If you want to send more than 1 byte as command to slave you need to go away from the smbus (which has a 8 bit command defined in specification). i2c has no such limitation in specification and since we want to have a longer than 1 byte command, we need additional function to handle it. With outside buffers we have also avoided endianness problems (if we would just define a u16 command instead of u8). Also there are now no limitations (as per i2c specification) of command length. Addressed read function is when we have a slave device which accepts commands longer than byte or some subcommands in same write string before issuing a repeat start before read cycle to read more than byte (or byte) from slave device.
Signed-off-by: Crt Mori <[email protected]> --- drivers/i2c/i2c-core.c | 40 ++++++++++++++++++++++++++++++++++++++++ include/linux/i2c.h | 4 ++++ 2 files changed, 44 insertions(+) diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c index 069a41f..bccf83f 100644 --- a/drivers/i2c/i2c-core.c +++ b/drivers/i2c/i2c-core.c @@ -2980,6 +2980,46 @@ int i2c_slave_unregister(struct i2c_client *client) EXPORT_SYMBOL_GPL(i2c_slave_unregister); #endif +/** + * i2c_addressed_read - writes read commands with desired length and read + * desired length of data. + * @client: Handle to slave device + * @command: Pointer to command location + * @cmd_len: Number of command bytes on command location + * @data: Pointer to read data location + * @data_len: Expected number of read bytes + * + * Addressed read on slave device when command is longer than byte. Returns + * negative errno on error and 0 on success. + */ +s32 i2c_addressed_read(const struct i2c_client *client, u8 *command, + u16 cmd_len, u8 *data, u16 data_len) +{ + s32 status; + struct i2c_msg msg[2] = { + { + .addr = client->addr, + .flags = client->flags, + .len = cmd_len, + .buf = command, + }, + { + .addr = client->addr, + .flags = client->flags | I2C_M_RD, + .len = data_len, + .buf = data, + }, + }; + + status = i2c_transfer(client->adapter, msg, 2); + + if (status < 0) + return status; + + return 0; +} +EXPORT_SYMBOL(i2c_addressed_read); + MODULE_AUTHOR("Simon G. Vogl <[email protected]>"); MODULE_DESCRIPTION("I2C-Bus main module"); MODULE_LICENSE("GPL"); diff --git a/include/linux/i2c.h b/include/linux/i2c.h index e83a738..d3cc1af 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -121,6 +121,10 @@ extern s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, extern s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command, u8 length, const u8 *values); + +s32 i2c_addressed_read(const struct i2c_client *client, u8 *command, + u16 cmd_len, u8 *data, u16 data_len); + #endif /* I2C */ /** -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
