I2C自编设备驱动设计

一、自编设备驱动模型



at24.c:

1. static int __init at24_init(void)
2. {
3. io_limit = rounddown_pow_of_two(io_limit);
4. return i2c_add_driver(&at24_driver);                                   //注册i2c驱动设备
5. }

at24_driver:

1. static struct i2c_driver at24_driver = {
2. .driver = {
3. .name = "at24",
4. .owner = THIS_MODULE,
5. },
6. .probe = at24_probe,                                                  //找到驱动对应的设备调用的函数
7. .remove = __devexit_p(at24_remove),
8. .id_table = at24_ids,                                                 //这个表里的设备都支持
9. };

at24_probe:

1. static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
2. {
3. struct at24_platform_data chip;
4. bool writable;
5. bool use_smbus = false;
6. struct at24_data *at24;
7. int err;
8. unsigned i, num_addresses;
9. kernel_ulong_t magic;
10. if (client->dev.platform_data) {
11. chip = *(struct at24_platform_data *)client->dev.platform_data;
12. } else {
13. if (!id->driver_data) {
14. err = -ENODEV;
15. goto err_out;
16. }
17. magic = id->driver_data;
18. chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
19. magic >>= AT24_SIZE_BYTELEN;
20. chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
21. /*
22. * This is slow, but we can't know all eeproms, so we better
23. * play safe. Specifying custom eeprom-types via platform_data
24. * is recommended anyhow.
25. */
26. chip.page_size = 1;
27. chip.setup = NULL;
28. chip.context = NULL;
29. }
30. if (!is_power_of_2(chip.byte_len))
31. dev_warn(&client->dev,
32. "byte_len looks suspicious (no power of 2)!\n");
33. if (!is_power_of_2(chip.page_size))
34. dev_warn(&client->dev,
35. "page_size looks suspicious (no power of 2)!\n");
36. /* Use I2C operations unless we're stuck with SMBus extensions. */
37. if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
38. if (chip.flags & AT24_FLAG_ADDR16) {
39. err = -EPFNOSUPPORT;
40. goto err_out;
41. }
42. if (!i2c_check_functionality(client->adapter,
43. I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
44. err = -EPFNOSUPPORT;
45. goto err_out;
46. }
47. use_smbus = true;
48. }
49. if (chip.flags & AT24_FLAG_TAKE8ADDR)
50. num_addresses = 8;
51. else
52. num_addresses =    DIV_ROUND_UP(chip.byte_len,
53. (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
54. at24 = kzalloc(sizeof(struct at24_data) +
55. num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
56. if (!at24) {
57. err = -ENOMEM;
58. goto err_out;
59. }
60. mutex_init(&at24->lock);
61. at24->use_smbus = use_smbus;
62. at24->chip = chip;
63. at24->num_addresses = num_addresses;
64. /*
65. * Export the EEPROM bytes through sysfs, since that's convenient.
66. * By default, only root should see the data (maybe passwords etc)
67. */
68. at24->bin.attr.name = "eeprom";
69. at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
70. at24->bin.read = at24_bin_read;
71. at24->bin.size = chip.byte_len;
72. at24->macc.read = at24_macc_read;
73. writable = !(chip.flags & AT24_FLAG_READONLY);
74. if (writable) {
75. if (!use_smbus || i2c_check_functionality(client->adapter,
76. I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
77. unsigned write_max = chip.page_size;
78. at24->macc.write = at24_macc_write;
79. at24->bin.write = at24_bin_write;                          //这里注册了at24_bin_write，用户的write函数的调用接口
80. at24->bin.attr.mode |= S_IWUSR;
81. if (write_max > io_limit)
82. write_max = io_limit;
83. if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
84. write_max = I2C_SMBUS_BLOCK_MAX;
85. at24->write_max = write_max;
86. /* buffer (data + address at the beginning) */
87. at24->writebuf = kmalloc(write_max + 2, GFP_KERNEL);
88. if (!at24->writebuf) {
89. err = -ENOMEM;
90. goto err_struct;
91. }
92. } else {
93. dev_warn(&client->dev,
94. "cannot write due to controller restrictions.");
95. }
96. }
97. at24->client[0] = client;
98. /* use dummy devices for multiple-address chips */
99. for (i = 1; i < num_addresses; i++) {
100. at24->client[i] = i2c_new_dummy(client->adapter,
101. client->addr + i);
102. if (!at24->client[i]) {
103. dev_err(&client->dev, "address 0x%02x unavailable\n",
104. client->addr + i);
105. err = -EADDRINUSE;
106. goto err_clients;
107. }
108. }
109. err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);          //创建一个文件应用程序实际上是在/sys目录下的文件，而这个文件就是它函数创建的。
110. if (err)
111. goto err_clients;
112. i2c_set_clientdata(client, at24);
113. dev_info(&client->dev, "%zu byte %s EEPROM %s\n",
114. at24->bin.size, client->name,
115. writable ? "(writable)" : "(read-only)");
116. dev_dbg(&client->dev,
117. "page_size %d, num_addresses %d, write_max %d%s\n",
118. chip.page_size, num_addresses,
119. at24->write_max,
120. use_smbus ? ", use_smbus" : "");
121. /* export data to kernel code */
122. if (chip.setup)
123. chip.setup(&at24->macc, chip.context);
124. return 0;
125. err_clients:
126. for (i = 1; i < num_addresses; i++)
127. if (at24->client[i])
128. i2c_unregister_device(at24->client[i]);
129. kfree(at24->writebuf);
130. err_struct:
131. kfree(at24);
132. err_out:
133. dev_dbg(&client->dev, "probe error %d\n", err);
134. return err;
135. }

at24_bin_write:

