soundwire: sysfs: cleanup the logic for creating the dp0 sysfs attributes

There's no need to special-case the dp0 sysfs attributes, the
is_visible() callback in the attribute group can handle that for us, so
add that and add it to the attribute group list making the logic simpler
overall.

This is a step on the way to moving all of the sysfs attribute handling
into the default driver core attribute group logic so that the soundwire
core does not have to do any of it manually.

Cc: Vinod Koul <[email protected]>
Cc: Bard Liao <[email protected]>
Cc: Pierre-Louis Bossart <[email protected]>
Cc: Sanyog Kale <[email protected]>
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Reviewed-by: Dan Williams <[email protected]>
Tested-By: Vijendar Mukunda <[email protected]>
Link: https://lore.kernel.org/r/2024013029-budget-mulled-5b34@gregkh
Signed-off-by: Vinod Koul <[email protected]>

Author: gregkh

drivers/soundwire/sysfs_slave.c

@@ -184,18 +184,40 @@ static struct attribute *dp0_attrs[] = {
 	NULL,
 };
 
+static umode_t dp0_attr_visible(struct kobject *kobj, struct attribute *attr,
+			      int n)
+{
+	struct sdw_slave *slave = dev_to_sdw_dev(kobj_to_dev(kobj));
+
+	if (slave->prop.dp0_prop)
+		return attr->mode;
+	return 0;
+}
+
+static bool dp0_group_visible(struct kobject *kobj)
+{
+	struct sdw_slave *slave = dev_to_sdw_dev(kobj_to_dev(kobj));
+
+	if (slave->prop.dp0_prop)
+		return true;
+	return false;
+}
+DEFINE_SYSFS_GROUP_VISIBLE(dp0);
+
 /*
  * we don't use ATTRIBUTES_GROUP here since we want to add a subdirectory
  * for dp0-level properties
  */
 static const struct attribute_group dp0_group = {
 	.attrs = dp0_attrs,
+	.is_visible = SYSFS_GROUP_VISIBLE(dp0),
 	.name = "dp0",
 };
 
 static const struct attribute_group *slave_groups[] = {
 	&slave_attr_group,
 	&sdw_slave_dev_attr_group,
+	&dp0_group,
 	NULL,
 };
 
@@ -207,12 +229,6 @@ int sdw_slave_sysfs_init(struct sdw_slave *slave)
 	if (ret < 0)
 		return ret;
 
-	if (slave->prop.dp0_prop) {
-		ret = devm_device_add_group(&slave->dev, &dp0_group);
-		if (ret < 0)
-			return ret;
-	}
-
 	if (slave->prop.source_ports || slave->prop.sink_ports) {
 		ret = sdw_slave_sysfs_dpn_init(slave);
 		if (ret < 0)