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

Cosmin Tanislav
2025-05-07T12:19:37Z

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(-)

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),
};

/**
--
2.49.0