On 01/06/2022 11:29, Stefan Herbrechtsmeier wrote:
> Hi Simon,
>
> I want to compress a FPGA Image on the fly via binman but this doesn't
> work. I have add a bintool implementation for gzip, add gzip support to
> comp_util.py and set `compress` and `compression` property in the binman
> node of the u-boot dtsi:
>
> fpga-2cg {
> compatible = "u-boot,fpga-legacy";
> description = "FPGA";
> type = "fpga";
> compression = "gzip";
> load = <(CONFIG_SYS_TEXT_BASE + 0x4000000)>;
>
> blob-ext {
> compress = "gzip";
> filename = "2cg.bit.bin";
> };
> };
>
> It works if I remove the `compress` property and use a `2cg.bit.bin.gz`
> or remove the header for gzip [1].
>
> Regarding the code binman add the compressed size as first word to the
> data [2]. The code in spl-fit.c doesn't remove the size [3]. Why is this
> size added?
I looked into this a tiny bit, git blame eventually ends up at:
> commit eb0f4a4cb40264a90a91e10e3ec00d1e0da7fb66
> Author: Simon Glass <s...@chromium.org>
> Date: 2019-07-20 12:24:06 -0600
>
> binman: Support replacing data in a cbfs
>
> At present binman cannot replace data within a CBFS since it does not
> allow rewriting of the files in that CBFS. Implement this by using the
> new WriteData() method to handle the case.
>
> Add a header to compressed data so that the amount of compressed data can
> be determined without reference to the size of the containing entry. This
> allows the entry to be larger that the contents, without causing errors in
> decompression. This is necessary to cope with a compressed device tree
> being updated in such a way that it shrinks after the entry size is
> already set (an obscure case). It is not used with CBFS since it has its
> own metadata for this. Increase the number of passes allowed to resolve
> the position of entries, to handle this case.
>
> Add a test for this new logic.
>
> Signed-off-by: Simon Glass <s...@chromium.org>
For the record, I dislike the size header, since as you found out it
turns the standard formats into custom formats that nothing else knows.
But I'm not familiar with binman's compression parts, I don't know what
would go wrong if the header is removed and how. I'm also not sure what
happens in the 'obscure case' the commit message mentions.
