I'm making my own image recipe and would still like to output the sdcard image as before for my iMX6, however I would like to move it from being based on an ext3 file system to ext4 (or potentially btrfs). For the life of me I can't work out what I need to override to achieve this. Adding ext4 as well as sdcard to the IMAGE_FSTYPES variable in my recipe in my own layer merely gives me both a .ext3 and .ext4 output, of which the .etx3 one appears to be used for the .sdcard image. Either that or it's ext4 mounting as ext3 at boot time... My image inherits core-image and installs CORE_IMAGE_BASE_INSTALL as the basis for my additions.
Any suggestions as to how I *should* be doing this?