[PATCH v2 0/3] kernel-fit-image: allow replacing kernel, handle compression in FIT recipe

[PATCH v2 0/3] kernel-fit-image: allow replacing kernel, handle compression in FIT recipe

[Nora Schiffer]

Add support for building alternative kernel images into a FIT image instead of
using linux.bin. An incomplete solution with a similar goal was added in in
commit 9c8ef2119949 ("kernel-fit-image: control kernel section with
FIT_LINUX_BIN") and subsequently reverted in commit 6eae261b6f52 ("Revert
"kernel-fit-image: control kernel section with FIT_LINUX_BIN"") due to missing
features, lack of tests and the submitter having abandoned their approach.

With the new approach, compression is now either handled as part of the
FIT image (KERNEL_FILENAME) or the image is considered to be compressed already
(KERNEL_FILENAME_COMPRESSED). The option to let the kernel recipe do the
compression and store the result in the image deploydir as linux.bin is
preserved for backwards compatibility, but will result in a deprecation warning.

Our main use case for this is to support building a FIT image with an EFI
application as kernel (with FIT_OS = "efi").


v2: do not hardcode kernel filename to bzImage in
    fitimage.KernelFitImageRecipeTests.test_fit_image_kernel_filename selftest
    to fix build on non-x86 machines in PATCH 2/3


Nora Schiffer (3):
  kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf
  kernel-fit-image: reintroduce option to replace kernel image
  kernel-fit-extra-artifacts: skip building linux.bin if unneeded

 .../kernel-fit-extra-artifacts.bbclass        |  4 +-
 meta/classes-recipe/kernel-fit-image.bbclass  | 53 ++++++++--
 meta/classes-recipe/kernel-uboot.bbclass      |  3 +-
 meta/conf/image-fitimage.conf                 | 27 +++++-
 meta/lib/oeqa/selftest/cases/fitimage.py      | 96 ++++++++++++++++++-
 5 files changed, 166 insertions(+), 17 deletions(-)

-- 
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Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
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[PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Nora Schiffer]

It is a bit weird that FIT_KERNEL_COMP_ALG also affects uImage creation,
as kernel-uboot.bbclass is used for both, but fixing that would
unnecessarily break backwards compatibility.

Signed-off-by: Nora Schiffer <nora.schiffer@ew.tq-group.com>
---
 meta/classes-recipe/kernel-uboot.bbclass | 3 +--
 meta/conf/image-fitimage.conf            | 3 +++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/meta/classes-recipe/kernel-uboot.bbclass b/meta/classes-recipe/kernel-uboot.bbclass
index fa28be1715..9beccc2dff 100644
--- a/meta/classes-recipe/kernel-uboot.bbclass
+++ b/meta/classes-recipe/kernel-uboot.bbclass
@@ -4,8 +4,7 @@
 # SPDX-License-Identifier: MIT
 #
 
-# fitImage kernel compression algorithm
-FIT_KERNEL_COMP_ALG ?= "gzip"
+require conf/image-fitimage.conf
 
 # Kernel image type passed to mkimage (i.e. kernel kernel_noload...)
 UBOOT_MKIMAGE_KERNEL_TYPE ?= "kernel"
diff --git a/meta/conf/image-fitimage.conf b/meta/conf/image-fitimage.conf
index a06d30e494..abb17186a5 100644
--- a/meta/conf/image-fitimage.conf
+++ b/meta/conf/image-fitimage.conf
@@ -48,6 +48,9 @@ FIT_OS ?= "linux"
 # DTBs are provided separately in a FIT image.
 FIT_LINUX_BIN ?= "linux.bin"
 
+# fitImage kernel compression algorithm
+FIT_KERNEL_COMP_ALG ?= "gzip"
+
 # Additional mkimage options for FIT image creation
 FIT_MKIMAGE_EXTRA_OPTS ?= ""
 
-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/

Re: [OE-core] [PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Richard Purdie]

