Add a callback function pointer to be executed after the adapter
performs a transfer. The purpose of such a callback is for a client
to execute some code while "owning" the bus entirely. Holding the
adapter lock is insufficient in the case where the client is behind a
mux, as the mux driver could perform mux selection operations on the
bus while locked.
Signed-off-by: Eddie James <eajames@xxxxxxxxxxxxx>
---
drivers/i2c/i2c-core-base.c | 3 +++
include/linux/i2c.h | 25 +++++++++++++++++++++++++
2 files changed, 28 insertions(+)
diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c
index d43db2c3876e..a46bfee2d845 100644
--- a/drivers/i2c/i2c-core-base.c
+++ b/drivers/i2c/i2c-core-base.c
@@ -2128,6 +2128,9 @@ int __i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
trace_i2c_result(adap, num, ret);
}
+ if (adap->xfer_callback)
+ adap->xfer_callback(adap->xfer_data, ret);
+
return ret;
}
EXPORT_SYMBOL(__i2c_transfer);
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index fbda5ada2afc..ea773f2ee9c8 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -747,6 +747,9 @@ struct i2c_adapter {
struct irq_domain *host_notify_domain;
struct regulator *bus_regulator;
+
+ void (*xfer_callback)(void *data, int xfer_rc);
+ void *xfer_data;
};
#define to_i2c_adapter(d) container_of(d, struct i2c_adapter, dev)
@@ -814,6 +817,7 @@ i2c_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
static inline void
i2c_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
{
+ adapter->xfer_callback = NULL;
adapter->lock_ops->unlock_bus(adapter, flags);
}
@@ -849,6 +853,27 @@ static inline void i2c_mark_adapter_resumed(struct i2c_adapter *adap)
i2c_unlock_bus(adap, I2C_LOCK_ROOT_ADAPTER);
}
+/**
+ * i2c_adapter_xfer_callback - Register a callback function that is executed
+ * when a transfer completes.
+ * @adap: Adapter to which the callback function will be registered
+ * @cb: The callback function pointer
+ * @data: The data to pass to the callback function
+ *
+ * This function should be called with the adapter locked with
+ * I2C_LOCK_ROOT_ADAPTER to ensure that the whole bus is idle while the
+ * callback executes.
+ * The callback is automatically removed when the bus is unlocked to avoid
+ * spurious executions of the callback.
+ */
+static inline void i2c_adapter_xfer_callback(struct i2c_adapter *adap,
+ void (*cb)(void *data, int rc),
+ void *data)
+{
+ adap->xfer_callback = cb;
+ adap->xfer_data = data;
+}
+
/* i2c adapter classes (bitmask) */
#define I2C_CLASS_HWMON (1<<0) /* lm_sensors, ... */
#define I2C_CLASS_DDC (1<<3) /* DDC bus on graphics adapters */
--
2.27.0
