i2c: smbus: add core function handling SMBus host-notify

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@st.com>
Reviewed-by: Pierre-Yves MORDRET <pierre-yves.mordret@st.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/i2c-smbus.c b/drivers/i2c/i2c-smbus.c
index dc01082..d3d06e3 100644 (file)
--- 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 1e4e0de..1ef4218 100644 (file)
--- 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);