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i2c: Kerneldoc for most I/O calls
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Provide kerneldoc for most of the I2C and SMBus I/O calls.  Add a
comment summarizing some fault reporting issues which affect the
ability to provide clean fault reports through I2C master transfer
calls.  (Making it hard to precisely specify their return values...)

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
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David Brownell authored and Jean Delvare committed Jul 14, 2008
1 parent ae7193f commit a1cdeda
Showing 1 changed file with 124 additions and 9 deletions.
133 changes: 124 additions & 9 deletions drivers/i2c/i2c-core.c
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Original file line number Diff line number Diff line change
Expand Up @@ -945,10 +945,39 @@ 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++) {
Expand Down Expand Up @@ -979,6 +1008,14 @@ int i2c_transfer(struct i2c_adapter * adap, struct i2c_msg *msgs, int num)
}
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;
Expand All @@ -998,6 +1035,14 @@ 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;
Expand Down Expand Up @@ -1303,6 +1348,13 @@ static int i2c_smbus_check_pec(u8 cpec, struct i2c_msg *msg)
return 0;
}

/**
* 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;
Expand All @@ -1315,13 +1367,29 @@ s32 i2c_smbus_read_byte(struct i2c_client *client)
}
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,
I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL);
}
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;
Expand All @@ -1334,6 +1402,15 @@ s32 i2c_smbus_read_byte_data(struct i2c_client *client, u8 command)
}
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;
Expand All @@ -1344,6 +1421,14 @@ 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;
Expand All @@ -1356,6 +1441,15 @@ s32 i2c_smbus_read_word_data(struct i2c_client *client, u8 command)
}
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;
Expand All @@ -1367,15 +1461,14 @@ 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
Expand All @@ -1399,6 +1492,16 @@ s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command,
}
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)
{
Expand Down Expand Up @@ -1615,9 +1718,21 @@ 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;
Expand All @@ -1627,11 +1742,11 @@ 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;
}
Expand Down

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