[PATCH 08/16] i2c: core: Introduce i2c_get_adapter_supplier()

Herve Codina
2025-04-07T14:56:23Z

The supplier device of an I2C adapter is the device that calls
i2c_add_adapter() or variants and i2c_del_adapter().

Most of the time this supplier device is the parent of the adapter dev.

Exceptions exist with i2c muxes. Indeed, in case of i2c muxes, the
parent of the adapter dev points to the adapter dev the mux is connected
to instead of the supplier of this adapter.

Introduce i2c_get_adapter_supplier() and a new supplier field in the
adapter structure in order to ease the adapter supplier retrieval.

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
---
drivers/i2c/i2c-core-base.c | 16 ++++++++++++++++
include/linux/i2c.h | 3 +++
2 files changed, 19 insertions(+)

diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index 7ad1ad5c8c3f..e3eeac0b2b49 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -1917,6 +1917,22 @@ struct i2c_adapter *i2c_get_adapter_by_fwnode(struct fwnode_handle *fwnode)
}
EXPORT_SYMBOL(i2c_get_adapter_by_fwnode);

+/**
+ * i2c_get_adapter_supplier() - Get the supplier of an adapter
+ * @adapter: the adapter to get the supplier from
+ *
+ * return:
+ * Look up and return the &struct device corresponding to the device supplying
+ * this adapter.
+ *
+ * The user must call put_device() once done with the supplier returned.
+ */
+struct device *i2c_get_adapter_supplier(struct i2c_adapter *adapter)
+{
+ return get_device(adapter->supplier ?: adapter->dev.parent);
+}
+EXPORT_SYMBOL(i2c_get_adapter_supplier);
+
static void i2c_parse_timing(struct device *dev, char *prop_name, u32 *cur_val_p,
u32 def_val, bool use_def)
{
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index 2e4903b7f7bc..04b85703bcd6 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -746,6 +746,7 @@ struct i2c_adapter {
int timeout; /* in jiffies */
int retries;
struct device dev; /* the adapter device */
+ struct device *supplier; /* the device that supply this adapter */
unsigned long locked_flags; /* owned by the I2C core */
#define I2C_ALF_IS_SUSPENDED 0
#define I2C_ALF_SUSPEND_REPORTED 1
@@ -913,6 +914,8 @@ struct i2c_adapter *i2c_get_adapter(int nr);
void i2c_put_adapter(struct i2c_adapter *adap);
unsigned int i2c_adapter_depth(struct i2c_adapter *adapter);

+struct device *i2c_get_adapter_supplier(struct i2c_adapter *adap);
+
void i2c_parse_fw_timings(struct device *dev, struct i2c_timings *t, bool use_defaults);

/* Return the functionality mask */
--
2.49.0