Merge branch 'i2c-for-linus' of git://jdelvare.pck.nerim.net/jdelvare-2.6
[pandora-kernel.git] / drivers / i2c / i2c-core.c
index d0175f4..0a79f76 100644 (file)
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/idr.h>
-#include <linux/seq_file.h>
 #include <linux/platform_device.h>
 #include <linux/mutex.h>
 #include <linux/completion.h>
 #include <linux/hardirq.h>
 #include <linux/irqflags.h>
-#include <linux/semaphore.h>
 #include <asm/uaccess.h>
 
 #include "i2c-core.h"
@@ -44,7 +42,9 @@
 static DEFINE_MUTEX(core_lock);
 static DEFINE_IDR(i2c_adapter_idr);
 
-#define is_newstyle_driver(d) ((d)->probe || (d)->remove)
+#define is_newstyle_driver(d) ((d)->probe || (d)->remove || (d)->detect)
+
+static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver);
 
 /* ------------------------------------------------------------------------- */
 
@@ -103,19 +103,14 @@ static int i2c_device_probe(struct device *dev)
 {
        struct i2c_client       *client = to_i2c_client(dev);
        struct i2c_driver       *driver = to_i2c_driver(dev->driver);
-       const struct i2c_device_id *id;
        int status;
 
-       if (!driver->probe)
+       if (!driver->probe || !driver->id_table)
                return -ENODEV;
        client->driver = driver;
        dev_dbg(dev, "probe\n");
 
-       if (driver->id_table)
-               id = i2c_match_id(driver->id_table, client);
-       else
-               id = NULL;
-       status = driver->probe(client, id);
+       status = driver->probe(client, i2c_match_id(driver->id_table, client));
        if (status)
                client->driver = NULL;
        return status;
@@ -208,7 +203,7 @@ static struct device_attribute i2c_dev_attrs[] = {
        { },
 };
 
-static struct bus_type i2c_bus_type = {
+struct bus_type i2c_bus_type = {
        .name           = "i2c",
        .dev_attrs      = i2c_dev_attrs,
        .match          = i2c_device_match,
@@ -219,6 +214,7 @@ static struct bus_type i2c_bus_type = {
        .suspend        = i2c_device_suspend,
        .resume         = i2c_device_resume,
 };
+EXPORT_SYMBOL_GPL(i2c_bus_type);
 
 
 /**
@@ -306,6 +302,14 @@ void i2c_unregister_device(struct i2c_client *client)
                return;
        }
 
+       if (adapter->client_unregister) {
+               if (adapter->client_unregister(client)) {
+                       dev_warn(&client->dev,
+                                "client_unregister [%s] failed\n",
+                                client->name);
+               }
+       }
+
        mutex_lock(&adapter->clist_lock);
        list_del(&client->list);
        mutex_unlock(&adapter->clist_lock);
@@ -416,6 +420,10 @@ static int i2c_do_add_adapter(struct device_driver *d, void *data)
        struct i2c_driver *driver = to_i2c_driver(d);
        struct i2c_adapter *adap = data;
 
+       /* Detect supported devices on that bus, and instantiate them */
+       i2c_detect(adap, driver);
+
+       /* Let legacy drivers scan this bus for matching devices */
        if (driver->attach_adapter) {
                /* We ignore the return code; if it fails, too bad */
                driver->attach_adapter(adap);
@@ -455,7 +463,7 @@ static int i2c_register_adapter(struct i2c_adapter *adap)
        if (adap->nr < __i2c_first_dynamic_bus_num)
                i2c_scan_static_board_info(adap);
 
-       /* let legacy drivers scan this bus for matching devices */
+       /* Notify drivers */
        dummy = bus_for_each_drv(&i2c_bus_type, NULL, adap,
                                 i2c_do_add_adapter);
 
@@ -561,8 +569,19 @@ static int i2c_do_del_adapter(struct device_driver *d, void *data)
 {
        struct i2c_driver *driver = to_i2c_driver(d);
        struct i2c_adapter *adapter = data;
+       struct i2c_client *client, *_n;
        int res;
 
