Re: [PATCH v12 02/25] firmware: arm_scmi: Allow registration of unknown-size events/reports

[Cristian Marussi <cristian.marussi@arm.com>]

On Tue, Sep 22, 2026 at 03:15:55PM +0200, David Hildenbrand (Arm) wrote:
> On 9/20/26 11:19, Cristian Marussi wrote:
> > Allow protocols to register events with build-time unknown sizes: such
> > events can be declared zero-sized and let the core SCMI stack perform the
> > needed safe-net boundary checks based on the configured transport size.
> 
> ok, so we have a maximum message size defined by the transport. We'll use that
> as payload size, and the report size just gets the additional ktime_t.
> 
> 
> >  	pd = scmi_allocate_registered_events_desc(ni, proto_id, ee->queue_sz,
> > @@ -807,7 +821,8 @@ int scmi_register_protocol_events(const struct scmi_handle *handle, u8 proto_id,
> >  		mutex_init(&r_evt->sources_mtx);
> >  
> >  		r_evt->report = devm_kzalloc(ni->handle->dev,
> > -					     evt->max_report_sz, GFP_KERNEL);
> > +					     evt->max_report_sz ?: max_report_sz,
> 
> Having two similarly named variables is a bit confusing. I wonder if you can
> somehow make it clearer in the latter case that it is the max_report_sz
> according to the transport.

Ok I'll do.

> 
> > +					     GFP_KERNEL);
> >  		if (!r_evt->report)
> >  			return -ENOMEM;
> >  
> > diff --git a/drivers/firmware/arm_scmi/notify.h b/drivers/firmware/arm_scmi/notify.h
> > index f18f98c5ab3b..c2eb4844c7db 100644
> > --- a/drivers/firmware/arm_scmi/notify.h
> > +++ b/drivers/firmware/arm_scmi/notify.h
> > @@ -18,8 +18,12 @@
> >  /**
> >   * struct scmi_event  - Describes an event to be supported
> >   * @id: Event ID
> > - * @max_payld_sz: Max possible size for the payload of a notification message
> > - * @max_report_sz: Max possible size for the report of a notification message
> > + * @max_payld_sz: Max possible size for the payload of a notification message.
> > + *		  Set to zero to use the maximum payload size allowed by the
> > + *		  transport.
> 
> "maximum payload size" is ph->hops->get_max_msg_size(ph) ? Should we call this
> "maximum message size" then?
>
Ok 
> > + * @max_report_sz: Max possible size for the report of a notification message.
> > + *		   Set to zero to use the maximum payload size allowed by the
> > + *		   transport plus the additional ktime_t timestamp.
> 
> Same here.
>
 
Ok

Thanks,
Cristian

> -- 
> Cheers,
> 
> David