i2c: atr: add static flag

Some I2C ATRs do not support dynamic remapping, only static mapping
of direct children.

Mappings will only be added or removed as a result of devices being
added or removed from a child bus.

The ATR pool will have to be big enough to accommodate all devices
expected to be added to the child buses.

Add a new flag that prevents old mappings to be replaced or new mappings
to be created in the alias finding code paths. That mens adding a flags
parameter to i2c_atr_new() and an i2c_atr_flags enum.

Signed-off-by: Cosmin Tanislav <demonsingur@gmail.com>
Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Reviewed-by: Romain Gantois <romain.gantois@bootlin.com>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>

Author: Demon000

drivers/i2c/i2c-atr.c

@@ -106,6 +106,7 @@ struct i2c_atr_chan {
  * @lock:      Lock for the I2C bus segment (see &struct i2c_lock_operations)
  * @lock_key:  Lock key for @lock
  * @max_adapters: Maximum number of adapters this I2C ATR can have
+ * @flags:     Flags for ATR
  * @alias_pool: Optional common pool of available client aliases
  * @i2c_nb:    Notifier for remote client add & del events
  * @adapter:   Array of adapters
@@ -122,6 +123,7 @@ struct i2c_atr {
 	struct mutex lock;
 	struct lock_class_key lock_key;
 	int max_adapters;
+	u32 flags;
 
 	struct i2c_atr_alias_pool *alias_pool;
 
@@ -339,12 +341,16 @@ i2c_atr_replace_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr)
 static struct i2c_atr_alias_pair *
 i2c_atr_get_mapping_by_addr(struct i2c_atr_chan *chan, u16 addr)
 {
+	struct i2c_atr *atr = chan->atr;
 	struct i2c_atr_alias_pair *c2a;
 
 	c2a = i2c_atr_find_mapping_by_addr(chan, addr);
 	if (c2a)
 		return c2a;
 
+	if (atr->flags & I2C_ATR_F_STATIC)
+		return NULL;
+
 	c2a = i2c_atr_create_mapping_by_addr(chan, addr);
 	if (c2a)
 		return c2a;
@@ -543,7 +549,7 @@ static int i2c_atr_attach_addr(struct i2c_adapter *adapter,
 	mutex_lock(&chan->alias_pairs_lock);
 
 	c2a = i2c_atr_create_mapping_by_addr(chan, addr);
-	if (!c2a)
+	if (!c2a && !(atr->flags & I2C_ATR_F_STATIC))
 		c2a = i2c_atr_replace_mapping_by_addr(chan, addr);
 
 	if (!c2a) {
@@ -703,7 +709,8 @@ static int i2c_atr_parse_alias_pool(struct i2c_atr *atr)
 }
 
 struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
-			    const struct i2c_atr_ops *ops, int max_adapters)
+			    const struct i2c_atr_ops *ops, int max_adapters,
+			    u32 flags)
 {
 	struct i2c_atr *atr;
 	int ret;
@@ -725,6 +732,7 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
 	atr->dev = dev;
 	atr->ops = ops;
 	atr->max_adapters = max_adapters;
+	atr->flags = flags;
 
 	if (parent->algo->master_xfer)
 		atr->algo.master_xfer = i2c_atr_master_xfer;

drivers/media/i2c/ds90ub960.c

@@ -1122,7 +1122,7 @@ static int ub960_init_atr(struct ub960_data *priv)
 	struct i2c_adapter *parent_adap = priv->client->adapter;
 
 	priv->atr = i2c_atr_new(parent_adap, dev, &ub960_atr_ops,
-				priv->hw_data->num_rxports);
+				priv->hw_data->num_rxports, 0);
 	if (IS_ERR(priv->atr))
 		return PTR_ERR(priv->atr);
 

drivers/misc/ti_fpc202.c

@@ -349,7 +349,7 @@ static int fpc202_probe(struct i2c_client *client)
 		goto disable_gpio;
 	}
 
-	priv->atr = i2c_atr_new(client->adapter, dev, &fpc202_atr_ops, 2);
+	priv->atr = i2c_atr_new(client->adapter, dev, &fpc202_atr_ops, 2, 0);
 	if (IS_ERR(priv->atr)) {
 		ret = PTR_ERR(priv->atr);
 		dev_err(dev, "failed to create i2c atr err %d\n", ret);

include/linux/i2c-atr.h

@@ -18,6 +18,19 @@ struct device;
 struct fwnode_handle;
 struct i2c_atr;
 
+/**
+ * enum i2c_atr_flags - Flags for an I2C ATR driver
+ *
+ * @I2C_ATR_F_STATIC: ATR does not support dynamic mapping, use static mapping.
+ *                    Mappings will only be added or removed as a result of
+ *                    devices being added or removed from a child bus.
+ *                    The ATR pool will have to be big enough to accomodate all
+ *                    devices expected to be added to the child buses.
+ */
+enum i2c_atr_flags {
+	I2C_ATR_F_STATIC = BIT(0),
+};
+
 /**
  * struct i2c_atr_ops - Callbacks from ATR to the device driver.
  * @attach_addr: Notify the driver of a new device connected on a child
@@ -65,6 +78,7 @@ struct i2c_atr_adap_desc {
  * @dev:          The device acting as an ATR
  * @ops:          Driver-specific callbacks
  * @max_adapters: Maximum number of child adapters
+ * @flags:        Flags for ATR
  *
  * The new ATR helper is connected to the parent adapter but has no child
  * adapters. Call i2c_atr_add_adapter() to add some.
@@ -74,7 +88,8 @@ struct i2c_atr_adap_desc {
  * Return: pointer to the new ATR helper object, or ERR_PTR
  */
 struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
-			    const struct i2c_atr_ops *ops, int max_adapters);
+			    const struct i2c_atr_ops *ops, int max_adapters,
+			    u32 flags);
 
 /**
  * i2c_atr_delete - Delete an I2C ATR helper.