remoteproc: core: Register the character device interface

Add the character device during rproc_add. This would create
a character device node at /dev/remoteproc<index>. Userspace
applications can interact with the remote processor using this
interface.
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>
Signed-off-by: Siddharth Gupta <sidgup@codeaurora.org>
Link: https://lore.kernel.org/r/1596044401-22083-3-git-send-email-sidgup@codeaurora.orgSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/remoteproc_core.c

@@ -1986,6 +1986,11 @@ int rproc_add(struct rproc *rproc)
 	/* create debugfs entries */
 	rproc_create_debug_dir(rproc);
 
+	/* add char device for this remoteproc */
+	ret = rproc_char_device_add(rproc);
+	if (ret < 0)
+		return ret;
+
 	/*
 	 * Remind ourselves the remote processor has been attached to rather
 	 * than booted by the remoteproc core.  This is important because the
@@ -2262,6 +2267,7 @@ int rproc_del(struct rproc *rproc)
 	mutex_unlock(&rproc->lock);
 
 	rproc_delete_debug_dir(rproc);
+	rproc_char_device_remove(rproc);
 
 	/* the rproc is downref'ed as soon as it's removed from the klist */
 	mutex_lock(&rproc_list_mutex);
@@ -2430,6 +2436,7 @@ static int __init remoteproc_init(void)
 {
 	rproc_init_sysfs();
 	rproc_init_debugfs();
+	rproc_init_cdev();
 	rproc_init_panic();
 
 	return 0;