Huawei MatePad 11 2021 (DBY-W09) — Kernel 4.19 Build Fix

Status: ✅ BUILD SUCCESSFUL Kernel 4.19.157 for Snapdragon 865 (Kona) — compiled with Clang + ld.lld on Ubuntu

This repository contains the HarmonyOS 3.0 open-source kernel for the Huawei MatePad 11 2021 (DBY-W09), patched to compile successfully with a modern Clang/LLVM toolchain on a contemporary Linux host.

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Device Specifications

Field	Value
Device	Huawei MatePad 11 2021
Model	DBY-W09
SoC	Qualcomm Snapdragon 865 (SM8250 / Kona)
Kernel	4.19.157
Architecture	AArch64 (ARM64)
Original OS	HarmonyOS 3.0.0
Board variants	DBY_W09_VA, DBY_W09_VB

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Build Instructions

Prerequisites

sudo apt install clang lld llvm gcc-aarch64-linux-gnu binutils-aarch64-linux-gnu

Build

git clone https://github.com/RobertoSiragusa/DBY-W09.git
cd DBY-W09

# Generate .config
yes "" | make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CC=clang \
  CLANG_TRIPLE=aarch64-linux-gnu- LD=ld.lld HOSTCFLAGS=-fcommon \
  merge_kona_defconfig

# Disable two incompatible options
sed -i 's/CONFIG_HUAWEI_PAGECACHE_HELPER=y/# CONFIG_HUAWEI_PAGECACHE_HELPER is not set/' .config
sed -i 's/CONFIG_IKHEADERS=y/# CONFIG_IKHEADERS is not set/' .config

# Build
make ARCH=arm64 CROSS_COMPILE=aarch64-linux-gnu- CC=clang \
  CLANG_TRIPLE=aarch64-linux-gnu- LD=ld.lld AR=llvm-ar NM=llvm-nm \
  OBJCOPY=llvm-objcopy OBJDUMP=llvm-objdump STRIP=llvm-strip \
  HOSTCFLAGS=-fcommon -j$(nproc) Image.gz 2>&1 | tee /tmp/build.log

Output: arch/arm64/boot/Image.gz

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Patches Applied — Problems & Solutions

This section documents every build failure encountered and exactly how it was resolved. The original source tree required extensive patching to compile with modern Clang/LLD.

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PATCH 1 — Global -Werror suppression for common clang warnings

Commit: dadededff

Problem: The root Makefile passed -Werror=strict-prototypes and -Werror=incompatible-pointer-types to Clang. Modern Clang (18+) is stricter than older GCC and treats hundreds of vendor driver patterns as errors:

• Functions declared without parameter lists: void foo() instead of void foo(void)
• Implicit pointer-type conversions between incompatible types
• Unused-but-set variables in vendor code

These caused hundreds of compilation failures across drivers/devkit/, drivers/hwsensor/, techpack/audio/, and many other subsystems.

Fix: Replaced the -Werror= flags with -Wno- equivalents in the root Makefile (KBUILD_CFLAGS):

# Before
KBUILD_CFLAGS += -Werror=strict-prototypes
KBUILD_CFLAGS += -Werror=incompatible-pointer-types

# After
KBUILD_CFLAGS += $(call cc-option,-Wno-strict-prototypes)
KBUILD_CFLAGS += $(call cc-option,-Wno-incompatible-pointer-types)
KBUILD_CFLAGS += $(call cc-option,-Wno-unused-but-set-variable)

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PATCH 2 — Individual source file fixes (void prototypes, CRLF, includes)

Commits: 3b7b4ba59, 39ac51834, 51b5a2ffb, a47f9b781, c65bdd4a0

Problem: Several vendor driver files had syntax issues that Clang rejected:

• Missing void in function parameter lists (required by C89/C99 standards)
• Windows-style CRLF line endings (\r\n) in .c files causing parse errors
• Angled includes (#include <relative/path.h>) for files that are not in system include paths

Affected files included:

• drivers/hwsensor/sensors_class.c, sensors_sysfs_als.c, sensors_sysfs_ps.c
• drivers/lbs/airoha_gps_driver.c (CRLF issue)
• drivers/nfc/pn547/pn547.c
• drivers/input/touchscreen/st/fts_lib/ftsIO.c, ftsTime.c
• 15+ files in drivers/devkit/tpkit/

Fix:

• Added void to all zero-argument function definitions
• Converted CRLF to LF in airoha_gps_driver.c
• Converted angled relative includes to quoted includes where appropriate

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PATCH 3 — TRACE_INCLUDE_PATH fixes for trace headers