+       /* Remove the devices we created ourselves */
+       list_for_each_entry_safe(client, _n, &driver->clients, detected) {
+               if (client->adapter == adapter) {
+                       dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
+                               client->name, client->addr);
+                       list_del(&client->detected);
+                       i2c_unregister_device(client);
+               }
+       }
+
        if (!driver->detach_adapter)
                return 0;
        res = driver->detach_adapter(adapter);
@@ -582,8 +601,7 @@ static int i2c_do_del_adapter(struct device_driver *d, void *data)
  */
 int i2c_del_adapter(struct i2c_adapter *adap)
 {
-       struct list_head  *item, *_n;
-       struct i2c_client *client;
+       struct i2c_client *client, *_n;
        int res = 0;
 
        mutex_lock(&core_lock);
@@ -604,10 +622,9 @@ int i2c_del_adapter(struct i2c_adapter *adap)
 
        /* detach any active clients. This must be done first, because
         * it can fail; in which case we give up. */
-       list_for_each_safe(item, _n, &adap->clients) {
+       list_for_each_entry_safe(client, _n, &adap->clients, list) {
                struct i2c_driver       *driver;
 
-               client = list_entry(item, struct i2c_client, list);
                driver = client->driver;
 
                /* new style, follow standard driver model */
@@ -646,6 +663,20 @@ EXPORT_SYMBOL(i2c_del_adapter);
 
 /* ------------------------------------------------------------------------- */
 
+static int __attach_adapter(struct device *dev, void *data)
+{
+       struct i2c_adapter *adapter = to_i2c_adapter(dev);
+       struct i2c_driver *driver = data;
+
+       i2c_detect(adapter, driver);
+
+       /* Legacy drivers scan i2c busses directly */
+       if (driver->attach_adapter)
+               driver->attach_adapter(adapter);
+
+       return 0;
+}
+
 /*
  * An i2c_driver is used with one or more i2c_client (device) nodes to access
  * i2c slave chips, on a bus instance associated with some i2c_adapter.  There
@@ -685,72 +716,70 @@ int i2c_register_driver(struct module *owner, struct i2c_driver *driver)
 
        pr_debug("i2c-core: driver [%s] registered\n", driver->driver.name);
 
-       /* legacy drivers scan i2c busses directly */
-       if (driver->attach_adapter) {
-               struct i2c_adapter *adapter;
-
-               down(&i2c_adapter_class.sem);
-               list_for_each_entry(adapter, &i2c_adapter_class.devices,
-                                   dev.node) {
-                       driver->attach_adapter(adapter);
-               }
-               up(&i2c_adapter_class.sem);
-       }
+       INIT_LIST_HEAD(&driver->clients);
+       /* Walk the adapters that are already present */
+       class_for_each_device(&i2c_adapter_class, driver, __attach_adapter);
 
        mutex_unlock(&core_lock);
        return 0;
 }
 EXPORT_SYMBOL(i2c_register_driver);
 
-/**
- * i2c_del_driver - unregister I2C driver
- * @driver: the driver being unregistered
- * Context: can sleep
- */
-void i2c_del_driver(struct i2c_driver *driver)
+static int __detach_adapter(struct device *dev, void *data)
 {
-       struct list_head   *item2, *_n;
-       struct i2c_client  *client;
-       struct i2c_adapter *adap;
+       struct i2c_adapter *adapter = to_i2c_adapter(dev);
+       struct i2c_driver *driver = data;
+       struct i2c_client *client, *_n;
 
-       mutex_lock(&core_lock);
+       list_for_each_entry_safe(client, _n, &driver->clients, detected) {
+               dev_dbg(&adapter->dev, "Removing %s at 0x%x\n",
+                       client->name, client->addr);
+               list_del(&client->detected);
+               i2c_unregister_device(client);
+       }
 
-       /* new-style driver? */
        if (is_newstyle_driver(driver))
-               goto unregister;
+               return 0;
 
