Hi!
2022-05-18 at 22:41, Eddie James wrote:
> 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);
> +
Have you actually tested this_ Because it is not handling your issue
AFAICT. The master_xfer for muxes include the select/deselect which
(potentially) does xfers on the parent bus, so your hook is in the
wrong place when a I2C mux is involved.
Also, the hook should probably trigger for SMBus xfers.
Cheers,
Peter
> 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 */
