[PATCH 15/26] ALSA: hda: cs35l41: Support reading subsystem id from ACPI

[Vitaly Rodionov <vitalyr@opensource.cirrus.com>]

From: Stefan Binding <sbinding@opensource.cirrus.com>

On some laptop models, the ACPI contains the unique
Subsystem ID, and this value should be preferred
over the value from the HDA driver.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>
Signed-off-by: Vitaly Rodionov <vitalyr@opensource.cirrus.com>
---
 sound/pci/hda/cs35l41_hda.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/sound/pci/hda/cs35l41_hda.c b/sound/pci/hda/cs35l41_hda.c
index c235b899aa04..81d6f4cf0166 100644
--- a/sound/pci/hda/cs35l41_hda.c
+++ b/sound/pci/hda/cs35l41_hda.c
@@ -533,6 +533,36 @@ static int cs35l41_hda_apply_properties(struct cs35l41_hda *cs35l41)
 	return cs35l41_hda_channel_map(cs35l41->dev, 0, NULL, 1, &hw_cfg->spk_pos);
 }
 
+static int cs35l41_get_acpi_sub_string(struct device *dev, struct acpi_device *adev,
+				       const char **subsysid)
+{
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *obj;
+	acpi_status status;
+	int ret = 0;
+
+	status = acpi_evaluate_object(adev->handle, "_SUB", NULL, &buffer);
+	if (ACPI_SUCCESS(status)) {
+		obj = buffer.pointer;
+		if (obj->type == ACPI_TYPE_STRING) {
+			*subsysid = devm_kstrdup(dev, obj->string.pointer, GFP_KERNEL);
+			if (*subsysid == NULL) {
+				dev_err(dev, "Cannot allocate Subsystem ID");
+				ret = -ENOMEM;
+			}
+		} else {
+			dev_warn(dev, "Warning ACPI _SUB did not return a string\n");
+			ret = -ENODEV;
+		}
+		acpi_os_free(buffer.pointer);
+	} else {
+		dev_dbg(dev, "Warning ACPI _SUB failed: %#x\n", status);
+		ret = -ENODEV;
+	}
+
+	return ret;
+}
+
 static int cs35l41_hda_read_acpi(struct cs35l41_hda *cs35l41, const char *hid, int id)
 {
 	struct cs35l41_hw_cfg *hw_cfg = &cs35l41->hw_cfg;
@@ -552,6 +582,12 @@ static int cs35l41_hda_read_acpi(struct cs35l41_hda *cs35l41, const char *hid, i
 	physdev = get_device(acpi_get_first_physical_node(adev));
 	acpi_dev_put(adev);
 
+	ret = cs35l41_get_acpi_sub_string(cs35l41->dev, adev, &cs35l41->acpi_subsystem_id);
+	if (ret)
+		dev_info(cs35l41->dev, "No Subsystem ID found in ACPI: %d", ret);
+	else
+		dev_dbg(cs35l41->dev, "Subsystem ID %s found", cs35l41->acpi_subsystem_id);
+
 	property = "cirrus,dev-index";
 	ret = device_property_count_u32(physdev, property);
 	if (ret <= 0)
-- 
2.32.0