        /* Have a look at each adapter, if clients of this driver are still
         * attached. If so, detach them to be able to kill the driver
         * afterwards.
         */
-       down(&i2c_adapter_class.sem);
-       list_for_each_entry(adap, &i2c_adapter_class.devices, dev.node) {
-               if (driver->detach_adapter) {
-                       if (driver->detach_adapter(adap)) {
-                               dev_err(&adap->dev, "detach_adapter failed "
-                                       "for driver [%s]\n",
-                                       driver->driver.name);
-                       }
-               } else {
-                       list_for_each_safe(item2, _n, &adap->clients) {
-                               client = list_entry(item2, struct i2c_client, list);
-                               if (client->driver != driver)
-                                       continue;
-                               dev_dbg(&adap->dev, "detaching client [%s] "
-                                       "at 0x%02x\n", client->name,
-                                       client->addr);
-                               if (driver->detach_client(client)) {
-                                       dev_err(&adap->dev, "detach_client "
-                                               "failed for client [%s] at "
-                                               "0x%02x\n", client->name,
-                                               client->addr);
-                               }
-                       }
+       if (driver->detach_adapter) {
+               if (driver->detach_adapter(adapter))
+                       dev_err(&adapter->dev,
+                               "detach_adapter failed for driver [%s]\n",
+                               driver->driver.name);
+       } else {
+               struct i2c_client *client, *_n;
+
+               list_for_each_entry_safe(client, _n, &adapter->clients, list) {
+                       if (client->driver != driver)
+                               continue;
+                       dev_dbg(&adapter->dev,
+                               "detaching client [%s] at 0x%02x\n",
+                               client->name, client->addr);
+                       if (driver->detach_client(client))
+                               dev_err(&adapter->dev, "detach_client "
+                                       "failed for client [%s] at 0x%02x\n",
+                                       client->name, client->addr);
                }
        }
-       up(&i2c_adapter_class.sem);
 
- unregister:
+       return 0;
+}
+
+/**
+ * i2c_del_driver - unregister I2C driver
+ * @driver: the driver being unregistered
+ * Context: can sleep
+ */
+void i2c_del_driver(struct i2c_driver *driver)
+{
+       mutex_lock(&core_lock);
+
+       class_for_each_device(&i2c_adapter_class, driver, __detach_adapter);
+
        driver_unregister(&driver->driver);
        pr_debug("i2c-core: driver [%s] unregistered\n", driver->driver.name);
 
@@ -863,8 +892,9 @@ EXPORT_SYMBOL(i2c_detach_client);
  */
 struct i2c_client *i2c_use_client(struct i2c_client *client)
 {
-       get_device(&client->dev);
-       return client;
+       if (client && get_device(&client->dev))
+               return client;
+       return NULL;
 }
 EXPORT_SYMBOL(i2c_use_client);
 
@@ -876,7 +906,8 @@ EXPORT_SYMBOL(i2c_use_client);
  */
 void i2c_release_client(struct i2c_client *client)
 {
-       put_device(&client->dev);
+       if (client)
+               put_device(&client->dev);
 }
 EXPORT_SYMBOL(i2c_release_client);
 
@@ -942,10 +973,39 @@ module_exit(i2c_exit);
  * ----------------------------------------------------
  */
 
+/**
+ * i2c_transfer - execute a single or combined I2C message
+ * @adap: Handle to I2C bus
+ * @msgs: One or more messages to execute before STOP is issued to
+ *     terminate the operation; each message begins with a START.
+ * @num: Number of messages to be executed.
+ *
+ * Returns negative errno, else the number of messages executed.
+ *
+ * Note that there is no requirement that each message be sent to
+ * the same slave address, although that is the most common model.
+ */
 int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
 {
        int ret;
 
