[bug#44543] gnu: raspberry-pi: Add helpers for config.txt file generation.

* gnu/packages/raspberry-pi.scm (raspi-config-file, raspi-custom.txt):
  New functions.
  (raspi-config.txt, raspi-u-boot-bootloader.txt, raspi-kernel.txt):
  New variables.
---
 gnu/packages/raspberry-pi.scm | 44 +++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

I'm waiting for Ludo to comment about the dots in the variable names.
(Apparently, to be forward-compatible with literal pairs, dots in variable names are not nice to use)

It would be nice to also have some clients of that stuff in that file.

I.e. actually boot the raspberry pi using some chainloader config.

Otherwise it's hard to say whether this is a good API.  When the API is actually
used it's much easier to say.

Hi Danny!

> It would be nice to also have some clients of that stuff in that file.
> 
> I.e. actually boot the raspberry pi using some chainloader config.
> 
> Otherwise it's hard to say whether this is a good API.  When the API is actually
> used it's much easier to say.

There will be more patches to come, then there will be a use of these functions.

The firmware blob using these files can’t be handled by Guix, this will have to be left as an exercise. But could I add a skeleton for it? Maybe something like this (but better using the copy-build-system): 

(define (raspi-firmware url version hash)
  (package
   (build-system trivial-build-system)
   (arguments
    '(#:modules
      ((guix build utils))
      #:builder (begin
                  (use-modules (guix build utils))
                  (let* ((source (assoc-ref %build-inputs "source"))
                         (out (assoc-ref %outputs "out"))
                         (boot (string-append out "/boot"))
                         (opt (string-append out "/opt")))
                    (mkdir-p boot)
                    (copy-recursively (string-append source "/boot") boot)
                    (delete-file (string-append boot "/kernel.img"))
                    (delete-file (string-append boot "/kernel7.img"))
                    (delete-file (string-append boot "/kernel7l.img"))
                    (delete-file (string-append boot "/kernel8.img"))
                    (mkdir-p opt)
                    (copy-recursively (string-append source "/opt") opt)
                    (delete-file-recursively (string-append opt "/vc/src"))
                    #t))))
…))

Further steps will be some functionality to modify the U-Boot configuration (done with Kconfig) and to have a specific U-Boot package.

Then I’ll care for a kernel.

The board will only boot if all of this is in place.

This is how I use it all currently (left out kernel, kernel-arguments, initrd-modules):

(operating-system
  (bootloader 
    (bootloader-configuration
      (bootloader (bootloader-chain
                   (list (file-append raspi-firmware "/boot/")
                         (file-append u-boot-rpi-3 "/libexec/u-boot.bin")
                         raspi-config.txt
                         raspi-u-boot-bootloader.txt
                         ;; Additional configurations to use.
                         (raspi-custom.txt '("disable_overscan=1"
                                             "hdmi_force_hotplug=1"
                                             "audio=on"
                                             "dtoverlay=gpio-ir"
                                             "dtoverlay=disable-wifi"
                                             "dtoverlay=vc4-fkms-v3d,cma-64")))
                   grub-efi-netboot-bootloader 
                   #:installer (install-grub-efi-netboot "efi/boot")
                   #:copy-files? #t))
      (theme
        (grub-theme
          (resolution 
            '(1920 . 1080))
             (image (file-append %artwork-repository "/grub/GuixSD-fully-black-16-9.svg"))))
      (target "/boot")
      (keyboard-layout keyboard-layout)))
…)

The above bootloader-chain could certainly be added to Guix, but leaving out the raspi-firmware and the raspi-custom.txt – maybe as a function to allow adding an own raspi-custom.txt. If someone copies the firmware by hand onto an SD card, then such a bootloader provided as e.g. raspi-grub-bootloader would work.


Bye

Stefan

Hi Stefan,

thanks!

On Mon, 16 Nov 2020 11:38:19 +0100
Stefan <stefan-guix@vodafonemail.de> wrote:

> The firmware blob using these files can’t be handled by Guix, this will have to be left as an exercise. But could I add a skeleton for it? Maybe something like this (but better using the copy-build-system): 

There is a free software Raspberry VC firmware on
https://github.com/librerpi/rpi-open-firmware/ (currently cannot handle graphics
and USB and lots of other important things--but it DOES boot) and development
is ongoing.

We can just package that free software firmware and use it.

I've already started packaging it for Guix.

> (operating-system
>   (bootloader 
>     (bootloader-configuration
>       (bootloader (bootloader-chain
>                    (list (file-append raspi-firmware "/boot/")
>                          (file-append u-boot-rpi-3 "/libexec/u-boot.bin")
>                          raspi-config.txt
>                          raspi-u-boot-bootloader.txt
>                          ;; Additional configurations to use.
>                          (raspi-custom.txt '("disable_overscan=1"
>                                              "hdmi_force_hotplug=1"
>                                              "audio=on"
>                                              "dtoverlay=gpio-ir"
>                                              "dtoverlay=disable-wifi"
>                                              "dtoverlay=vc4-fkms-v3d,cma-64")))
>                    grub-efi-netboot-bootloader 
>                    #:installer (install-grub-efi-netboot "efi/boot")
>                    #:copy-files? #t))

I advice to add a user-level function for a free software Raspberry Pi 3 efi
netboot bootloader to Guix (and a non-efi-netboot one, too, maybe).

Something like

(define (raspi-3-efi-netboot-bootloader efi-boot custom-text)
  (bootloader-chain like you do above custom-text))

I don't think that it's reasonable to expect the user to use bootloader-chain
by himself (it's not user-friendly to have to do that).

> The above bootloader-chain could certainly be added to Guix, but leaving out the raspi-firmware and the raspi-custom.txt – maybe as a function to allow adding an own raspi-custom.txt. If someone copies the firmware by hand onto an SD card, then such a bootloader provided as e.g. raspi-grub-bootloader would work.

Yeah.