i2c: Document struct i2c_msg (a64ec07d) · Commits · 戴 / test

drivers/i2c/i2c-core.c

+16 −1

Original line number	Diff line number	Diff line
		@@ -1307,7 +1307,22 @@ s32 i2c_smbus_write_word_data(struct i2c_client *client, u8 command, u16 value)
		}
		EXPORT_SYMBOL(i2c_smbus_write_word_data);

		/* Returns the number of read bytes */
		/**
		* i2c_smbus_read_block_data - SMBus block read request
		* @client: Handle to slave device
		* @command: Command byte issued to let the slave know what data should
		* be returned
		* @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.
		*
		* Note that using this function requires that the client's adapter support
		* the I2C_FUNC_SMBUS_READ_BLOCK_DATA functionality. Not all adapter drivers
		* support this; its emulation through I2C messaging relies on a specific
		* mechanism (I2C_M_RECV_LEN) which may not be implemented.
		*/
		s32 i2c_smbus_read_block_data(struct i2c_client *client, u8 command,
		u8 *values)
		{

include/linux/i2c.h

+42 −9

Original line number	Diff line number	Diff line
		@@ -443,18 +443,51 @@ static inline int i2c_adapter_id(struct i2c_adapter *adap)
		}
		#endif /* __KERNEL__ */

		/*
		* I2C Message - used for pure i2c transaction, also from /dev interface
		/**
		* struct i2c_msg - an I2C transaction segment beginning with START
		* @addr: Slave address, either seven or ten bits. When this is a ten
		* bit address, I2C_M_TEN must be set in @flags and the adapter
		* must support I2C_FUNC_10BIT_ADDR.
		* @flags: I2C_M_RD is handled by all adapters. No other flags may be
		* provided unless the adapter exported the relevant I2C_FUNC_*
		* flags through i2c_check_functionality().
		* @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
		* 32 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 (one or more of IGNORE_NAK, NO_RD_ACK, NOSTART, and REV_DIR_ADDR).
		*/
		struct i2c_msg {
		__u16 addr; /* slave address */
		__u16 flags;
		#define I2C_M_TEN 0x10 /* we have a ten bit chip address */
		#define I2C_M_RD 0x01
		#define I2C_M_NOSTART 0x4000
		#define I2C_M_REV_DIR_ADDR 0x2000
		#define I2C_M_IGNORE_NAK 0x1000
		#define I2C_M_NO_RD_ACK 0x0800
		#define I2C_M_TEN 0x0010 /* this is a ten bit chip address */
		#define I2C_M_RD 0x0001 /* read data, from slave to master */
		#define I2C_M_NOSTART 0x4000 /* if I2C_FUNC_PROTOCOL_MANGLING */
		#define I2C_M_REV_DIR_ADDR 0x2000 /* if I2C_FUNC_PROTOCOL_MANGLING */
		#define I2C_M_IGNORE_NAK 0x1000 /* if I2C_FUNC_PROTOCOL_MANGLING */
		#define I2C_M_NO_RD_ACK 0x0800 /* if I2C_FUNC_PROTOCOL_MANGLING */
		#define I2C_M_RECV_LEN 0x0400 /* length will be first received byte */
		__u16 len; /* msg length */
		__u8 buf; / pointer to msg data */

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