The bcm27xx/bcm2708 all-kmods CI build fails when modpost reaches the
DesignWare I2C core module:
ERROR: modpost: "__aeabi_uldivmod"
[drivers/i2c/busses/i2c-designware-core.ko] undefined!
This is triggered by CONFIG_ALL_KMODS=y. The old 32-bit Raspberry Pi
subtargets do not normally select this driver for runtime use, but all-kmods
forces the kmod package to be built anyway. On 32-bit ARM, raw 64-bit
division in a module can cause GCC to emit the ARM EABI helper
__aeabi_uldivmod, which is not available as a kernel module symbol.
The failing reference comes from i2c-designware-master.c, where clock_calc()
uses raw u64 division for SCL timing calculations (introduced with commit
3805d13c3ead21494f7d00aa44f10e3656363d4c in rpi-6.18.y / "i2c: designware:
Support non-standard bus speeds"). That is a kernel-side portability issue,
but these old bcm27xx subtargets do not use DesignWare I2C hardware. They
use the Broadcom I2C controller instead.
The failure is emitted for i2c-designware-core.ko, so guard the hidden core
package itself rather than only guarding the platform or PCI frontend package.
This prevents CONFIG_ALL_KMODS from selecting the failing core module directly
on the affected 32-bit bcm27xx subtargets.
DesignWare I2C is relevant for newer Raspberry Pi 5 / RP1 based systems, so
keep it available for bcm2712.
A similar issue was reported by NixOS for Raspberry Pi ARM builds, where
i2c-designware-core.ko failed with the same unresolved __aeabi_uldivmod symbol.
Their workaround was to disable the DesignWare I2C symbols for older Raspberry
Pi targets that do not need them.
Link: https://github.com/NixOS/nixpkgs/issues/464515
Until the underlying ARM32 kernel-side issue is fixed, avoid building
the DesignWare core package on bcm2708, bcm2709 and bcm2710.
Signed-off-by: Joshua Covington <joshuacov@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/23703
Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
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