firmware: arm_scmi: Refactor reset domain handling

Introduce scmi_reset_domain_lookup() to centralize domain ID validation
and unify error reporting behaviour across the SCMI reset protocol.

All reset domain operations are updated to use the new helper, removing
duplicated validation logic and ensuring consistent handling of invalid
domain IDs and lookup failures. This simplifies the internal flow and
improves robustness of the reset protocol implementation.

Suggested-by: Cristian Marussi <cristian.marussi@arm.com>
Signed-off-by: Artem Shimko <a.shimko.dev@gmail.com>
Message-Id: <20251123163557.230530-1-a.shimko.dev@gmail.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

Author: Artem Shimko

drivers/firmware/arm_scmi/reset.c

@@ -98,6 +98,17 @@ static int scmi_reset_attributes_get(const struct scmi_protocol_handle *ph,
 	return ret;
 }
 
+static struct reset_dom_info *
+scmi_reset_domain_lookup(const struct scmi_protocol_handle *ph, u32 domain)
+{
+	struct scmi_reset_info *pi = ph->get_priv(ph);
+
+	if (domain >= pi->num_domains)
+		return ERR_PTR(-EINVAL);
+
+	return pi->dom_info + domain;
+}
+
 static int
 scmi_reset_domain_attributes_get(const struct scmi_protocol_handle *ph,
 				 struct scmi_reset_info *pinfo,
@@ -156,20 +167,25 @@ static int scmi_reset_num_domains_get(const struct scmi_protocol_handle *ph)
 static const char *
 scmi_reset_name_get(const struct scmi_protocol_handle *ph, u32 domain)
 {
-	struct scmi_reset_info *pi = ph->get_priv(ph);
+	struct reset_dom_info *dom_info;
 
-	struct reset_dom_info *dom = pi->dom_info + domain;
+	dom_info = scmi_reset_domain_lookup(ph, domain);
+	if (IS_ERR(dom_info))
+		return "unknown";
 
-	return dom->name;
+	return dom_info->name;
 }
 
 static int scmi_reset_latency_get(const struct scmi_protocol_handle *ph,
 				  u32 domain)
 {
-	struct scmi_reset_info *pi = ph->get_priv(ph);
-	struct reset_dom_info *dom = pi->dom_info + domain;
+	struct reset_dom_info *dom_info;
+
+	dom_info = scmi_reset_domain_lookup(ph, domain);
+	if (IS_ERR(dom_info))
+		return PTR_ERR(dom_info);
 
-	return dom->latency_us;
+	return dom_info->latency_us;
 }
 
 static int scmi_domain_reset(const struct scmi_protocol_handle *ph, u32 domain,
@@ -178,14 +194,13 @@ static int scmi_domain_reset(const struct scmi_protocol_handle *ph, u32 domain,
 	int ret;
 	struct scmi_xfer *t;
 	struct scmi_msg_reset_domain_reset *dom;
-	struct scmi_reset_info *pi = ph->get_priv(ph);
-	struct reset_dom_info *rdom;
+	struct reset_dom_info *dom_info;
 
-	if (domain >= pi->num_domains)
-		return -EINVAL;
+	dom_info = scmi_reset_domain_lookup(ph, domain);
+	if (IS_ERR(dom_info))
+		return PTR_ERR(dom_info);
 
-	rdom = pi->dom_info + domain;
-	if (rdom->async_reset && flags & AUTONOMOUS_RESET)
+	if (dom_info->async_reset && flags & AUTONOMOUS_RESET)
 		flags |= ASYNCHRONOUS_RESET;
 
 	ret = ph->xops->xfer_get_init(ph, RESET, sizeof(*dom), 0, &t);
@@ -238,15 +253,16 @@ static const struct scmi_reset_proto_ops reset_proto_ops = {
 static bool scmi_reset_notify_supported(const struct scmi_protocol_handle *ph,
 					u8 evt_id, u32 src_id)
 {
-	struct reset_dom_info *dom;
-	struct scmi_reset_info *pi = ph->get_priv(ph);
+	struct reset_dom_info *dom_info;
 
-	if (evt_id != SCMI_EVENT_RESET_ISSUED || src_id >= pi->num_domains)
+	if (evt_id != SCMI_EVENT_RESET_ISSUED)
 		return false;
 
-	dom = pi->dom_info + src_id;
+	dom_info = scmi_reset_domain_lookup(ph, src_id);
+	if (IS_ERR(dom_info))
+		return false;
 
-	return dom->reset_notify;
+	return dom_info->reset_notify;
 }
 
 static int scmi_reset_notify(const struct scmi_protocol_handle *ph,