[PATCH] soundwire: bus: iterate DT compatibles for class-ID match

[Srinivas Kandagatla]

sdw_of_find_slaves() reads only the first "compatible" string on a
SoundWire slave DT node and rejects the node if that string does not
parse as sdwVMMMPPPPXX.  This prevents the standard DT convention of
placing a vendor-variant compatible ahead of the SoundWire class-ID
compatible:

    compatible = "vendor,partname", "sdwVMMMPPPPXX";

Iterate every string in the compatible property and accept the first
one that parses as a SoundWire class ID.  The vendor-variant string
remains visible to driver probe callbacks via device_is_compatible()
for mode/variant disambiguation.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxxxxxxxx>
---
 drivers/soundwire/slave.c | 28 +++++++++++++++++++---------
 1 file changed, 19 insertions(+), 9 deletions(-)

diff --git a/drivers/soundwire/slave.c b/drivers/soundwire/slave.c
index e0c49cbcb1ba..a7d2938b031d 100644
--- a/drivers/soundwire/slave.c
+++ b/drivers/soundwire/slave.c
@@ -243,17 +243,27 @@ int sdw_of_find_slaves(struct sdw_bus *bus)
 		const char *compat = NULL;
 		struct sdw_slave_id id;
 		const __be32 *addr;
+		struct property *prop;
+		bool matched = false;
 
-		ret = of_property_read_string(node, "compatible", &compat);
-		if (ret)
-			continue;
-
-		ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx", &sdw_version,
-			     &id.mfg_id, &id.part_id, &id.class_id);
+		/*
+		 * Iterate the compatible list so DT nodes can carry a
+		 * vendor-variant compatible ahead of the SoundWire class-ID
+		 * compatible (e.g. "vendor,part", "sdwVMMMPPPPXX").
+		 */
+		of_property_for_each_string(node, "compatible", prop, compat) {
+			ret = sscanf(compat, "sdw%01x%04hx%04hx%02hhx",
+				     &sdw_version, &id.mfg_id, &id.part_id,
+				     &id.class_id);
+			if (ret == 4) {
+				matched = true;
+				break;
+			}
+		}
 
-		if (ret != 4) {
-			dev_err(dev, "Invalid compatible string found %s\n",
-				compat);
+		if (!matched) {
+			dev_err(dev, "%pOFn: no SoundWire class-ID compatible\n",
+				node);
 			continue;
 		}
 
-- 
2.53.0