On Mon, 2026-07-27 at 11:05 +0200, Nora Schiffer via lists.openembedded.org wrote:
> It is a bit weird that FIT_KERNEL_COMP_ALG also affects uImage creation,
> as kernel-uboot.bbclass is used for both, but fixing that would
> unnecessarily break backwards compatibility.
> 
> Signed-off-by: Nora Schiffer <nora.schiffer@ew.tq-group.com>
> ---
>  meta/classes-recipe/kernel-uboot.bbclass | 3 +--
>  meta/conf/image-fitimage.conf            | 3 +++
>  2 files changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/meta/classes-recipe/kernel-uboot.bbclass b/meta/classes-recipe/kernel-uboot.bbclass
> index fa28be1715..9beccc2dff 100644
> --- a/meta/classes-recipe/kernel-uboot.bbclass
> +++ b/meta/classes-recipe/kernel-uboot.bbclass
> @@ -4,8 +4,7 @@
>  # SPDX-License-Identifier: MIT
>  #
>  
> -# fitImage kernel compression algorithm
> -FIT_KERNEL_COMP_ALG ?= "gzip"
> +require conf/image-fitimage.conf
>  
>  # Kernel image type passed to mkimage (i.e. kernel kernel_noload...)
>  UBOOT_MKIMAGE_KERNEL_TYPE ?= "kernel"
> diff --git a/meta/conf/image-fitimage.conf b/meta/conf/image-fitimage.conf
> index a06d30e494..abb17186a5 100644
> --- a/meta/conf/image-fitimage.conf
> +++ b/meta/conf/image-fitimage.conf
> @@ -48,6 +48,9 @@ FIT_OS ?= "linux"
>  # DTBs are provided separately in a FIT image.
>  FIT_LINUX_BIN ?= "linux.bin"
>  
> +# fitImage kernel compression algorithm
> +FIT_KERNEL_COMP_ALG ?= "gzip"
> +
>  # Additional mkimage options for FIT image creation
>  FIT_MKIMAGE_EXTRA_OPTS ?= ""
> 

We're realising that the kernel classes are a bit of a tangled spiders
web and we want to improve things and clean things up.

Adding a dependency on "fit" from the "uboot" class does therefore feed
a bit backward as you note.

You mention not breaking backwards compatibility. I think given the
other work we're thinking about, it might be worth considering that and
seeing if we can avoid tangling things up even further.

Cheers,

Richard

Re: [OE-core] [PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Nora Schiffer]

On Thu, 2026-07-30 at 11:43 +0100, Richard Purdie wrote:
> On Mon, 2026-07-27 at 11:05 +0200, Nora Schiffer via lists.openembedded.org wrote:
> > It is a bit weird that FIT_KERNEL_COMP_ALG also affects uImage creation,
> > as kernel-uboot.bbclass is used for both, but fixing that would
> > unnecessarily break backwards compatibility.
> > 
> > Signed-off-by: Nora Schiffer <nora.schiffer@ew.tq-group.com>
> > ---
> >  meta/classes-recipe/kernel-uboot.bbclass | 3 +--
> >  meta/conf/image-fitimage.conf            | 3 +++
> >  2 files changed, 4 insertions(+), 2 deletions(-)
> > 
> > diff --git a/meta/classes-recipe/kernel-uboot.bbclass b/meta/classes-recipe/kernel-uboot.bbclass
> > index fa28be1715..9beccc2dff 100644
> > --- a/meta/classes-recipe/kernel-uboot.bbclass
> > +++ b/meta/classes-recipe/kernel-uboot.bbclass
> > @@ -4,8 +4,7 @@
> >  # SPDX-License-Identifier: MIT
> >  #
> >  
> > -# fitImage kernel compression algorithm
> > -FIT_KERNEL_COMP_ALG ?= "gzip"
> > +require conf/image-fitimage.conf
> >  
> >  # Kernel image type passed to mkimage (i.e. kernel kernel_noload...)
> >  UBOOT_MKIMAGE_KERNEL_TYPE ?= "kernel"
> > diff --git a/meta/conf/image-fitimage.conf b/meta/conf/image-fitimage.conf
> > index a06d30e494..abb17186a5 100644
> > --- a/meta/conf/image-fitimage.conf
> > +++ b/meta/conf/image-fitimage.conf
> > @@ -48,6 +48,9 @@ FIT_OS ?= "linux"
> >  # DTBs are provided separately in a FIT image.
> >  FIT_LINUX_BIN ?= "linux.bin"
> >  
> > +# fitImage kernel compression algorithm
> > +FIT_KERNEL_COMP_ALG ?= "gzip"
> > +
> >  # Additional mkimage options for FIT image creation
> >  FIT_MKIMAGE_EXTRA_OPTS ?= ""
> > 
> 
> We're realising that the kernel classes are a bit of a tangled spiders
> web and we want to improve things and clean things up.
> 
> Adding a dependency on "fit" from the "uboot" class does therefore feed
> a bit backward as you note.
> 
> You mention not breaking backwards compatibility. I think given the
> other work we're thinking about, it might be worth considering that and
> seeing if we can avoid tangling things up even further.
> 
> Cheers,
> 
> Richard

Okay, new plan: Change uboot_prep_kimage to accept the compression algorithm as
an argument, so we can use different variables when calling it from kernel-
uimage.bbclass and kernel-fit-extra-artifacts.bbclass. kernel-uimage.bbclass
could then use a separate variable UBOOT_MKIMAGE_KERNEL_COMP_ALG instead of
reusing the FIT one.

