Qi is a lightweight bootloader for OpenMoko Freerunner phones. It can be installed to the beginning of the NAND flash to load a kernel and an initramfs from either an SD card or NAND flash.
Freerunner has three types of non-volatile storage: NOR flash, NAND flash and an SD card. NOR flash is read-only and holds a copy of the U-boot bootloader:
$ sudo strings /dev/mtd0 | egrep "^(U-Boot|Qi) "
U-Boot 1.3.2-moko12 (May 9 2008 - 10:28:48)
Code in NOR flash is executed only if AUX button is held when you hit POWER button to boot the system. You can use U-boot to flash NAND partitions using the DFU protocol. Qi does not support DFU.
NAND flash is divided into several partitions. This mapping is passed as a commandline argument to Linux so you can view it simply by reading /proc/mtd:
$ cat /proc/mtd
dev: size erasesize name
mtd0: 00200000 00010000 "physmap-flash.0"
mtd1: 00040000 00020000 "qi"
mtd2: 00040000 00020000 "depr-ub-env"
mtd3: 00820000 00020000 "kernel"
mtd4: 000a0000 00020000 "depr"
mtd5: 00040000 00020000 "identity-ext2"
mtd6: 0f680000 00020000 "rootfs"
You can check what bootloader exists in the begining of the NAND flash by running e.g.:
$ sudo strings /dev/mtd1 | egrep "^(U-Boot|Qi) "
Qi Bootloader s3c2442 ginger debian_20100107-1
Qi support both uSD and uSDHC cards. It can parse a regular MSDOS partition table and has a read-only ext2 filesystem driver which seems to work also with ext3 (with or without journaling) and ext4 without extents.
Qi tries to boot from five different locations. It moves to the next entry in the list below if it fails to load a kernel or if you hit AUX while Qi is reading the kernel or the initramfs:
Boot option 1
Kernel: /boot/uImage-GTA02.bin from SD partition 1
Initramfs: /boot/initrd-GTA02.bin from SD partition 1
Extra arguments: /boot/append-GTA02.bin from SD partition 1
Boot option 2
Kernel: /boot/uImage-GTA02.bin.2 from SD partition 1
Initramfs: /boot/initrd-GTA02.bin.2 from SD partition 1
Extra arguments: /boot/append-GTA02.bin.2 from SD partition 1
Boot option 3
Kernel: /boot/uImage-GTA02.bin from SD partition 2
Initramfs: /boot/initrd-GTA02.bin from SD partition 2
Extra arguments: /boot/append-GTA02.bin from SD partition 2
Boot option 4
Kernel: /boot/uImage-GTA02.bin from SD partition 3
Initramfs: /boot/initrd-GTA02.bin from SD partition 3
Extra arguments: /boot/append-GTA02.bin from SD partition 3
Boot option 5
Kernel: kernel partition from NAND flash (/dev/mtd3)
Initramfs: not supported
Extra arguments: not supported
The kernel can be either in uImage or zImage format. Qi understands symlinks.
Additional documentation is available in the README file and OpenMoko wiki.