The value you should specify for the block_size attribute depends on the physical block size of the flash device given in the manufacturer's data sheet and on how the flash device is configured in your hardware (specifically the interleave).
Here are some examples:
| If you have: | Set block_size to: |
|---|---|
| An 8-bit flash interface and are using an 8-bit device with a 64 KB block size | 64 KB |
| A 16-bit flash interface and are using two interleaved 8-bit flash devices with a 64 KB block size | 128 KB |
| A 16-bit flash interface and are using a 16-bit flash device with a 64 KB block size | 64 KB |
| A 32-bit flash interface and are using four interleaved 8-bit flash devices with a 64 KB block size | 256 KB |
Notice that you don't have to specify any details (other than the block size) about the actual flash devices used in your system.