xref: /openbmc/linux/include/uapi/linux/i2c.h (revision 21500aa8)
1 /* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
2 /*
3  * i2c.h - definitions for the I2C bus interface
4  *
5  * Copyright (C) 1995-2000 Simon G. Vogl
6  * With some changes from Kyösti Mälkki <kmalkki@cc.hut.fi> and
7  * Frodo Looijaard <frodol@dds.nl>
8  */
9 
10 #ifndef _UAPI_LINUX_I2C_H
11 #define _UAPI_LINUX_I2C_H
12 
13 #include <linux/types.h>
14 
15 /**
16  * struct i2c_msg - an I2C transaction segment beginning with START
17  *
18  * @addr: Slave address, either 7 or 10 bits. When this is a 10 bit address,
19  *   %I2C_M_TEN must be set in @flags and the adapter must support
20  *   %I2C_FUNC_10BIT_ADDR.
21  *
22  * @flags:
23  *   Supported by all adapters:
24  *   %I2C_M_RD: read data (from slave to master). Guaranteed to be 0x0001!
25  *
26  *   Optional:
27  *   %I2C_M_DMA_SAFE: the buffer of this message is DMA safe. Makes only sense
28  *     in kernelspace, because userspace buffers are copied anyway
29  *
30  *   Only if I2C_FUNC_10BIT_ADDR is set:
31  *   %I2C_M_TEN: this is a 10 bit chip address
32  *
33  *   Only if I2C_FUNC_SMBUS_READ_BLOCK_DATA is set:
34  *   %I2C_M_RECV_LEN: message length will be first received byte
35  *
36  *   Only if I2C_FUNC_NOSTART is set:
37  *   %I2C_M_NOSTART: skip repeated start sequence
38 
39  *   Only if I2C_FUNC_PROTOCOL_MANGLING is set:
40  *   %I2C_M_NO_RD_ACK: in a read message, master ACK/NACK bit is skipped
41  *   %I2C_M_IGNORE_NAK: treat NACK from client as ACK
42  *   %I2C_M_REV_DIR_ADDR: toggles the Rd/Wr bit
43  *   %I2C_M_STOP: force a STOP condition after the message
44  *
45  * @len: Number of data bytes in @buf being read from or written to the I2C
46  *   slave address. For read transactions where %I2C_M_RECV_LEN is set, the
47  *   caller guarantees that this buffer can hold up to %I2C_SMBUS_BLOCK_MAX
48  *   bytes in addition to the initial length byte sent by the slave (plus,
49  *   if used, the SMBus PEC); and this value will be incremented by the number
50  *   of block data bytes received.
51  *
52  * @buf: The buffer into which data is read, or from which it's written.
53  *
54  * An i2c_msg is the low level representation of one segment of an I2C
55  * transaction.  It is visible to drivers in the @i2c_transfer() procedure,
56  * to userspace from i2c-dev, and to I2C adapter drivers through the
57  * @i2c_adapter.@master_xfer() method.
58  *
59  * Except when I2C "protocol mangling" is used, all I2C adapters implement
60  * the standard rules for I2C transactions.  Each transaction begins with a
61  * START.  That is followed by the slave address, and a bit encoding read
62  * versus write.  Then follow all the data bytes, possibly including a byte
63  * with SMBus PEC.  The transfer terminates with a NAK, or when all those
64  * bytes have been transferred and ACKed.  If this is the last message in a
65  * group, it is followed by a STOP.  Otherwise it is followed by the next
66  * @i2c_msg transaction segment, beginning with a (repeated) START.
67  *
68  * Alternatively, when the adapter supports %I2C_FUNC_PROTOCOL_MANGLING then
69  * passing certain @flags may have changed those standard protocol behaviors.
70  * Those flags are only for use with broken/nonconforming slaves, and with
71  * adapters which are known to support the specific mangling options they need.
