debian: add kernel_preinst.d hook

On kernel upgrades (w/o version change, but no guarantee that there was
no ABI change), uninstall && unbuild all AUTOINSTALL=yes modules
currently built for the kernel to ensure they get rebuilt by the
kernel_postinst.d hook.
No-op on initial installation of a kernel version.

.gitignore

@@ -9,6 +9,7 @@ dkms.service
 dkms_common.postinst
 debian_kernel_install.d
 debian_kernel_postinst.d
+debian_kernel_preinst.d
 debian_kernel_prerm.d
 redhat_kernel_install.d
 

Makefile

@@ -40,6 +40,7 @@ GENERATED= \
 	dkms.service \
 	debian_kernel_install.d \
 	debian_kernel_postinst.d \
+	debian_kernel_preinst.d \
 	debian_kernel_prerm.d \
 	redhat_kernel_install.d
 
@@ -82,6 +83,7 @@ install-debian: install
 	install -D -m 0755 debian_kernel_install.d $(DESTDIR)$(KINSTALL)/40-dkms.install
 	install -D -m 0755 debian_kernel_postinst.d $(DESTDIR)$(KCONF)/postinst.d/dkms
 	install -D -m 0755 debian_kernel_postinst.d $(DESTDIR)$(KCONF)/header_postinst.d/dkms
+	install -D -m 0755 debian_kernel_preinst.d $(DESTDIR)$(KCONF)/preinst.d/dkms
 	install -D -m 0755 debian_kernel_prerm.d $(DESTDIR)$(KCONF)/prerm.d/dkms
 
 install-doc:

debian_kernel_preinst.d.in

@@ -0,0 +1,11 @@
+#!/bin/sh
+
+# This script is triggered when the kernel (linux-image) package is being
+# installed/upgraded.  We're passed the version of the kernel being installed.
+inst_kern=$1
+
+if command -v dkms > /dev/null; then
+    dkms kernel_preinst -k "$inst_kern"
+fi
+
+exit 0