If a given compression algorithm for the kernel image is not usable on the host system, there is no point prompting for it. We can use the kconfig preprocessing feature to check if the command is available or not. I've chosen to test this using "which", which exits with success if the given command exists in PATH (or it is an absolute path), which mimics exactly how it would be found in the kernel's Makefiles. This uses the make variables that are set in Makefile and/or the command line, so you can do e.g. make KGZIP=pigz menuconfig and it will test for the correct program. I am intentionally adding these dependencies to e.g. KERNEL_LZ4, as opposed to HAVE_KERNEL_LZ4, since the latter are "select"-ed unconditionally by the architectures that use them, so they are not suitable for depending on anything else. I've put RFC in the subject as maybe there are downsides to this that I'm not aware of. Signed-off-by: Vegard Nossum <vegard.nossum@xxxxxxxxxx> --- init/Kconfig | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/init/Kconfig b/init/Kconfig index 11f8a845f259d..f03f2b7962027 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -250,6 +250,7 @@ choice config KERNEL_GZIP bool "Gzip" depends on HAVE_KERNEL_GZIP + depends on $(success,which $(KGZIP)) help The old and tried gzip compression. It provides a good balance between compression ratio and decompression speed. @@ -257,6 +258,7 @@ config KERNEL_GZIP config KERNEL_BZIP2 bool "Bzip2" depends on HAVE_KERNEL_BZIP2 + depends on $(success,which $(KBZIP2)) help Its compression ratio and speed is intermediate. Decompression speed is slowest among the choices. The kernel @@ -267,6 +269,7 @@ config KERNEL_BZIP2 config KERNEL_LZMA bool "LZMA" depends on HAVE_KERNEL_LZMA + depends on $(success,which $(LZMA)) help This compression algorithm's ratio is best. Decompression speed is between gzip and bzip2. Compression is slowest. @@ -275,6 +278,7 @@ config KERNEL_LZMA config KERNEL_XZ bool "XZ" depends on HAVE_KERNEL_XZ + depends on $(success,which $(XZ)) help XZ uses the LZMA2 algorithm and instruction set specific BCJ filters which can improve compression ratio of executable @@ -290,6 +294,7 @@ config KERNEL_XZ config KERNEL_LZO bool "LZO" depends on HAVE_KERNEL_LZO + depends on $(success,which $(KLZOP)) help Its compression ratio is the poorest among the choices. The kernel size is about 10% bigger than gzip; however its speed @@ -298,6 +303,7 @@ config KERNEL_LZO config KERNEL_LZ4 bool "LZ4" depends on HAVE_KERNEL_LZ4 + depends on $(success,which $(LZ4)) help LZ4 is an LZ77-type compressor with a fixed, byte-oriented encoding. A preliminary version of LZ4 de/compression tool is available at @@ -310,6 +316,7 @@ config KERNEL_LZ4 config KERNEL_ZSTD bool "ZSTD" depends on HAVE_KERNEL_ZSTD + depends on $(success,which $(ZSTD)) help ZSTD is a compression algorithm targeting intermediate compression with fast decompression speed. It will compress better than GZIP and -- 2.23.0.718.g5ad94255a8