A more radical approach would be to skip the deprecation of using a linux.bin
generated by the kernel recipe as a FIT image's kernel and drop support
immediately. This would result in kernel-fit-extra-artifacts.bbclass not needing
kernel-uboot.bbclass anymore, and maybe kernel-fit-extra-artifacts.bbclass could
then be dropped in favor of listing setup.bin in KERNEL_IMAGETYPES if it is
needed.

I'm a bit worried doing all that at once might cause too much breakage, and I
think an incremental approach with deprecation warnings works fine here, but of
course that also depends on the other work you want to do.

Let me know which direction you prefer for the next iteration of these patches.

Best,
Nora



> 
> 

-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/

Re: [OE-core] [PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Richard Purdie]

On Thu, 2026-07-30 at 13:15 +0200, Nora Schiffer wrote:
> On Thu, 2026-07-30 at 11:43 +0100, Richard Purdie wrote:
> 
> Okay, new plan: Change uboot_prep_kimage to accept the compression algorithm as
> an argument, so we can use different variables when calling it from kernel-
> uimage.bbclass and kernel-fit-extra-artifacts.bbclass. kernel-uimage.bbclass
> could then use a separate variable UBOOT_MKIMAGE_KERNEL_COMP_ALG instead of
> reusing the FIT one.
> 
> A more radical approach would be to skip the deprecation of using a linux.bin
> generated by the kernel recipe as a FIT image's kernel and drop support
> immediately.

Can you see from the commit history who might have been using that? Do
you think there are many people relying upon it? If that functionality
doesn't make much sense and wouldn't or shouldn't be used by people,
I'm fine with actually removing it, as long as we're clear about why it
likely isn't needed or is inefficient (or whatever) and what the
alternative is.

A lot of the time I think we support too many code paths when we should
try and encourage people to do the "best" known things.

Cheers,

Richard

Re: [OE-core] [PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Nora Schiffer]

On Thu, 2026-07-30 at 14:09 +0100, Richard Purdie wrote:
> On Thu, 2026-07-30 at 13:15 +0200, Nora Schiffer wrote:
> > On Thu, 2026-07-30 at 11:43 +0100, Richard Purdie wrote:
> > 
> > Okay, new plan: Change uboot_prep_kimage to accept the compression algorithm as
> > an argument, so we can use different variables when calling it from kernel-
> > uimage.bbclass and kernel-fit-extra-artifacts.bbclass. kernel-uimage.bbclass
> > could then use a separate variable UBOOT_MKIMAGE_KERNEL_COMP_ALG instead of
> > reusing the FIT one.
> > 
> > A more radical approach would be to skip the deprecation of using a linux.bin
> > generated by the kernel recipe as a FIT image's kernel and drop support
> > immediately.
> 
> Can you see from the commit history who might have been using that? Do
> you think there are many people relying upon it? If that functionality
> doesn't make much sense and wouldn't or shouldn't be used by people,
> I'm fine with actually removing it, as long as we're clear about why it
> likely isn't needed or is inefficient (or whatever) and what the
> alternative is.
> 
> A lot of the time I think we support too many code paths when we should
> try and encourage people to do the "best" known things.

Right now using linux.bin is the only way to build a FIT image using kernel-fit-
image.bbclass - my patch 2/3 introduces the option to use something different
instead of linux.bin. As currently implemented, the patch results in a
deprecation warning for *all* BSPs that build FIT images, but that seems
preferable to breaking such BSPs.

Making FIT_KERNEL_FILENAME default to KERNEL_IMAGETYPE would keep the FIT image
working where KERNEL_IMAGETYPE is the correct image to include in the FIT, but
it would differ from the current generation of linux.bin in kernel-uboot.bbclass
in most cases. As far as I can tell this should work as intended on platforms
that set KERNEL_IMAGETYPE to "Image"; types like zImage and bzImage would result
in double compression with the default settings, and most other types would just
be unbootable. I don't think we should go with this solution.

Best,
Nora


-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/

Re: [OE-core] [PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Richard Purdie]

