On Fri, 14 Oct 2011, Stephen Warren wrote: > Nicolas Pitre wrote at Friday, October 14, 2011 2:45 PM: > > On Fri, 14 Oct 2011, Stephen Warren wrote: > ... > > > I did originally briefly look into getting U-Boot to boot a zImage, but > > > that looked like a far more invasive patch. There were rumours of some > > > chip's custom U-Boot already having such support, but I couldn't find > > > it, nor any evidence of such support in mainline U-Boot. > > > > FRom my clone of the u-Boot repo: > > > > $ git grep -l zImage > > README > > arch/sh/lib/zimageboot.c > > arch/x86/lib/zimage.c > > ... > > > > Even the name of some of those files clearly hints zImage support. > > > > In any case, loading zImage should be even simpler than loading uImage. > > It is the same as loading uImage except that you just have to skip the > > checking and relocating steps. > > Just by way of background in case anyone is wondering why I wrote the > patch I did: > > Those files both implement custom commands "zimageboot" and "zboot". I > was looking for integration with the existing "bootm" command. > > The advantage of re-using "bootm" for this is that it already supports > all the stuff like setting up kernel command-lines, initrds, knowing how > to pass the FDT to the kernel, and whatever other OS-specific setup might > be required. Absolutely. And that is a must-have. > The disadvantage of adding zImage support to bootm is that I'd have to > teach a bunch of U-Boot image handling code about a new image format; it > already knows about "legacy uImage", "FIT" images, and I'd have to add a > third "zImage" format. Doing so would at least require adding a lot of > "case IMAGE_FORMAT_ZIMAGE" everywhere, but it'd probably be best to add > some kind of vtable for image formats to move all the image-format > knowledge into format-specific files, leaving the users of the images > with much smaller code. > > I didn't feel like making such a large change. Hence, I chose to make a > small change to the existing uImage support. And that change is certainly valuable. Some people do want the extra feature from the uImage format. REmoving its absolute address limitation is a good thing. However, also supporting zImage directly on ARM doesn't have to be that hard. Instead of adding "case IMAGE_FORMAT_ZIMAGE" everywhere, all you would have to do is to load zImage in memory according to the load address provided as an argument to the command, and then fake a uImage load by artificially creating the uImage header at run time with the data that u-Boot needs later on. Nicolas -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
