Compiling kernel modules

[ilario]

Dear all,
I am trying to have the kernel ad5360 module available (for communicating via SPI to a bipolar multi-channel DAC).

I could not find an updated guide for compiling a kernel, so I report here my FAILED attempt, hoping that you can suggest me how to succeed.

On a side note, for compiling a custom kernel, it would be convenient to have on the Olimex repository also the linux-headers-* and the linux-source-* packages (suggested also here).

I performed these steps directly on the target A64-OLinuXino-2Ge8G-IND in order to not worry with the cross-compilation stuff.

1) make a backup of your /boot/kernel.itb file (it was verrrry useful for recovering the broken system)

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cp /boot/kernel.itb /boot/kernel.itb-20231116
2) get the source code

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mkdir ~/kernel
cd ~/kernel
git clone --depth=1 https://github.com/OLIMEX/linux-olimex -b release-20230725-v5.10.180
The specified branch points to the latest available code in that repository as of today.
I specified --depth=1 to avoid overheating, swapping and rebooting of the A64-olinuxino (anyway the box was open and I installed a huge heat sink (that fits perfectly inside the black metal box)).

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cd linux-olimex
3) apply the current kernel configuration

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cp /proc/config.gz .
gunzip config.gz
mv config .config
make oldconfig
4) select the wanted modules

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make menuconfig...look for the module and select it...

5) compile it as a Debian package

To package the new kernel as a .deb package seems the most convenient option to me. Found the command here.

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make bindeb-pkg KDEB_PKGVERSION=$(make kernelversion)-1
6) install the package with dpkg

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cd ..
dpkg -i linux-image-5.10.180-olimex+_5.10.180-1_arm64.deb
7) reboot

(actually the reboot often fails for me (approx 50% of times), I have to poweroff (from the OS), then unplug and plug again)

hit the problem

In my case the system was stuck at the bootloader. Connecting a serial-to-USB adapter, I saw these messages:

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[...]
mmc0 is current device
Scanning mmc 0:1...
Found U-Boot script /boot/boot.scr
2274 bytes read in 2 ms (1.1 MiB/s)
## Executing script at 4fc00000
U-boot loaded from SD
Boot script loaded from mmc
Checking for /uEnv.txt...
Checking for /boot/uEnv.txt...
610 bytes read in 1 ms (595.7 KiB/s)
Loaded environment from /boot/uEnv.txt
Loading FIT image...
37739691 bytes read in 1618 ms (22.2 MiB/s)
## Loading kernel from FIT Image at 58000000 ...
    Using 'config-8861' configuration
    Trying 'kernel-1' kernel subimage
      Description:  Linux kernel 5.10.180-olimex+
      Type:         Kernel Image
      Compression:  uncompressed
      Data Start:   0x580000d4
      Data Size:    20051976 Bytes = 19.1 MiB
      Architecture: AArch64
      OS:           Linux
      Load Address: 0x40080000
      Entry Point:  0x40080000
      Hash algo:    crc32
      Hash value:   62c3ae8d
      Hash algo:    sha1
      Hash value:   4a758e3a90da6390220db741fb285add5cd708fb
    Verifying Hash Integrity ... crc32+ sha1+ OK
## Loading ramdisk from FIT Image at 58000000 ...
    Using 'config-8861' configuration
    Trying 'ramdisk-1' ramdisk subimage
      Description:  Ramdisk for kernel 5.10.180-olimex+
      Type:         RAMDisk Image
      Compression:  Unknown Compression
      Data Start:   0x5931fa14
      Data Size:    17536353 Bytes = 16.7 MiB
      Architecture: AArch64
      OS:           Linux
      Load Address: 0x4fe00000
      Entry Point:  0x4fe00000
      Hash algo:    crc32
      Hash value:   6fc8f1a9
      Hash algo:    sha1
      Hash value:   9b5bef05889c72d7e7c03a5d818834af2a634209
    Verifying Hash Integrity ... crc32+ sha1+ OK
    Loading ramdisk from 0x5931fa14 to 0x4fe00000
WARNING: 'compression' nodes for ramdisks are deprecated, please fix
your .its file!
## Loading fdt from FIT Image at 58000000 ...
    Using 'config-8861' configuration
    Trying 'fdt-3' fdt subimage
      Description:  unavailable
      Type:         Flat Device Tree
      Compression:  uncompressed
      Data Start:   0x5a3e762c
      Data Size:    28737 Bytes = 28.1 KiB
      Architecture: AArch64
      Load Address: 0x4fa00000
      Hash algo:    crc32
      Hash value:   8812a397
      Hash algo:    sha1
      Hash value:   e7381def5b4518beef225212a863c0ce5e13f53e
    Verifying Hash Integrity ... crc32+ sha1+ OK
    Loading fdt from 0x5a3e762c to 0x4fa00000
## Loading fdt from FIT Image at 58000000 ...
    Trying 'overlay-1' fdt subimage
      Description:  unavailable
      Type:         Flat Device Tree
      Compression:  uncompressed
      Data Start:   0x5a3fcec4
      Data Size:    330 Bytes = 330 Bytes
      Architecture: AArch64
      Load Address: 0x4fa10000
      Hash algo:    crc32
      Hash value:   4feb8819
      Hash algo:    sha1
      Hash value:   5a2294834f1bb2916cdbcde98423a535ef16022f
    Verifying Hash Integrity ... crc32+ sha1+ OK
    Loading fdt from 0x5a3fcec4 to 0x4fa10000
failed on fdt_overlay_apply(): FDT_ERR_NOTFOUND
base fdt does did not have a /__symbols__ node
make sure you've compiled with -@
Could not find a valid device tree
SCRIPT FAILED: continuing...
libfdt fdt_check_header(): FDT_ERR_BADMAGIC
Scanning disk mmc@1c0f000.blk...
** Unrecognized filesystem type **
[...]
9) restore your working system

in order to recover the system I powered it off, took out the SD memory card, plugged it to my laptop and restored the backup of the /boot/kernel.itb file.

Then it booted fine, I removed the custom kernel using apt

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apt remove linux-image-5.10.180-olimex+
and reinstalled the official kernel using

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apt reinstall linux-image-5.10.180-olimex

What am I doing wrong?
Where can I find the right kernel compilation guide?

[ilario]

Just realized that there is a guide for this at the end of the Olimage-guide document!

Comparing what I did with those instructions, seems I was missing the

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DTC_FLAGS=-@flag in my make command.
Will try and confirm here if it works.