On Thu, 2026-07-30 at 15:35 +0200, Nora Schiffer wrote:
> On Thu, 2026-07-30 at 14:09 +0100, Richard Purdie wrote:
> > On Thu, 2026-07-30 at 13:15 +0200, Nora Schiffer wrote:
> > > On Thu, 2026-07-30 at 11:43 +0100, Richard Purdie wrote:
> > > 
> > > Okay, new plan: Change uboot_prep_kimage to accept the compression algorithm as
> > > an argument, so we can use different variables when calling it from kernel-
> > > uimage.bbclass and kernel-fit-extra-artifacts.bbclass. kernel-uimage.bbclass
> > > could then use a separate variable UBOOT_MKIMAGE_KERNEL_COMP_ALG instead of
> > > reusing the FIT one.
> > > 
> > > A more radical approach would be to skip the deprecation of using a linux.bin
> > > generated by the kernel recipe as a FIT image's kernel and drop support
> > > immediately.
> > 
> > Can you see from the commit history who might have been using that? Do
> > you think there are many people relying upon it? If that functionality
> > doesn't make much sense and wouldn't or shouldn't be used by people,
> > I'm fine with actually removing it, as long as we're clear about why it
> > likely isn't needed or is inefficient (or whatever) and what the
> > alternative is.
> > 
> > A lot of the time I think we support too many code paths when we should
> > try and encourage people to do the "best" known things.
> 
> Right now using linux.bin is the only way to build a FIT image using kernel-fit-
> image.bbclass - my patch 2/3 introduces the option to use something different
> instead of linux.bin. As currently implemented, the patch results in a
> deprecation warning for *all* BSPs that build FIT images, but that seems
> preferable to breaking such BSPs.
> 
> Making FIT_KERNEL_FILENAME default to KERNEL_IMAGETYPE would keep the FIT image
> working where KERNEL_IMAGETYPE is the correct image to include in the FIT, but
> it would differ from the current generation of linux.bin in kernel-uboot.bbclass
> in most cases. As far as I can tell this should work as intended on platforms
> that set KERNEL_IMAGETYPE to "Image"; types like zImage and bzImage would result
> in double compression with the default settings, and most other types would just
> be unbootable. I don't think we should go with this solution.

Right, that does not sound like a good outcome. It also means that
linux.bin isn't really deprecated though as the commit messages hinted
at :/.

This is why I'm asking questions since I really haven't looked into
this in detail. I'm just very worried about the spaghetti nature of our
classes and really don't want to make it worse.

Cheers,

Richard

Re: [OE-core] [PATCH v2 1/3] kernel-uboot: move FIT_KERNEL_COMP_ALG to image-fitimage.conf

[Nora Schiffer]

On Thu, 2026-07-30 at 14:50 +0100, Richard Purdie wrote:
> On Thu, 2026-07-30 at 15:35 +0200, Nora Schiffer wrote:
> > On Thu, 2026-07-30 at 14:09 +0100, Richard Purdie wrote:
> > > On Thu, 2026-07-30 at 13:15 +0200, Nora Schiffer wrote:
> > > > On Thu, 2026-07-30 at 11:43 +0100, Richard Purdie wrote:
> > > > 
> > > > Okay, new plan: Change uboot_prep_kimage to accept the compression algorithm as
> > > > an argument, so we can use different variables when calling it from kernel-
> > > > uimage.bbclass and kernel-fit-extra-artifacts.bbclass. kernel-uimage.bbclass
> > > > could then use a separate variable UBOOT_MKIMAGE_KERNEL_COMP_ALG instead of
> > > > reusing the FIT one.
> > > > 
> > > > A more radical approach would be to skip the deprecation of using a linux.bin
> > > > generated by the kernel recipe as a FIT image's kernel and drop support
> > > > immediately.
> > > 
> > > Can you see from the commit history who might have been using that? Do
> > > you think there are many people relying upon it? If that functionality
> > > doesn't make much sense and wouldn't or shouldn't be used by people,
> > > I'm fine with actually removing it, as long as we're clear about why it
> > > likely isn't needed or is inefficient (or whatever) and what the
> > > alternative is.
> > > 
> > > A lot of the time I think we support too many code paths when we should
> > > try and encourage people to do the "best" known things.
> > 
> > Right now using linux.bin is the only way to build a FIT image using kernel-fit-
> > image.bbclass - my patch 2/3 introduces the option to use something different
> > instead of linux.bin. As currently implemented, the patch results in a
> > deprecation warning for *all* BSPs that build FIT images, but that seems
> > preferable to breaking such BSPs.
> > 
> > Making FIT_KERNEL_FILENAME default to KERNEL_IMAGETYPE would keep the FIT image
> > working where KERNEL_IMAGETYPE is the correct image to include in the FIT, but
> > it would differ from the current generation of linux.bin in kernel-uboot.bbclass
> > in most cases. As far as I can tell this should work as intended on platforms
> > that set KERNEL_IMAGETYPE to "Image"; types like zImage and bzImage would result
> > in double compression with the default settings, and most other types would just
> > be unbootable. I don't think we should go with this solution.
> 
> Right, that does not sound like a good outcome. It also means that
> linux.bin isn't really deprecated though as the commit messages hinted
> at :/.

My goal is to deprecate it though - linux.bin generation has some weirdness that
we should get rid of in my opinion, at least for FIT images (I don't have an
opinion about uImage build). Thus patch 2

- implements an alternative approach that avoids the weirdness
- warns users to switch to the new approach (to set KERNEL_IMAGETYPE(S) and
  FIT_KERNEL_FILENAME appropriately), without immediately breaking existing
  BSPs.

