xref: /aosp_15_r20/external/coreboot/src/include/device/i2c_bus.h (revision b9411a12aaaa7e1e6a6fb7c5e057f44ee179a49c)
1 /* SPDX-License-Identifier: GPL-2.0-only */
2 
3 #ifndef _DEVICE_I2C_BUS_H_
4 #define _DEVICE_I2C_BUS_H_
5 
6 #include <stddef.h>
7 #include <stdint.h>
8 #include <device/i2c.h>
9 #include <device/device.h>
10 
11 /* I2C bus operation for ramstage drivers */
12 struct i2c_bus_operations {
13 	int (*transfer)(struct device *, const struct i2c_msg *, size_t count);
14 };
15 
16 /**
17  * Determine device presence at a given slave address.
18  */
19 bool i2c_dev_detect(struct device *dev, unsigned int addr);
20 
21 /*
22  * Returns the first upstream facing link whose bus implements either
23  * `i2c_bus_operations` *or* `smbus_bus_operations`.
24  *
25  * If not NULL, guarantees that `->dev`, `->dev->ops` and either
26  * `->dev->ops->ops_i2c_bus` or `->dev->ops->ops_smbus_bus` are
27  * not NULL.
28  */
29 struct bus *i2c_link(const struct device *dev);
30 
31 /*
32  * Shorthand for `i2c_link(dev)->dev`.
33  *
34  * Returns NULL if i2c_link(dev) returns NULL.
35  */
i2c_busdev(const struct device * dev)36 static inline DEVTREE_CONST struct device *i2c_busdev(const struct device *dev)
37 {
38 	struct bus *const link = i2c_link(dev);
39 	return link ? link->dev : NULL;
40 }
41 
42 /*
43  * Slave driver interface functions. These will look for the next
44  * `i2c_bus_operations` *or* `smbus_bus_operations` and perform the
45  * respective transfers.
46  *
47  * The interface is limited to what current slave drivers demand.
48  * Extend as required.
49  *
50  * All functions return a negative `enum cb_err` value on error.
51  * Either CB_ERR, CB_ERR_ARG or any CB_I2C_* (cf. include/types.h).
52  */
53 
54 /*
55  * Reads one byte.
56  * Compatible to smbus_recv_byte().
57  *
58  * Returns the read byte on success, negative `enum cb_err` value on error.
59  */
60 int i2c_dev_readb(struct device *);
61 
62 /*
63  * Writes the byte `val`.
64  * Compatible to smbus_send_byte().
65  *
66  * Returns 0 on success, negative `enum cb_err` value on error.
67  */
68 int i2c_dev_writeb(struct device *, uint8_t val);
69 
70 /*
71  * Sends the register offset `off` and reads one byte.
72  * Compatible to smbus_read_byte().
73  *
74  * Returns the read byte on success, negative `enum cb_err` value on error.
75  */
76 int i2c_dev_readb_at(struct device *, uint8_t off);
77 
78 /*
79  * Sends the register offset `off` followed by the byte `val`.
80  * Compatible to smbus_write_byte().
81  *
82  * Returns 0 on success, negative `enum cb_err` value on error.
83  */
84 int i2c_dev_writeb_at(struct device *, uint8_t off, uint8_t val);
85 
86 /*
87  * Sends the 16-bit register offset `off` and reads `len` bytes into `buf`.
88  *
89  * Returns the number of bytes read on success, negative `enum cb_err`
90  * value on error.
91  */
92 int i2c_dev_read_at16(struct device *, uint8_t *buf, size_t len, uint16_t off);
93 /*
94  * Sends the 8-bit register offset `off` and reads `len` bytes into `buf`.
95  *
96  * Returns the number of bytes read on success, negative `enum cb_err`
97  * value on error.
98  */
99 int i2c_dev_read_at(struct device *, uint8_t *buf, size_t len, uint8_t off);
100 /*
101  * Sends the 8-bit register offset `off` and writes `len` bytes from `buf`.
102  *
103  * Returns the number of bytes written on success, negative `enum cb_err`
104  * value on error.
105  */
106 int i2c_dev_write_at(struct device *, uint8_t *buf, size_t len, uint8_t off);
107 
108 #endif	/* _DEVICE_I2C_BUS_H_ */
109