I'm not sure this is the best way to approach it, as what you add
is not really a partition format.
I'd suggest checking for the LUKS signature in the atari partition
parser instead - that way the code is automatically built when the
atari partition parser is built in, and not built when not needed.
Minor nitpick:
> + if (memcmp(data, LUKS_MAGIC_1ST_V1, 8) == 0
> + || memcmp(data, LUKS_MAGIC_2ND_V1, 8) == 0) {
The || goes at the end of the line for the linux coding style, and the
continuing line is indented either after the opening brace or by an
extra tab vs the following code:
if (memcmp(data, LUKS_MAGIC_1ST_V1, 8) == 0 ||
memcmp(data, LUKS_MAGIC_2ND_V1, 8) == 0) {