Commits: 8f72b3311, a2987b84f

Problem: The Linux kernel trace subsystem uses a macro TRACE_INCLUDE_PATH to locate trace header files at compile time. Files using CREATE_TRACE_POINTS need -I$(srctree) in their compiler flags so the trace framework can find TRACE_INCLUDE_PATH/TRACE_INCLUDE_FILE.h. Multiple trace files had incorrect or missing paths:

• techpack/display/rotator/sde_rotator_trace.h
• techpack/camera/drivers/cam_utils/cam_trace.h
• fs/hmdfs/hmdfs_trace.h

Fix:

• Set correct absolute TRACE_INCLUDE_PATH in each trace header
• Added -I$(srctree) via CFLAGS_<file>.o only for files that use CREATE_TRACE_POINTS, avoiding the flag leaking to files that don't need it

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PATCH 4 — techpack Makefile ccflags ordering bug

Commits: 75a0e93ef, 98286e884

Problem: In kbuild, ccflags-y applies to files compiled in the same directory as the Makefile. For files in subdirectories, you must use subdir-ccflags-y. Additionally, ccflags-y placed after obj-y declarations is ignored by kbuild for subdirectory targets.

techpack/audio/Makefile had include paths declared as ccflags-y after obj-y += asoc/, meaning files in asoc/ (like kona.c) never received the -I$(srctree)/techpack/audio/include flag — causing them to fail to find <soc/snd_event.h>, <dsp/q6afe-v2.h>, and similar headers.

Fix:

# Before (broken)
obj-y += soc/
obj-y += asoc/
ccflags-y += -I$(srctree)/techpack/audio/include

# After (correct)
subdir-ccflags-y += -I$(srctree)/techpack/audio/include
subdir-ccflags-y += -I$(srctree)/techpack/audio/include/uapi
subdir-ccflags-y += -I$(srctree)/drivers/devkit/audiokit
obj-y += soc/
obj-y += asoc/

Same fix applied to drivers/devkit/audiokit/smartpakit/Makefile and drivers/devkit/lcdkit/lcdkit3.0/Makefile.

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PATCH 5 — ROOT CAUSE: 109 auto-generated stub headers shadowing real headers

Commit: 270e49714

Problem — The root cause of most build failures:

An early attempted fix (commit 70ebef47e) created 109 empty stub header files inside include/ subdirectories:

include/comm/device_node.h        ← empty stub
include/authority/authentication.h ← empty stub
include/codecs/bolero/*.h         ← empty stubs
include/dsm_audio/dsm_audio.h    ← empty stub
include/boxid/boxid.h             ← empty stub
... (109 total)

Each stub looked like:

/* Auto-generated stub header */
#ifndef _COMM_DEVICE_NODE_H_
#define _COMM_DEVICE_NODE_H_
#endif

Because include/ appears early in the compiler's include search path (via -I./include), these empty stubs were found before the real headers in:

• fs/hmdfs/comm/device_node.h (real hmdfs header)
• fs/hmdfs/authority/authentication.h (real auth header with hmdfs_check_cred etc.)
• drivers/devkit/audiokit/dsm_audio/dsm_audio.h (real DSM header)

This caused cascading failures where functions like hmdfs_check_cred(), hmdfs_override_creds(), CAPABILITY_P2P, LINK_TYPE_P2P, DSM_SMARTPA_BUF_SIZE, and AUDIO_CODEC appeared as undeclared identifiers — even though their real definitions existed and were correct.

Fix: Deleted all 109 auto-generated stub headers:

grep -rl "Auto-generated stub" include/ | xargs rm -f

Then fixed the hmdfs Makefile include paths to use absolute $(srctree) paths so headers are found correctly regardless of compilation directory:

ccflags-y += -I$(srctree)/fs/hmdfs -I$(srctree)/fs/hmdfs/comm -I$(src) -Wall

And added per-file CFLAGS_<file>.o with -Wno-implicit-function-declaration -Wno-int-conversion for files in comm/ and DFS_1_0/ that depend on the hmdfs include chain.

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PATCH 6 — hmdfs authentication.h stubs for non-Android builds

Commit: 270e49714, c1bdfdffc

Problem: fs/hmdfs/authority/authentication.h defines hmdfs_check_cred(), hmdfs_override_creds(), hmdfs_revert_creds(), hmdfs_override_fsids(), and hmdfs_revert_fsids() only inside #ifdef CONFIG_HMDFS_ANDROID. Files that call these functions without the ifdef guard would fail if the config wasn't active.

