Re: [PATCH v2] kbuild: switch from lz4c to lz4 for compression

[Greg KH <gregkh@linuxfoundation.org>]

On Thu, Nov 14, 2024 at 03:56:44PM +0100, Parth Pancholi wrote:
> From: Parth Pancholi <parth.pancholi@toradex.com>
> 
> Replace lz4c with lz4 for kernel image compression.
> Although lz4 and lz4c are functionally similar, lz4c has been deprecated
> upstream since 2018. Since as early as Ubuntu 16.04 and Fedora 25, lz4
> and lz4c have been packaged together, making it safe to update the
> requirement from lz4c to lz4.
> 
> Consequently, some distributions and build systems, such as OpenEmbedded,
> have fully transitioned to using lz4. OpenEmbedded core adopted this
> change in commit fe167e082cbd ("bitbake.conf: require lz4 instead of
> lz4c"), causing compatibility issues when building the mainline kernel
> in the latest OpenEmbedded environment, as seen in the errors below.
> 
> This change also updates the LZ4 compression commands to make it backward
> compatible by replacing stdin and stdout with the '-' option, due to some
> unclear reason, the stdout keyword does not work for lz4 and '-' works for
> both. In addition, this modifies the legacy '-c1' with '-9' which is also
> compatible with both. This fixes the mainline kernel build failures with
> the latest master OpenEmbedded builds associated with the mentioned
> compatibility issues.
> 
> LZ4     arch/arm/boot/compressed/piggy_data
> /bin/sh: 1: lz4c: not found
> ...
> ...
> ERROR: oe_runmake failed
> 
> Cc: stable@vger.kernel.org

What bug does this resolve that it needs to be backported to stable
kernels?

thanks,

greg k-h