[PATCH] software node: Implement device_get_match_data fwnode callback

[Sui Jingfeng]

This makes it possible to support (and/or test) a few drivers that
originates from DT World on the x86-64 platform. Originally, those
drivers using the of_device_get_match_data() function to get match
data. For example, drivers/gpu/drm/bridge/simple-bridge.c and
drivers/gpu/drm/bridge/display-connector.c. Those drivers works very
well in the DT world, however, there is no counterpart to
of_device_get_match_data() when porting them to the x86 platform,
because x86 CPUs lack DT support.

By replacing it with device_get_match_data() and creating a software
graph that mimics the OF graph, everything else works fine, except that
there isn't an out-of-box replacement for the of_device_get_match_data()
function. Because the software node backend of the fwnode framework lacks
an implementation for the device_get_match_data callback.

Implement device_get_match_data fwnode callback fwnode callback to fill
this gap. Device drivers or platform setup codes are expected to provide
a "compatible" string property. The value of this string property is used
to match against the compatible entries in the of_device_id table. Which
is consistent with the original usage style.

Signed-off-by: Sui Jingfeng <sui.jingfeng@xxxxxxxxx>
---
 drivers/base/swnode.c | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c
index 36512fb75a20..3670094592f2 100644
--- a/drivers/base/swnode.c
+++ b/drivers/base/swnode.c
@@ -8,6 +8,7 @@
 
 #include <linux/device.h>
 #include <linux/kernel.h>
+#include <linux/mod_devicetable.h>
 #include <linux/property.h>
 #include <linux/slab.h>
 
@@ -379,6 +380,30 @@ static void software_node_put(struct fwnode_handle *fwnode)
 	kobject_put(&swnode->kobj);
 }
 
+static const void *
+software_node_get_match_data(const struct fwnode_handle *fwnode,
+			     const struct device *dev)
+{
+	struct swnode *swnode = to_swnode(fwnode);
+	const struct of_device_id *matches = dev->driver->of_match_table;
+	const char *val = NULL;
+	int ret;
+
+	ret = property_entry_read_string_array(swnode->node->properties,
+					       "compatible", &val, 1);
+	if (ret < 0 || !val)
+		return NULL;
+
+	while (matches && matches->compatible[0]) {
+		if (!strcmp(matches->compatible, val))
+			return matches->data;
+
+		matches++;
+	}
+
+	return NULL;
+}
+
 static bool software_node_property_present(const struct fwnode_handle *fwnode,
 					   const char *propname)
 {
@@ -665,6 +690,7 @@ software_node_graph_parse_endpoint(const struct fwnode_handle *fwnode,
 static const struct fwnode_operations software_node_ops = {
 	.get = software_node_get,
 	.put = software_node_put,
+	.device_get_match_data = software_node_get_match_data,
 	.property_present = software_node_property_present,
 	.property_read_int_array = software_node_read_int_array,
 	.property_read_string_array = software_node_read_string_array,
-- 
2.34.1