From: Maciej Strozek <mstrozek@opensource.cirrus.com>

Use a device property "cirrus,firmware-uid" to get the unique firmware
identifier instead of using ACPI _SUB.

There will not usually be a _SUB in Soundwire nodes. The ACPI can use a
_DSD section for custom properties.

There is also a need to support instantiating this driver using software
nodes. This is for systems where the CS35L56 is a back-end device and the
ACPI refers only to the front-end audio device - there will not be any ACPI
references to CS35L56.

Signed-off-by: Maciej Strozek <mstrozek@opensource.cirrus.com>
Signed-off-by: Richard Fitzgerald <rf@opensource.cirrus.com>
---
 sound/soc/codecs/cs35l56.c | 31 ++++++++++++++-----------------
 1 file changed, 14 insertions(+), 17 deletions(-)

diff --git a/sound/soc/codecs/cs35l56.c b/sound/soc/codecs/cs35l56.c
index 3a9ec8724cc1..1f4cee097119 100644
--- a/sound/soc/codecs/cs35l56.c
+++ b/sound/soc/codecs/cs35l56.c
@@ -5,7 +5,6 @@
 // Copyright (C) 2023 Cirrus Logic, Inc. and
 //                    Cirrus Logic International Semiconductor Ltd.
 
-#include <linux/acpi.h>
 #include <linux/completion.h>
 #include <linux/debugfs.h>
 #include <linux/delay.h>
@@ -1029,26 +1028,24 @@ static int cs35l56_dsp_init(struct cs35l56_private *cs35l56)
 	return 0;
 }
 
-static int cs35l56_acpi_get_name(struct cs35l56_private *cs35l56)
+static int cs35l56_get_firmware_uid(struct cs35l56_private *cs35l56)
 {
-	acpi_handle handle = ACPI_HANDLE(cs35l56->base.dev);
-	const char *sub;
+	const char *prop;
+	int ret;
 
-	/* If there is no ACPI_HANDLE, there is no ACPI for this system, return 0 */
-	if (!handle)
+	ret = device_property_read_string(cs35l56->base.dev, "cirrus,firmware-uid",
+					  &prop);
+	/*
+	 * If bad sw node property, return 0 and fallback to legacy firmware path
+	 */
+	if (ret < 0)
 		return 0;
 
-	sub = acpi_get_subsystem_id(handle);
-	if (IS_ERR(sub)) {
-		/* If bad ACPI, return 0 and fallback to legacy firmware path, otherwise fail */
-		if (PTR_ERR(sub) == -ENODATA)
-			return 0;
-		else
-			return PTR_ERR(sub);
-	}
+	cs35l56->dsp.system_name = kstrdup(prop, GFP_KERNEL);
+	if (cs35l56->dsp.system_name == NULL)
+		return -ENOMEM;
 
-	cs35l56->dsp.system_name = sub;
-	dev_dbg(cs35l56->base.dev, "Subsystem ID: %s\n", cs35l56->dsp.system_name);
+	dev_dbg(cs35l56->base.dev, "Firmware UID: %s\n", cs35l56->dsp.system_name);
 
 	return 0;
 }
@@ -1095,7 +1092,7 @@ int cs35l56_common_probe(struct cs35l56_private *cs35l56)
 		gpiod_set_value_cansleep(cs35l56->base.reset_gpio, 1);
 	}
 
-	ret = cs35l56_acpi_get_name(cs35l56);
+	ret = cs35l56_get_firmware_uid(cs35l56);
 	if (ret != 0)
 		goto err;
 
-- 
2.30.2

On Wed, Aug 16, 2023 at 05:49:06PM +0100, Richard Fitzgerald wrote:
> From: Maciej Strozek <mstrozek@opensource.cirrus.com>
> 
> Use a device property "cirrus,firmware-uid" to get the unique firmware
> identifier instead of using ACPI _SUB.
> 
> There will not usually be a _SUB in Soundwire nodes. The ACPI can use a
> _DSD section for custom properties.
> 
> There is also a need to support instantiating this driver using software
> nodes. This is for systems where the CS35L56 is a back-end device and the
> ACPI refers only to the front-end audio device - there will not be any ACPI
> references to CS35L56.

Are there any existing systems (or might there be given that the driver
is in released kernels already) which rely on _SUB?

On 16/8/23 18:03, Mark Brown wrote:
> On Wed, Aug 16, 2023 at 05:49:06PM +0100, Richard Fitzgerald wrote:
>> From: Maciej Strozek <mstrozek@opensource.cirrus.com>
>>
>> Use a device property "cirrus,firmware-uid" to get the unique firmware
>> identifier instead of using ACPI _SUB.
>>
>> There will not usually be a _SUB in Soundwire nodes. The ACPI can use a
>> _DSD section for custom properties.
>>
>> There is also a need to support instantiating this driver using software
>> nodes. This is for systems where the CS35L56 is a back-end device and the
>> ACPI refers only to the front-end audio device - there will not be any ACPI
>> references to CS35L56.
> 
> Are there any existing systems (or might there be given that the driver
> is in released kernels already) which rely on _SUB?

No. Nothing has been released with CS35L56.

On Wed, Aug 16, 2023 at 06:09:52PM +0100, Richard Fitzgerald wrote:
> On 16/8/23 18:03, Mark Brown wrote:
> > On Wed, Aug 16, 2023 at 05:49:06PM +0100, Richard Fitzgerald wrote:

> > > There is also a need to support instantiating this driver using software
> > > nodes. This is for systems where the CS35L56 is a back-end device and the
> > > ACPI refers only to the front-end audio device - there will not be any ACPI
> > > references to CS35L56.

> > Are there any existing systems (or might there be given that the driver
> > is in released kernels already) which rely on _SUB?

> No. Nothing has been released with CS35L56.

And nobody's going to pick up a kernel with the old binding when they're
putting together a product?  If we're going to make this change it
should be sent as a fix in order to minimise the risk of that happening
but this patch doesn't apply against for-6.5, could you rebase please?