72  */
73 struct i2c_msg {
74 	__u16 addr;
75 	__u16 flags;
76 #define I2C_M_RD		0x0001	/* guaranteed to be 0x0001! */
77 #define I2C_M_TEN		0x0010	/* use only if I2C_FUNC_10BIT_ADDR */
78 #define I2C_M_DMA_SAFE		0x0200	/* use only in kernel space */
79 #define I2C_M_RECV_LEN		0x0400	/* use only if I2C_FUNC_SMBUS_READ_BLOCK_DATA */
80 #define I2C_M_NO_RD_ACK		0x0800	/* use only if I2C_FUNC_PROTOCOL_MANGLING */
81 #define I2C_M_IGNORE_NAK	0x1000	/* use only if I2C_FUNC_PROTOCOL_MANGLING */
82 #define I2C_M_REV_DIR_ADDR	0x2000	/* use only if I2C_FUNC_PROTOCOL_MANGLING */
83 #define I2C_M_NOSTART		0x4000	/* use only if I2C_FUNC_NOSTART */
84 #define I2C_M_STOP		0x8000	/* use only if I2C_FUNC_PROTOCOL_MANGLING */
85 	__u16 len;
86 	__u8 *buf;
87 };
88 
89 /* To determine what functionality is present */
90 
91 #define I2C_FUNC_I2C			0x00000001
92 #define I2C_FUNC_10BIT_ADDR		0x00000002 /* required for I2C_M_TEN */
93 #define I2C_FUNC_PROTOCOL_MANGLING	0x00000004 /* required for I2C_M_IGNORE_NAK etc. */
94 #define I2C_FUNC_SMBUS_PEC		0x00000008
95 #define I2C_FUNC_NOSTART		0x00000010 /* required for I2C_M_NOSTART */
96 #define I2C_FUNC_SLAVE			0x00000020
97 #define I2C_FUNC_SMBUS_BLOCK_PROC_CALL	0x00008000 /* SMBus 2.0 or later */
98 #define I2C_FUNC_SMBUS_QUICK		0x00010000
99 #define I2C_FUNC_SMBUS_READ_BYTE	0x00020000
100 #define I2C_FUNC_SMBUS_WRITE_BYTE	0x00040000
101 #define I2C_FUNC_SMBUS_READ_BYTE_DATA	0x00080000
102 #define I2C_FUNC_SMBUS_WRITE_BYTE_DATA	0x00100000
103 #define I2C_FUNC_SMBUS_READ_WORD_DATA	0x00200000
104 #define I2C_FUNC_SMBUS_WRITE_WORD_DATA	0x00400000
105 #define I2C_FUNC_SMBUS_PROC_CALL	0x00800000
106 #define I2C_FUNC_SMBUS_READ_BLOCK_DATA	0x01000000 /* required for I2C_M_RECV_LEN */
107 #define I2C_FUNC_SMBUS_WRITE_BLOCK_DATA 0x02000000
108 #define I2C_FUNC_SMBUS_READ_I2C_BLOCK	0x04000000 /* I2C-like block xfer  */
109 #define I2C_FUNC_SMBUS_WRITE_I2C_BLOCK	0x08000000 /* w/ 1-byte reg. addr. */
110 #define I2C_FUNC_SMBUS_HOST_NOTIFY	0x10000000 /* SMBus 2.0 or later */
111 
112 #define I2C_FUNC_SMBUS_BYTE		(I2C_FUNC_SMBUS_READ_BYTE | \
113 					 I2C_FUNC_SMBUS_WRITE_BYTE)
114 #define I2C_FUNC_SMBUS_BYTE_DATA	(I2C_FUNC_SMBUS_READ_BYTE_DATA | \
115 					 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)
116 #define I2C_FUNC_SMBUS_WORD_DATA	(I2C_FUNC_SMBUS_READ_WORD_DATA | \
117 					 I2C_FUNC_SMBUS_WRITE_WORD_DATA)
118 #define I2C_FUNC_SMBUS_BLOCK_DATA	(I2C_FUNC_SMBUS_READ_BLOCK_DATA | \
119 					 I2C_FUNC_SMBUS_WRITE_BLOCK_DATA)
120 #define I2C_FUNC_SMBUS_I2C_BLOCK	(I2C_FUNC_SMBUS_READ_I2C_BLOCK | \
121 					 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)
122 
123 #define I2C_FUNC_SMBUS_EMUL		(I2C_FUNC_SMBUS_QUICK | \
124 					 I2C_FUNC_SMBUS_BYTE | \
125 					 I2C_FUNC_SMBUS_BYTE_DATA | \
126 					 I2C_FUNC_SMBUS_WORD_DATA | \
127 					 I2C_FUNC_SMBUS_PROC_CALL | \
128 					 I2C_FUNC_SMBUS_WRITE_BLOCK_DATA | \
129 					 I2C_FUNC_SMBUS_I2C_BLOCK | \
130 					 I2C_FUNC_SMBUS_PEC)
131 
132 /* if I2C_M_RECV_LEN is also supported */
133 #define I2C_FUNC_SMBUS_EMUL_ALL		(I2C_FUNC_SMBUS_EMUL | \
134 					 I2C_FUNC_SMBUS_READ_BLOCK_DATA | \
135 					 I2C_FUNC_SMBUS_BLOCK_PROC_CALL)
136 
137 /*
138  * Data for SMBus Messages
139  */
140 #define I2C_SMBUS_BLOCK_MAX	32	/* As specified in SMBus standard */
141 union i2c_smbus_data {
142 	__u8 byte;
143 	__u16 word;
144 	__u8 block[I2C_SMBUS_BLOCK_MAX + 2]; /* block[0] is used for length */
145 			       /* and one more for user-space compatibility */
146 };
147 
148 /* i2c_smbus_xfer read or write markers */
149 #define I2C_SMBUS_READ	1
150 #define I2C_SMBUS_WRITE	0
151 
152 /* SMBus transaction types (size parameter in the above functions)
153    Note: these no longer correspond to the (arbitrary) PIIX4 internal codes! */
154 #define I2C_SMBUS_QUICK		    0
155 #define I2C_SMBUS_BYTE		    1
156 #define I2C_SMBUS_BYTE_DATA	    2
157 #define I2C_SMBUS_WORD_DATA	    3
158 #define I2C_SMBUS_PROC_CALL	    4
159 #define I2C_SMBUS_BLOCK_DATA	    5
160 #define I2C_SMBUS_I2C_BLOCK_BROKEN  6
161 #define I2C_SMBUS_BLOCK_PROC_CALL   7		/* SMBus 2.0 */
162 #define I2C_SMBUS_I2C_BLOCK_DATA    8
163 
164 #endif /* _UAPI_LINUX_I2C_H */
165