I feel like implementing the new way without the deprecation warning would just
result in users keeping the old solution longer, thus requiring us to preserve
support for using linux.bin.

Best,
Nora


-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/

[PATCH v2 2/3] kernel-fit-image: reintroduce option to replace kernel image

[Nora Schiffer]

A similar feature was added in commit 9c8ef2119949 ("kernel-fit-image:
control kernel section with FIT_LINUX_BIN") and subsequently reverted in
commit 6eae261b6f52 ("Revert "kernel-fit-image: control kernel section
with FIT_LINUX_BIN"") due to its incomplete implementation and lack of
tests. Reintroduce an improved version:

- The FIT_LINUX_BIN variable (which had been left unused) is renamed to
  FIT_KERNEL_FILENAME. It can now actually be used to select a different
  file from DEPLOY_DIR_IMAGE. The file will be compressed using
  FIT_KERNEL_COMP_ALG, rather than than letting the kernel recipe handle
  this through kernel-fit-extra-artifacts.bbclass.
- Alternatively, FIT_KERNEL_FILENAME_COMPRESSED can be used to select a
  pre-compressed file from DEPLOY_DIR_IMAGE. In this case,
  FIT_KERNEL_COMP_ALG only controls the "compression" field of the
  generated FIT image.
- To avoid breaking backwards compatibility,
  FIT_KERNEL_FILENAME_COMPRESSED defaults to "linux.bin". As a special
  case, the compression algorithm will be read from "linux_comp" for
  linux.bin.
- Add tests.

Signed-off-by: Nora Schiffer <nora.schiffer@ew.tq-group.com>
---
 meta/classes-recipe/kernel-fit-image.bbclass | 53 +++++++++--
 meta/conf/image-fitimage.conf                | 24 ++++-
 meta/lib/oeqa/selftest/cases/fitimage.py     | 96 +++++++++++++++++++-
 3 files changed, 159 insertions(+), 14 deletions(-)

diff --git a/meta/classes-recipe/kernel-fit-image.bbclass b/meta/classes-recipe/kernel-fit-image.bbclass
index 3ace09ef5c..4ace6871f8 100644
--- a/meta/classes-recipe/kernel-fit-image.bbclass
+++ b/meta/classes-recipe/kernel-fit-image.bbclass
@@ -64,6 +64,7 @@ def apply_dtbvendored(d,dtb):
 
 python do_compile() {
     import shutil
+    import subprocess
     import oe.fitimage
 
     itsfile = "fit-image.its"
@@ -88,12 +89,52 @@ python do_compile() {
     )
 
     # Prepare a kernel image section.
-    shutil.copyfile(os.path.join(kernel_deploydir, "linux.bin"), "linux.bin")
-    with open(os.path.join(kernel_deploydir, "linux_comp")) as linux_comp_f:
-        linux_comp = linux_comp_f.read()
-    root_node.fitimage_emit_section_kernel("kernel-1", "linux.bin", linux_comp,
-        d.getVar('UBOOT_LOADADDRESS'), d.getVar('UBOOT_ENTRYPOINT'),
-        d.getVar('UBOOT_MKIMAGE_KERNEL_TYPE'), d.getVar("UBOOT_ENTRYSYMBOL"))
+    kernel = d.getVar('FIT_KERNEL_FILENAME')
+    kernel_compressed = d.getVar('FIT_KERNEL_FILENAME_COMPRESSED')
+    kernel_comp_alg = d.getVar('FIT_KERNEL_COMP_ALG')
+
+    COMP_ALGS = {
+        'gzip': ['gzip', '-9', '--stdout'],
+        'lzo': ['lzop', '-9', '--stdout'],
+        'lzma': ['xz', '--format=lzma', '-f', '-6', '--stdout'],
+    }
+
+    if kernel and kernel_comp_alg == 'none':
+        kernel_compressed = kernel
+        kernel = None
+    elif not kernel and kernel_compressed == 'linux.bin':
+        # Backwards compatibility
+        bb.warn('FIT_KERNEL_FILENAME_COMPRESSED = "linux.bin" is deprecated. Set FIT_KERNEL_FILENAME or FIT_KERNEL_FILENAME_COMPRESSED explicitly.')
+        with open(os.path.join(kernel_deploydir, "linux_comp")) as linux_comp_f:
+            kernel_comp_alg = linux_comp_f.read()
+
+    if kernel:
+        kernel_path = os.path.join(kernel_deploydir, kernel)
+        kernel_name = os.path.basename(kernel) + '.compressed'
+
+        try:
+            cmd = COMP_ALGS[kernel_comp_alg] + [kernel_path]
+        except KeyError:
+            bb.fatal(f"Unknown algorithm {kernel_comp_alg} in FIT_KERNEL_COMP_ALG.")
+
+        with open(kernel_name, 'wb') as f:
+            try:
+                subprocess.run(cmd, check=True, stdout=f, stderr=subprocess.PIPE)
+            except subprocess.CalledProcessError as e:
+                bb.fatal(f"Command '{' '.join(cmd)}' failed with return code {e.returncode}\nstderr: {e.stderr.decode()}")
+
+    elif kernel_compressed:
+        kernel_path = os.path.join(kernel_deploydir, kernel_compressed)
+        kernel_name = os.path.basename(kernel_compressed)
+        shutil.copyfile(kernel_path, kernel_name)
+
+    # FIT_KERNEL_FILENAME or FIT_KERNEL_FILENAME_COMPRESSED was set
+    if kernel_name:
+        root_node.fitimage_emit_section_kernel("kernel-1", kernel_name, kernel_comp_alg,
+                                               d.getVar('UBOOT_LOADADDRESS'),
+                                               d.getVar('UBOOT_ENTRYPOINT'),
+                                               d.getVar('UBOOT_MKIMAGE_KERNEL_TYPE'),
+                                               d.getVar("UBOOT_ENTRYSYMBOL"))
 
