[U-Boot] [PATCH v2 3/3] image: Allow images to indicate they're loadable at any address

Wolfgang Denk
2011-11-08T22:46:58Z

Dear Stephen Warren,

In message <4EB9ACDF.90702@nvidia.com> you wrote:
>
> > What would happen if we just create a new image type IH_TYPE_ZIMAGE?
>
> That would cover the kernel uImage case. We'd also need a new image type
> for "use in place" FDTs, since that also gets relocated to the image
> load address before use. I think initrds don't for some reason.

Did you check how PPC handles this? We usually load the DTB as a
separate file (the plain DTB, not any image) and just pass it's
address to the bootm command. U-Boot then knows how to handle the DTB
on a specific board.

Why would an image type for DTBs be needed?

> Another advantage of directly recognizing non-uImage-wrapper zImage,
> initrd, and FDT (in either bootm or bootz), is that distros wouldn't
> have to run mkimage ever; they could just dump the kernel in e.g.
> /boot/zImage (plus say /boot/initrd.img and /boot/fdt.bin), and expect
> U-Boot to pick it up and use it without any further processing. This
> would isolate more of the distro kernel install scripts from U-Boot, and
> keep them generic.

I have no real preference for one implementation versus the other. My
gut feeling is that bootm + IH_TYPE_ZIMAGE is much more straightfor-
ward, leaner and easier to implement. But it will add the 64 byte
uImage header which might be a nuisance in some cases. On the other
hand, bootz as to implement all the existing code again for handling
ramdisk/initrd and DTB, basicly identically. And you miss features
you might find useful in some cases - like that uImages have a name,
a timestamp, or a checksum, so you can identify and verify what has
been loaded.

I would go for IH_TYPE_ZIMAGE, but I'm not going to implement it.

Best regards,

Wolfgang Denk

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