+       /* REVISIT the fault reporting model here is weak:
+        *
+        *  - When we get an error after receiving N bytes from a slave,
+        *    there is no way to report "N".
+        *
+        *  - When we get a NAK after transmitting N bytes to a slave,
+        *    there is no way to report "N" ... or to let the master
+        *    continue executing the rest of this combined message, if
+        *    that's the appropriate response.
+        *
+        *  - When for example "num" is two and we successfully complete
+        *    the first message but get an error part way through the
+        *    second, it's unclear whether that should be reported as
+        *    one (discarding status on the second message) or errno
+        *    (discarding status on the first one).
+        */
+
        if (adap->algo->master_xfer) {
 #ifdef DEBUG
                for (ret = 0; ret < num; ret++) {
@@ -971,11 +1031,19 @@ int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
                return ret;
        } else {
                dev_dbg(&adap->dev, "I2C level transfers not supported\n");
-               return -ENOSYS;
+               return -EOPNOTSUPP;
        }
 }
 EXPORT_SYMBOL(i2c_transfer);
 
+/**
+ * i2c_master_send - issue a single I2C message in master transmit mode
+ * @client: Handle to slave device
+ * @buf: Data that will be written to the slave
+ * @count: How many bytes to write
+ *
+ * Returns negative errno, or else the number of bytes written.
+ */
 int i2c_master_send(struct i2c_client *client,const char *buf ,int count)
 {
        int ret;
@@ -995,6 +1063,14 @@ int i2c_master_send(struct i2c_client *client,const char *buf ,int count)
 }
 EXPORT_SYMBOL(i2c_master_send);
 
+/**
+ * i2c_master_recv - issue a single I2C message in master receive mode
+ * @client: Handle to slave device
+ * @buf: Where to store data read from slave
+ * @count: How many bytes to read
+ *
+ * Returns negative errno, or else the number of bytes read.
+ */
 int i2c_master_recv(struct i2c_client *client, char *buf ,int count)
 {
        struct i2c_adapter *adap=client->adapter;
@@ -1103,7 +1179,7 @@ int i2c_probe(struct i2c_adapter *adapter,
 
                dev_warn(&adapter->dev, "SMBus Quick command not supported, "
                         "can't probe for chips\n");
-               return -1;
+               return -EOPNOTSUPP;
        }
 
        /* Probe entries are done second, and are not affected by ignore
@@ -1157,6 +1233,179 @@ int i2c_probe(struct i2c_adapter *adapter,
 }
 EXPORT_SYMBOL(i2c_probe);
 