Fix: Added a #ifndef CONFIG_HMDFS_ANDROID block at the end of the header with safe no-op stubs:

#ifndef CONFIG_HMDFS_ANDROID
static inline void hmdfs_check_cred(unsigned int user_id, const struct cred *cred) {}
static inline const struct cred *hmdfs_override_creds(const struct cred *new)
{
    return override_creds(new);
}
static inline void hmdfs_revert_creds(const struct cred *old)
{
    if (old) revert_creds(old);
}
static inline const struct cred *hmdfs_override_fsids(struct hmdfs_sb_info *sbi, bool b)
{
    return NULL;
}
static inline void hmdfs_revert_fsids(const struct cred *old) {}
#endif /* !CONFIG_HMDFS_ANDROID */

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PATCH 7 — Conflicting static inline stubs removed after real headers restored

Commit: 434fa4654

Problem: After PATCH 5 removed the stub headers, the real dsm_audio/dsm_audio.h and sde/sde_connector.h became visible again. But intermediate patches had added static inline fallback stubs directly into source files:

• techpack/audio/asoc/kona.c — stub for audio_dsm_report_info()
• drivers/devkit/audiokit/smartpakit/smartpakit_i2c_ops.c — stubs for DSM_SMARTPA_BUF_SIZE, audio_dsm_report_info(), boxid_read()
• drivers/devkit/lcdkit/.../lcd_kit_utils.c — stubs for to_sde_connector(), _sde_connector_report_panel_dead()

The real headers declare these as non-static functions. Clang error:

error: static declaration of 'audio_dsm_report_info' follows non-static declaration

Fix: Removed all conflicting static inline stubs from the three source files. The real implementations in dsm_audio.h and sde_connector.h are now found correctly via the fixed include paths.

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PATCH 8 — techpack_autoconf.h missing after git reset

Commit: 149044bc4

Problem: The root Makefile passes techpack_autoconf.h as a global forced-include:

KBUILD_CPPFLAGS := -D__KERNEL__ -include $(srctree)/include/generated/techpack_autoconf.h

This file consolidates CONFIG_ values from techpack/*/config/*.conf files (e.g. konacamera.conf, konaauto.conf, konadisp.conf) that set configs like CONFIG_SPECTRA_CAMERA=y, CONFIG_SND_SOC_KONA=y, etc. These .conf values bypass the .config system.

The file is generated at build time and is not tracked by git. After git reset --hard, it was deleted, causing the very first step of the build to fail:

<built-in>:3:10: fatal error: './include/generated/techpack_autoconf.h' file not found

Fix:

• Committed include/generated/techpack_autoconf.h directly to the repository
• Added a Makefile rule to regenerate it automatically if missing:

$(srctree)/include/generated/techpack_autoconf.h:
    @mkdir -p $(srctree)/include/generated
    @echo "/* Auto-generated from techpack .conf files */" > $@
    # ... reads all .conf files and generates #define statements

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PATCH 9 — qcacld WiFi driver: -Warray-parameter error

Commit: c5807cd43

Problem: Clang 18 added -Warray-parameter as a new warning that catches array parameter type mismatches. The qcacld WiFi driver (drivers/qcacld/) had functions like:

void populate_mdie(struct mac_context *mac,
                   tDot11fIEMobilityDomain *pDot11f,
                   uint8_t mdie[SIR_MDIE_SIZE])  // ← mismatched bound

With -Werror active in the driver's build flags, this became a fatal error.

Fix: Added -Wno-array-parameter to global KBUILD_CFLAGS in root Makefile:

KBUILD_CFLAGS += $(call cc-option,-Wno-array-parameter)

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PATCH 10 — Linker error: R_AARCH64_ABS32 relocation with ld.lld

Commit: 9e052bf7d

Problem: ld.lld rejected the build with:

ld.lld: error: relocation R_AARCH64_ABS32 cannot be used against symbol
'__crc_gsi_write_channel_scratch'; recompile with -fPIC

CONFIG_MODVERSIONS=y causes the kernel to embed CRC checksums for all exported symbols. On AArch64, these CRCs are stored using R_AARCH64_ABS32 (32-bit absolute) relocations. This is incompatible with ld.lld, which requires position-independent addressing for non-relocatable sections.

This is a known upstream issue with ld.lld + CONFIG_MODVERSIONS on AArch64.

Fix: Disabled CONFIG_MODVERSIONS in arch/arm64/configs/merge_kona_defconfig:

# CONFIG_MODVERSIONS is not set

Safe to disable: MODVERSIONS is only needed when loading out-of-tree kernel modules that were compiled against a different kernel. For an integrated build with all drivers in-tree, it provides no benefit.

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PATCH 11 — Linker error: undefined symbol: __read_overflow2

Commit: 9e052bf7d

Problem: CONFIG_FORTIFY_SOURCE=y enables compile-time buffer overflow detection in string functions (memcpy, strcpy, etc.). When the compiler cannot statically determine that a copy is safe, it emits a call to __read_overflow2() which is declared as a __compiletime_error — it should never actually appear in the final binary because the optimizer eliminates the dead code branch.

