Re: [PATCH] arm/tegra: select AUTO_ZRELADDR by default

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 10/14/2011 04:01 PM, 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.
> 
> 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.
> 
> Now admittedly I did say I didn't find any traces of zImage support, which
> isn't what I'm saying here; I guess I forgot about the stuff I did find
> soon after I chose the path of modifying the uImage formats.
> 

FYI, this exact topic has been discussed on the Linaro weekly
boot-architecture call and list. The discussion has been more general in
terms of what can be done to make installing and updating kernels
easier/work for distros.

https://wiki.linaro.org/OfficeofCTO/BootArchitecture

Rob