[PATCH v2 08/17] classes: image: introduce size measuring function, for before do_*_image

[Henning Schild <henning.schild@siemens.com>]

Measure the size and export it to the variable ROOTFS_SIZE just before
the imaging step. The concept is inspired by OE.

Issue:
The size of the rootfs is required for all sort of images, at the moment
Isar only supports one "real" image. Later patches will introduce
another image. And this patch prepares for that by moving the size
measurement into our image base class.

Impact:
 - Issue is solved
 - nothing changes for users

Signed-off-by: Henning Schild <henning.schild@siemens.com>
---
 meta/classes/ext4-img.bbclass |  7 ++-----
 meta/classes/image.bbclass    | 19 +++++++++++++++++++
 2 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/meta/classes/ext4-img.bbclass b/meta/classes/ext4-img.bbclass
index 8a978e6..d19d036 100644
--- a/meta/classes/ext4-img.bbclass
+++ b/meta/classes/ext4-img.bbclass
@@ -1,9 +1,6 @@
 # This software is a part of ISAR.
 # Copyright (C) 2015-2017 ilbers GmbH
 
-# Extra space for rootfs in MB
-ROOTFS_EXTRA ?= "64"
-
 ROOTFS_TYPE = "ext4"
 
 EXT4_IMAGE_FILE = "${DEPLOY_DIR_IMAGE}/${PN}-${DISTRO}-${MACHINE}.ext4.img"
@@ -14,8 +11,7 @@ do_ext4_image[stamp-extra-info] = "${DISTRO}-${MACHINE}"
 do_ext4_image() {
     rm -f ${EXT4_IMAGE_FILE}
 
-    ROOTFS_SIZE=`sudo du -sm ${IMAGE_ROOTFS} |  awk '{print $1 + ${ROOTFS_EXTRA};}'`
-    dd if=/dev/zero of=${EXT4_IMAGE_FILE} bs=1M count=${ROOTFS_SIZE}
+    dd if=/dev/zero of=${EXT4_IMAGE_FILE} bs=1k count=${ROOTFS_SIZE}
 
     sudo mkfs.ext4 -F ${EXT4_IMAGE_FILE}
 
@@ -33,3 +29,4 @@ do_ext4_image() {
 }
 
 addtask ext4_image before do_build after do_copy_boot_files
+do_ext4_image[prefuncs] = 'set_image_size'
diff --git a/meta/classes/image.bbclass b/meta/classes/image.bbclass
index a6537f9..2243860 100644
--- a/meta/classes/image.bbclass
+++ b/meta/classes/image.bbclass
@@ -5,6 +5,9 @@ IMAGE_INSTALL ?= ""
 IMAGE_TYPE    ?= "ext4-img"
 IMAGE_ROOTFS   = "${WORKDIR}/rootfs"
 
+# Extra space for rootfs in MB
+ROOTFS_EXTRA ?= "64"
+
 def get_image_name(d, name_link):
     S = d.getVar("IMAGE_ROOTFS", True)
     path_link = os.path.join(S, name_link)
@@ -15,6 +18,22 @@ def get_image_name(d, name_link):
                                                  '/'))
     return ""
 
+def get_rootfs_size(d):
+    import subprocess
+    rootfs_extra = int(d.getVar("ROOTFS_EXTRA", True))
+
+    output = subprocess.check_output(['sudo', 'du', '-s', '--block-size=1k',
+                                      d.getVar("IMAGE_ROOTFS", True)])
+    base_size = int(output.split()[0])
+
+    return base_size + rootfs_extra * 1024
+
+python set_image_size () {
+    rootfs_size = get_rootfs_size(d)
+    d.setVar('ROOTFS_SIZE', str(rootfs_size))
+    d.setVarFlag('ROOTFS_SIZE', 'export', '1')
+}
+
 # These variables are used by wic and start_vm
 KERNEL_IMAGE ?= "${@get_image_name(d, 'vmlinuz')}"
 INITRD_IMAGE ?= "${@get_image_name(d, 'initrd.img')}"
-- 
2.16.1