i2c: core changes for slave support

Finally(!), make Linux support being an I2C slave. Most of the existing
infrastructure is reused. We mainly add i2c_slave_register/unregister()
calls which tells i2c bus drivers to activate the slave mode. Then, they
also get a callback to report slave events to.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

2 files changed, 78 insertions, 0 deletions

diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index 3105bd273f70..c09d06bf4d9b 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -24,6 +24,7 @@
    (c) 2013  Wolfram Sang <wsa@the-dreams.de>
    I2C ACPI code Copyright (C) 2014 Intel Corp
    Author: Lan Tianyu <tianyu.lan@intel.com>
+   I2C slave support (c) 2014 by Wolfram Sang <wsa@sang-engineering.com>
  */
 
 #include <linux/module.h>
@@ -2911,6 +2912,54 @@ trace:
 }
 EXPORT_SYMBOL(i2c_smbus_xfer);
 
+int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb)
+{
+        int ret;
+
+        if (!client || !slave_cb)
+                return -EINVAL;
+
+        if (!(client->flags & I2C_CLIENT_TEN)) {
+                /* Enforce stricter address checking */
+                ret = i2c_check_addr_validity(client->addr);
+                if (ret)
+                        return ret;
+        }
+
+        if (!client->adapter->algo->reg_slave)
+                return -EOPNOTSUPP;
+
+        client->slave_cb = slave_cb;
+
+        i2c_lock_adapter(client->adapter);
+        ret = client->adapter->algo->reg_slave(client);
+        i2c_unlock_adapter(client->adapter);
+
+        if (ret)
+                client->slave_cb = NULL;
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(i2c_slave_register);
+
+int i2c_slave_unregister(struct i2c_client *client)
+{
+        int ret;
+
+        if (!client->adapter->algo->unreg_slave)
+                return -EOPNOTSUPP;
+
+        i2c_lock_adapter(client->adapter);
+        ret = client->adapter->algo->unreg_slave(client);
+        i2c_unlock_adapter(client->adapter);
+
+        if (ret == 0)
+                client->slave_cb = NULL;
+
+        return ret;
+}
+EXPORT_SYMBOL_GPL(i2c_slave_unregister);
+
 MODULE_AUTHOR("Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 MODULE_DESCRIPTION("I2C-Bus main module");
 MODULE_LICENSE("GPL");
diff --git a/include/linux/i2c.h b/include/linux/i2c.h
index b556e0ab946f..a720d9921b47 100644
--- a/include/linux/i2c.h
+++ b/include/linux/i2c.h
@@ -46,6 +46,8 @@ struct i2c_client;
 struct i2c_driver;
 union i2c_smbus_data;
 struct i2c_board_info;
+enum i2c_slave_event;
+typedef int (*i2c_slave_cb_t)(struct i2c_client *, enum i2c_slave_event, u8 *);
 
 struct module;
 
@@ -209,6 +211,8 @@ struct i2c_driver {
  * @irq: indicates the IRQ generated by this device (if any)
  * @detected: member of an i2c_driver.clients list or i2c-core's
  *      userspace_devices list
+ * @slave_cb: Callback when I2C slave mode of an adapter is used. The adapter
+ *      calls it to pass on slave events to the slave driver.
  *
  * An i2c_client identifies a single device (i.e. chip) connected to an
  * i2c bus. The behaviour exposed to Linux is defined by the driver
@@ -224,6 +228,7 @@ struct i2c_client {
         struct device dev;              /* the device structure         */
         int irq;                        /* irq issued by device         */
         struct list_head detected;
+        i2c_slave_cb_t slave_cb;        /* callback for slave mode      */
 };
 #define to_i2c_client(d) container_of(d, struct i2c_client, dev)
 
@@ -246,6 +251,25 @@ static inline void i2c_set_clientdata(struct i2c_client *dev, void *data)
         dev_set_drvdata(&dev->dev, data);
 }
 
+/* I2C slave support */
+
+enum i2c_slave_event {
+        I2C_SLAVE_REQ_READ_START,
+        I2C_SLAVE_REQ_READ_END,
+        I2C_SLAVE_REQ_WRITE_START,
+        I2C_SLAVE_REQ_WRITE_END,
+        I2C_SLAVE_STOP,
+};
+
+extern int i2c_slave_register(struct i2c_client *client, i2c_slave_cb_t slave_cb);
+extern int i2c_slave_unregister(struct i2c_client *client);
+
+static inline int i2c_slave_event(struct i2c_client *client,
+                                  enum i2c_slave_event event, u8 *val)
+{
+        return client->slave_cb(client, event, val);
+}
+
 /**
  * struct i2c_board_info - template for device creation
  * @type: chip type, to initialize i2c_client.name
@@ -352,6 +376,8 @@ i2c_register_board_info(int busnum, struct i2c_board_info const *info,
  *   into I2C transfers instead.
  * @functionality: Return the flags that this algorithm/adapter pair supports
  *   from the I2C_FUNC_* flags.
+ * @reg_slave: Register given client to I2C slave mode of this adapter
+ * @unreg_slave: Unregister given client from I2C slave mode of this adapter
  *
  * The following structs are for those who like to implement new bus drivers:
  * i2c_algorithm is the interface to a class of hardware solutions which can
@@ -377,6 +403,9 @@ struct i2c_algorithm {
 
         /* To determine what the adapter supports */
         u32 (*functionality) (struct i2c_adapter *);
+
+        int (*reg_slave)(struct i2c_client *client);
+        int (*unreg_slave)(struct i2c_client *client);
 };
 
 /**