Re: [ptxdist] [PATCH] image-root-cpio: Add compressor options to the env.

[Michael Olbrich <m.olbrich@pengutronix.de>]

On Thu, Mar 03, 2022 at 11:25:05PM +0100, Christian Melki wrote:
> * xz needs crc32 instead of crc64 for the kernel cpio.

Good point. I didn't know about that.

> * Set zstd compression level to the same as for the kernel (19).

Makes sense.

> * Use multithreading for zstd (deterministic, afaiu).

It is. I looked into this because I was curious. And it makes sense. zstd
was developed at a time when reproducibility was already important.

> Actively decided against -T0 for xz, as compression
> is not deterministic when number of threads varies.

We definitively want to be reproducible here.

> Signed-off-by: Christian Melki <christian.melki@t2data.com>
> ---
>  rules/image-root-cpio.make | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/rules/image-root-cpio.make b/rules/image-root-cpio.make
> index fdb0ccfff..eb09dd53e 100644
> --- a/rules/image-root-cpio.make
> +++ b/rules/image-root-cpio.make
> @@ -26,6 +26,9 @@ IMAGE_ROOT_CPIO_CONFIG	:= cpio.config
>  
>  IMAGE_ROOT_CPIO_ENV := \
>  	FORMAT="newc" \
> +	ZSTD_CLEVEL="19" \
> +	ZSTD_NBTHREADS="0" \
> +	XZ_OPT="--check=crc32" \
>  	COMPRESS=$(call remove_quotes, $(PTXCONF_IMAGE_ROOT_CPIO_COMPRESSION_UTIL))

Add the options to the PTXCONF_IMAGE_ROOT_CPIO_COMPRESSION_UTIL defaults
and keep the quotes here:

	COMPRESS=$(PTXCONF_IMAGE_ROOT_CPIO_COMPRESSION_UTIL)

genimage explicitly does not quote to make to possible to specify the
compressor with options. At least I thinks that should work.

And maybe we could add a IMAGE_ROOT_CPIO_COMPRESSION_MODE_CUSTOM and then
add 'prompt "suffix" if IMAGE_ROOT_CPIO_COMPRESSION_MODE_CUSTOM' to the
suffix and similar for the util.

This way the user could tweak things if absolutely necessary.

What do you think?

Michael

>  
>  ifdef PTXCONF_IMAGE_ROOT_CPIO
> -- 
> 2.30.2
> 
> 
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