarations
> +==============================
> +
> +The QEMU Object Model (QOM) provides a framework for handling objects
> +in the base C language. The first declaration of a storage or class
> +structure should always be the parent and leave a visual space between
> +that declaration and the new code.
> +
> +.. code-block:: c
> +
> +    typedef struct MyDeviceState {
> +        DeviceState parent_obj;
> +
> +        /* Properties */
> +        int prop_a;
> +        char *prob_b;
> +        /* Other stuff */
> +        int internal_state;
> +    } MyDeviceState;
> +
> +    typedef struct MyDeviceClass {
> +        ObjectClass parent_class;

This one should be DeviceClass in this particular example.

> +        void (*new_fn1)(void);
> +        bool (*new_fn2)(CPUState *);
> +   } MyDeviceClass;
> +
> +See :ref:`qom` for more details.

A couple of points:

1) It is probably worth removing the typedefs given that they are handled by the 
various QOM macros

2) There should be mention of the fixed names "parent_obj" and "parent_class" 
for
the first declaration.

How about something like this:


QEMU Object Model Declarations
==============================

The QEMU Object Model (QOM) provides a framework for handling objects
in the base C language. The first declaration of a storage or class
structure should always be the parent and leave a visual space between
that declaration and the new code.

For a storage structure the first declaration should always be called
"parent_obj" and for a class structure the first member should always
be called "parent_class" as below:

.. code-block:: c

    struct MyDeviceState {
        DeviceState parent_obj;

        /* Properties */
        int prop_a;
        char *prob_b;
        /* Other stuff */
        int internal_state;
    };

    struct MyDeviceClass {
        DeviceClass parent_class;

        void (*new_fn1)(void);
        bool (*new_fn2)(CPUState *);
    };

Note that there is no need to provide typedefs for QOM structures since these are 
generated automatically by the QOM declaration macros. See :ref:`qom` for more details.


ATB,

Mark.