[alsa-devel] [PATCH 1/8] soundwire: intel: filter SoundWire controller device search

[Pierre-Louis Bossart]

The convention is that the SoundWire controller device is a child of
the HDAudio controller. However there can be more than one child
exposed in the DSDT table, and the current namespace walk returns the
last device.

Add a filter and terminate early when a valid _ADR is provided,
otherwise keep iterating to find the next child.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 drivers/soundwire/intel_init.c | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/drivers/soundwire/intel_init.c b/drivers/soundwire/intel_init.c
index d3d6b54c5791..f85db67d05f0 100644
--- a/drivers/soundwire/intel_init.c
+++ b/drivers/soundwire/intel_init.c
@@ -150,6 +150,12 @@ static acpi_status sdw_intel_acpi_cb(acpi_handle handle, u32 level,
 {
 	struct sdw_intel_res *res = cdata;
 	struct acpi_device *adev;
+	acpi_status status;
+	u64 adr;
+
+	status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL, &adr);
+	if (ACPI_FAILURE(status))
+		return AE_OK; /* keep going */
 
 	if (acpi_bus_get_device(handle, &adev)) {
 		pr_err("%s: Couldn't find ACPI handle\n", __func__);
@@ -157,7 +163,18 @@ static acpi_status sdw_intel_acpi_cb(acpi_handle handle, u32 level,
 	}
 
 	res->handle = handle;
-	return AE_OK;
+
+	/*
+	 * On some Intel platforms, multiple children of the HDAS
+	 * device can be found, but only one of them is the SoundWire
+	 * controller. The SNDW device is always exposed with
+	 * Name(_ADR, 0x40000000) so filter accordingly
+	 */
+	if (adr != 0x40000000)
+		return AE_OK; /* keep going */
+
+	/* device found, stop namespace walk */
+	return AE_CTRL_TERMINATE;
 }
 
 /**
-- 
2.17.1