[bug#31416] [PATCH 1/4] system: Add os-with-u-boot.

[Danny Milosavljevic <dannym@scratchpost.org>]

* gnu/system/install.scm (os-with-u-boot): New procedure.
* gnu/packages/bootloaders.scm (make-u-boot-package): Export.
* doc/guix.texi (Building the Installation Image for ARM boards): New
subsection.
---
 doc/guix.texi                | 21 +++++++++++++++++++++
 gnu/packages/bootloaders.scm |  2 +-
 gnu/system/install.scm       | 16 +++++++++++++++-
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 637c9c3f4..b2b173ded 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -8733,6 +8733,27 @@ Have a look at @file{gnu/system/install.scm} in the source tree,
 and see also @ref{Invoking guix system} for more information
 about the installation image.
 
+@subsection Building the Installation Image for ARM boards
+
+Many ARM boards require a board-specific bootloader in order to boot.
+
+If you build an entire disk image and the is not still available otherwise
+(on another available drive etc), it's advisable to build an image that
+includes the bootloader, specifically:
+
+@example
+guix system disk-image --system=armhf-linux -e '((@ (gnu system install) os-with-u-boot) (@ (gnu system install) installation-os) "A20-OLinuXino-Lime2")'
+@end example
+
+Or if you don't cross compile:
+
+@example
+guix system disk-image -e '((@ (gnu system install) os-with-u-boot) (@ (gnu system install) installation-os) "A20-OLinuXino-Lime2")'
+@end example
+
+"A20-OLinuXino-Lime2" is the name of the board.  If you specify an invalid
+board, you get a list.
+
 @node System Configuration
 @section System Configuration
 
diff --git a/gnu/packages/bootloaders.scm b/gnu/packages/bootloaders.scm
index c0a0101c5..526e53384 100644
--- a/gnu/packages/bootloaders.scm
+++ b/gnu/packages/bootloaders.scm
@@ -359,7 +359,7 @@ tree binary files.  These are board description files used by Linux and BSD.")
 also initializes the boards (RAM etc).")
     (license license:gpl2+)))
 
-(define (make-u-boot-package board triplet)
+(define-public (make-u-boot-package board triplet)
   "Returns a u-boot package for BOARD cross-compiled for TRIPLET."
   (let ((same-arch? (if (string-prefix? (%current-system)
                                         (gnu-triplet->nix-system triplet))
diff --git a/gnu/system/install.scm b/gnu/system/install.scm
index a2917e485..b563e8b5b 100644
--- a/gnu/system/install.scm
+++ b/gnu/system/install.scm
@@ -52,7 +52,8 @@
             mx6cuboxi-installation-os
             nintendo-nes-classic-edition-installation-os
             novena-installation-os
-            wandboard-installation-os))
+            wandboard-installation-os
+            os-with-u-boot))
 
 ;;; Commentary:
 ;;;
@@ -386,6 +387,19 @@ You have been warned.  Thanks for being so brave.\x1b[0m
                      nvi                          ;:wq!
                      %base-packages))))
 
+(define* (os-with-u-boot os board #:key (bootloader-target "/dev/mmcblk0")
+                         (triplet "arm-linux-gnueabihf"))
+  "Given OS, amend it with the u-boot bootloader for BOARD,
+installed to BOOTLOADER-TARGET (a drive), compiled for TRIPLET.
+
+If you want a serial console, make sure to specify one in your
+operating-system's kernel-arguments (\"console=ttyS0\" or similar)."
+  (operating-system (inherit os)
+    (bootloader (bootloader-configuration
+                 (bootloader (bootloader (inherit u-boot-bootloader)
+                              (package (make-u-boot-package board triplet))))
+                 (target bootloader-target)))))
+
 (define* (embedded-installation-os bootloader bootloader-target tty
                                    #:key (extra-modules '()))
   "Return an installation os for embedded systems.