Re: [PATCH v2 1/5] qdev: add user_creatable_requires_machine_allowance class flag

[Peter Maydell]

On Thu, 31 Mar 2022 at 13:19, Damien Hedde <damien.hedde@greensocs.com> wrote:
>
> This flag will be used in device_add to check if
> the device needs special allowance from the machine
> model.
>
> It will replace the current check based only on the
> device being a TYPE_SYB_BUS_DEVICE.
>
> Signed-off-by: Damien Hedde <damien.hedde@greensocs.com>
> ---
>
> v2:
>  + change the flag name and put it just below user_creatable
> ---
>  include/hw/qdev-core.h | 9 +++++++++
>  hw/core/qdev.c         | 1 +
>  hw/core/sysbus.c       | 1 +
>  3 files changed, 11 insertions(+)
>
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 92c3d65208..6a040fcd3b 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -122,6 +122,15 @@ struct DeviceClass {
>       * TODO remove once we're there
>       */
>      bool user_creatable;
> +    /*
> +     * Some devices can be user created under certain conditions (eg:
> +     * specific machine support for sysbus devices), but it is
> +     * preferable to prevent global allowance for the reasons
> +     * described above.
> +     * This flag is an additional constraint over user_creatable:
> +     * user_creatable still needs to be set to true.
> +     */
> +    bool user_creatable_requires_machine_allowance;

"allowance" doesn't have the meaning you seem to be trying to give it here.
(It means "the amount of something you're allowed to have", like
a baggage allowance, or "an amount of money you're given for something",
like a travel allowance.)

Do you mean "user creatable only if the machine permits it" ?

More generally, the pluggable-sysbus stuff is an awful hack
that I wish we didn't have to have. I'm not sure I want to see
us expanding the use of it to other device types...

thanks
-- PMM