     # Prepare a DTB image section
     kernel_devicetree = d.getVar('KERNEL_DEVICETREE')
diff --git a/meta/conf/image-fitimage.conf b/meta/conf/image-fitimage.conf
index abb17186a5..f7b1ffdfd5 100644
--- a/meta/conf/image-fitimage.conf
+++ b/meta/conf/image-fitimage.conf
@@ -41,12 +41,28 @@ FIT_SUPPORTED_INITRAMFS_FSTYPES ?= "cpio.lz4 cpio.lzo cpio.lzma cpio.xz cpio.zst
 # to load a kernel with EFI stub as an EFI application.
 FIT_OS ?= "linux"
 
-# Allow user to support special use cases where the kernel binary is
-# not included in the FIT image itself.
+# Select the binary included as kernel image in the FIT image.
+# This allows the user to support special use cases where the kernel binary is
+# not included in the FIT image itself or a different image is used as kernel.
 # This is particularly useful for UKI-based setups, where the kernel
 # and initramfs are bundled into a Unified Kernel Image (UKI), and
-# DTBs are provided separately in a FIT image.
-FIT_LINUX_BIN ?= "linux.bin"
+# DTBs are provided separately in a FIT image, as well as providing the option
+# to include an EFI application as the kernel.
+#
+# Will be compressed using FIT_KERNEL_COMP_ALG. See also
+# FIT_KERNEL_FILENAME_COMPRESSED.
+FIT_KERNEL_FILENAME ?= ""
+
+# Precompressed kernel image. FIT_KERNEL_COMP_ALG is used to fill the
+# "compression" property in the FIT image, so it must match the used
+# compression algorithm. As a special case, if FIT_KERNEL_FILENAME_COMPRESSED
+# is set to "linux.bin", the compression algorithm is read from the "linux_comp"
+# file instead for backwards compatiblity; this behavior is deprecated.
+#
+# If both FIT_KERNEL_FILENAME and FIT_KERNEL_FILENAME_COMPRESSED are set,
+# FIT_KERNEL_FILENAME takes precedence. Unset both to generate a FIT image
+# without kernel section.
+FIT_KERNEL_FILENAME_COMPRESSED ?= "linux.bin"
 
 # fitImage kernel compression algorithm
 FIT_KERNEL_COMP_ALG ?= "gzip"
diff --git a/meta/lib/oeqa/selftest/cases/fitimage.py b/meta/lib/oeqa/selftest/cases/fitimage.py
index 451878aafd..5d54059b54 100644
--- a/meta/lib/oeqa/selftest/cases/fitimage.py
+++ b/meta/lib/oeqa/selftest/cases/fitimage.py
@@ -677,6 +677,8 @@ class KernelFitImageBase(FitImageTestCase):
             'FIT_DESC',
             'FIT_HASH_ALG',
             'FIT_KERNEL_COMP_ALG',
+            'FIT_KERNEL_FILENAME',
+            'FIT_KERNEL_FILENAME_COMPRESSED',
             'FIT_LOADABLES',
             'FIT_LOADABLE_ENTRYPOINT',
             'FIT_LOADABLE_LOADADDRESS',
@@ -909,17 +911,39 @@ class KernelFitImageBase(FitImageTestCase):
         uboot_rd_loadaddress = bb_vars.get('UBOOT_RD_LOADADDRESS')
         uboot_rd_entrypoint = bb_vars.get('UBOOT_RD_ENTRYPOINT')
 
