[RFC PATCH 1/1] remoteproc: Introduce rproc_get_by_id API

[Ben Levinsky <ben.levinsky@xilinx.com>]

Allow users of remoteproc the ability to get a handle to an rproc by
passing in node that has parent rproc device and an ID that matches
an expected rproc struct's index field.

This enables to get rproc structure for remoteproc drivers that manage
more than 1 remote processor (e.g. TI and Xilinx R5 drivers).

Signed-off-by: Ben Levinsky <ben.levinsky@xilinx.com>
---
 drivers/remoteproc/remoteproc_core.c | 64 +++++++++++++++++++++++++++-
 include/linux/remoteproc.h           |  1 +
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
index 775df165eb45..6f7058bcc80c 100644
--- a/drivers/remoteproc/remoteproc_core.c
+++ b/drivers/remoteproc/remoteproc_core.c
@@ -40,6 +40,7 @@
 #include <linux/virtio_ring.h>
 #include <asm/byteorder.h>
 #include <linux/platform_device.h>
+#include <linux/of_platform.h>
 
 #include "remoteproc_internal.h"
 
@@ -2203,13 +2204,74 @@ struct rproc *rproc_get_by_phandle(phandle phandle)
 
 	return rproc;
 }
+
+/**
+ * rproc_get_by_id() - find a remote processor by ID
+ * @phandle: phandle to the rproc
+ * @id: Index into rproc list that uniquely identifies the rproc struct
+ *
+ * Finds an rproc handle using the remote processor's index, and then
+ * return a handle to the rproc. Before returning, ensure that the
+ * parent node's driver is still loaded.
+ *
+ * This function increments the remote processor's refcount, so always
+ * use rproc_put() to decrement it back once rproc isn't needed anymore.
+ *
+ * Return: rproc handle on success, and NULL on failure
+ */
+
+struct rproc *rproc_get_by_id(phandle phandle, unsigned int id)
+{
+	struct rproc *rproc = NULL, *r;
+	struct platform_device *parent_pdev;
+	struct device_node *np;
+
+	np = of_find_node_by_phandle(phandle);
+	if (!np)
+		return NULL;
+
+	parent_pdev = of_find_device_by_node(np->parent);
+	if (!parent_pdev) {
+		dev_err(&parent_pdev->dev,
+			"no platform device for node %pOF\n", np);
+		of_node_put(np);
+		return NULL;
+	}
+
+	/* prevent underlying implementation from being removed */
+	if (!try_module_get(parent_pdev->dev.driver->owner)) {
+		dev_err(&parent_pdev->dev, "can't get owner\n");
+		of_node_put(np);
+		return NULL;
+	}
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(r, &rproc_list, node) {
+		if (r->index == id) {
+			rproc = r;
+			get_device(&rproc->dev);
+			break;
+		}
+	}
+	rcu_read_unlock();
+
+	of_node_put(np);
+
+	return rproc;
+}
+EXPORT_SYMBOL(rproc_get_by_id);
 #else
 struct rproc *rproc_get_by_phandle(phandle phandle)
 {
 	return NULL;
 }
-#endif
 EXPORT_SYMBOL(rproc_get_by_phandle);
+struct rproc *rproc_get_by_id(phandle phandle, unsigned int id)
+{
+	return NULL;
+}
+EXPORT_SYMBOL(rproc_get_by_id);
+#endif
 
 /**
  * rproc_set_firmware() - assign a new firmware
diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
index 3cde845ba26e..10961fae0f77 100644
--- a/include/linux/remoteproc.h
+++ b/include/linux/remoteproc.h
@@ -645,6 +645,7 @@ struct rproc_vdev {
 };
 
 struct rproc *rproc_get_by_phandle(phandle phandle);
+struct rproc *rproc_get_by_id(phandle phandle, unsigned int id);
 struct rproc *rproc_get_by_child(struct device *dev);
 
 struct rproc *rproc_alloc(struct device *dev, const char *name,
-- 
2.25.1