linux-kernel - [PATCH v2 2/2] ASoC: cs35l41: Fallback to reading Subsystem ID property if not ACPI

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Message-ID: <20250912154759.279661-3-sbinding@opensource.cirrus.com>
Date: Fri, 12 Sep 2025 16:47:45 +0100
From: Stefan Binding <sbinding@...nsource.cirrus.com>
To: Mark Brown <broonie@...nel.org>, Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
Cc: linux-sound@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, patches@...nsource.cirrus.com,
        Stefan Binding <sbinding@...nsource.cirrus.com>
Subject: [PATCH v2 2/2] ASoC: cs35l41: Fallback to reading Subsystem ID property if not ACPI

If ACPI is not used, then there is currently no way of reading a
Subsystem ID property used for a system name to uniquely identify
the system in order to load the correct firmware and tuning.
Add a new property which can be read from device tree to be able to set
the system name.

Signed-off-by: Stefan Binding <sbinding@...nsource.cirrus.com>
---
 sound/soc/codecs/cs35l41.c | 77 ++++++++++++++++++++++----------------
 1 file changed, 44 insertions(+), 33 deletions(-)

diff --git a/sound/soc/codecs/cs35l41.c b/sound/soc/codecs/cs35l41.c
index 224d65987a8d..d7e3d89de652 100644
--- a/sound/soc/codecs/cs35l41.c
+++ b/sound/soc/codecs/cs35l41.c
@@ -7,6 +7,7 @@
 // Author: David Rhodes <david.rhodes@...rus.com>
 
 #include <linux/acpi.h>
+#include <acpi/acpi_bus.h>
 #include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/init.h>
@@ -1147,45 +1148,55 @@ static int cs35l41_dsp_init(struct cs35l41_private *cs35l41)
 	return ret;
 }
 
-#ifdef CONFIG_ACPI
-static int cs35l41_acpi_get_name(struct cs35l41_private *cs35l41)
+static int cs35l41_get_system_name(struct cs35l41_private *cs35l41)
 {
 	struct acpi_device *adev = ACPI_COMPANION(cs35l41->dev);
-	acpi_handle handle = acpi_device_handle(adev);
-	const char *hid;
-	const char *sub;
-
-	/* If there is no acpi_device, there is no ACPI for this system, return 0 */
-	if (!adev)
-		return 0;
+	const char *sub = NULL;
+	const char *tmp;
+	int ret = 0;
 
-	sub = acpi_get_subsystem_id(handle);
-	if (IS_ERR(sub)) {
-		/* If no _SUB, fallback to _HID, otherwise fail */
-		if (PTR_ERR(sub) == -ENODATA) {
-			hid = acpi_device_hid(adev);
-			/* If dummy hid, return 0 and fallback to legacy firmware path */
-			if (!strcmp(hid, "device"))
-				return 0;
-			sub = kstrdup(hid, GFP_KERNEL);
-			if (!sub)
-				sub = ERR_PTR(-ENOMEM);
-
-		} else
-			return PTR_ERR(sub);
+	/* If there is no acpi_device, there is no ACPI for this system, skip checking ACPI */
+	if (adev) {
+		acpi_handle handle = acpi_device_handle(adev);
+
+		sub = acpi_get_subsystem_id(handle);
+		ret = PTR_ERR(sub);
+		if (ret) {
+			sub = NULL;
+			/* If no _SUB, fallback to _HID, otherwise fail */
+			if (ret == -ENODATA) {
+				tmp = acpi_device_hid(adev);
+				/* If dummy hid, return 0 and fallback to legacy firmware path */
+				if (!strcmp(tmp, "device")) {
+					ret = 0;
+					goto err;
+				}
+				sub = kstrdup(tmp, GFP_KERNEL);
+				if (!sub) {
+					ret = -ENOMEM;
+					goto err;
+				}
+			}
+		}
+	} else {
+		if (!device_property_read_string(cs35l41->dev, "cirrus,subsystem-id", &tmp)) {
+			sub = kstrdup(tmp, GFP_KERNEL);
+			if (!sub) {
+				ret = -ENOMEM;
+				goto err;
+			}
+		}
 	}
 
-	cs35l41->dsp.system_name = sub;
-	dev_dbg(cs35l41->dev, "Subsystem ID: %s\n", cs35l41->dsp.system_name);
+err:
+	if (sub) {
+		cs35l41->dsp.system_name = sub;
+		dev_info(cs35l41->dev, "Subsystem ID: %s\n", cs35l41->dsp.system_name);
+	} else
+		dev_warn(cs35l41->dev, "Subsystem ID not found\n");
 
-	return 0;
-}
-#else
-static int cs35l41_acpi_get_name(struct cs35l41_private *cs35l41)
-{
-	return 0;
+	return ret;
 }
-#endif /* CONFIG_ACPI */
 
 int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *hw_cfg)
 {
@@ -1317,7 +1328,7 @@ int cs35l41_probe(struct cs35l41_private *cs35l41, const struct cs35l41_hw_cfg *
 		goto err;
 	}
 
-	ret = cs35l41_acpi_get_name(cs35l41);
+	ret = cs35l41_get_system_name(cs35l41);
 	if (ret < 0)
 		goto err;
 
-- 
2.43.0