[PATCH] wic: bootimg-efi-isar: Add support for loading device tree files

[Jan Kiszka]

From: Jan Kiszka <jan.k...@siemens.com>

For device tree using systems, add support to set a custom devices tree
during UEFI boot. This requires to copy the DTB file to the boot
partition and to add the respective loader entries to the configuration
files.

Both grub and systemd-boot support only loading a specific device tree.
Therefore refuse to work if DTB_FILES contains more than one entry.

This has been tested with grub from bullseye and systemd from
bullseye-backport. The latter is needed as only systemd 250 gained the
required feature.

Out of scope are overlays (only supported by systemd-boot) as well as
unified kernel images (practically broken on non-x86 with current
toolchains).

Signed-off-by: Jan Kiszka <jan.k...@siemens.com>
---
meta/classes/imagetypes_wic.bbclass | 2 +-
.../wic/plugins/source/bootimg-efi-isar.py | 39 +++++++++++++------
2 files changed, 29 insertions(+), 12 deletions(-)

diff --git a/meta/classes/imagetypes_wic.bbclass b/meta/classes/imagetypes_wic.bbclass
index 61a74d4a..3a577f71 100644
--- a/meta/classes/imagetypes_wic.bbclass
+++ b/meta/classes/imagetypes_wic.bbclass
@@ -106,7 +106,7 @@ WICVARS += "\
ROOTFS_SIZE STAGING_DATADIR STAGING_DIR STAGING_LIBDIR TARGET_SYS TRANSLATED_TARGET_ARCH"

# Isar specific vars used in our plugins
-WICVARS += "DISTRO DISTRO_ARCH"
+WICVARS += "DISTRO DISTRO_ARCH DTB_FILES"

python do_rootfs_wicenv () {
wicvars = d.getVar('WICVARS', True)
diff --git a/meta/scripts/lib/wic/plugins/source/bootimg-efi-isar.py b/meta/scripts/lib/wic/plugins/source/bootimg-efi-isar.py
index a24e04f3..aff51e81 100644
--- a/meta/scripts/lib/wic/plugins/source/bootimg-efi-isar.py
+++ b/meta/scripts/lib/wic/plugins/source/bootimg-efi-isar.py
@@ -58,13 +58,12 @@ class BootimgEFIPlugin(SourcePlugin):
raise WicError("configfile is specified but failed to "
"get it from %s." % configfile)

- initrd = source_params.get('initrd')
+ bootimg_dir = get_bitbake_var("DEPLOY_DIR_IMAGE")
+ if not bootimg_dir:
+ raise WicError("Couldn't find DEPLOY_DIR_IMAGE, exiting")

+ initrd = source_params.get('initrd')
if initrd:
- bootimg_dir = get_bitbake_var("DEPLOY_DIR_IMAGE")
- if not bootimg_dir:
- raise WicError("Couldn't find DEPLOY_DIR_IMAGE, exiting")
-
initrds = initrd.split(';')
for rd in initrds:
cp_cmd = "cp %s/%s %s" % (bootimg_dir, rd, hdddir)
@@ -72,6 +71,13 @@ class BootimgEFIPlugin(SourcePlugin):
else:
logger.debug("Ignoring missing initrd")

+ dtb_files = (get_bitbake_var("DTB_FILES") or '').split()
+ if dtb_files:
+ if len(dtb_files) > 1:
+ raise WicError("Only one DTB support in grub configuration, exiting")
+ cp_cmd = "cp %s/%s %s" % (bootimg_dir, dtb_files[0], hdddir)
+ exec_cmd(cp_cmd, True)
+
if not custom_cfg:
# Create grub configuration using parameters from wks file
bootloader = creator.ks.bootloader
@@ -108,6 +114,9 @@ class BootimgEFIPlugin(SourcePlugin):
grubefi_conf += " /%s" % rd
grubefi_conf += "\n"

+ if dtb_files:
+ grubefi_conf += "devicetree /%s\n" % dtb_files[0]
+
grubefi_conf += "}\n"

logger.debug("Writing grubefi config %s/hdd/boot/EFI/BOOT/grub.cfg",
@@ -134,14 +143,12 @@ class BootimgEFIPlugin(SourcePlugin):
loader_conf += "default boot\n"
loader_conf += "timeout %d\n" % bootloader.timeout

- initrd = source_params.get('initrd')
+ bootimg_dir = get_bitbake_var("DEPLOY_DIR_IMAGE")
+ if not bootimg_dir:
+ raise WicError("Couldn't find DEPLOY_DIR_IMAGE, exiting")

