| Message ID | 20220518204119.38943-2-eajames@linux.ibm.com |
|---|---|
| State | New |
| Headers | show |
| Series | i2c: core and si7020: Add adapter transfer callback | expand |
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@linux.ibm.com> > --- > 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 */
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 */
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@linux.ibm.com> --- drivers/i2c/i2c-core-base.c | 3 +++ include/linux/i2c.h | 25 +++++++++++++++++++++++++ 2 files changed, 28 insertions(+)