linux-kernel - [PATCH 2/8] firmware: arm_scmi: Add bound iterators support

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Message-ID: <20250813114609.1305571-3-cristian.marussi@arm.com>
Date: Wed, 13 Aug 2025 12:46:03 +0100
From: Cristian Marussi <cristian.marussi@....com>
To: linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	arm-scmi@...r.kernel.org,
	linux-pm@...r.kernel.org
Cc: sudeep.holla@....com,
	james.quinlan@...adcom.com,
	f.fainelli@...il.com,
	vincent.guittot@...aro.org,
	etienne.carriere@...com,
	peng.fan@....nxp.com,
	michal.simek@....com,
	quic_sibis@...cinc.com,
	dan.carpenter@...aro.org,
	d-gole@...com,
	souvik.chakravarty@....com,
	Cristian Marussi <cristian.marussi@....com>
Subject: [PATCH 2/8] firmware: arm_scmi: Add bound iterators support

SCMI core stack provides some common helpers to handle in a unified way
multipart message replies: such iterator-helpers, when run, currently
process by default the whole set of available resources.

Introduce an alternative way to run the initialized iterator on a limited
range of resources.

Signed-off-by: Cristian Marussi <cristian.marussi@....com>
---
 drivers/firmware/arm_scmi/driver.c    | 21 +++++++++++++++++++--
 drivers/firmware/arm_scmi/protocols.h |  6 ++++++
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 65bd545c0cb1..62f9cdd508c3 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -1832,7 +1832,8 @@ static void *scmi_iterator_init(const struct scmi_protocol_handle *ph,
 	return i;
 }
 
-static int scmi_iterator_run(void *iter)
+static int __scmi_iterator_run(void *iter, unsigned int *start,
+			       unsigned int *end)
 {
 	int ret = -EINVAL;
 	struct scmi_iterator_ops *iops;
@@ -1847,6 +1848,9 @@ static int scmi_iterator_run(void *iter)
 	ph = i->ph;
 	st = &i->state;
 
+	if (start)
+		st->desc_index = *start;
+
 	do {
 		iops->prepare_message(i->msg, st->desc_index, i->priv);
 		ret = ph->xops->do_xfer(ph, i->t);
@@ -1879,7 +1883,8 @@ static int scmi_iterator_run(void *iter)
 		 * check for both returned and remaining to avoid infinite
 		 * loop due to buggy firmware
 		 */
-	} while (st->num_returned && st->num_remaining);
+	} while (st->num_returned && st->num_remaining &&
+		 (!end || (st->desc_index <= min(*end, st->max_resources - 1))));
 
 out:
 	/* Finalize and destroy iterator */
@@ -1889,6 +1894,17 @@ static int scmi_iterator_run(void *iter)
 	return ret;
 }
 
+static int scmi_iterator_run(void *iter)
+{
+	return __scmi_iterator_run(iter, NULL, NULL);
+}
+
+static int scmi_iterator_run_bound(void *iter, unsigned int *start,
+				   unsigned int *end)
+{
+	return __scmi_iterator_run(iter, start, end);
+}
+
 struct scmi_msg_get_fc_info {
 	__le32 domain;
 	__le32 message_id;
@@ -2075,6 +2091,7 @@ static const struct scmi_proto_helpers_ops helpers_ops = {
 	.get_max_msg_size = scmi_common_get_max_msg_size,
 	.iter_response_init = scmi_iterator_init,
 	.iter_response_run = scmi_iterator_run,
+	.iter_response_run_bound = scmi_iterator_run_bound,
 	.protocol_msg_check = scmi_protocol_msg_check,
 	.fastchannel_init = scmi_common_fastchannel_init,
 	.fastchannel_db_ring = scmi_common_fastchannel_db_ring,
diff --git a/drivers/firmware/arm_scmi/protocols.h b/drivers/firmware/arm_scmi/protocols.h
index 8a96b78331f2..a48e212ac0e1 100644
--- a/drivers/firmware/arm_scmi/protocols.h
+++ b/drivers/firmware/arm_scmi/protocols.h
@@ -257,6 +257,10 @@ struct scmi_fc_info {
  *			provided in @ops.
  * @iter_response_run: A common helper to trigger the run of a previously
  *		       initialized iterator.
+ * @iter_response_run_bound: A common helper to trigger the run of a previously
+ *			     initialized iterator, but only within the
+ *			     specified, optional, @start and @end resource
+ *			     indexes.
  * @protocol_msg_check: A common helper to check is a specific protocol message
  *			is supported.
  * @fastchannel_init: A common helper used to initialize FC descriptors by
@@ -273,6 +277,8 @@ struct scmi_proto_helpers_ops {
 				    unsigned int max_resources, u8 msg_id,
 				    size_t tx_size, void *priv);
 	int (*iter_response_run)(void *iter);
+	int (*iter_response_run_bound)(void *iter,
+				       unsigned int *start, unsigned int *end);
 	int (*protocol_msg_check)(const struct scmi_protocol_handle *ph,
 				  u32 message_id, u32 *attributes);
 	void (*fastchannel_init)(const struct scmi_protocol_handle *ph,
-- 
2.47.0