+ initrd = source_params.get('initrd')
if initrd and source_params.get('create-unified-kernel-image') != "true":
- # obviously we need to have a common common deploy var
- bootimg_dir = get_bitbake_var("DEPLOY_DIR_IMAGE")
- if not bootimg_dir:
- raise WicError("Couldn't find DEPLOY_DIR_IMAGE, exiting")
-
initrds = initrd.split(';')
for rd in initrds:
cp_cmd = "cp %s/%s %s" % (bootimg_dir, rd, hdddir)
@@ -149,6 +156,13 @@ class BootimgEFIPlugin(SourcePlugin):
else:
logger.debug("Ignoring missing initrd")

+ dtb_files = (get_bitbake_var("DTB_FILES") or '').split()
+ if dtb_files:
+ if len(dtb_files) > 1:
+ raise WicError("Only one DTB support in grub configuration, exiting")
+ cp_cmd = "cp %s/%s %s" % (bootimg_dir, dtb_files[0], hdddir)
+ exec_cmd(cp_cmd, True)
+
logger.debug("Writing systemd-boot config "
"%s/hdd/boot/loader/loader.conf", cr_workdir)
cfg = open("%s/hdd/boot/loader/loader.conf" % cr_workdir, "w")
@@ -197,6 +211,9 @@ class BootimgEFIPlugin(SourcePlugin):
for rd in initrds:
boot_conf += "initrd /%s\n" % rd

+ if dtb_files:
+ boot_conf += "devicetree /%s\n" % dtb_files[0]
+
if source_params.get('create-unified-kernel-image') != "true":
logger.debug("Writing systemd-boot config "
"%s/hdd/boot/loader/entries/boot.conf", cr_workdir)
--
2.35.3

[Henning Schild]

Am Sun, 10 Jul 2022 22:51:44 +0200
schrieb Jan Kiszka <jan.k...@siemens.com>:

This file is a fork from OE with very minimal non-functional changes to
make it into Isar. I am afraid that feature will have to make it via OE.

Henning

[Jan Kiszka]

Right, from

bootimg-efi-isar.py | 65 +++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 59 insertions(+), 6 deletions(-)

to

bootimg-efi-isar.py | 104 +++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 87 insertions(+), 17 deletions(-)

The problem is that OE core has no DTB_FILES, and seems like not even a
concept of injecting DTBs via the bootloader, thus passing them to wic.

Jan

--
Siemens AG, Technology
Competence Center Embedded Linux

[Henning Schild]

Am Mon, 11 Jul 2022 17:14:09 +0200

If you look carefully you will see that what you propose is the only
new feature. And most of the other code is a "trivial" grub template
... which one could shrink, but it is not worth it. In other places i
invested a lot to make it hopefully easy to maintain, not to make it
look small.

What you suggest is a pretty big change, which is going to be pretty
hard to maintain. If we really need to go down that road ... we need
testing for that.

> The problem is that OE core has no DTB_FILES, and seems like not even
> a concept of injecting DTBs via the bootloader, thus passing them to
> wic.

Then prepare an "additional boot files" patch for OE. ... but wait. It
already has "custom_cfg". There is "initrd" which can specify multiple
files to copy, so i guess all you need is to write it down differently.
Carry the generated config+yourdiff as custom_cfg and set initrd=foo to
initrd=foo;my.dtb to get that file copied, done without a patch.

Henning

> Jan
>

[Jan Kiszka]

The change is not "big".

>
>> The problem is that OE core has no DTB_FILES, and seems like not even
>> a concept of injecting DTBs via the bootloader, thus passing them to
>> wic.
>
> Then prepare an "additional boot files" patch for OE. ... but wait. It
> already has "custom_cfg". There is "initrd" which can specify multiple
> files to copy, so i guess all you need is to write it down differently.
> Carry the generated config+yourdiff as custom_cfg and set initrd=foo to
> initrd=foo;my.dtb to get that file copied, done without a patch.

Look, we surely don't want to ask users for much more than setting
DTB_FILES in order to inject their DTB into the boot loader. That rules
out custom configs and the existing primitive interface.

But I will explore if OE has an opinion on setting "devicetree" in grub
and systemd-boot configs. If that is at least positive in general, maybe
some less elegant API than this one is possible, and it will generate
one line less of deviation that this patch. If not, we will move forward
with our API.

Meanwhile: Happy Isar forking...