1. static ssize_t at24_bin_write(struct kobject *kobj, struct bin_attribute *attr,
2. char *buf, loff_t off, size_t count)
3. {
4. struct at24_data *at24;
5. at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
6. return at24_write(at24, buf, off, count);                        //调用at24_write
7. }

at24_write:

1. static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
2. size_t count)
3. {
4. ssize_t retval = 0;
5. if (unlikely(!count))
6. return count;
7. mutex_lock(&at24->lock);
8. while (count) {
9. ssize_t    status;
10. status = at24_eeprom_write(at24, buf, off, count);                    //调用at24_eeprom_write
11. if (status <= 0) {
12. if (retval == 0)
13. retval = status;
14. break;
15. }
16. buf += status;
17. off += status;
18. count -= status;
19. retval += status;
20. }
21. mutex_unlock(&at24->lock);
22. return retval;
23. }

at24_eeprom_write:

1. static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
2. unsigned offset, size_t count)
3. {
4. struct i2c_client *client;
5. struct i2c_msg msg;
6. ssize_t status;
7. unsigned long timeout, write_time;
8. unsigned next_page;
9. /* Get corresponding I2C address and adjust offset */
10. client = at24_translate_offset(at24, &offset);
11. /* write_max is at most a page */
12. if (count > at24->write_max)
13. count = at24->write_max;
14. /* Never roll over backwards, to the start of this page */
15. next_page = roundup(offset + 1, at24->chip.page_size);
16. if (offset + count > next_page)
17. count = next_page - offset;
18. /* If we'll use I2C calls for I/O, set up the message */                     //I2C的消息
19. if (!at24->use_smbus) {
20. int i = 0;
21. msg.addr = client->addr;
22. msg.flags = 0;
23. /* msg.buf is u8 and casts will mask the values */
24. msg.buf = at24->writebuf;
25. if (at24->chip.flags & AT24_FLAG_ADDR16)
26. msg.buf[i++] = offset >> 8;
27. msg.buf[i++] = offset;                                          //提供偏移地址
28. memcpy(&msg.buf[i], buf, count);                                //拷贝用户发送数据
29. msg.len = i + count;                                            //设置长度
30. }
31. /*
32. * Writes fail if the previous one didn't complete yet. We may
33. * loop a few times until this one succeeds, waiting at least
34. * long enough for one entire page write to work.
35. */
36. timeout = jiffies + msecs_to_jiffies(write_timeout);
37. do {
38. write_time = jiffies;
39. if (at24->use_smbus) {
40. status = i2c_smbus_write_i2c_block_data(client,
41. offset, count, buf);
42. if (status == 0)
43. status = count;
44. } else {
45. status = i2c_transfer(client->adapter, &msg, 1);                     //交给I2C控制器完成
46. if (status == 1)
47. status = count;
48. }
49. dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
50. count, offset, status, jiffies);
51. if (status == count)
52. return count;
53. /* REVISIT: at HZ=100, this is sloooow */
54. msleep(1);
55. } while (time_before(write_time, timeout));
56. return -ETIMEDOUT;
57. }

i2c_transfer:

1. int i2c_transfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
2. {
3. int ret;
4. if (adap->algo->master_xfer) {
5. #ifdef DEBUG
6. for (ret = 0; ret < num; ret++) {
7. dev_dbg(&adap->dev, "master_xfer[%d] %c, addr=0x%02x, "
8. "len=%d%s\n", ret, (msgs[ret].flags & I2C_M_RD)
9. ? 'R' : 'W', msgs[ret].addr, msgs[ret].len,
10. (msgs[ret].flags & I2C_M_RECV_LEN) ? "+" : "");
11. }
12. #endif
13. if (in_atomic() || irqs_disabled()) {
14. ret = mutex_trylock(&adap->bus_lock);
15. if (!ret)
16. /* I2C activity is ongoing. */
17. return -EAGAIN;
18. } else {
19. mutex_lock_nested(&adap->bus_lock, adap->level);
20. }
21. ret = adap->algo->master_xfer(adap,msgs,num);                   //调用控制器中的算法
22. mutex_unlock(&adap->bus_lock);
23. return ret;
24. } else {
25. dev_dbg(&adap->dev, "I2C level transfers not supported\n");
26. return -EOPNOTSUPP;
27. }
28. }

然后看一下i2c_bin_read:

1. static ssize_t at24_bin_read(struct kobject *kobj, struct bin_attribute *attr,
2. char *buf, loff_t off, size_t count)
3. {
4. struct at24_data *at24;
5. at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
6. return at24_read(at24, buf, off, count);                               //调用at24_read
7. }

at24_read:

1. static ssize_t at24_read(struct at24_data *at24,
2. char *buf, loff_t off, size_t count)
3. {
4. ssize_t retval = 0;
5. if (unlikely(!count))
6. return count;
7. mutex_lock(&at24->lock);
8. while (count) {
9. ssize_t    status;
10. status = at24_eeprom_read(at24, buf, off, count);                  //继续调用at24_eeprom_read
11. if (status <= 0) {
12. if (retval == 0)
13. retval = status;
14. break;
15. }
16. buf += status;
17. off += status;
18. count -= status;
19. retval += status;
20. }
21. mutex_unlock(&at24->lock);
22. return retval;
23. }

at24_eeprom_read:

1. static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
2. unsigned offset, size_t count)
3. {
4. struct i2c_msg msg[2];
5. u8 msgbuf[2];
6. struct i2c_client *client;
7. int status, i;
8. memset(msg, 0, sizeof(msg));
9. client = at24_translate_offset(at24, &offset);
10. if (count > io_limit)
11. count = io_limit;
12. /* Smaller eeproms can work given some SMBus extension calls */
13. if (at24->use_smbus) {
14. if (count > I2C_SMBUS_BLOCK_MAX)
15. count = I2C_SMBUS_BLOCK_MAX;
16. status = i2c_smbus_read_i2c_block_data(client, offset,
17. count, buf);
18. dev_dbg(&client->dev, "smbus read %zu@%d --> %d\n",
19. count, offset, status);
20. return (status < 0) ? -EIO : status;
21. }
22. i = 0;
23. if (at24->chip.flags & AT24_FLAG_ADDR16)
24. msgbuf[i++] = offset >> 8;
25. msgbuf[i++] = offset;                                                //设置偏移
26. msg[0].addr = client->addr;                                          //第一条消息，提供从设备地址
27. msg[0].buf = msgbuf;
28. msg[0].len = i;
29. msg[1].addr = client->addr;                                          //第二条消息
30. msg[1].flags = I2C_M_RD;                                             //flags是读
31. msg[1].buf = buf;                                                    //提供数据量
32. msg[1].len = count;
33. status = i2c_transfer(client->adapter, msg, 2);
34. dev_dbg(&client->dev, "i2c read %zu@%d --> %d\n",
35. count, offset, status);
36. if (status == 2)
37. return count;
38. else if (status >= 0)
39. return -EIO;
40. else
41. return status;
42. }

二、对驱动程序的修改和移植

I2C设备的注册：

1. static void __init tq2440_machine_init(void)
2. {
3. s3c24xx_fb_set_platdata(&tq2440_fb_info);
4. s3c_i2c0_set_platdata(NULL);
5. platform_add_devices(tq2440_devices, ARRAY_SIZE(tq2440_devices));
6. EmbedSky_machine_init();
7. s3c2410_gpio_setpin(S3C2410_GPG12, 0);
8. s3c2410_gpio_cfgpin(S3C2410_GPG12, S3C2410_GPIO_OUTPUT);
9. s3c24xx_udc_set_platdata(&EmbedSky_udc_cfg);
10. }

增加设备：

1. static struct at24_platform_data at24c02 = {
2. .byte_len = 2048 / 8,
3. .page_size = 8,
4. .flags = 0,
5. };
6. static struct i2c_board_info __initdata tq2440_i2c_devices[] = {
7. {
8. I2C_BOARD_INFO("24c02", 0x50),
9. .platform_data = &at24c02,
10. },
11. };

然后在tq2440_machine_init中添加：

1. i2c_register_board_info(0, tq2440_i2c_devices, ARRAY_SIZE(tq2440_i2c_devices));

然后添加头文件：

1. #include <linux/i2c.h>
2. #include <linux/i2c/at24.h>

然后会在开发板/sys/bus/i2c/devices/有一个0-0050的目录，有一个eeprom文件。



编写i2c-app.c文件：

1. #include <stdio.h>
2. #include <sys/types.h>
3. #include <sys/stat.h>
4. #include <fcntl.h>
5. #include <unistd.h>
6. int main()
7. {
8. char write_data[256],read_data[256];
9. int fd;
10. int i = 0;
11. //打开at24c02对应的sys文件
12. fd = open("/sys/bus/i2c/devices/0-0050/eeprom", O_RDWR);
13. //写入数据
14. for(i=0;i<256;i++)
15. write_data[i] = i;
16. lseek(fd, 0, SEEK_SET);
17. write(fd, write_data, 256);
18. //读出数据
19. lseek(fd, 0, SEEK_SET);
20. read(fd, read_data, 256);
21. //打印对比
22. for(i=0;i<256;i++)
23. {
24. if(i%16 == 0) printf("\r\n");
25. printf("%3d ",read_data[i]);
26. }
27. printf("\n");
28. close(fd);
29. }