[PATCH v2 8/9] i2c: atr: add static flag

Cosmin Tanislav
2025-02-25T11:39:59Z

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

Add a new flag that prevents old mappings to be replaced or new mappings
to be created in the alias finding code paths.

Signed-off-by: Cosmin Tanislav <demonsingur@gmail.com>
---
drivers/i2c/i2c-atr.c | 16 ++++++++++++----
include/linux/i2c-atr.h | 20 +++++++++++++++++---
2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index d8748d71ae15..f7b853f55630 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/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_create_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_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_STATIC))
c2a = i2c_atr_replace_mapping_by_addr(chan, addr);

if (!c2a) {
@@ -702,8 +708,9 @@ static int i2c_atr_parse_alias_pool(struct i2c_atr *atr)
return ret;
}

-struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
- const struct i2c_atr_ops *ops, int max_adapters)
+struct i2c_atr *i2c_atr_new_flags(struct i2c_adapter *parent, struct device *dev,
+ 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;
@@ -752,7 +760,7 @@ struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,

return ERR_PTR(ret);
}
-EXPORT_SYMBOL_NS_GPL(i2c_atr_new, "I2C_ATR");
+EXPORT_SYMBOL_NS_GPL(i2c_atr_new_flags, "I2C_ATR");

void i2c_atr_delete(struct i2c_atr *atr)
{
diff --git a/include/linux/i2c-atr.h b/include/linux/i2c-atr.h
index 1c3a5bcd939f..2f79d0d9140f 100644
--- a/include/linux/i2c-atr.h
+++ b/include/linux/i2c-atr.h
@@ -18,6 +18,15 @@ struct device;
struct fwnode_handle;
struct i2c_atr;

+/**
+ * enum i2c_atr_flags - Flags for an I2C ATR driver
+ *
+ * @I2C_ATR_STATIC: ATR does not support dynamic mapping, use static mapping
+ */
+enum i2c_atr_flags {
+ I2C_ATR_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
@@ -60,11 +69,12 @@ struct i2c_atr_adap_desc {
};

/**
- * i2c_atr_new() - Allocate and initialize an I2C ATR helper.
+ * i2c_atr_new_flags() - Allocate and initialize an I2C ATR helper.
* @parent: The parent (upstream) adapter
* @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.
@@ -73,8 +83,12 @@ 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);
+struct i2c_atr *i2c_atr_new_flags(struct i2c_adapter *parent, struct device *dev,
+ const struct i2c_atr_ops *ops, int max_adapters,
+ u32 flags);
+
+#define i2c_atr_new(parent, dev, ops, max_adapters) \
+ i2c_atr_new_flags(parent, dev, ops, max_adapters, 0)

/**
* i2c_atr_delete - Delete an I2C ATR helper.
--
2.48.1