Current SCMI implementation supports only receiving arrays from the
SCMI server and provides helpers to process received data. It uses
msg_max_size value to determine maximum message size that can be
transmitted via selected protocol. When sending arrays to SCMI server
this value should be checked by the Client driver to prevent
overflowing protocol buffers.
That's why scmi_get_max_msg_size call was introduced.

Signed-off-by: Oleksii Moisieiev <oleksii_moisieiev@epam.com>
---
 drivers/firmware/arm_scmi/common.h |  3 +++
 drivers/firmware/arm_scmi/driver.c | 16 ++++++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index c46dc5215af7..3db97f59bc59 100644
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -286,6 +286,9 @@ int scmi_xfer_raw_inflight_register(const struct scmi_handle *handle,
 int scmi_xfer_raw_wait_for_message_response(struct scmi_chan_info *cinfo,
 					    struct scmi_xfer *xfer,
 					    unsigned int timeout_ms);
+
+int scmi_get_max_msg_size(const struct scmi_protocol_handle *ph);
+
 #ifdef CONFIG_ARM_SCMI_TRANSPORT_MAILBOX
 extern const struct scmi_desc scmi_mailbox_desc;
 #endif
diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 729201d8f935..f15e9b2b21f3 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -1152,6 +1152,22 @@ int scmi_xfer_raw_wait_for_message_response(struct scmi_chan_info *cinfo,
 	return ret;
 }
 
+/**
+ * scmi_get_max_msg_size  - An helper to get currently configured
+ * maximum message size.
+ *
+ * @ph: SCMI protocol handle
+ *
+ * Return: Maximum message size for the current protocol.
+ */
+int scmi_get_max_msg_size(const struct scmi_protocol_handle *ph)
+{
+	const struct scmi_protocol_instance *pi = ph_to_pi(ph);
+	struct scmi_info *info = handle_to_scmi_info(pi->handle);
+
+	return info->desc->max_msg_size;
+}
+
 /**
  * do_xfer() - Do one transfer
  *
-- 
2.25.1

On Fri, Oct 27, 2023 at 06:28:09AM +0000, Oleksii Moisieiev wrote:
> Current SCMI implementation supports only receiving arrays from the
> SCMI server and provides helpers to process received data. It uses
> msg_max_size value to determine maximum message size that can be
> transmitted via selected protocol. When sending arrays to SCMI server
> this value should be checked by the Client driver to prevent
> overflowing protocol buffers.
> That's why scmi_get_max_msg_size call was introduced.
> 

Hi Oleksii,

indeed given the new variable sized v3.2 SCMI requests (instead of
responses) this common helper is now needed for the protocols to be
able to properly size and chunk their command requests, BUT this is
a new core helper that has potentially to be available to any future
protocol so it has to be exposed as a common helpers in helpers_ops
(like iterators or extended_name helpers), if NOT this common method
won't be available to protocols when compiled as distinct loadable
modules (vendor-modules can be defined and built as LKM)

Thanks,
Cristian