+        kernel_filename = bb_vars.get('FIT_KERNEL_FILENAME')
+        kernel_filename_compressed = bb_vars.get('FIT_KERNEL_FILENAME_COMPRESSED')
+        kernel_comp_alg = bb_vars['FIT_KERNEL_COMP_ALG']
+
+        if kernel_filename:
+            kernel_name = os.path.basename(kernel_filename)
+            if kernel_comp_alg != 'none':
+                kernel_name += '.compressed'
+        elif kernel_filename_compressed:
+            kernel_name = os.path.basename(kernel_filename_compressed)
+
         its_field_check = [
             'description = "%s";' % bb_vars['FIT_DESC'],
             'description = "Linux kernel";',
             'type = "' + str(bb_vars['UBOOT_MKIMAGE_KERNEL_TYPE']) + '";',
-            # 'compression = "' + str(bb_vars['FIT_KERNEL_COMP_ALG']) + '";', defined based on files in TMPDIR, not ideal...
-            'data = /incbin/("linux.bin");',
+        ]
+
+        # Compression test skipped for deprecated linux.bin handling, as that
+        # would be based on files in TMPDIR
+        if kernel_filename or kernel_filename_compressed != 'linux.bin':
+            its_field_check.append('compression = "%s";' % kernel_comp_alg)
+
+        if kernel_name:
+            its_field_check.append('data = /incbin/("%s");' % kernel_name)
+
+        # Field order of its_field_check and the generated ITS must match
+        its_field_check += [
             'arch = "' + str(bb_vars['UBOOT_ARCH']) + '";',
             'os = "%s";' % bb_vars['FIT_OS'],
             'load = <' + str(bb_vars['UBOOT_LOADADDRESS']) + '>;',
             'entry = <' + str(bb_vars['UBOOT_ENTRYPOINT']) + '>;',
         ]
+
         if initramfs_image and initramfs_image_bundle != "1":
             its_field_check.append('type = "ramdisk";')
             if uboot_rd_loadaddress:
@@ -1272,6 +1296,23 @@ PREFERRED_PROVIDER_virtual/dtb = "test-dtbs-as-ext"
         self._gen_atf_tee_dummy_images(bb_vars)
         self._test_fitimage(bb_vars)
 
+    def test_fit_image_kernel_filename(self):
+        """
+        Summary:     Check if FIT image and Image Tree Source (its) are built
+                     and the Image Tree Source has the correct fields.
+        Expected:    1. fitImage and Image Tree Source can be built
+                     2. Filename and compression are as expected in the ITS
+                     3. Filename is as expected in the fitImage
+        """
+        config = """
+FIT_KERNEL_FILENAME = "${KERNEL_IMAGETYPE}"
+FIT_KERNEL_COMP_ALG = "none"
+"""
+        config = self._config_add_kernel_classes(config)
+        self.write_config(config)
+        bb_vars = self._fit_get_bb_vars()
+        self._test_fitimage(bb_vars)
+
 
     def test_sign_fit_image_configurations(self):
         """
@@ -1506,11 +1547,12 @@ class FitImagePyTests(KernelFitImageBase):
             'FIT_DESC': "Kernel fitImage for a dummy distro",
             'FIT_GENERATE_KEYS': "0",
             'FIT_HASH_ALG': "sha256",
+            'FIT_KERNEL_COMP_ALG': "gzip",
+            'FIT_KERNEL_FILENAME_COMPRESSED': "linux.bin",
             'FIT_KEY_GENRSA_ARGS': "-F4",
             'FIT_KEY_REQ_ARGS': "-batch -new",
             'FIT_KEY_SIGN_PKCS': "-x509",
             'FIT_LOADABLES': "",
-            'FIT_LINUX_BIN': "linux.bin",
             'FIT_OS': "linux",
             'FIT_PAD_ALG': "pkcs-1.5",
             'FIT_SIGN_ALG': "rsa2048",
@@ -1549,6 +1591,19 @@ class FitImagePyTests(KernelFitImageBase):
                 debug_output = "\n".join([f"{key} = {value}" for key, value in bb_vars_overrides.items()])
                 self.logger.debug("bb_vars overrides:\n%s" % debug_output)
 
+        kernel = bb_vars.get('FIT_KERNEL_FILENAME')
+        kernel_compressed = bb_vars.get('FIT_KERNEL_FILENAME_COMPRESSED')
+        kernel_comp_alg = bb_vars.get('FIT_KERNEL_COMP_ALG')
+
+        if kernel and kernel_comp_alg == 'none':
+            kernel_compressed = kernel
+            kernel = None
+
+        if kernel:
+            kernel_name = os.path.basename(kernel) + '.compressed'
+        elif kernel_compressed:
+            kernel_name = os.path.basename(kernel_compressed)
+
         root_node = oe.fitimage.ItsNodeRootKernel(
             bb_vars["FIT_DESC"], bb_vars["FIT_ADDRESS_CELLS"],
             bb_vars['HOST_PREFIX'], bb_vars['UBOOT_ARCH'], bb_vars['FIT_OS'],
@@ -1561,7 +1616,8 @@ class FitImagePyTests(KernelFitImageBase):
             oe.types.boolean(bb_vars['FIT_SIGN_INDIVIDUAL']), bb_vars['UBOOT_SIGN_IMG_KEYNAME']
         )
 
