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SubjectRE: [RFC] buildtar: add case for riscv architecture
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> -----Original Message-----
> From: linux-kernel-owner@vger.kernel.org <linux-kernel-
> owner@vger.kernel.org> On Behalf Of Palmer Dabbelt
> Sent: Saturday, September 14, 2019 6:30 PM
> To: mail@aurabindo.in
> Cc: Troy Benjegerdes <troy.benjegerdes@sifive.com>; Paul Walmsley
> <paul.walmsley@sifive.com>; aou@eecs.berkeley.edu; linux-
> riscv@lists.infradead.org; linux-kernel@vger.kernel.org; linux-
> kbuild@vger.kernel.org
> Subject: Re: [RFC] buildtar: add case for riscv architecture
>
> On Wed, 11 Sep 2019 05:54:07 PDT (-0700), mail@aurabindo.in wrote:
> >
> >
> >> None of the available RiscV platforms that I’m aware of use compressed
> images, unless there are some new bootloaders I haven’t seen yet.
> >>
> >
> > I noticed that default build image is Image.gz, which is why I thought its a
> good idea to copy it into the tarball. Does such a copy not make sense at this
> point ?
>
> Image.gz can't be booted directly: it's just Image that's been compressed
> with the standard gzip command. A bootloader would have to decompress
> that image before loading it into memory, which requires extra bootloader
> support.
> Contrast that with the zImage style images (which are vmlinuz on x86), which
> are self-extracting and therefor require no bootloader support. The
> examples for u-boot all use the "booti" command, which expects
> uncompressed images.
> Poking around I couldn't figure out a way to have u-boot decompress the
> images, but that applies to arm64 as well so I'm not sure if I'm missing
> something.
>
> If I was doing this, I'd copy over arch/riscv/boot/Image and call it
> "/boot/image-${KERNELRELEASE}", as calling it vmlinuz is a bit confusing to
> me because I'd expect vmlinuz to be a self-extracting compressed
> executable and not a raw gzip file.

On the contrary, it is indeed possible to boot Image.gz directly using
U-Boot booti command so this patch would be useful.

Atish had got it working on U-Boot but he has deferred booti Image.gz
support due to few more dependent changes. May be he can share
more info.

Regards,
Anup
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