[PATCH v3 1/2] i2c: smbus: add core function handling SMBus host-notify

[Pierre Yves MORDRET]

Hi Alain

Look good for me

Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret at st.com>

Best Regards

On 8/3/20 7:17 AM, Alain Volmat wrote:
> SMBus Host-Notify protocol, from the adapter point of view
> consist of receiving a message from a client, including the
> client address and some other data.
> 
> It can be simply handled by creating a new slave device
> and registering a callback performing the parsing of the
> message received from the client.
> 
> This commit introduces two new core functions
>   * i2c_new_slave_host_notify_device
>   * i2c_free_slave_host_notify_device
> that take care of registration of the new slave device and
> callback and will call i2c_handle_smbus_host_notify once a
> Host-Notify event is received.
> 
> Signed-off-by: Alain Volmat <alain.volmat at st.com>
> ---
>  v3: move smbus host-notify slave code into i2c-smbus.c file
>      rework slave callback index handling
>      add sanity check in slave free function
>  v2: identical to v1
>  drivers/i2c/i2c-smbus.c   | 107 ++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/i2c-smbus.h |  12 ++++++
>  2 files changed, 119 insertions(+)
> 
> diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
> index dc0108287ccf..d3d06e3b4f3b 100644
> --- a/drivers/i2c/i2c-smbus.c
> +++ b/drivers/i2c/i2c-smbus.c
> @@ -197,6 +197,113 @@ EXPORT_SYMBOL_GPL(i2c_handle_smbus_alert);
>  
>  module_i2c_driver(smbalert_driver);
>  
> +#if IS_ENABLED(CONFIG_I2C_SLAVE)
> +#define SMBUS_HOST_NOTIFY_LEN	3
> +struct i2c_slave_host_notify_status {
> +	u8 index;
> +	u8 addr;
> +};
> +
> +static int i2c_slave_host_notify_cb(struct i2c_client *client,
> +				    enum i2c_slave_event event, u8 *val)
> +{
> +	struct i2c_slave_host_notify_status *status = client->dev.platform_data;
> +
> +	switch (event) {
> +	case I2C_SLAVE_WRITE_RECEIVED:
> +		/* We only retrieve the first byte received (addr)
> +		 * since there is currently no support to retrieve the data
> +		 * parameter from the client.
> +		 */
> +		if (status->index == 0)
> +			status->addr = *val;
> +		if (status->index < U8_MAX)
> +			status->index++;
> +		break;
> +	case I2C_SLAVE_STOP:
> +		if (status->index == SMBUS_HOST_NOTIFY_LEN)
> +			i2c_handle_smbus_host_notify(client->adapter,
> +						     status->addr);
> +		fallthrough;
> +	case I2C_SLAVE_WRITE_REQUESTED:
> +		status->index = 0;
> +		break;
> +	case I2C_SLAVE_READ_REQUESTED:
> +	case I2C_SLAVE_READ_PROCESSED:
> +		*val = 0xff;
> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * i2c_new_slave_host_notify_device - get a client for SMBus host-notify support
> + * @adapter: the target adapter
> + * Context: can sleep
> + *
> + * Setup handling of the SMBus host-notify protocol on a given I2C bus segment.
> + *
> + * Handling is done by creating a device and its callback and handling data
> + * received via the SMBus host-notify address (0x8)
> + *
> + * This returns the client, which should be ultimately freed using
> + * i2c_free_slave_host_notify_device(); or an ERRPTR to indicate an error.
> + */
> +struct i2c_client *i2c_new_slave_host_notify_device(struct i2c_adapter *adapter)
> +{
> +	struct i2c_board_info host_notify_board_info = {
> +		I2C_BOARD_INFO("smbus_host_notify", 0x08),
> +		.flags  = I2C_CLIENT_SLAVE,
> +	};
> +	struct i2c_slave_host_notify_status *status;
> +	struct i2c_client *client;
> +	int ret;
> +
> +	status = kzalloc(sizeof(struct i2c_slave_host_notify_status),
> +			 GFP_KERNEL);
> +	if (!status)
> +		return ERR_PTR(-ENOMEM);
> +
> +	host_notify_board_info.platform_data = status;
> +
> +	client = i2c_new_client_device(adapter, &host_notify_board_info);
> +	if (IS_ERR(client)) {
> +		kfree(status);
> +		return client;
> +	}
> +
> +	ret = i2c_slave_register(client, i2c_slave_host_notify_cb);
> +	if (ret) {
> +		i2c_unregister_device(client);
> +		kfree(status);
> +		return ERR_PTR(ret);
> +	}
> +
> +	return client;
> +}
> +EXPORT_SYMBOL_GPL(i2c_new_slave_host_notify_device);
> +
> +/**
> + * i2c_free_slave_host_notify_device - free the client for SMBus host-notify
> + * support
> + * @client: the client to free
> + * Context: can sleep
> + *
> + * Free the i2c_client allocated via i2c_new_slave_host_notify_device
> + */
> +void i2c_free_slave_host_notify_device(struct i2c_client *client)
> +{
> +	if (IS_ERR_OR_NULL(client))
> +		return;
> +
> +	i2c_slave_unregister(client);
> +	kfree(client->dev.platform_data);
> +	i2c_unregister_device(client);
> +}
> +EXPORT_SYMBOL_GPL(i2c_free_slave_host_notify_device);
> +#endif
> +
>  /*
>   * SPD is not part of SMBus but we include it here for convenience as the
>   * target systems are the same.
> diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
> index 1e4e0de4ef8b..1ef421818d3a 100644
> --- a/include/linux/i2c-smbus.h
> +++ b/include/linux/i2c-smbus.h
> @@ -38,6 +38,18 @@ static inline int of_i2c_setup_smbus_alert(struct i2c_adapter *adap)
>  	return 0;
>  }
>  #endif
> +#if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_I2C_SLAVE)
> +struct i2c_client *i2c_new_slave_host_notify_device(struct i2c_adapter *adapter);
> +void i2c_free_slave_host_notify_device(struct i2c_client *client);
> +#else
> +static inline struct i2c_client *i2c_new_slave_host_notify_device(struct i2c_adapter *adapter)
> +{
> +	return ERR_PTR(-ENOSYS);
> +}
> +static inline void i2c_free_slave_host_notify_device(struct i2c_client *client)
> +{
> +}
> +#endif
>  
>  #if IS_ENABLED(CONFIG_I2C_SMBUS) && IS_ENABLED(CONFIG_DMI)
>  void i2c_register_spd(struct i2c_adapter *adap);
>