/*
This program is hereby placed into the public domain.
Of course the program is provided without warranty of any kind.
*/
#include <sys/ioctl.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <time.h>
#include <linux/i2c.h>
#include <linux/i2c-dev.h>

/*
  this program can read 24C16 (and probably smaller ones, too)
  I wrote it as a quick and dirty hack because my satellite receiver
  hung again... so I had to reprogram the eeprom where is stores it's
  settings.
 */

#define DEFAULT_I2C_BUS      "/dev/i2c-0"
#define DEFAULT_EEPROM_ADDR  0x50         /* the 24C16 sits on i2c address 0x50 */
#define DEFAULT_NUM_PAGES    8            /* we default to a 24C16 eeprom which has 8 pages */
#define BYTES_PER_PAGE       256          /* one eeprom page is 256 byte */
#define MAX_BYTES            8            /* max number of bytes to write in one chunk */
       /* ... note: 24C02 and 24C01 only allow 8 bytes to be written in one chunk.   *
        *  if you are going to write 24C04,8,16 you can change this to 16            */

/* write len bytes (stored in buf) to eeprom at address addr, page-offset offset */
/* if len=0 (buf may be NULL in this case) you can reposition the eeprom's read-pointer */
/* return 0 on success, -1 on failure */
int eeprom_write(int fd,
		 unsigned int addr,
		 unsigned int offset,
		 unsigned char *buf,
		 unsigned char len
){
	struct i2c_rdwr_ioctl_data msg_rdwr;
	struct i2c_msg             i2cmsg;
	int i;
	char _buf[MAX_BYTES + 1];

	if(len>MAX_BYTES){
	    fprintf(stderr,"I can only write MAX_BYTES bytes at a time!\n");
	    return -1;
	}

	if(len+offset >256){
	    fprintf(stderr,"Sorry, len(%d)+offset(%d) > 256 (page boundary)\n",
			len,offset);
	    return -1;
	}

	_buf[0]=offset;    /* _buf[0] is the offset into the eeprom page! */
	for(i=0;i<len;i++) /* copy buf[0..n] -> _buf[1..n+1] */
	    _buf[1+i]=buf[i];

	msg_rdwr.msgs = &i2cmsg;
	msg_rdwr.nmsgs = 1;

	i2cmsg.addr  = addr;
	i2cmsg.flags = 0;
	i2cmsg.len   = 1+len;
	i2cmsg.buf   = _buf;

	if((i=ioctl(fd,I2C_RDWR,&msg_rdwr))<0){
	    perror("ioctl()");
	    fprintf(stderr,"ioctl returned %d\n",i);
	    return -1;
	}

	if(len>0)
	    fprintf(stderr,"Wrote %d bytes to eeprom at 0x%02x, offset %08x\n",
		    len,addr,offset);
	else
	    fprintf(stderr,"Positioned pointer in eeprom at 0x%02x to offset %08x\n",
		    addr,offset);

	return 0;
}

/* read len bytes stored in eeprom at address addr, offset offset in array buf */
/* return -1 on error, 0 on success */
int eeprom_read(int fd,
		 unsigned int addr,
		 unsigned int offset,
		 unsigned char *buf,
		 unsigned char len
){
	struct i2c_rdwr_ioctl_data msg_rdwr;
	struct i2c_msg             i2cmsg;
	int i;

	if(len>MAX_BYTES){
	    fprintf(stderr,"I can only write MAX_BYTES bytes at a time!\n");
	    return -1;
	}

	if(eeprom_write(fd,addr,offset,NULL,0)<0)
	    return -1;

	msg_rdwr.msgs = &i2cmsg;
	msg_rdwr.nmsgs = 1;

	i2cmsg.addr  = addr;
	i2cmsg.flags = I2C_M_RD;
	i2cmsg.len   = len;
	i2cmsg.buf   = buf;

	if((i=ioctl(fd,I2C_RDWR,&msg_rdwr))<0){
	    perror("ioctl()");
	    fprintf(stderr,"ioctl returned %d\n",i);
	    return -1;
	}

	fprintf(stderr,"Read %d bytes from eeprom at 0x%02x, offset %08x\n",
		len,addr,offset);

	return 0;
}


int main(int argc, char **argv){
    int i,j;

    /* filedescriptor and name of device */
    int d; 
    char *dn=DEFAULT_I2C_BUS;

    /* filedescriptor and name of data file */
    int f=-1;
    char *fn=NULL;

    unsigned int addr=DEFAULT_EEPROM_ADDR;
    int rwmode=0;
    int pages=DEFAULT_NUM_PAGES;

