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[v5,8/9] i2c: atr: add static flag

Message ID 20250507121917.2364416-9-demonsingur@gmail.com
State New
Headers show
Series i2c: atr: allow usage of nested ATRs | expand

Commit Message

Cosmin Tanislav May 7, 2025, 12:19 p.m. UTC 
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 accomodate 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.

Signed-off-by: Cosmin Tanislav <demonsingur@gmail.com>
---
 drivers/i2c/i2c-atr.c   | 6 +++++-
 include/linux/i2c-atr.h | 7 +++++++
 2 files changed, 12 insertions(+), 1 deletion(-)
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Patch

diff --git a/drivers/i2c/i2c-atr.c b/drivers/i2c/i2c-atr.c
index 121cabbdb85d..76d70efdf190 100644
--- a/drivers/i2c/i2c-atr.c
+++ b/drivers/i2c/i2c-atr.c
@@ -341,12 +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;
@@ -545,7 +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) {
diff --git a/include/linux/i2c-atr.h b/include/linux/i2c-atr.h
index 5082f4dd0e23..5aaab1598084 100644
--- a/include/linux/i2c-atr.h
+++ b/include/linux/i2c-atr.h
@@ -20,8 +20,15 @@  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),
 };
 
 /**