@@ -3476,6 +3476,20 @@ system and gives an overview of their function and contents.
variable, see the ":ref:`dev-manual/customizing-images:customizing images using custom \`\`image_features\`\` and \`\`extra_image_features\`\``"
section in the Yocto Project Development Tasks Manual.
+ :term:`IMAGE_FILE_MAXSIZE`
+ Specifies the maximum size in kilobytes to create the image file for a
+ specific image type, which corresponds to the value set in
+ :term:`IMAGE_FSTYPES`, (e.g. ``ext3``,
+ ``btrfs``, and so forth). When setting this variable, you should use
+ an override for the associated type. Here is an example::
+
+ IMAGE_FILE_MAXSIZE:ext4 = "8192"
+
+ It overrides the :term:`IMAGE_OVERHEAD_FACTOR` and
+ :term:`IMAGE_ROOTFS_EXTRA_SPACE` mechanism for some filesystems.
+ If the maximum size is below the required size to store the rootfs content,
+ the operation will fail.
+
:term:`IMAGE_FSTYPES`
Specifies the formats the OpenEmbedded build system uses during the
build when creating the root filesystem. For example, setting
@@ -54,6 +54,13 @@ def imagetypes_getdepends(d):
# Sort the set so that ordering is consistant
return " ".join(sorted(deps))
+def get_max_image_size(d, fs):
+ max_size = d.getVar("IMAGE_FILE_MAXSIZE:%s" % fs)
+ if max_size is not None:
+ return max_size
+
+ return 0
+
XZ_COMPRESSION_LEVEL ?= "-9"
XZ_INTEGRITY_CHECK ?= "crc32"
It returns 0 if the variable is not set for this filesystem. In case of fixed partitionning where the rootfs partition can't exceed an amount of bytes, there is currently no automatic and no generic way to have this requirement met in any case. Until now, ROOTFS_SIZE value got from directory_size() does not takes into account the size of required metadata for the filesystem itself (and does not work well for other block size than 4k BTW). Obviously it's a difficult task which depends on rootfs size and filesystem type. The workaround was to set IMAGE_OVERHEAD_FACTOR and IMAGE_ROOTFS_EXTRA_SPACE to add the required extra margins. But when the final rootfs is closed to the maximum size, it's difficult to adjust them correctly And if you remove or add new recipes in your image, you've to recompute these margins to have enough space for these metadata when the rootfs is small, and to not have too big final file when the rootfs is big. It's cumbersome and error prone to just have a build failure when the final output can't be flashed into the partition. The solution is to follow how it's implemented in buildroot by having a specific variable, here IMAGE_FILE_MAXSIZE, to create the final sparse file and trying to fill it with the content of rootfs. If there is enough space, margins are well compressed and does not consume space in the filesystem. If there is no enough space, an error is triggered to warm the developer before trying to use it in the device. If IMAGE_FILE_MAXSIZE is not set, the idea is to keep the previous behaviour for compatibility reason and to met other requirements. Signed-off-by: Charles-Antoine Couret <charles-antoine.couret@mind.be> --- documentation/ref-manual/variables.rst | 14 ++++++++++++++ meta/classes-recipe/image_types.bbclass | 7 +++++++ 2 files changed, 21 insertions(+)