+/* Separate detection function for new-style drivers */
+static int i2c_detect_address(struct i2c_client *temp_client, int kind,
+                             struct i2c_driver *driver)
+{
+       struct i2c_board_info info;
+       struct i2c_adapter *adapter = temp_client->adapter;
+       int addr = temp_client->addr;
+       int err;
+
+       /* Make sure the address is valid */
+       if (addr < 0x03 || addr > 0x77) {
+               dev_warn(&adapter->dev, "Invalid probe address 0x%02x\n",
+                        addr);
+               return -EINVAL;
+       }
+
+       /* Skip if already in use */
+       if (i2c_check_addr(adapter, addr))
+               return 0;
+
+       /* Make sure there is something at this address, unless forced */
+       if (kind < 0) {
+               if (i2c_smbus_xfer(adapter, addr, 0, 0, 0,
+                                  I2C_SMBUS_QUICK, NULL) < 0)
+                       return 0;
+
+               /* prevent 24RF08 corruption */
+               if ((addr & ~0x0f) == 0x50)
+                       i2c_smbus_xfer(adapter, addr, 0, 0, 0,
+                                      I2C_SMBUS_QUICK, NULL);
+       }
+
+       /* Finally call the custom detection function */
+       memset(&info, 0, sizeof(struct i2c_board_info));
+       info.addr = addr;
+       err = driver->detect(temp_client, kind, &info);
+       if (err) {
+               /* -ENODEV is returned if the detection fails. We catch it
+                  here as this isn't an error. */
+               return err == -ENODEV ? 0 : err;
+       }
+
+       /* Consistency check */
+       if (info.type[0] == '\0') {
+               dev_err(&adapter->dev, "%s detection function provided "
+                       "no name for 0x%x\n", driver->driver.name,
+                       addr);
+       } else {
+               struct i2c_client *client;
+
+               /* Detection succeeded, instantiate the device */
+               dev_dbg(&adapter->dev, "Creating %s at 0x%02x\n",
+                       info.type, info.addr);
+               client = i2c_new_device(adapter, &info);
+               if (client)
+                       list_add_tail(&client->detected, &driver->clients);
+               else
+                       dev_err(&adapter->dev, "Failed creating %s at 0x%02x\n",
+                               info.type, info.addr);
+       }
+       return 0;
+}
+
+static int i2c_detect(struct i2c_adapter *adapter, struct i2c_driver *driver)
+{
+       const struct i2c_client_address_data *address_data;
+       struct i2c_client *temp_client;
+       int i, err = 0;
+       int adap_id = i2c_adapter_id(adapter);
+
+       address_data = driver->address_data;
+       if (!driver->detect || !address_data)
+               return 0;
+
+       /* Set up a temporary client to help detect callback */
+       temp_client = kzalloc(sizeof(struct i2c_client), GFP_KERNEL);
+       if (!temp_client)
+               return -ENOMEM;
+       temp_client->adapter = adapter;
+
+       /* Force entries are done first, and are not affected by ignore
+          entries */
+       if (address_data->forces) {
+               const unsigned short * const *forces = address_data->forces;
+               int kind;
+
+               for (kind = 0; forces[kind]; kind++) {
+                       for (i = 0; forces[kind][i] != I2C_CLIENT_END;
+                            i += 2) {
+                               if (forces[kind][i] == adap_id
+                                || forces[kind][i] == ANY_I2C_BUS) {
+                                       dev_dbg(&adapter->dev, "found force "
+                                               "parameter for adapter %d, "
+                                               "addr 0x%02x, kind %d\n",
+                                               adap_id, forces[kind][i + 1],
+                                               kind);
+                                       temp_client->addr = forces[kind][i + 1];
+                                       err = i2c_detect_address(temp_client,
+                                               kind, driver);
+                                       if (err)
+                                               goto exit_free;
+                               }
+                       }
+               }
+       }
+
+       /* Stop here if we can't use SMBUS_QUICK */
+       if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_QUICK)) {
+               if (address_data->probe[0] == I2C_CLIENT_END
+                && address_data->normal_i2c[0] == I2C_CLIENT_END)
+                       goto exit_free;
+
+               dev_warn(&adapter->dev, "SMBus Quick command not supported, "
+                        "can't probe for chips\n");
+               err = -EOPNOTSUPP;
+               goto exit_free;
+       }
+
+       /* Stop here if the classes do not match */
+       if (!(adapter->class & driver->class))
+               goto exit_free;
+
+       /* Probe entries are done second, and are not affected by ignore
+          entries either */
+       for (i = 0; address_data->probe[i] != I2C_CLIENT_END; i += 2) {
+               if (address_data->probe[i] == adap_id
+                || address_data->probe[i] == ANY_I2C_BUS) {
+                       dev_dbg(&adapter->dev, "found probe parameter for "
+                               "adapter %d, addr 0x%02x\n", adap_id,
+                               address_data->probe[i + 1]);
+                       temp_client->addr = address_data->probe[i + 1];
+                       err = i2c_detect_address(temp_client, -1, driver);
+                       if (err)
+                               goto exit_free;
+               }
+       }
+
+       /* Normal entries are done last, unless shadowed by an ignore entry */
+       for (i = 0; address_data->normal_i2c[i] != I2C_CLIENT_END; i += 1) {
+               int j, ignore;
+
+               ignore = 0;
+               for (j = 0; address_data->ignore[j] != I2C_CLIENT_END;
+                    j += 2) {
+                       if ((address_data->ignore[j] == adap_id ||
+                            address_data->ignore[j] == ANY_I2C_BUS)
+                        && address_data->ignore[j + 1]
+                           == address_data->normal_i2c[i]) {
+                               dev_dbg(&adapter->dev, "found ignore "
+                                       "parameter for adapter %d, "
+                                       "addr 0x%02x\n", adap_id,
+                                       address_data->ignore[j + 1]);
+                               ignore = 1;
+                               break;
+                       }
+               }
+               if (ignore)
+                       continue;
+
+               dev_dbg(&adapter->dev, "found normal entry for adapter %d, "
+                       "addr 0x%02x\n", adap_id,
+                       address_data->normal_i2c[i]);
+               temp_client->addr = address_data->normal_i2c[i];
+               err = i2c_detect_address(temp_client, -1, driver);
+               if (err)
+                       goto exit_free;
+       }
+
+ exit_free:
+       kfree(temp_client);
+       return err;
+}
+
 struct i2c_client *
 i2c_new_probed_device(struct i2c_adapter *adap,
                      struct i2c_board_info *info,
@@ -1295,29 +1544,38 @@ static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
        if (rpec != cpec) {
                pr_debug("i2c-core: Bad PEC 0x%02x vs. 0x%02x\n",
                        rpec, cpec);
-               return -1;
+               return -EBADMSG;
        }
        return 0;
 }
 
