On 10/01/2020 16.30, Marc-André Lureau wrote:
> Let's factor out the code to format a help string for a property. We
> are going to reuse it in qdev next, which will bring some consistency.
>
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   include/qom/object.h    | 13 +++++++++++++
>   qom/object_interfaces.c | 39 +++++++++++++++++++++++----------------
>   2 files changed, 36 insertions(+), 16 deletions(-)
>
> diff --git a/include/qom/object.h b/include/qom/object.h
> index 933e5c6cb9..a28e37a648 100644
> --- a/include/qom/object.h
> +++ b/include/qom/object.h
> @@ -1854,6 +1854,19 @@ Object *container_get(Object *root, const char *path);
>    */
>   size_t object_type_get_instance_size(const char *typename);
>   
> +/**
> + * object_property_help:
> + * @name: the name of the property
> + * @type: the type of the property
> + * @defval: the default value
> + * @description: description of the property
> + *
> + * Returns: a user-friendly formatted string describing the property
> + * for help purposes.
> + */
> +char *object_property_help(const char *name, const char *type,
> +                           const char *defval, const char *description);
> +
>   G_DEFINE_AUTOPTR_CLEANUP_FUNC(Object, object_unref)
>   
>   #endif
> diff --git a/qom/object_interfaces.c b/qom/object_interfaces.c
> index edb4cc4a3d..b7157d6ab0 100644
> --- a/qom/object_interfaces.c
> +++ b/qom/object_interfaces.c
> @@ -158,6 +158,25 @@ int user_creatable_add_opts_foreach(void *opaque, QemuOpts *opts, Error **errp)
>       return 0;
>   }
>   
> +char *object_property_help(const char *name, const char *type,
> +                           const char *defval, const char *description)
> +{
> +    GString *str = g_string_new(NULL);
> +
> +    g_string_append_printf(str, "  %s=<%s>", name, type);
> +    if (defval) {
> +        g_string_append_printf(str, " (default: %s)", defval);
> +    }

  Hi!

There is something weird going on wit the default value text...

When I run:

$ qemu-system-x86_64 -device isa-fdc,help

I get:

isa-fdc options:
   bootindexA=<int32>
   bootindexB=<int32>
   dma=<uint32>           -  (default: (null))
   driveA=<str>           - Node name or ID of a block device to use as a backend
   driveB=<str>           - Node name or ID of a block device to use as a backend
   fallback=<FdcDriveType> - FDC drive type, 144/288/120/none/auto (default: (null))
   fdtypeA=<FdcDriveType> - FDC drive type, 144/288/120/none/auto (default: (null))
   fdtypeB=<FdcDriveType> - FDC drive type, 144/288/120/none/auto (default: (null))
   iobase=<uint32>        -  (default: (null))
   irq=<uint32>           -  (default: (null))

Why is it showing "(null)" as default values?