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

[Wolfgang Denk]

Dear Simon Glass,

In message <CAPnjgZ2aRP5Hn-3jREa=OfGs0K7Ny9b2mWP3pwPBRW5svL3Aew at mail.gmail.com> you wrote:
> 
> > Firstly, there is not just u-Boot out there.  And since the layout
> > optimization for Linux when decompressing is by definition Linux
> > specific, this better live in zImage than be duplicated in every
> > bootloaders.
> 
> Actually I was talking about the case where U-Boot does the
> decompression. You have said it is supported above. I don't suggest
> that it be the only option, only that it be an option. Perhaps only
> U-Boot will use it, but that is fine. U-Boot is a popular boot loader.


Thanks a lot for bringing up these arguments.

> If the boot loader puts the pieces in the right place, decompressed
> and ready to go, we could presumably avoid this code in the kernel:
> 
>  1096  4860 27129 arch/arm/boot/compressed/head.S
>    13    53   304 arch/arm/boot/compressed/big-endian.S
>    50   153  1267 arch/arm/boot/compressed/decompress.c
>  1096  4860 27129 arch/arm/boot/compressed/head.S
>    47   214  1238 arch/arm/boot/compressed/head-sa1100.S
>   139   650  3537 arch/arm/boot/compressed/head-shark.S
>   150   619  3564 arch/arm/boot/compressed/head-sharpsl.S
>    53   263  1685 arch/arm/boot/compressed/head-shmobile.S
>    41   179   992 arch/arm/boot/compressed/head-xscale.S
>   134   571  2868 arch/arm/boot/compressed/ll_char_wr.S
>   124   324  3011 arch/arm/boot/compressed/Makefile
>   208   589  3812 arch/arm/boot/compressed/misc.c
>   260   604  5289 arch/arm/boot/compressed/ofw-shark.c
>     6    10   145 arch/arm/boot/compressed/piggy.gzip.S
>     6    10   145 arch/arm/boot/compressed/piggy.lzma.S
>     6    10   144 arch/arm/boot/compressed/piggy.lzo.S
>    70   226  1481 arch/arm/boot/compressed/vmlinux.lds.in
>  2403  9335 56611 total

I think you can even add the actual (de-) compressor routines.

> That gives the kernel what it wants. How can we give U-Boot what it
> wants, which is apparently the ability to decompress the kernel itself
> and arrange everything in memory at the right place? Wolfgang
> complains that patches to do this have been repeatedly rejected in the
> kernel. If this is the FIT image, how about adding a 'fitImage' make
> target?

It would not only be FIT images.  Why not support old uImage format in
a "proper" way?  In most cases people do not need the features
provided by FIT images, and they prefer the simplicity of uImages.


Thanks again.

Best regards,

Wolfgang Denk

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