dump I2C EEPROM memory from Linux device ioctl

dump_i2c_eeprom.c

#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>

#include <linux/i2c-dev.h>


#define READ_SIZE	(256)
#define NB_PAGES	(256)


/* UTILS **********************************************************************/
void hexprint(const uint8_t *input, const int input_length)
{
	int i = 0;

	for (i = 0; i < input_length; i++) {
		if (i%16 == 0) {
			printf("\n");
		}
		printf("%02x ", input[i]);
	}
	printf("\n");
}

void dump_to_file(const char *output_file_path,
		  const uint8_t *buffer, const int buffer_length)
{
	int output_file = open(output_file_path, O_RDWR|O_APPEND|O_CREAT);
	if (output_file < 0) {
		printf("Failed opening output file %s\n", output_file_path);
		return;
	}

	write(output_file, buffer, buffer_length);
}


/* MAIN ***********************************************************************/
int main(int argc, char *argv[])
{
	/* got these values from i2cdetect */
	const char *i2c_device = "/dev/i2c-2";
	const int device_address = 0x50;

	/* open the i2c device file */
	int file = open(i2c_device, O_RDWR);
	if (file < 0) {
		printf("Failed opening %s\n", i2c_device);
		return 1;
	}

	if (ioctl(file, I2C_SLAVE, device_address) < 0) {
		printf("Failed addressing device at %02X\n", device_address);
		close(file);
		return 1;
	}

	int i = 0;
	for (i = 0; i < NB_PAGES; i++) {
		char buf[READ_SIZE] = {0};

		if (read(file, buf, READ_SIZE) != READ_SIZE) {
			printf("Failed reading\n");
			close(file);
			return 1;
		}

		//hexprint(buf, READ_SIZE);
		dump_to_file(argv[1], buf, READ_SIZE);
	}

	close(file);

	return 0;
}

Check my fork.. it's even easier.. all that is missing is a simple write:

write(file,'\x00\x00',2); // ADDRESS

before the read cycle.

25c256 have 16 bit HI then LO, as address.
Smaller eeproms have only 8 so the write must be one byte only.

note: when writing back instead, you must write the address (2 bytes) followed by the data (32bytes maximum), and wait at least 3ms between the writes.

here is the full backup and restore program which now includes also the "aknowledge polling" (before I had just an ugly usleep function).

https://gist.github.com/Zibri/cf8ac0b311301aeeaa8910c7da824bff