[PATCH 1/9] platform/x86: lenovo-wmi-capdata: Only allocate sub-master info when necessary

[Rong Zhang]

When capdata00 declares no fan test support, there is no need to
allocate sub-master info as it's basically unused except for the
priv->sub_master->sub_component_list == ERR_PTR(-ENODEV) placeholder.

Therefore, only allocate priv->sub_master when necessary, otherwise its
absence implies the absence of sub-component. With that,
PTR_ERR(sub_component_list) == -ENODEV is repurposed for the following
changes to represent stubbed sub-component.

Signed-off-by: Rong Zhang <i@xxxxxxxx>
---
 drivers/platform/x86/lenovo/wmi-capdata.c | 36 ++++++++++++++++++-------------
 1 file changed, 21 insertions(+), 15 deletions(-)

diff --git a/drivers/platform/x86/lenovo/wmi-capdata.c b/drivers/platform/x86/lenovo/wmi-capdata.c
index d5e961566136..c9e4380a70d2 100644
--- a/drivers/platform/x86/lenovo/wmi-capdata.c
+++ b/drivers/platform/x86/lenovo/wmi-capdata.c
@@ -101,9 +101,11 @@ struct lwmi_cd_priv {
 	struct lwmi_cd_sub_master_priv {
 		struct device *master_dev;
 		cd_list_cb_t master_cb;
-		struct cd_list *sub_component_list; /* ERR_PTR(-ENODEV) implies no sub-component. */
+		struct cd_list *sub_component_list; /* ERR_PTR(-ENODEV) implies stubbed
+						     * sub-component.
+						     */
 		bool registered;                    /* Has the sub-master been registered? */
-	} *sub_master;
+	} *sub_master;                              /* NULL implies no sub-component. */
 };
 
 struct cd_list {
@@ -258,6 +260,12 @@ static int lwmi_cd_component_bind(struct device *cd_dev,
 	case LENOVO_CAPABILITY_DATA_00:
 		binder->cd00_list = priv->list;
 
+		/* Missing sub-master info implies missing sub-component. */
+		if (!priv->sub_master) {
+			binder->cd_fan_list_cb(om_dev, NULL);
+			break;
+		}
+
 		priv->sub_master->master_dev = om_dev;
 		priv->sub_master->master_cb = binder->cd_fan_list_cb;
 		lwmi_cd_call_master_cb(priv);
@@ -288,13 +296,9 @@ static void lwmi_cd_component_unbind(struct device *cd_dev,
 {
 	struct lwmi_cd_priv *priv = dev_get_drvdata(cd_dev);
 
-	switch (priv->list->type) {
-	case LENOVO_CAPABILITY_DATA_00:
+	if (priv->sub_master) {
 		priv->sub_master->master_dev = NULL;
 		priv->sub_master->master_cb = NULL;
-		return;
-	default:
-		return;
 	}
 }
 
@@ -369,17 +373,19 @@ static int lwmi_cd_sub_master_add(struct lwmi_cd_priv *priv,
 	struct component_match *master_match = NULL;
 	int ret;
 
+	/*
+	 * If the sub-master has no sub-component, there is no need to allocate
+	 * or register the sub-master. The master callback will be called with
+	 * NULL on master <-> sub-master bind to inform the master about the
+	 * absence of sub-component.
+	 */
+	if (sub_component_type == CD_TYPE_NONE)
+		return 0;
+
 	priv->sub_master = devm_kzalloc(&priv->wdev->dev, sizeof(*priv->sub_master), GFP_KERNEL);
 	if (!priv->sub_master)
 		return -ENOMEM;
 
-	if (sub_component_type == CD_TYPE_NONE) {
-		/* The master callback will be called with NULL on bind. */
-		priv->sub_master->sub_component_list = ERR_PTR(-ENODEV);
-		priv->sub_master->registered = false;
-		return 0;
-	}
-
 	/*
 	 * lwmi_cd_match() needs a pointer to enum lwmi_cd_type, but on-stack
 	 * data cannot be used here. Steal one from lwmi_cd_table.
@@ -404,7 +410,7 @@ static int lwmi_cd_sub_master_add(struct lwmi_cd_priv *priv,
  */
 static void lwmi_cd_sub_master_del(struct lwmi_cd_priv *priv)
 {
-	if (!priv->sub_master->registered)
+	if (!priv->sub_master || !priv->sub_master->registered)
 		return;
 
 	component_master_del(&priv->wdev->dev, &lwmi_cd_sub_master_ops);

-- 
2.55.0