Re: [PATCH v2 3/4] powerpc/boot: Add bzip2 support for uImage

[Christophe Leroy]

On 04/25/2019 02:37 PM, Adam Borowski wrote:
> On Tue, Apr 23, 2019 at 02:20:43PM +0000, Christophe Leroy wrote:
> > This patch allows to generate bzip2 compressed uImage
>
> Please don't add bzip2 support, that's a waste of your time as we're trying
> to remove it kernel-wide.  There's a patchset to retire compressors beaten
> by alternatives on the whole speed-to-size curve; reposting it is overdue.
>
> It does:
> * add ZSTD (fast and strong)
> * remove BZIP2 (obsolete, only user in kernel)
> * remove LZMA (redundant with XZ, uses a private copy of its library)
> * makes Kconfig prose talk badly about LZO (used elsewhere in the kernel)
>
> I believe only three compressors are worth using here: XZ, ZSTD, LZ4.
> GZIP must stay because of ubiquitous support, the rest should go.

Ok. Initially the purpose was to add lzma, then I took the opportunity 
to add all compressors supported by u-boot uImage files which are 'none, 
bzip2, gzip, lzma, lzo':

[root@po16846vm linux-powerpc]# mkimage -C -h

Invalid Compression Type - valid names are: none, bzip2, gzip, lzma, lzo
Usage: mkimage -l image
          -l ==> list image header information
       mkimage [-x] -A arch -O os -T type -C comp -a addr -e ep -n name 
-d data_file[:data_file...] image


So I can leave bzip2 aside.

xz, zstd and lz4 are not supported by the uImage format as far as I know 
so we have to keep lzma which gives a far better compression ratio than 
gzip (gzipped uImage don't fit in my board's NOR Flash while lzmaed 
uImage does).

Christophe


> > --- a/arch/powerpc/Kconfig
> > +++ b/arch/powerpc/Kconfig
> > @@ -199,6 +199,7 @@ config PPC
> > +	select HAVE_KERNEL_BZIP2		if DEFAULT_UIMAGE
> > --- a/arch/powerpc/boot/Makefile
> > +++ b/arch/powerpc/boot/Makefile
> > @@ -23,6 +23,7 @@ all: $(obj)/zImage
> > +compress-$(CONFIG_KERNEL_BZIP2)   := CONFIG_KERNEL_BZIP2
> > @@ -259,6 +260,7 @@ endif
> > +compressor-$(CONFIG_KERNEL_BZIP2) := bz2
> > --- a/arch/powerpc/boot/wrapper
> > +++ b/arch/powerpc/boot/wrapper
> > @@ -137,7 +137,7 @@ while [ "$#" -gt 0 ]; do
> > -        [ "$1" != "gz" -o "$1" != "xz" -o "$1" != "lzma" -o "$1" != "none" ] || usage
> > +        [ "$1" != "gz" -o "$1" != "xz" -o "$1" != "lzma" -o "$1" != "bz2" -o "$1" != "none" ] || usage
> > @@ -149,6 +149,9 @@ while [ "$#" -gt 0 ]; do
> > +	if [ $uboot_comp = "bz2" ]; then
> > +		uboot_comp=bzip2
> > +	fi
> > @@ -377,6 +380,9 @@ if [ -z "$cacheit" -o ! -f "$vmz$compression" -o "$vmz$compression" -ot "$kernel
> > +    .bz2)
> > +        bzip2 -f "$vmz.$$"
> > +	;;
>
>
> Meow!