-        root_node.fitimage_emit_section_kernel("kernel-1", "linux.bin", "none",
+        root_node.fitimage_emit_section_kernel("kernel-1",
+            kernel_name, kernel_comp_alg,
             bb_vars.get('UBOOT_LOADADDRESS'), bb_vars.get('UBOOT_ENTRYPOINT'),
             bb_vars.get('UBOOT_MKIMAGE_KERNEL_TYPE'), bb_vars.get("UBOOT_ENTRYSYMBOL")
         )
@@ -1651,6 +1707,38 @@ class FitImagePyTests(KernelFitImageBase):
         with self.assertRaises(BBHandledException):
             self._test_fitimage_py(bb_vars_overrides)
 
+    def test_fitimage_py_conf_kernel_filename_compression(self):
+        """Test FIT_KERNEL_FILENAME and FIT_KERNEL_COMP_ALG functionality"""
+        bb_vars_overrides = {
+            'FIT_KERNEL_FILENAME': "path/to/my/Image",
+            'FIT_KERNEL_COMP_ALG': "gzip",
+        }
+        self._test_fitimage_py(bb_vars_overrides)
+
+    def test_fitimage_py_conf_kernel_filename_compression_none(self):
+        """Test FIT_KERNEL_FILENAME and FIT_KERNEL_COMP_ALG functionality"""
+        bb_vars_overrides = {
+            'FIT_KERNEL_FILENAME': "path/to/my/Image",
+            'FIT_KERNEL_COMP_ALG': "none",
+        }
+        self._test_fitimage_py(bb_vars_overrides)
+
+    def test_fitimage_py_conf_kernel_filename_compressed(self):
+        """Test FIT_KERNEL_FILENAME_COMPRESSED functionality"""
+        bb_vars_overrides = {
+            'FIT_KERNEL_FILENAME_COMPRESSED': "path/to/my/Image",
+            'FIT_KERNEL_COMP_ALG': "gzip",
+        }
+        self._test_fitimage_py(bb_vars_overrides)
+
+    def test_fitimage_py_conf_kernel_filename_compressed_none(self):
+        """Test FIT_KERNEL_FILENAME_COMPRESSED functionality"""
+        bb_vars_overrides = {
+            'FIT_KERNEL_FILENAME_COMPRESSED': "path/to/my/Image",
+            'FIT_KERNEL_COMP_ALG': "none",
+        }
+        self._test_fitimage_py(bb_vars_overrides)
+
     def test_fitimage_py_conf_loadables(self):
         """Test FIT_LOADABLES basic functionality"""
         bb_vars_overrides = {
-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/

[PATCH v2 3/3] kernel-fit-extra-artifacts: skip building linux.bin if unneeded

[Nora Schiffer]

The linux.bin generation logic is both complex and inflexible. With the
introduction of FIT_KERNEL_FILENAME[_COMPRESSED], building linux.bin can
be skipped if any of the two variables is set to a non-default value, as
kernel-fit-image.bbclass will handle the compression itself.

Signed-off-by: Nora Schiffer <nora.schiffer@ew.tq-group.com>
---
 meta/classes-recipe/kernel-fit-extra-artifacts.bbclass | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/meta/classes-recipe/kernel-fit-extra-artifacts.bbclass b/meta/classes-recipe/kernel-fit-extra-artifacts.bbclass
index 385fe9895a..02e7d1273f 100644
--- a/meta/classes-recipe/kernel-fit-extra-artifacts.bbclass
+++ b/meta/classes-recipe/kernel-fit-extra-artifacts.bbclass
@@ -11,7 +11,9 @@ inherit kernel-uboot
 
 kernel_do_deploy:append() {
 	# Provide the kernel artifacts to post processing recipes e.g. for creating a FIT image
-	uboot_prep_kimage "$deployDir"
+	if [ -z "${FIT_KERNEL_FILENAME}" ] && [ "${FIT_KERNEL_FILENAME_COMPRESSED}" = 'linux.bin' ]; then
+		uboot_prep_kimage "$deployDir"
+	fi
 	# For x86 a setup.bin needs to be include"d in a fitImage as well
 	if [ -e ${KERNEL_OUTPUT_DIR}/setup.bin ]; then
 		install -D "${B}/${KERNEL_OUTPUT_DIR}/setup.bin" "$deployDir/"
-- 
TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
Amtsgericht München, HRB 105018
Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
https://www.tq-group.com/