[PATCH 1/1] add zchunk compression support

[Felix Moessbauer <felix.moessbauer@siemens.com>]

This patch adds support to compress images with zchunk. The compression
format is optimized for delta transfers, by ensuring that small changes
on the input also only invalidate some blocks of the output.

There are not yet many configuration options available, but once
available, they can be added to the ZCK_DEFAULTS variable.

Signed-off-by: Felix Moessbauer <felix.moessbauer@siemens.com>
---
 meta/classes/imagetypes.bbclass | 5 ++++-
 meta/conf/bitbake.conf          | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/meta/classes/imagetypes.bbclass b/meta/classes/imagetypes.bbclass
index a80a6da5..3639662b 100644
--- a/meta/classes/imagetypes.bbclass
+++ b/meta/classes/imagetypes.bbclass
@@ -93,7 +93,7 @@ IMAGE_CMD:ubi() {
 IMAGE_CMD:ubi[depends] = "${PN}:do_transform_template"
 
 # image conversions
-IMAGE_CONVERSIONS = "gz xz zst"
+IMAGE_CONVERSIONS = "gz xz zst zck"
 
 CONVERSION_CMD:gz = "${SUDO_CHROOT} sh -c 'gzip -f -9 -n -c --rsyncable ${IMAGE_FILE_CHROOT} > ${IMAGE_FILE_CHROOT}.gz'"
 CONVERSION_DEPS:gz = "gzip"
@@ -103,3 +103,6 @@ CONVERSION_DEPS:xz = "xz-utils"
 
 CONVERSION_CMD:zst = "${SUDO_CHROOT} sh -c 'zstd -c --sparse ${ZSTD_DEFAULTS} ${IMAGE_FILE_CHROOT} > ${IMAGE_FILE_CHROOT}.zst'"
 CONVERSION_DEPS:zst = "zstd"
+
+CONVERSION_CMD:zck = "${SUDO_CHROOT} sh -c 'cd $(dirname ${IMAGE_FILE_CHROOT}); zck ${ZCK_DEFAULTS} ${IMAGE_FILE_CHROOT}'"
+CONVERSION_DEPS:zck = "zchunk"
diff --git a/meta/conf/bitbake.conf b/meta/conf/bitbake.conf
index c660660a..f73e4838 100644
--- a/meta/conf/bitbake.conf
+++ b/meta/conf/bitbake.conf
@@ -144,6 +144,9 @@ ZSTD_LEVEL ?= "19"
 ZSTD_DEFAULTS ?= "--rsyncable -${ZSTD_LEVEL} --threads=${ZSTD_THREADS}"
 ZSTD_DEFAULTS[vardepsexclude] += "ZSTD_LEVEL ZSTD_THREADS"
 
+# Default compression settings for zchunk
+ZCK_DEFAULTS ?= ""
+
 BBINCLUDELOGS ??= "yes"
 
 # Add event handlers for bitbake
-- 
2.34.1