[PATCH] dracut-module: add DRACUT_FORCE_DRIVERS

["'Quirin Gylstorff' via isar-users" <isar-users@googlegroups.com>]

Some drivers are not loaded by udev in the initrd, e.g. watchdog drivers
which have to be serviced by systemd before the root file system is
mounted. dracut provides force_drivers for this, but it is a global
option.

Add DRACUT_FORCE_DRIVERS to the dracut-module class. The listed drivers
are installed regardless of hostonly mode and loaded early via
rd.driver.pre, same as dracut's force_drivers, but only if the module
is part of the initrd. The module depends on kernel-modules, which
evaluates rd.driver.pre.

Signed-off-by: Quirin Gylstorff <quirin.gylstorff@siemens.com>
---
 doc/user_manual.md                                 |  5 +++++
 meta/classes-recipe/dracut-module.bbclass          | 14 ++++++++++++++
 .../dracut-module/files/module-setup.sh.tmpl       | 10 ++++++++++
 3 files changed, 29 insertions(+)

diff --git a/doc/user_manual.md b/doc/user_manual.md
index a134903d..09ac080b 100644
--- a/doc/user_manual.md
+++ b/doc/user_manual.md
@@ -1877,6 +1877,11 @@ It is controlled by following variables:
 
 - `DRACUT_REQUIRED_BINARIES` defines the binaries required by the module.
 - `DRACUT_MODULE_DEPENDENCIES` defines dependencies to other dracut modules.
+- `DRACUT_FORCE_DRIVERS` defines kernel drivers which are installed into the
+initrd regardless of hostonly mode and loaded early via `rd.driver.pre`,
+like dracut's `force_drivers` option. It adds a dependency to the dracut
+module `kernel-modules`. A machine can set it with
+`DRACUT_FORCE_DRIVERS:pn-<recipe> = "lpc_ich iTCO_wdt"`.
 - `DRACUT_MODULE_NO` defines the module number which prefixes the module name
 to determine the execution order. The default is `50`.
 - `DRACUT_MODULE_NAME` defines the name of the module which is used to install the
diff --git a/meta/classes-recipe/dracut-module.bbclass b/meta/classes-recipe/dracut-module.bbclass
index 6fce979a..6d32a4ac 100644
--- a/meta/classes-recipe/dracut-module.bbclass
+++ b/meta/classes-recipe/dracut-module.bbclass
@@ -22,6 +22,9 @@ DRACUT_MODULE_PATH = "${D}/usr/lib/dracut/modules.d/${DRACUT_MODULE_NO}${DRACUT_
 
 DRACUT_REQUIRED_BINARIES ??= ""
 DRACUT_MODULE_DEPENDENCIES ??= ""
+# Kernel drivers installed regardless of hostonly and loaded early via
+# rd.driver.pre (same semantics as dracut's force_drivers)
+DRACUT_FORCE_DRIVERS ??= ""
 DRACUT_CHECK_CONTENT_FILE_NAME ??= ""
 DRACUT_DEPENDS_CONTENT_FILE_NAME ??= ""
 DRACUT_CMDLINE_CONTENT_FILE_NAME ??= ""
@@ -71,7 +74,18 @@ TEMPLATE_FILES:append = " \
 TEMPLATE_VARS:append = " \
     DRACUT_REQUIRED_BINARIES \
     DRACUT_MODULE_DEPENDENCIES \
+    DRACUT_FORCE_DRIVERS \
+    DRACUT_MODULE_NAME \
     "
+
+python do_validate_dracut_force_drivers() {
+    import re
+    for drv in (d.getVar('DRACUT_FORCE_DRIVERS') or '').split():
+        if not re.fullmatch(r'[A-Za-z0-9_-]+', drv):
+            bb.fatal(f"Invalid driver name '{drv}' in DRACUT_FORCE_DRIVERS")
+}
+addtask validate_dracut_force_drivers before do_transform_template after do_patch
+
 python do_add_additional_dracut_configuration() {
     workdir = os.path.normpath(d.getVar('WORKDIR'))
     module_setup = d.getVar('DRACUT_MODULE_SETUP')
diff --git a/meta/recipes-initramfs/dracut-module/files/module-setup.sh.tmpl b/meta/recipes-initramfs/dracut-module/files/module-setup.sh.tmpl
index b38ae50c..9fc5af93 100644
--- a/meta/recipes-initramfs/dracut-module/files/module-setup.sh.tmpl
+++ b/meta/recipes-initramfs/dracut-module/files/module-setup.sh.tmpl
@@ -15,11 +15,16 @@ check() {
 # Module dependency requirements.
 depends() {
     echo "${DRACUT_MODULE_DEPENDENCIES}"
+    # rd.driver.pre is evaluated by the kernel-modules module
+    [ -z "${DRACUT_FORCE_DRIVERS}" ] || echo "kernel-modules"
     # ISAR_DRACUT_DEPENDS
     return 0
 
 }
 installkernel() {
+    if [ -n "${DRACUT_FORCE_DRIVERS}" ]; then
+        hostonly='' instmods -c ${DRACUT_FORCE_DRIVERS} || return 1
+    fi
     # ISAR_DRACUT_KERNELINSTALL
     return 0
 }
@@ -38,5 +43,10 @@ install() {
             exit 1
         fi
     done
+    for driver in ${DRACUT_FORCE_DRIVERS}; do
+        mkdir -p "$initdir/etc/cmdline.d"
+        echo "rd.driver.pre=$driver" >> \
+            "$initdir/etc/cmdline.d/20-force-drivers-${DRACUT_MODULE_NAME}.conf"
+    done
     # ISAR_DRACUT_INSTALL
 }
-- 
2.55.0

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