    int force=0; /* suppress warning on write! */
    
    while((i=getopt(argc,argv,"d:a:p:wyf:h"))>=0){
	switch(i){
	case 'h':
	    fprintf(stderr,"%s [-d dev] [-a adr] [-p pgs] [-w] [-y] [-f file]\n",argv[0]);
	    fprintf(stderr,"\tdev: device, e.g. /dev/i2c-0    (def)\n");
	    fprintf(stderr,"\tadr: base address of eeprom, eg 0xA0 (def)\n");
	    fprintf(stderr,"\tpgs: number of pages to read, eg 8 (def)\n");
	    fprintf(stderr,"\t-w : write to eeprom (default is reading!)\n");
	    fprintf(stderr,"\t-y : suppress warning when writing (default is to warn!)\n");
	    fprintf(stderr,"\t-f file: copy eeprom contents to/from file\n");
	    fprintf(stderr,"\t         (default for read is test only; for write is all zeros)\n");
	    fprintf(stderr,"Note on pages/addresses:\n");
	    fprintf(stderr,"\teeproms with more than 256 byte appear as if they\n");
	    fprintf(stderr,"\twere several eeproms with consecutive addresses on the bus\n");
	    fprintf(stderr,"\tso we might as well address several separate eeproms with\n");
	    fprintf(stderr,"\tincreasing addresses....\n\n");
	    exit(1);
	    break;
	case 'd':
	    dn=optarg;
	    break;
	case 'a':
	    if(sscanf(optarg,"0x%x",&addr)!=1){
		fprintf(stderr,"Cannot parse '%s' as addrs., example: 0xa0\n",
			optarg);
		exit(1);
	    }
	    break;
	case 'p':
	    if(sscanf(optarg,"%d",&pages)!=1){
		fprintf(stderr,"Cannot parse '%s' as number of pages, example: 8\n",
			optarg);
		exit(1);
	    }
	    break;
	case 'w':
	    rwmode++;
	    break;
	case 'f':
	    fn=optarg;
	    break;
	case 'y':
	    force++;
	    break;
	}

    }
   
    fprintf(stderr,"base-address of eeproms       : 0x%02x\n",addr);
    fprintf(stderr,"number of pages to read       : %d (0x%02x .. 0x%02x)\n",
		    pages,addr,addr+pages-1);

    if(fn){
	if(!rwmode) /* if we are reading, *WRITE* to file */
	    f=open(fn,O_WRONLY|O_CREAT,0666);
	else /* if we are writing to eeprom, *READ* from file */
	    f=open(fn,O_RDONLY);
	if(f<0){
	    fprintf(stderr,"Could not open data-file %s for reading or writing\n",fn);
	    perror(fn);
	    exit(1);
	}
	fprintf(stderr,"file opened for %7s       : %s\n",rwmode?"reading":"writing",fn);
	fprintf(stderr,"            on filedescriptor : %d\n",f);
    }

    if((d=open(dn,O_RDWR))<0){
	fprintf(stderr,"Could not open i2c at %s\n",dn);
	perror(dn);
	exit(1);
    }

    fprintf(stderr,"i2c-devicenode is             : %s\n",dn);
    fprintf(stderr,"            on filedescriptor : %d\n\n",d);

    /***
     *** I'm not the one to blame of you screw your computer!
     ***/
    if(rwmode && ! force){
	unsigned char warnbuf[4];
	fprintf(stderr,"**WARNING**\n");
	fprintf(stderr," - \tYou have chosen to WRITE to this eeprom.\n");
	fprintf(stderr,"\tMake sure that this tiny chip is *NOT* vital to the\n");
	fprintf(stderr,"\toperation of your computer as you can easily corrupt\n");
	fprintf(stderr,"\tthe configuration memory of your SDRAM-memory-module,\n");
	fprintf(stderr,"\tyour IBM ThinkPad or whatnot...! Fixing these errors can be\n");
	fprintf(stderr,"\ta time-consuming and very costly process!\n\n");
	fprintf(stderr,"Things to consider:\n");
	fprintf(stderr," - \tYou can have more than one i2c-bus, check in /proc/bus/i2c\n");
	fprintf(stderr,"\tand specify the correct one with -d\n");
	fprintf(stderr,"\tright now you have chosen to use '%s'\n",dn);
	fprintf(stderr," - \tA eeprom can occupy several i2c-addresses (one per page)\n");
	fprintf(stderr,"\tso please make sure that there is no vital eeprom in your computer\n");
	fprintf(stderr,"\tsitting at addresses between 0x%02x and 0x%02x\n",addr,addr+pages-1);

	fprintf(stderr,"Enter 'yes' to continue:");
	fflush(stderr);
	if(!fgets(warnbuf,sizeof(warnbuf),stdin)){
	    fprintf(stderr,"\nCould not read confirmation from stdin!\n");
	    exit(1);
	}
	if(strncmp(warnbuf,"yes",3)){
	    fprintf(stderr,"\n** ABORTING WRITE! **, you did not answer 'yes'\n");
	    exit(1);
	}
    }

    for(i=0;i<pages;i++){
	unsigned char buf[BYTES_PER_PAGE];

	if(rwmode){

	    if(f>=0){
		j=read(f,buf,sizeof(buf));
		if(j<0){
		    fprintf(stderr,"Cannot read from file '%s'\n",fn);
		    perror(fn);
		    exit(1);
		}
		if(j!=sizeof(buf)){
		    fprintf(stderr,"File '%s' is too small, padding eeprom with zeroes\n",fn);
		    while(j<sizeof(buf))
			buf[j++]=0;
		}
	    } else {
		for(j=0;j<sizeof(buf);j++)
		    buf[j]=0;
	    }
            for(j=0;j<(BYTES_PER_PAGE/MAX_BYTES);j++)
		if(eeprom_write(d,addr+i,j*MAX_BYTES,buf+(j*MAX_BYTES),MAX_BYTES)<0)
		    exit(1);
	} else {
            for(j=0;j<(BYTES_PER_PAGE/MAX_BYTES);j++)
		if(eeprom_read(d,addr+i,j*MAX_BYTES,buf+(j*MAX_BYTES),MAX_BYTES)<0)
		    exit(1);
	}


	if(!rwmode && f>=0){
	    j=write(f,buf,sizeof(buf));
	    if(j!=sizeof(buf)){
		fprintf(stderr,"Cannot write to file '%s'\n",fn);
		perror(fn);
		exit(1);
	    }
	}

    }

    if(f>=0)
	close(f);

    close(d);

    exit(0);

}