@bozoid,

Thanks for your findings!

I haven't investigated this yet, but I think the /dev/mmcblk* devices are created by udev, which is started in /etc/init.d/rcS, which is the first script run by upstart after /sbin/preinit passes control to it.

Have a look in /etc/udev/rules.d/92-n770.rules as well as /lib/udev/mmc_id (which provides a suitable name to udev). mmc_id gives the SLOT_NUM 1 to the external MMC and SLOT_NUM 0 to the internal MMC (even though the kernel appears to detect the external MMC first and then the internal one, so udev effectively swaps the slot numbers).