[PATCH 1/4] i2c: smbus: add core function handling SMBus host-notify

Alain Volmat
2020-05-05T05:52:54Z

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_smbus_host_notify_device
* i2c_free_smbus_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@st.com>
---
drivers/i2c/i2c-core-smbus.c | 105 +++++++++++++++++++++++++++++++++++
include/linux/i2c-smbus.h | 2 +
2 files changed, 107 insertions(+)

diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c
index b34d2ff06931..0c7e135c73e1 100644
--- a/drivers/i2c/i2c-core-smbus.c
+++ b/drivers/i2c/i2c-core-smbus.c
@@ -708,3 +708,108 @@ int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter)
}
EXPORT_SYMBOL_GPL(of_i2c_setup_smbus_alert);
#endif
+
+struct i2c_smbus_host_notify_status {
+ bool notify_start;
+ u8 addr;
+};
+
+static int i2c_smbus_host_notify_cb(struct i2c_client *client,
+ enum i2c_slave_event event, u8 *val)
+{
+ struct i2c_smbus_host_notify_status *status = client->dev.platform_data;
+ int ret;
+
+ switch (event) {
+ case I2C_SLAVE_WRITE_REQUESTED:
+ status->notify_start = true;
+ break;
+ case I2C_SLAVE_WRITE_RECEIVED:
+ /* We only retrieve the first byte received (addr)
+ * since there is currently no way to retrieve the data
+ * parameter from the client.
+ */
+ if (!status->notify_start)
+ break;
+ status->addr = *val;
+ status->notify_start = false;
+ break;
+ case I2C_SLAVE_STOP:
+ ret = i2c_handle_smbus_host_notify(client->adapter,
+ status->addr);
+ if (ret < 0) {
+ dev_warn(&client->adapter->dev, "failed to handle host_notify (%d)\n",
+ ret);
+ return ret;
+ }
+ break;
+ default:
+ /* Only handle necessary events */
+ break;
+ }
+
+ return 0;
+}
+
+/**
+ * i2c_new_smbus_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_smbus_host_notify_device(); or an ERRPTR to indicate an error.
+ */
+struct i2c_client *i2c_new_smbus_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_smbus_host_notify_status *status;
+ struct i2c_client *client;
+ int ret;
+
+ status = kzalloc(sizeof(struct i2c_smbus_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_smbus_host_notify_cb);
+ if (ret) {
+ i2c_unregister_device(client);
+ kfree(status);
+ return ERR_PTR(ret);
+ }
+
+ return client;
+}
+EXPORT_SYMBOL_GPL(i2c_new_smbus_host_notify_device);
+
+/**
+ * i2c_free_smbus_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_smbus_host_notify_device
+ */
+void i2c_free_smbus_host_notify_device(struct i2c_client *client)
+{
+ i2c_slave_unregister(client);
+ kfree(client->dev.platform_data);
+ i2c_unregister_device(client);
+}
+EXPORT_SYMBOL_GPL(i2c_free_smbus_host_notify_device);
diff --git a/include/linux/i2c-smbus.h b/include/linux/i2c-smbus.h
index 8c5459034f92..926f6d8ae30d 100644
--- a/include/linux/i2c-smbus.h
+++ b/include/linux/i2c-smbus.h
@@ -38,5 +38,7 @@ static inline int of_i2c_setup_smbus_alert(struct i2c_adapter *adap)
return 0;
}
#endif
+struct i2c_client *i2c_new_smbus_host_notify_device(struct i2c_adapter *adapter);
+void i2c_free_smbus_host_notify_device(struct i2c_client *client);

#endif /* _LINUX_I2C_SMBUS_H */
--
2.17.1