1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
|
/*
* Bitbanging I2C bus driver using the GPIO API
*
* Copyright (C) 2007 Atmel Corporation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/i2c.h>
#include <linux/i2c-algo-bit.h>
#include <linux/i2c-gpio.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <asm/gpio.h>
/* Toggle SDA by changing the direction of the pin */
static void i2c_gpio_setsda_dir(void *data, int state)
{
struct i2c_gpio_platform_data *pdata = data;
if (state)
gpio_direction_input(pdata->sda_pin);
else
gpio_direction_output(pdata->sda_pin, 0);
}
/*
* Toggle SDA by changing the output value of the pin. This is only
* valid for pins configured as open drain (i.e. setting the value
* high effectively turns off the output driver.)
*/
static void i2c_gpio_setsda_val(void *data, int state)
{
struct i2c_gpio_platform_data *pdata = data;
gpio_set_value(pdata->sda_pin, state);
}
/* Toggle SCL by changing the direction of the pin. */
static void i2c_gpio_setscl_dir(void *data, int state)
{
struct i2c_gpio_platform_data *pdata = data;
if (state)
gpio_direction_input(pdata->scl_pin);
else
gpio_direction_output(pdata->scl_pin, 0);
}
/*
* Toggle SCL by changing the output value of the pin. This is used
* for pins that are configured as open drain and for output-only
* pins. The latter case will break the i2c protocol, but it will
* often work in practice.
*/
static void i2c_gpio_setscl_val(void *data, int state)
{
struct i2c_gpio_platform_data *pdata = data;
gpio_set_value(pdata->scl_pin, state);
}
int i2c_gpio_getsda(void *data)
{
struct i2c_gpio_platform_data *pdata = data;
return gpio_get_value(pdata->sda_pin);
}
int i2c_gpio_getscl(void *data)
{
struct i2c_gpio_platform_data *pdata = data;
return gpio_get_value(pdata->scl_pin);
}
static int __init i2c_gpio_probe(struct platform_device *pdev)
{
struct i2c_gpio_platform_data *pdata;
struct i2c_algo_bit_data *bit_data;
struct i2c_adapter *adap;
int ret;
pdata = pdev->dev.platform_data;
if (!pdata)
return -ENXIO;
ret = -ENOMEM;
adap = kzalloc(sizeof(struct i2c_adapter), GFP_KERNEL);
if (!adap)
goto err_alloc_adap;
bit_data = kzalloc(sizeof(struct i2c_algo_bit_data), GFP_KERNEL);
if (!bit_data)
goto err_alloc_bit_data;
ret = gpio_request(pdata->sda_pin, "sda");
if (ret)
goto err_request_sda;
ret = gpio_request(pdata->scl_pin, "scl");
if (ret)
goto err_request_scl;
if (pdata->sda_is_open_drain) {
gpio_direction_output(pdata->sda_pin, 1);
bit_data->setsda = i2c_gpio_setsda_val;
} else {
gpio_direction_input(pdata->sda_pin);
bit_data->setsda = i2c_gpio_setsda_dir;
}
if (pdata->scl_is_open_drain || pdata->scl_is_output_only) {
gpio_direction_output(pdata->scl_pin, 1);
bit_data->setscl = i2c_gpio_setscl_val;
} else {
gpio_direction_input(pdata->scl_pin);
bit_data->setscl = i2c_gpio_setscl_dir;
}
if (!pdata->scl_is_output_only)
bit_data->getscl = i2c_gpio_getscl;
bit_data->getsda = i2c_gpio_getsda;
if (pdata->udelay)
bit_data->udelay = pdata->udelay;
else if (pdata->scl_is_output_only)
bit_data->udelay = 50; /* 10 kHz */
else
bit_data->udelay = 5; /* 100 kHz */
if (pdata->timeout)
bit_data->timeout = pdata->timeout;
else
bit_data->timeout = HZ / 10; /* 100 ms */
bit_data->data = pdata;
adap->owner = THIS_MODULE;
snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id);
adap->algo_data = bit_data;
adap->dev.parent = &pdev->dev;
/*
* If "dev->id" is negative we consider it as zero.
* The reason to do so is to avoid sysfs names that only make
* sense when there are multiple adapters.
*/
adap->nr = pdev->id >= 0 ? pdev->id : 0;
ret = i2c_bit_add_numbered_bus(adap);
if (ret)
goto err_add_bus;
platform_set_drvdata(pdev, adap);
dev_info(&pdev->dev, "using pins %u (SDA) and %u (SCL%s)\n",
pdata->sda_pin, pdata->scl_pin,
pdata->scl_is_output_only
? ", no clock stretching" : "");
return 0;
err_add_bus:
gpio_free(pdata->scl_pin);
err_request_scl:
gpio_free(pdata->sda_pin);
err_request_sda:
kfree(bit_data);
err_alloc_bit_data:
kfree(adap);
err_alloc_adap:
return ret;
}
static int __exit i2c_gpio_remove(struct platform_device *pdev)
{
struct i2c_gpio_platform_data *pdata;
struct i2c_adapter *adap;
adap = platform_get_drvdata(pdev);
pdata = pdev->dev.platform_data;
i2c_del_adapter(adap);
gpio_free(pdata->scl_pin);
gpio_free(pdata->sda_pin);
kfree(adap->algo_data);
kfree(adap);
return 0;
}
static struct platform_driver i2c_gpio_driver = {
.driver = {
.name = "i2c-gpio",
.owner = THIS_MODULE,
},
.remove = __exit_p(i2c_gpio_remove),
};
static int __init i2c_gpio_init(void)
{
int ret;
ret = platform_driver_probe(&i2c_gpio_driver, i2c_gpio_probe);
if (ret)
printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret);
return ret;
}
module_init(i2c_gpio_init);
static void __exit i2c_gpio_exit(void)
{
platform_driver_unregister(&i2c_gpio_driver);
}
module_exit(i2c_gpio_exit);
MODULE_AUTHOR("Haavard Skinnemoen <hskinnemoen@atmel.com>");
MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver");
MODULE_LICENSE("GPL");
|