-s32 i2c_smbus_write_quick(struct i2c_client *client, u8 value)
-{
-       return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
-                             value,0,I2C_SMBUS_QUICK,NULL);
-}
-EXPORT_SYMBOL(i2c_smbus_write_quick);
-
+/**
+ * i2c_smbus_read_byte - SMBus "receive byte" protocol
+ * @client: Handle to slave device
+ *
+ * This executes the SMBus "receive byte" protocol, returning negative errno
+ * else the byte received from the device.
+ */
 s32 i2c_smbus_read_byte(struct i2c_client *client)
 {
        union i2c_smbus_data data;
-       if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
-                          I2C_SMBUS_READ,0,I2C_SMBUS_BYTE, &data))
-               return -1;
-       else
-               return data.byte;
+       int status;
+
+       status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+                               I2C_SMBUS_READ, 0,
+                               I2C_SMBUS_BYTE, &data);
+       return (status < 0) ? status : data.byte;
 }
 EXPORT_SYMBOL(i2c_smbus_read_byte);
 
+/**
+ * i2c_smbus_write_byte - SMBus "send byte" protocol
+ * @client: Handle to slave device
+ * @value: Byte to be sent
+ *
+ * This executes the SMBus "send byte" protocol, returning negative errno
+ * else zero on success.
+ */
 s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value)
 {
        return i2c_smbus_xfer(client->adapter,client->addr,client->flags,
@@ -1325,17 +1583,35 @@ s32 i2c_smbus_write_byte(struct i2c_client *client, u8 value)
 }
 EXPORT_SYMBOL(i2c_smbus_write_byte);
 
+/**
+ * i2c_smbus_read_byte_data - SMBus "read byte" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ *
+ * This executes the SMBus "read byte" protocol, returning negative errno
+ * else a data byte received from the device.
+ */
 s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command)
 {
        union i2c_smbus_data data;
-       if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
-                          I2C_SMBUS_READ,command, I2C_SMBUS_BYTE_DATA,&data))
-               return -1;
-       else
-               return data.byte;
+       int status;
+
+       status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+                               I2C_SMBUS_READ, command,
+                               I2C_SMBUS_BYTE_DATA, &data);
+       return (status < 0) ? status : data.byte;
 }
 EXPORT_SYMBOL(i2c_smbus_read_byte_data);
 
+/**
+ * i2c_smbus_write_byte_data - SMBus "write byte" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @value: Byte being written
+ *
+ * This executes the SMBus "write byte" protocol, returning negative errno
+ * else zero on success.
+ */
 s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value)
 {
        union i2c_smbus_data data;
@@ -1346,17 +1622,35 @@ s32 i2c_smbus_write_byte_data(struct i2c_client *client, u8 command, u8 value)
 }
 EXPORT_SYMBOL(i2c_smbus_write_byte_data);
 
+/**
+ * i2c_smbus_read_word_data - SMBus "read word" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ *
+ * This executes the SMBus "read word" protocol, returning negative errno
+ * else a 16-bit unsigned "word" received from the device.
+ */
 s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command)
 {
        union i2c_smbus_data data;
-       if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
-                          I2C_SMBUS_READ,command, I2C_SMBUS_WORD_DATA, &data))
-               return -1;
-       else
-               return data.word;
+       int status;
+
+       status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+                               I2C_SMBUS_READ, command,
+                               I2C_SMBUS_WORD_DATA, &data);
+       return (status < 0) ? status : data.word;
 }
 EXPORT_SYMBOL(i2c_smbus_read_word_data);
 
