On Thursday 17 December 2009 02:31:36 Matt Hsu wrote: > Summary: Refactoring Qi, lightweight bootloader. > > Proposer: Matt Hsu > > > Description: > > Qi (named by Alan Cox on Openmoko kernel list) is a minimal bootloader that > "breathes life" into Linux. Its goal is to stay close to the minimum > needed Which bits does it do? Every piece of software needs something to initialize the DRAM controller. After that, they could presumably just jump to a known location in flash that the kernel lives at, and the kernel can decompress itself and so on. Doing just that much can probably be done in 4k pretty easily. (I gloss over the kernel command line and root filesystem location, which can be hardwired into the image if you really don't care about providing the developer with a UI.) However, if that's your minimum then you can't use the bootloader to re-flash the device, which is kind of handy. (It gives you an un-bricking fallback short of pulling out a jtag.) But doing that requires things like a network driver, TCP/IP stack, tftp implementation, serial driver, command line interpreter, and so on. And of course code to erase and write flash blocks for your flash chip du jour, plus knowledge of the flash layout. (In theory, said knowledge comes from parsing a device tree.) I still live in hope that somebody will split the first part (coreboot) out from the second part (grub) in embedded bootloaders. It's sad that the PC has a tradition of orthogonality here but the embedded world treats it as a single opaque lump. > http://wiki.openmoko.org/wiki/Qi Looking at the screen shot there, you've got code to parse ext2 filesystems. What is your definition of "minimal"? Rationale for not providing a boot menu is you don't want to mess with video init. I don't think I've actually seen an embedded bootloader that messes with video, they do serial console instead, and you have a screen shot of serial console messages so apparently the serial driver part is there... Confused, Rob -- Latency is more important than throughput. It's that simple. - Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
