[PATCH v4 3/8] ASoC: SDCA: expose class SoundWire probe/remove as library

[Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>]

Split the internal class_sdw_probe/class_sdw_remove functions into
caller-friendly library helpers:

  sdca_class_probe(sdw, drv)
  sdca_class_remove(drv)

The class_sdw_probe/class_sdw_remove callbacks of the built-in
class_sdw_driver are now thin wrappers that allocate a bare
sdca_class_drv, stash it in drvdata, and defer to the exported
helpers.

The exported sdca_class_probe() takes a caller-owned struct
sdca_class_drv * so codec-specific SoundWire drivers can embed the
class state in their own priv struct, own dev_set_drvdata() themselves,
and avoid a second allocation.  No functional change for the built-in
driver.

This lays the groundwork for codec-specific SDCA SoundWire drivers
that want to compose the class-side probe with their own quirks; the
next patches add the class_ops mechanism on top.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@oss.qualcomm.com>
---
 include/sound/sdca_class.h  |  4 +++
 sound/soc/sdca/sdca_class.c | 62 +++++++++++++++++++++++++++++++------
 2 files changed, 57 insertions(+), 9 deletions(-)

diff --git a/include/sound/sdca_class.h b/include/sound/sdca_class.h
index ce2ed5f33e7a..9e6b0eab8a0e 100644
--- a/include/sound/sdca_class.h
+++ b/include/sound/sdca_class.h
@@ -33,6 +33,10 @@ struct sdca_class_drv {
 	struct work_struct boot_work;
 };
 
+/* Library helpers used by codec-specific SDCA SoundWire drivers. */
+int sdca_class_probe(struct sdw_slave *sdw, struct sdca_class_drv *drv);
+void sdca_class_remove(struct sdca_class_drv *drv);
+
 /*
  * PM helpers.  Codec drivers embed sdca_class_drv in their own priv,
  * own dev_set_drvdata(), and compose these into their own dev_pm_ops:
diff --git a/sound/soc/sdca/sdca_class.c b/sound/soc/sdca/sdca_class.c
index a092ebaa620a..0e6dead41495 100644
--- a/sound/soc/sdca/sdca_class.c
+++ b/sound/soc/sdca/sdca_class.c
@@ -136,18 +136,31 @@ static void class_boot_work(struct work_struct *work)
 	pm_runtime_put_sync(drv->dev);
 }
 
-static int class_sdw_probe(struct sdw_slave *sdw, const struct sdw_device_id *id)
+/**
+ * sdca_class_probe - SDCA class SoundWire slave probe helper
+ * @sdw: SoundWire slave
+ * @drv: caller-allocated sdca_class_drv storage.  The caller (a codec
+ *       driver, or the built-in class_sdw_driver in this file) owns the
+ *       allocation and sets its own dev_set_drvdata() -- the framework
+ *       does not touch drvdata.  Typically embedded in the codec's own
+ *       priv struct so codec drivers can keep per-slave state.
+ *
+ * Codec-specific SoundWire drivers call this from their .probe after
+ * allocating a struct sdca_class_drv (usually embedded in their own
+ * priv) and setting drvdata to their priv.  The framework fills in the
+ * sdca_class_drv fields, sets up the class regmap, and queues the
+ * deferred boot work.
+ */
+int sdca_class_probe(struct sdw_slave *sdw, struct sdca_class_drv *drv)
 {
 	struct device *dev = &sdw->dev;
 	struct regmap_config *dev_config;
-	struct sdca_class_drv *drv;
 	int ret;
 
 	sdca_lookup_swft(sdw);
 
-	drv = devm_kzalloc(dev, sizeof(*drv), GFP_KERNEL);
 	if (!drv)
-		return -ENOMEM;
+		return -EINVAL;
 
 	dev_config = devm_kmemdup(dev, &class_dev_regmap_config,
 				  sizeof(*dev_config), GFP_KERNEL);
@@ -159,8 +172,6 @@ static int class_sdw_probe(struct sdw_slave *sdw, const struct sdw_device_id *id
 	mutex_init(&drv->regmap_lock);
 	mutex_init(&drv->init_lock);
 
-	dev_set_drvdata(drv->dev, drv);
-
 	INIT_WORK(&drv->boot_work, class_boot_work);
 
 	dev_config->lock_arg = &drv->regmap_lock;
@@ -185,14 +196,47 @@ static int class_sdw_probe(struct sdw_slave *sdw, const struct sdw_device_id *id
 
 	return 0;
 }
+EXPORT_SYMBOL_NS_GPL(sdca_class_probe, "SND_SOC_SDCA_CLASS");
 
-static void class_sdw_remove(struct sdw_slave *sdw)
+static int class_sdw_probe(struct sdw_slave *sdw, const struct sdw_device_id *id)
 {
-	struct device *dev = &sdw->dev;
-	struct sdca_class_drv *drv = dev_get_drvdata(dev);
+	struct sdca_class_drv *drv;
+
+	/*
+	 * Pure-generic SDCA parts: no codec priv to embed, so allocate a
+	 * bare sdca_class_drv here and stash it in drvdata for the
+	 * built-in PM ops to fetch.
+	 */
+	drv = devm_kzalloc(&sdw->dev, sizeof(*drv), GFP_KERNEL);
+	if (!drv)
+		return -ENOMEM;
 
+	dev_set_drvdata(&sdw->dev, drv);
+
+	return sdca_class_probe(sdw, drv);
+}
+
+/**
+ * sdca_class_remove - SDCA class SoundWire slave remove helper
+ * @drv: caller-owned sdca_class_drv (the one handed to sdca_class_probe()).
+ *
+ * Cancels the deferred boot work so devres can safely free @drv and the
+ * embedding codec priv without racing class_boot_work.  Codec-specific
+ * SoundWire drivers that call sdca_class_probe() must call this from
+ * their .remove with the same drv pointer they passed to probe.
+ */
+void sdca_class_remove(struct sdca_class_drv *drv)
+{
 	cancel_work_sync(&drv->boot_work);
 }
+EXPORT_SYMBOL_NS_GPL(sdca_class_remove, "SND_SOC_SDCA_CLASS");
+
+static void class_sdw_remove(struct sdw_slave *sdw)
+{
+	struct sdca_class_drv *drv = dev_get_drvdata(&sdw->dev);
+
+	sdca_class_remove(drv);
+}
 
 /**
  * sdca_class_system_suspend - SDCA class system suspend helper
-- 
2.53.0