Commit 0c43ea54 authored Mar 02, 2010 by Zhangfei Gao Committed by Jean Delvare Mar 02, 2010

i2c: Document the message size limit



i2c_master_send & i2c_master_recv do not support more than 64 kb
transfer, since msg.len is u16.

Signed-off-by: Zhangfei Gao <zgao6@marvell.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

parent eec74a25

Documentation/i2c/writing-clients

+3 −2

Original line number	Diff line number	Diff line
		@@ -318,8 +318,9 @@ Plain I2C communication
		These routines read and write some bytes from/to a client. The client
		contains the i2c address, so you do not have to include it. The second
		parameter contains the bytes to read/write, the third the number of bytes
		to read/write (must be less than the length of the buffer.) Returned is
		the actual number of bytes read/written.
		to read/write (must be less than the length of the buffer, also should be
		less than 64k since msg.len is u16.) Returned is the actual number of bytes
		read/written.

		int i2c_transfer(struct i2c_adapter adap, struct i2c_msg msg,
		int num);

drivers/i2c/i2c-core.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -1183,7 +1183,7 @@ 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
		* @count: How many bytes to write, must be less than 64k since msg.len is u16
		*
		* Returns negative errno, or else the number of bytes written.
		*/
		@@ -1210,7 +1210,7 @@ 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
		* @count: How many bytes to read, must be less than 64k since msg.len is u16
		*
		* Returns negative errno, or else the number of bytes read.
		*/

include/linux/i2c.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -53,6 +53,7 @@ struct i2c_board_info;
		* on a bus (or read from them). Apart from two basic transfer functions to
		* transmit one message at a time, a more complex version can be used to
		* transmit an arbitrary number of messages without interruption.
		* @count must be be less than 64k since msg.len is u16.
		*/
		extern int i2c_master_send(struct i2c_client client, const char buf,
		int count);