From 54d40d81eed80794f5c232b4c4699bb3d5f2181f Mon Sep 17 00:00:00 2001
From: AI Dev <ai@openipc.org>
Date: Sat, 7 Nov 2026 09:25:57 +0000
Subject: [PATCH] ambarella-osdrv-s3l: stop the build when the kernel moves
 iav.ko's offsets

The prebuilt modules hard-code struct offsets and carry no __versions, so a
kernel config that moves them builds, boots and loads them, and fails only at
the first /dev/iav ioctl. CI cannot see that: #2778 passed every check while it
would have broken iav.ko on every S3L image.

The package now compiles a probe against the built kernel with its own Kbuild,
and stops if inode->i_cdev or file->private_data is not where iav_open expects.
---
 .../ambarella-osdrv-s3l.mk                    | 21 +++++++++++++++++++
 .../legacy/ambarella-osdrv-s3l/src/abi/Kbuild |  1 +
 .../ambarella-osdrv-s3l/src/abi/abi_probe.c   | 14 +++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 general/package/legacy/ambarella-osdrv-s3l/src/abi/Kbuild
 create mode 100644 general/package/legacy/ambarella-osdrv-s3l/src/abi/abi_probe.c

diff --git a/general/package/legacy/ambarella-osdrv-s3l/ambarella-osdrv-s3l.mk b/general/package/legacy/ambarella-osdrv-s3l/ambarella-osdrv-s3l.mk
index 9b3b2e17c..8ae5608d3 100644
--- a/general/package/legacy/ambarella-osdrv-s3l/ambarella-osdrv-s3l.mk
+++ b/general/package/legacy/ambarella-osdrv-s3l/ambarella-osdrv-s3l.mk
@@ -11,8 +11,29 @@ AMBARELLA_OSDRV_S3L_LICENSE = MIT (load_ucode), PROPRIETARY (modules, microcode)
 # load_ucode puts the DSP microcode in place. files/firmware is the generic set
 # from Ambarella's S3L SDK release 2.5.0_20181109 (2018/10/28, 284712.282649),
 # not from a camera's stock firmware, which the tree does not accept (#2767).
+#
+# The prebuilt modules hard-code struct offsets and carry no __versions, so a
+# kernel config that moves them builds, boots and loads the modules, and fails
+# only at the first /dev/iav ioctl. iav_open reads inode->i_cdev at 272 and
+# writes file->private_data at 112: CONFIG_LBDAF moves the first (#2763), and
+# CONFIG_QUOTA on top of it moved it again (#2778). So the kernel's own Kbuild
+# compiles src/abi against this kernel, and the build stops on a mismatch.
+AMBARELLA_OSDRV_S3L_DEPENDENCIES = linux
+AMBARELLA_OSDRV_S3L_IAV_OFFSETS = INODE_I_CDEV:272 FILE_PRIVATE_DATA:112
+
 define AMBARELLA_OSDRV_S3L_BUILD_CMDS
 	$(MAKE) $(TARGET_CONFIGURE_OPTS) -C $(@D) load_ucode
+	$(LINUX_MAKE_ENV) $(MAKE) -C $(LINUX_DIR) $(LINUX_MAKE_FLAGS) \
+		M=$(@D)/abi abi_probe.s
+	for want in $(AMBARELLA_OSDRV_S3L_IAV_OFFSETS); do \
+		name=$${want%%:*}; \
+		got=$$(sed -n "s/^->$$name [#$$]*\([0-9]*\) .*/\1/p" $(@D)/abi/abi_probe.s); \
+		if [ "$$got" != "$${want#*:}" ]; then \
+			echo "ambarella-osdrv-s3l: $$name is '$$got' in this kernel," \
+				"iav.ko needs $${want#*:}: check the kernel config" >&2; \
+			exit 1; \
+		fi; \
+	done
 endef
 
 define AMBARELLA_OSDRV_S3L_INSTALL_TARGET_CMDS
diff --git a/general/package/legacy/ambarella-osdrv-s3l/src/abi/Kbuild b/general/package/legacy/ambarella-osdrv-s3l/src/abi/Kbuild
new file mode 100644
index 000000000..a0f4fa02d
--- /dev/null
+++ b/general/package/legacy/ambarella-osdrv-s3l/src/abi/Kbuild
@@ -0,0 +1 @@
+obj-m := abi_probe.o
diff --git a/general/package/legacy/ambarella-osdrv-s3l/src/abi/abi_probe.c b/general/package/legacy/ambarella-osdrv-s3l/src/abi/abi_probe.c
new file mode 100644
index 000000000..12e5273da
--- /dev/null
+++ b/general/package/legacy/ambarella-osdrv-s3l/src/abi/abi_probe.c
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Not a module: Kbuild compiles this to assembly only, with the kernel's own
+ * headers and flags, so the package can read the offsets the prebuilt iav.ko
+ * depends on. See ambarella-osdrv-s3l.mk.
+ */
+#include <linux/fs.h>
+#include <linux/kbuild.h>
+
+void abi_probe(void)
+{
+	DEFINE(INODE_I_CDEV, offsetof(struct inode, i_cdev));
+	DEFINE(FILE_PRIVATE_DATA, offsetof(struct file, private_data));
+}