prototype snap components building

[Dimitri John Ledkov]

prototype snap components building with snapcraft from latest/edge/components

examples are available at https://github.com/snapcore/snapcraft/tree/feature/components/tests/spread/core22/components

the goal is to fork https://git.launchpad.net/~canonical-kernel-snaps/+git/kernel-snaps-uc22/tree/snapcraft.yaml?h=hwe

and add components

 - iwlwifi component that stages .ko from linux-modules-iwlwifi-generic-hwe-22.04 and stages the matching required firmware files for that .ko

 - ipu6 component that stages .ko from linux-modules-ivsc-generic-hwe-22.04 and linux-modules-ipu6-generic-hwe-22.04 and any firmware files they require

 - nvidia comonenets that stages .o files an firmware from linux-modules-nvidia-535-server-generic-hwe-22.04

[Jesse Sung (wenchien)]

As a quick test, I tried with the following changes and found that the component file contains only the component.yaml file:

--- a/snapcraft.yaml
+++ b/snapcraft.yaml
@@ -11,6 +11,13 @@ architectures:
   - build-on: [amd64]
   - build-on: [arm64]

+components:
+ iwlwifi:
+ type: test
+ summary: iwlwifi modules
+ description: iwlwifi modules
+ version: "0.1"
+
 parts:
   kernel:
     # Need .ko.zst support from u23.10 for backport
@@ -25,8 +32,10 @@ parts:
       - kmod
     stage-packages:
       - linux-image-uc-generic-hwe-22.04
+ - linux-modules-iwlwifi-generic-hwe-22.04
     organize:
       boot: ./
+ lib/modules/6.5.0-15-generic/ubuntu/iwlwifi: (component/iwlwifi)/modules/6.5.0-15-generic/ubuntu/iwlwifi
       lib/firmware: firmware
       lib/modules: modules
       usr/share/doc: doc

The line in organize needs to be
modules/6.5.0-15-generic/ubuntu/iwlwifi: (component/iwlwifi)/modules/6.5.0-15-generic/ubuntu/iwlwifi
to make the files actually go into the component file.

[Jesse Sung (wenchien)]

The ABI string in the path is an issue for organize since we don't want it to be hard-coded in the yaml file.

[Dimitri John Ledkov (xnox)]

we do calculate the ABI later on, can one use vairable in the dictionary key? I can't remember if this was ever possible.

[Callahan Kovacs (mr-cal)]

Currently, craft-parts only supports predefined SNAPCRAFT_ and CRAFT_ variables in `organize` keys and values:

CRAFT_ARCH_BUILD_FOR
CRAFT_ARCH_BUILD_ON
CRAFT_ARCH_TRIPLET
CRAFT_ARCH_TRIPLET_BUILD_FOR
CRAFT_ARCH_TRIPLET_BUILD_ON
CRAFT_PARALLEL_BUILD_COUNT
CRAFT_PRIME
CRAFT_PROJECT_DIR
CRAFT_PROJECT_NAME
CRAFT_STAGE
CRAFT_TARGET_ARCH
SNAPCRAFT_ARCH_TRIPLET
SNAPCRAFT_PARALLEL_BUILD_COUNT
SNAPCRAFT_PRIME
SNAPCRAFT_PROJECT_DIR
SNAPCRAFT_PROJECT_GRADE
SNAPCRAFT_PROJECT_NAME
SNAPCRAFT_PROJECT_VERSION
SNAPCRAFT_STAGE
SNAPCRAFT_TARGET_ARCH

Globs in the key is a possibility (modules/*/ubuntu/iwlwifi) but that won't fully solve this problem. Anyways, I don't know if globs are officially supported by craft-parts (although they work for me).

[Jesse Sung (wenchien)]

If iwlwifi is moved into a standalone part then we don't need to put the ABI string in the dictionary key:
https://git.launchpad.net/~wenchien/+git/kernel-snaps-uc22/commit/?id=f766de2b42fbbfde76585b15ce39ee5d5079ccd4

"iwlwifi.firmware-list" can be used as a hint in part kernel for moving relevant firmware files into the component, though since most of them are also used by the in-tree iwlwifi, we should only move the ones that are exclusively used by the component and keep others in the snap. "trim-firmware" may or may not need some rework depending on how we are going to list the firmware files used by components only.

[Jesse Sung (wenchien)]

Another thing to consider is the module dependencies. Since those files are read-only in the snap file, how are we going to update the info when there's a component being installed or removed?

[Dimitri John Ledkov (xnox)]

Trying to build that in launchpad seems to hang the upload step https://launchpad.net/~canonical-kernel-snaps/canonical-kernel-snaps/+snap/hwe-kernel-test-component/+build/2376991