UM0851 datasheet(84/245 Pages) STMICROELECTRONICS

84 / 245 page

Communication device drivers

UM0851

84/245

Doc ID 16604 Rev 2

This shows four different I2C chip devices, all controlled by the same EEPROM driver. To

locate the controlling driver,you can look in the /sys/bus/i2c/drivers directory or in the

directory of the chip device itself and read the name file.

$ cat /sys/devices/platform/spear_i2c.6/i2c-0/0-0050/name

eeprom

Read and write

To read and write from the user space, you need binary attribute. The structure used for this

is:

static struct bin_attribute eeprom_attr = {

.attr = {

.name = "eeprom",

.mode = S_IRWXUGO,

.owner = THIS_MODULE,

.size = EEPROM_SIZE,

.read = eeprom_read,

}

Cleaning up

When the I2C chip device is removed from the system, by unloading either the I2C bus

driver or the I2C chip driver, the I2C core calls the detach_client() function specified in the

struct i2c_driver. This is usually a simple function, as it can be seen in the example driver's

implementation.

static int eeprom_detach_client(struct i2c_client *client)

{

int err;

sysfs_remove_bin_file(&client->dev.kobj, &xxx_attr);

err = i2c_detach_client(client);

if (err)

return err;

kfree(i2c_get_clientdata(client));

return 0;

}

While the i2c_attach_client() function is called to register the struct i2c_client with the I2C

core, the i2c_detach_client() function is used to unregister it. If that function succeeds, the

memory the driver has allocated for the I2C device needs to be freed before returning from

the function.

This example driver does not specifically remove the sysfs files from the sysfs core. This

step is done automatically in the driver core within the i2c_detach_client() function. But if

necessary, you can remove the file manually using a call to device_remove_file.

4.5.5

I2C driver performance

The driver performance was evaluated using the following setup:

●

Target device: SPEAr600

–

CPU: 332 MHz - AHB: 166 MHz - DDR: 333 MHz

–

M24C04 EEPROM (size: 512 Bytes, block size: 16 Bytes)

UM0851 bảng dữ liệu(PDF) 84 Page - STMicroelectronics

UM0851 bảng dữ liệu(HTML) 84 Page - STMicroelectronics

Html Pages

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 ...More

bảng dữ liệu tải về

Link URL