However, some vendor driver code compiled with certain optimization patterns left a reference to __read_overflow2 in the object file, and the symbol has no definition anywhere in the kernel (by design — it's only meant as a compile-time trap).

ld.lld: error: undefined symbol: __read_overflow2

Fix: Added weak definitions of all __read_overflow* and __write_overflow symbols to lib/string.c:

void __read_overflow(void) {}
EXPORT_SYMBOL(__read_overflow);
void __read_overflow2(void) {}
EXPORT_SYMBOL(__read_overflow2);
void __read_overflow3(void) {}
EXPORT_SYMBOL(__read_overflow3);
void __write_overflow(void) {}
EXPORT_SYMBOL(__write_overflow);

These are no-ops that satisfy the linker. In practice they should never be called at runtime because the fortify checks that trigger them are always paired with bounds checks that would panic the kernel first.

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PATCH 12 — Linker error: undefined symbol: get_bootdevice_type

Commits: 9e052bf7d, 49512ac64

Problem: Multiple drivers (drivers/scsi/ufs/ufshcd_mas_extend.c, drivers/mmc/core/mmc.c, drivers/mmc/host/sdhci-msm.c) call get_bootdevice_type() to detect whether the boot device is UFS or eMMC.

The function exists in two parallel directories:

• drivers/bootdevice/proc_boot.c — legacy version, defines get_bootdevice_type()
• drivers/bootdevices/proc_boot.c — extended UFS/MMC version, calls but does not define get_bootdevice_type()

drivers/bootdevices/ is compiled when CONFIG_HUAWEI_QCOM_UFS=y (which is set). drivers/bootdevice/ was not referenced anywhere in drivers/Makefile. The function therefore had no definition at link time.

An initial fix incorrectly added obj-y += bootdevice/ to drivers/Makefile, which caused the opposite problem — both directories were compiled and all set_bootdevice_* functions appeared as duplicate symbols:

ld.lld: error: duplicate symbol: set_bootdevice_type
ld.lld: error: duplicate symbol: set_bootdevice_name
... (13 duplicate symbols total)

Fix: Kept only bootdevices/ in the build (the correct directory for UFS), and added the missing get_bootdevice_type() definition directly into drivers/bootdevices/proc_boot.c:

enum bootdevice_type get_bootdevice_type(void)
{
    return bootdevice.type;
}
EXPORT_SYMBOL(get_bootdevice_type);

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Summary Table

#	Commit	Problem	Fix
1	dadededff	-Werror=strict-prototypes rejects hundreds of vendor files	Replace with -Wno-strict-prototypes globally
2	51b5a2ffb	Missing void, CRLF, bad includes in vendor drivers	Fix prototypes, line endings, quoted includes
3	8f72b3311	Wrong TRACE_INCLUDE_PATH in trace headers	Fix paths, add -I$(srctree) only where needed
4	75a0e93ef	ccflags-y after obj-y ignored for subdirs	Change to subdir-ccflags-y, move before obj-y
5	270e49714	ROOT CAUSE: 109 empty stub headers shadow real headers	Delete all stubs from include/, fix hmdfs paths
6	270e49714	hmdfs functions missing outside CONFIG_HMDFS_ANDROID	Add #ifndef stubs in authentication.h
7	434fa4654	Static inline stubs conflict with non-static real declarations	Remove stubs now that real headers are visible
8	149044bc4	techpack_autoconf.h missing after git reset --hard	Commit file to repo + add generation rule
9	c5807cd43	qcacld: -Warray-parameter treated as error	Add -Wno-array-parameter to KBUILD_CFLAGS
10	9e052bf7d	MODVERSIONS + ld.lld = R_AARCH64_ABS32 relocation error	Disable CONFIG_MODVERSIONS in defconfig
11	9e052bf7d	__read_overflow2 undefined at link time	Add weak no-op definitions in lib/string.c
12	49512ac64	get_bootdevice_type undefined; then duplicate symbols	Add definition to bootdevices/proc_boot.c only

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Notes

• CONFIG_HUAWEI_PAGECACHE_HELPER and CONFIG_IKHEADERS must be disabled post-defconfig via sed as shown in the build instructions — they cause compilation failures with modern toolchains.
• The .conf files in techpack/*/config/kona*.conf force certain CONFIG_ values regardless of .config. This is why techpack_autoconf.h must exist before compilation starts.
• CONFIG_HMDFS_ANDROID=y is required and already set in merge_kona_defconfig. The hmdfs filesystem uses Android credential management that must be enabled.