/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */ /* * i2c.h - definitions for the I2C bus interface * * Copyright (C) 1995-2000 Simon G. Vogl * With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and * Frodo Looijaard <frodol@dds.nl>
*/
/** * struct i2c_msg - an I2C transaction segment beginning with START * * @addr: Slave address, either 7 or 10 bits. When this is a 10 bit address, * %I2C_M_TEN must be set in @flags and the adapter must support * %I2C_FUNC_10BIT_ADDR. * * @flags: * Supported by all adapters: * %I2C_M_RD: read data (from slave to master). Guaranteed to be 0x0001! If * not set, the transaction is interpreted as write. * * Optional: * %I2C_M_DMA_SAFE: the buffer of this message is DMA safe. Makes only sense * in kernelspace, because userspace buffers are copied anyway * * Only if I2C_FUNC_10BIT_ADDR is set: * %I2C_M_TEN: this is a 10 bit chip address * * Only if I2C_FUNC_SMBUS_READ_BLOCK_DATA is set: * %I2C_M_RECV_LEN: message length will be first received byte * * Only if I2C_FUNC_NOSTART is set: * %I2C_M_NOSTART: skip repeated start sequence
* Only if I2C_FUNC_PROTOCOL_MANGLING is set: * %I2C_M_NO_RD_ACK: in a read message, master ACK/NACK bit is skipped * %I2C_M_IGNORE_NAK: treat NACK from client as ACK * %I2C_M_REV_DIR_ADDR: toggles the Rd/Wr bit * %I2C_M_STOP: force a STOP condition after the message * * @len: Number of data bytes in @buf being read from or written to the I2C * slave address. For read transactions where %I2C_M_RECV_LEN is set, the * caller guarantees that this buffer can hold up to %I2C_SMBUS_BLOCK_MAX * bytes in addition to the initial length byte sent by the slave (plus, * if used, the SMBus PEC); and this value will be incremented by the number * of block data bytes received. * * @buf: The buffer into which data is read, or from which it's written. * * An i2c_msg is the low level representation of one segment of an I2C * transaction. It is visible to drivers in the @i2c_transfer() procedure, * to userspace from i2c-dev, and to I2C adapter drivers through the * @i2c_adapter.@master_xfer() method. * * Except when I2C "protocol mangling" is used, all I2C adapters implement * the standard rules for I2C transactions. Each transaction begins with a * START. That is followed by the slave address, and a bit encoding read * versus write. Then follow all the data bytes, possibly including a byte * with SMBus PEC. The transfer terminates with a NAK, or when all those * bytes have been transferred and ACKed. If this is the last message in a * group, it is followed by a STOP. Otherwise it is followed by the next * @i2c_msg transaction segment, beginning with a (repeated) START. * * Alternatively, when the adapter supports %I2C_FUNC_PROTOCOL_MANGLING then * passing certain @flags may have changed those standard protocol behaviors. * Those flags are only for use with broken/nonconforming slaves, and with * adapters which are known to support the specific mangling options they need.
*/ struct i2c_msg {
__u16 addr;
__u16 flags; #define I2C_M_RD 0x0001 /* guaranteed to be 0x0001! */ #define I2C_M_TEN 0x0010 /* use only if I2C_FUNC_10BIT_ADDR */ #define I2C_M_DMA_SAFE 0x0200 /* use only in kernel space */ #define I2C_M_RECV_LEN 0x0400 /* use only if I2C_FUNC_SMBUS_READ_BLOCK_DATA */ #define I2C_M_NO_RD_ACK 0x0800 /* use only if I2C_FUNC_PROTOCOL_MANGLING */ #define I2C_M_IGNORE_NAK 0x1000 /* use only if I2C_FUNC_PROTOCOL_MANGLING */ #define I2C_M_REV_DIR_ADDR 0x2000 /* use only if I2C_FUNC_PROTOCOL_MANGLING */ #define I2C_M_NOSTART 0x4000 /* use only if I2C_FUNC_NOSTART */ #define I2C_M_STOP 0x8000 /* use only if I2C_FUNC_PROTOCOL_MANGLING */
__u16 len;
__u8 *buf;
};
/* if I2C_M_RECV_LEN is also supported */ #define I2C_FUNC_SMBUS_EMUL_ALL (I2C_FUNC_SMBUS_EMUL | \
I2C_FUNC_SMBUS_READ_BLOCK_DATA | \
I2C_FUNC_SMBUS_BLOCK_PROC_CALL)
/* * Data for SMBus Messages
*/ #define I2C_SMBUS_BLOCK_MAX 32 /* As specified in SMBus standard */ union i2c_smbus_data {
__u8 byte;
__u16 word;
__u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */ /* and one more for user-space compatibility */
};
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