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

On Tue, Sep 22, 2026 at 03:15:55PM +0200, David Hildenbrand (Arm) wrote:

On 9/20/26 11:19, Cristian Marussi wrote:

quoted

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.

quoted

 	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.

quoted

+					     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 

quoted

+ * @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