/**
* 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.
+ *
+ * @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!
+ *
+ * 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
* 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
+ * 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).
+ * adapters which are known to support the specific mangling options they need.
*/
struct i2c_msg {
- __u16 addr; /* slave address */
+ __u16 addr;
__u16 flags;
-#define I2C_M_RD 0x0001 /* read data, from slave to master */
- /* I2C_M_RD is guaranteed to be 0x0001! */
-#define I2C_M_TEN 0x0010 /* this is a ten bit chip address */
-#define I2C_M_DMA_SAFE 0x0200 /* the buffer of this message is DMA safe */
- /* makes only sense in kernelspace */
- /* userspace buffers are copied anyway */
-#define I2C_M_RECV_LEN 0x0400 /* length will be first received byte */
-#define I2C_M_NO_RD_ACK 0x0800 /* if I2C_FUNC_PROTOCOL_MANGLING */
-#define I2C_M_IGNORE_NAK 0x1000 /* if I2C_FUNC_PROTOCOL_MANGLING */
-#define I2C_M_REV_DIR_ADDR 0x2000 /* if I2C_FUNC_PROTOCOL_MANGLING */
-#define I2C_M_NOSTART 0x4000 /* if I2C_FUNC_NOSTART */
-#define I2C_M_STOP 0x8000 /* if I2C_FUNC_PROTOCOL_MANGLING */
- __u16 len; /* msg length */
- __u8 *buf; /* pointer to msg data */
+#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;
};
/* To determine what functionality is present */
#define I2C_FUNC_I2C 0x00000001
-#define I2C_FUNC_10BIT_ADDR 0x00000002
-#define I2C_FUNC_PROTOCOL_MANGLING 0x00000004 /* I2C_M_IGNORE_NAK etc. */
+#define I2C_FUNC_10BIT_ADDR 0x00000002 /* required for I2C_M_TEN */
+#define I2C_FUNC_PROTOCOL_MANGLING 0x00000004 /* required for I2C_M_IGNORE_NAK etc. */
#define I2C_FUNC_SMBUS_PEC 0x00000008
-#define I2C_FUNC_NOSTART 0x00000010 /* I2C_M_NOSTART */
+#define I2C_FUNC_NOSTART 0x00000010 /* required for I2C_M_NOSTART */
#define I2C_FUNC_SLAVE 0x00000020
-#define I2C_FUNC_SMBUS_BLOCK_PROC_CALL 0x00008000 /* SMBus 2.0 */
+#define I2C_FUNC_SMBUS_BLOCK_PROC_CALL 0x00008000 /* SMBus 2.0 or later */
#define I2C_FUNC_SMBUS_QUICK 0x00010000
#define I2C_FUNC_SMBUS_READ_BYTE 0x00020000
#define I2C_FUNC_SMBUS_WRITE_BYTE 0x00040000
#define I2C_FUNC_SMBUS_READ_WORD_DATA 0x00200000
#define I2C_FUNC_SMBUS_WRITE_WORD_DATA 0x00400000
#define I2C_FUNC_SMBUS_PROC_CALL 0x00800000
-#define I2C_FUNC_SMBUS_READ_BLOCK_DATA 0x01000000
+#define I2C_FUNC_SMBUS_READ_BLOCK_DATA 0x01000000 /* required for I2C_M_RECV_LEN */
#define I2C_FUNC_SMBUS_WRITE_BLOCK_DATA 0x02000000
#define I2C_FUNC_SMBUS_READ_I2C_BLOCK 0x04000000 /* I2C-like block xfer */
#define I2C_FUNC_SMBUS_WRITE_I2C_BLOCK 0x08000000 /* w/ 1-byte reg. addr. */
-#define I2C_FUNC_SMBUS_HOST_NOTIFY 0x10000000
+#define I2C_FUNC_SMBUS_HOST_NOTIFY 0x10000000 /* SMBus 2.0 or later */
#define I2C_FUNC_SMBUS_BYTE (I2C_FUNC_SMBUS_READ_BYTE | \
I2C_FUNC_SMBUS_WRITE_BYTE)
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