+/**
+ * i2c_smbus_write_word_data - SMBus "write word" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @value: 16-bit "word" being written
+ *
+ * This executes the SMBus "write word" protocol, returning negative errno
+ * else zero on success.
+ */
 s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value)
 {
        union i2c_smbus_data data;
@@ -1368,15 +1662,14 @@ s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value)
 EXPORT_SYMBOL(i2c_smbus_write_word_data);
 
 /**
- * i2c_smbus_read_block_data - SMBus block read request
+ * i2c_smbus_read_block_data - SMBus "block read" protocol
  * @client: Handle to slave device
- * @command: Command byte issued to let the slave know what data should
- *     be returned
+ * @command: Byte interpreted by slave
  * @values: Byte array into which data will be read; big enough to hold
  *     the data returned by the slave.  SMBus allows at most 32 bytes.
  *
- * Returns the number of bytes read in the slave's response, else a
- * negative number to indicate some kind of error.
+ * This executes the SMBus "block read" protocol, returning negative errno
+ * else the number of data bytes in the slave's response.
  *
  * Note that using this function requires that the client's adapter support
  * the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality.  Not all adapter drivers
@@ -1387,17 +1680,29 @@ s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command,
                              u8 *values)
 {
        union i2c_smbus_data data;
+       int status;
 
-       if (i2c_smbus_xfer(client->adapter, client->addr, client->flags,
-                          I2C_SMBUS_READ, command,
-                          I2C_SMBUS_BLOCK_DATA, &data))
-               return -1;
+       status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+                               I2C_SMBUS_READ, command,
+                               I2C_SMBUS_BLOCK_DATA, &data);
+       if (status)
+               return status;
 
        memcpy(values, &data.block[1], data.block[0]);
        return data.block[0];
 }
 EXPORT_SYMBOL(i2c_smbus_read_block_data);
 
+/**
+ * i2c_smbus_write_block_data - SMBus "block write" protocol
+ * @client: Handle to slave device
+ * @command: Byte interpreted by slave
+ * @length: Size of data block; SMBus allows at most 32 bytes
+ * @values: Byte array which will be written.
+ *
+ * This executes the SMBus "block write" protocol, returning negative errno
+ * else zero on success.
+ */
 s32 i2c_smbus_write_block_data(struct i2c_client *client, u8 command,
                               u8 length, const u8 *values)
 {
@@ -1418,14 +1723,16 @@ s32 i2c_smbus_read_i2c_block_data(struct i2c_client *client, u8 command,
                                  u8 length, u8 *values)
 {
        union i2c_smbus_data data;
+       int status;
 
        if (length > I2C_SMBUS_BLOCK_MAX)
                length = I2C_SMBUS_BLOCK_MAX;
        data.block[0] = length;
-       if (i2c_smbus_xfer(client->adapter,client->addr,client->flags,
-                             I2C_SMBUS_READ,command,
-                             I2C_SMBUS_I2C_BLOCK_DATA,&data))
-               return -1;
+       status = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
+                               I2C_SMBUS_READ, command,
+                               I2C_SMBUS_I2C_BLOCK_DATA, &data);
+       if (status < 0)
+               return status;
 
        memcpy(values, &data.block[1], data.block[0]);
        return data.block[0];
@@ -1466,6 +1773,7 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                                };
        int i;
        u8 partial_pec = 0;
+       int status;
 
