This question is regarding understanding linux kernel driver at24 that handles most I2C EEPROM devices (located at kernel/drivers/misc/eeprom/at24.c).

1. I am not able to figure out who calls the read/write routines within the at24 driver. I don't see a file operations (fops) structure being initialized with a .read or .write entry within the driver

Initially I thought the I2C bus driver must be invoking them in response to user I2C operations. To find this I added debug statements within those routines and invoked a test program from user space which reads and writes to the eeprom. The reads and writes are successful but none of the debug prints get printed from the at24 device driver read or write routines.

2. Another related question is about the platform data. There is no good documentation except for some comments about what should go in the fields byte_len and page_size. Is byte_len which is defined as /* size (sum of all address) */ for say a 2K eeprom equal to 2Kbits/8 (bits per byte) = 256.

Is Page size the bytes within a single page = 8 bytes ?

I tried all possible values but the kernel prints errors in response at init time and so asking here.

For your first question, the interface to the driver is not through char or block, it is through the sysfs. A file will be created in the sysfs and when you access this file the read and write functions will be called. read/write functions are registered with the sysfs like this:

sysfs_bin_attr_init(&at24->bin);
at24->bin.attr.name = "eeprom";
at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
at24->bin.read = at24_bin_read;
at24->bin.size = chip.byte_len;

at24->bin.write = at24_bin_write;
at24->bin.attr.mode |= S_IWUSR;
err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);

A file with name 'eeprom' will be created in the sysfs.

byte_len will be size of eeprom in bytes and page_size will be page size in bytes for writes.