Question about using I2C_IOCTL_EXEC to read data over I2C

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

I am trying to get data from a temperature/pressure sensor connected via i2c 
to a banana pi running NetBSD current. I understand the I2C protocol but I am 
having a bit of difficulty understanding what appears on the wire when the 
I2C_IOCTL_EXEC is called with the various op commands. By trial and error I 
seem to have been able to read the data, but want to check a few things in 
case I am doing it all wrong :-)

The device appears at address 0x77 (it's a BMP085) with i2cscan, the data 
sheet indicates the read address=0xEF/write address=0xEE. I just put 0x77 in 
the address field and assume the read/write bit on the wire is added based on 
the op code (I2C_OP_WRITE, I2C_OP_READ etc).

The device has R/O calibration data in 22 contiguous registers starting at 
0xAA->0xBF. Linux programs seem to grab the data in one go starting at 0xAA. 
The other registers needed to initiate a sensor data grab are R/W - you write 
a control byte into the 0xF4 register, wait a bit and then read the data from 
another register set.

A naive attempt to read the calibration data using:

    command = 0xAA ;
    iie.iie_op = I2C_OP_READ ;
    iie.iie_addr = 0x77 ;
    iie.iie_cmd = &command ;
    iie.iie_cmdlen = 1 ;
    iie.iie_buf = &caldata[0] ;
    iie.iie_buflen = 22;
    if ((ioctl(iicfd, I2C_IOCTL_EXEC, &iie)) !=0) {
        printf("read failed %d\n",errno) ;
        exit(1) ;
   }

actually seemed to work OK, but I don't understand why!

I had expected to need a I2C_OP_WRITE first followed by a I2C_OP_READ_STOP. 
The former would send a start bit, the device addr/write bit and the target 
register. The latter would send a (re)start bit, device addr/read bit, pull 
the data back and issue a stop. Maybe because the register I am addressing is 
R/O there is no need for a write and what I am doing is correct... (or do I 
need a I2C_OP_READ_STOP)

Could someone explain what actually gets sent on the wire for the various ops:

I2C_OP_READ
I2C_OP_READ_WITH_STOP
I2C_OP_WRITE
I2C_OP_WRITE_WITH_STOP
I2C_OP_READ_BLOCK 
I2C_OP_WRITE_BLOCK

and what difference block operations make as man ICC(4) is terse to say the 
least.

Cheers,
Dave