[ctl] ICCom control channel handler

* Added an ICCom control channel handler.
  It it is intended to be used in ICCom instances direct
  communication (like protocol negotiations, for example).
  So messages sent via control channel are consumed by ICCom directly.

Author: Bosch-SW

include/linux/iccom.h

@@ -28,6 +28,12 @@
 
 // the channel value which is interpreted as (any/all) channel(s)
 #define ICCOM_ANY_CHANNEL_VALUE -1
+// This channel is used to control the ICCom internal flows,
+// like embedded acks, protocol advancement negotiations, etc.
+//
+// This channel is not to be exposed outside the ICCom, so pls don't
+// try to use it for any other communication.
+#define ICCOM_CTL_CHANNEL 0
 
 
 // number of error types to be tracked

src/iccom.c

@@ -4328,6 +4328,20 @@ static inline void __iccom_statistics_init(struct iccom_dev *iccom)
 	atomic_long_set(&iccom->p->statistics.messages_ready_in_storage, 0);
 }
 
+// Handles the iccom ctl channel messages. Those messages
+// include protocol negotiations messages, embedded
+// ack messages, etc..
+//
+// @channel must always be ICCOM_CTL_CHANNEL.
+// @consumer_data points to iccom_dev.
+static bool __iccom_ctl_msg_handler(unsigned int channel
+                  , void *msg_data, size_t msg_len
+                  , void *consumer_data)
+{
+	// here the ctl handling logic shall be
+	return false;
+}
+
 /* -------------------------- KERNEL SPACE API --------------------------*/
 
 // API
@@ -4457,6 +4471,9 @@ int iccom_flush(struct iccom_dev *iccom)
 //      as global callback for all channels.
 //      NOTE: global callback is used only when specific channel
 //          callback is not set.
+//		NOTE: the ICCOM_CTL_CHANNEL is reserved for the internal
+//			ICCom communications, it will not be possible to use it
+//			from outside of the ICCom.
 // @message_ready_callback {valid ptr || NULL} the pointer to the
 //      callback which is to be called when channel gets a message
 //      ready. NULL value disables the callback function on the channel.
@@ -4488,6 +4505,12 @@ int iccom_set_channel_callback(struct iccom_dev *iccom
 		iccom_err("broken callback pointer provided");
 		return -EINVAL;
 	}
+	if (channel == ICCOM_CTL_CHANNEL) {
+		iccom_err("channel %d is reserved for iccom internal ctl messages"
+				  " so, can not assign a custom callback to it"
+				  , ICCOM_CTL_CHANNEL);
+		return -EINVAL;
+	}
 
 	return iccom_msg_storage_set_channel_callback(
 			&iccom->p->rx_messages, channel
@@ -4519,6 +4542,12 @@ int iccom_remove_channel_callback(struct iccom_dev *iccom
 	ICCOM_CHECK_XFER_DEVICE("broken xfer device", return -ENODEV);
 	ICCOM_CHECK_CHANNEL("bad channel", return -EBADSLT);
 	ICCOM_CHECK_CLOSING("will not invoke", return -EBADFD);
+	if (channel == ICCOM_CTL_CHANNEL) {
+		iccom_err("channel %d is reserved for iccom internal ctl messages"
+				  " so, can not remove it's callback"
+				  , ICCOM_CTL_CHANNEL);
+		return -EINVAL;
+	}
 	return iccom_msg_storage_reset_channel_callback(
 			&iccom->p->rx_messages, channel);
 }
@@ -4832,10 +4861,17 @@ int iccom_init(struct iccom_dev *iccom, struct platform_device *pdev)
 		goto free_private;
 	}
 
+	if (iccom_msg_storage_set_channel_callback(
+			&iccom->p->rx_messages, ICCOM_CTL_CHANNEL
+			, __iccom_ctl_msg_handler , iccom) < 0) {
+		iccom_err("Could not register ctl channel clbk.");
+		goto free_msg_storage;
+	}
+
 	res = __iccom_init_packages_storage(iccom);
 	if (res < 0) {
 		iccom_err("Could not initialize packages storage.");
-		goto free_msg_storage;
+		goto unregister_ctl_msgs_handler;
 	}
 
 	iccom->p->last_rx_package_id = ICCOM_PACKAGE_HAVE_NOT_RECEIVED_ID;
@@ -4884,6 +4920,9 @@ int iccom_init(struct iccom_dev *iccom, struct platform_device *pdev)
 	mutex_destroy(&iccom->p->sysfs_test_ch_lock);
 free_pkg_storage:
 	__iccom_free_packages_storage(iccom);
+unregister_ctl_msgs_handler:
+	iccom_msg_storage_reset_channel_callback(
+		&iccom->p->rx_messages, ICCOM_CTL_CHANNEL);
 free_msg_storage:
 	iccom_msg_storage_free(&iccom->p->rx_messages);
 free_private: