It just displays 0x0 for the raw video resolution instead of e.g. 1856x1044 etc.. it does works find on normal nightly builds and even works with 10-12bit experimental builds that I compile.
That means, for some reason, raw_update_params() failed. There are some consistency checks done, in particular on the optical black area - so if the image has e.g. some lines of garbage at the bottom, these tests will fail.
To skip these checks, I just hardcode the black level value temporarily (in autodetect_black_level, write some reasonable values for both black_level and black_stdev_x100, and comment out the autodetection).
I don't think it has anything to do with ROM contents. More likely, if the raw buffer does not update completely (read: the EDMAC transfers fewer bytes than declared raw buffer size), the last lines from the buffer will contain whatever it happened to be in memory when allocating it (and that's non-deterministic). The above patch will let you preview incomplete buffers (both in raw_diag and in the raw recorder's "grayscale" preview).
Regarding bricking issues, currently 5D2 can be emulated in QEMU, so if it happens, should be recoverable (unless you erase the bootloader somehow). A nice research project would be emulating the flash ROM routines, then jumping to random addresses (
only in QEMU, never on real camera!!!) and checking what would happen (whether you can reflash parts of the ROM by mistake, and then, how to prevent these actions). See
this PR, but it's really just scratching the surface.