        msgbuf0[0] = command;
        switch(size) {
@@ -1515,10 +1823,10 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                } else {
                        msg[0].len = data->block[0] + 2;
                        if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 2) {
-                               dev_err(&adapter->dev, "smbus_access called with "
-                                      "invalid block write size (%d)\n",
-                                      data->block[0]);
-                               return -1;
+                               dev_err(&adapter->dev,
+                                       "Invalid block write size %d\n",
+                                       data->block[0]);
+                               return -EINVAL;
                        }
                        for (i = 1; i < msg[0].len; i++)
                                msgbuf0[i] = data->block[i-1];
@@ -1528,10 +1836,10 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                num = 2; /* Another special case */
                read_write = I2C_SMBUS_READ;
                if (data->block[0] > I2C_SMBUS_BLOCK_MAX) {
-                       dev_err(&adapter->dev, "%s called with invalid "
-                               "block proc call size (%d)\n", __func__,
+                       dev_err(&adapter->dev,
+                               "Invalid block write size %d\n",
                                data->block[0]);
-                       return -1;
+                       return -EINVAL;
                }
                msg[0].len = data->block[0] + 2;
                for (i = 1; i < msg[0].len; i++)
@@ -1546,19 +1854,18 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                } else {
                        msg[0].len = data->block[0] + 1;
                        if (msg[0].len > I2C_SMBUS_BLOCK_MAX + 1) {
-                               dev_err(&adapter->dev, "i2c_smbus_xfer_emulated called with "
-                                      "invalid block write size (%d)\n",
-                                      data->block[0]);
-                               return -1;
+                               dev_err(&adapter->dev,
+                                       "Invalid block write size %d\n",
+                                       data->block[0]);
+                               return -EINVAL;
                        }
                        for (i = 1; i <= data->block[0]; i++)
                                msgbuf0[i] = data->block[i];
                }
                break;
        default:
-               dev_err(&adapter->dev, "smbus_access called with invalid size (%d)\n",
-                      size);
-               return -1;
+               dev_err(&adapter->dev, "Unsupported transaction %d\n", size);
+               return -EOPNOTSUPP;
        }
 
        i = ((flags & I2C_CLIENT_PEC) && size != I2C_SMBUS_QUICK
@@ -1576,13 +1883,15 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
                        msg[num-1].len++;
        }
 
-       if (i2c_transfer(adapter, msg, num) < 0)
-               return -1;
+       status = i2c_transfer(adapter, msg, num);
+       if (status < 0)
+               return status;
 
        /* Check PEC if last message is a read */
        if (i && (msg[num-1].flags & I2C_M_RD)) {
-               if (i2c_smbus_check_pec(partial_pec, &msg[num-1]) < 0)
-                       return -1;
+               status = i2c_smbus_check_pec(partial_pec, &msg[num-1]);
+               if (status < 0)
+                       return status;
        }
 
        if (read_write == I2C_SMBUS_READ)
@@ -1610,9 +1919,21 @@ static s32 i2c_smbus_xfer_emulated(struct i2c_adapter * adapter, u16 addr,
        return 0;
 }
 
-
+/**
+ * i2c_smbus_xfer - execute SMBus protocol operations
+ * @adapter: Handle to I2C bus
+ * @addr: Address of SMBus slave on that bus
+ * @flags: I2C_CLIENT_* flags (usually zero or I2C_CLIENT_PEC)
+ * @read_write: I2C_SMBUS_READ or I2C_SMBUS_WRITE
+ * @command: Byte interpreted by slave, for protocols which use such bytes
+ * @protocol: SMBus protocol operation to execute, such as I2C_SMBUS_PROC_CALL
+ * @data: Data to be read or written
+ *
+ * This executes an SMBus protocol operation, and returns a negative
+ * errno code else zero on success.
+ */
 s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,
-                   char read_write, u8 command, int size,
+                  char read_write, u8 command, int protocol,
                    union i2c_smbus_data * data)
 {
        s32 res;
@@ -1622,11 +1943,11 @@ s32 i2c_smbus_xfer(struct i2c_adapter * adapter, u16 addr, unsigned short flags,
        if (adapter->algo->smbus_xfer) {
                mutex_lock(&adapter->bus_lock);
                res = adapter->algo->smbus_xfer(adapter,addr,flags,read_write,
-                                               command,size,data);
+                                               command, protocol, data);
                mutex_unlock(&adapter->bus_lock);
        } else
                res = i2c_smbus_xfer_emulated(adapter,addr,flags,read_write,
-                                             command,size,data);
+                                             command, protocol, data);
 
        return res;
 }