[FFe] flash-kernel displays wrong "selected" DTB on various Pi models

The problem is reproducible:

Create file /etc/flash-kernel/machine with content

   Raspberry Pi 400 Rev 1.0

on any arm64 system and run flash-kernel:

$ sudo flash-kernel $(uname -r)
Using DTB: bcm2711-rpi-4-b.dtb
Installing /lib/firmware/6.2.0-1013-raspi/device-tree/broadcom/bcm2711-rpi-4-b.dtb into /boot/dtbs/6.2.0-1013-raspi/./bcm2711-rpi-4-b.dtb
Taking backup of bcm2711-rpi-4-b.dtb.
Installing new bcm2711-rpi-4-b.dtb.
flash-kernel: installing version 6.2.0-1013-raspi

The following change is enough to fix the issue:
--- db/all.db 2023-06-22 14:18:53.000000000 +0000
+++ /usr/share/flash-kernel/db/all.db 2023-10-02 11:46:14.211402418 +0000
@@ -1823,7 +1805,7 @@
 Machine: Raspberry Pi 4 Model B Rev 1.2
 Machine: Raspberry Pi 4 Model B Rev 1.4
 Machine: Raspberry Pi 4 Model B Rev 1.5
-Machine: Raspberry Pi *
+Machine: Raspberry Pi 4 *
 Kernel-Flavors: raspi raspi-nolpae
 Method: pi
 DTB-Id: bcm2711-rpi-4-b.dtb

Status changed to 'Confirmed' because the bug affects multiple users.

You are correct that the "wrong" DTB is picked in the case of flash-kernel not recognizing the specific model in question. However, this doesn't matter provided the "Method" of the selected entry is "pi" (which it is, as they're currently the only entry that uses this method).

The "pi" method specifically copies *all* DTBs (and overlays) found to the boot partition, deliberately, to permit boot media to be moved between Pi models. However, the way flash-kernel works it still reports the "selected" DTB at the top of the output (and then goes on to copy all the found DTBs anyway).

 Still, I should add an entry for the Pi 5, and move the "Raspberry Pi *" catch-all down to that (and adjust the other catch-alls for various board revisions).

Hello Dave,

when using GRUB to boot via EFI the devicetree command in grub.cfg will use the device-tree in /boot/dtb-$(uname -r). It is important that this device-tree matches the actual machine.

Best regards

Heinrich

@xypron Sure, that matters if you're using GRUB via EFI, but none of the Pi images do. I'll patch this to fix it because it does look sloppy on our part, but this is basically a cosmetic fix -- it doesn't change which DTBs are copied because in the case of the Raspberry Pi images all DTBs are always copied.

It also doesn't affect any non-Pi boards because none of them match "Raspberry Pi *" (at least I'd be rather surprised if they do!).

Can we not just leave 'DTB-Id' empty and then the whole copying of the single/running DTB is skipped?

@juergh That would be the "proper" way to fix this, but the last time I tried that it broke several other places in flash-kernel. It might be easier now, but I don't fancy that invasive a change in an FFe. I ought to look into it for the next cycle, though (really I ought to look into completely overhauling the rather hacky "pi" method and stop it spewing pages of output into the terminal every time it runs, and speed it up further for that matter).

FFe granted

This bug was fixed in the package flash-kernel - 3.107ubuntu2

---------------
flash-kernel (3.107ubuntu2) mantic; urgency=medium

  * Use generic-revision catch-alls for each model rather than relying on a
    single Pi catch-all to avoid a confusing selection of "the one DTB" for a
    given board (even though all other DTBs will still be copied anyway)
    (LP: #2038087)
    - Add missing Pi Zero 2W entry
    - Add missing Pi 5B entry

 -- Dave Jones <email address hidden> Mon, 02 Oct 2023 12:59:44 +0100