Subject: Re: bug#40538: installer: Support uvesafb to install on machines without KMS.

From: "pelzflorian (Florian Pelz)" <[email-masked]>
Date: Sat, 11 Apr 2020 20:43:46 +0200

On Fri, Apr 10, 2020 at 04:38:37PM +0200, Ludovic Courtès wrote:
> > +     (if (member (%current-system) '("x86_64-linux" "i686-linux"))
> > +         ;; Load uvesafb to show installer when no KMS is available.
> > +         `(,(service kernel-module-loader-service-type '("uvesafb"))
> > +           [...]
> 
> This is not quite correct because here ‘%current-system’ is evaluated at
> the top level, when (gnu tests install) is loaded.  So on my laptop,
> it’s always "x86_64-linux", regardless of any ‘-s’ flags.  Also, it
> ignores ‘--target’.
> 
> Can we arrange to make it unconditional?
> 
> One way to do that (not great), would be to make it an activation
> snippet: since activation snippets are written as monadic code, we can
> reliably check ‘%current-system’ & ‘%current-target-system’ from there.
> (For lack of a solution like <https://issues.guix.gnu.org/issue/29296>.)

Please consider the attached patch.  I chose to go without
kernel-module-loader-service (only copying its requirements field)
because I do not know how to conditionally extend or start another
Shepherd service from an activation snippet.

I tested it on QEMU with and without nomodeset.  With a previous Guix
System install image, it stayed black when adding a nomodeset kernel
parameter.  I will test again on real hardware now, but previous
testing of uvesafb-enabled installer images proved successful unlike
non-uvesafb images.

Feel free to adapt the patch or not include it.  Or tell me to change
it if there is time.

Regards,
Florian
>From 85a95ce758384979a0aae3bc9065197c74862b4b Mon Sep 17 00:00:00 2001
From: Florian Pelz <[email-masked]>
Date: Sat, 11 Apr 2020 18:56:37 +0200
Subject: [PATCH] installer: Load uvesafb kernel module.
MIME-Version: 1.0
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Fixes <https://bugs.gnu.org/40538>.

Machines without Kernel Mode Setting (those with many old and current AMD
GPUs, SiS GPUs, …) need uvesafb to show the GUI installer.  Some may also need
a kernel parameter like nomodeset or vga=793, but we leave that for the user
to specify in GRUB.

* gnu/system/install.scm (uvesafb-shepherd-service): New procedure.
(uvesafb-service-type): New variable.
(%uvesafb-service): New variable.
(%installation-services): Add it.
---
 gnu/system/install.scm | 47 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 45 insertions(+), 2 deletions(-)

diff --git a/gnu/system/install.scm b/gnu/system/install.scm
index c15c2c7814..73a013bed0 100644
--- a/gnu/system/install.scm
+++ b/gnu/system/install.scm
@@ -4,6 +4,7 @@
 ;;; Copyright © 2016 Andreas Enge <[email-masked]>
 ;;; Copyright © 2017 Marius Bakke <[email-masked]>
 ;;; Copyright © 2017, 2019 Tobias Geerinckx-Rice <[email-masked]>
+;;; Copyright © 2020 Florian Pelz <[email-masked]>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -27,6 +28,7 @@
   #:use-module (guix gexp)
   #:use-module (guix store)
   #:use-module (guix monads)
+  #:use-module (guix modules)
   #:use-module ((guix packages) #:select (package-version))
   #:use-module ((guix store) #:select (%store-prefix))
   #:use-module (gnu installer)
@@ -50,6 +52,7 @@
   #:use-module (gnu packages texinfo)
   #:use-module (gnu packages compression)
   #:use-module (gnu packages nvi)
+  #:use-module (gnu packages xorg)
   #:use-module (ice-9 match)
   #:use-module (srfi srfi-26)
   #:export (installation-os
@@ -273,7 +276,6 @@ the user's target storage device rather than on the RAM disk."
 (define %configuration-template-service
   (service configuration-template-service-type #t))
 
-
 (define %nscd-minimal-caches
   ;; Minimal in-memory caching policy for nscd.
   (list (nscd-cache (database 'hosts)
@@ -287,6 +289,41 @@ the user's target storage device rather than on the RAM disk."
                     (persistent? #f)
                     (max-database-size (* 5 (expt 2 20)))))) ;5 MiB
 
+
+;; These define a service to load the uvesafb kernel module with the
+;; appropriate options.  The GUI installer needs it when the machine does not
+;; support Kernel Mode Setting.  Otherwise kmscon is missing /dev/fb0.
+(define (uvesafb-shepherd-service _)
+  (list (shepherd-service
+         (documentation "Load uvesafb.")
+         (provision '(uvesafb))
+         (requirement '(file-systems))
+         (start (with-imported-modules (source-module-closure '((guix utils)))
+                  #~(begin
+                      (use-modules (guix utils))
+                      (lambda ()
+                        ;; uvesafb is only supported on x86 and x86_64.
+                        (if (member (%current-system)
+                                    '("x86_64-linux" "i686-linux"))
+                            (invoke #+(file-append kmod "/bin/modprobe")
+                                    "uvesafb"
+                                    (string-append "v86d=" #$v86d "/sbin/v86d")
+                                    "mode_option=1024x768")
+                            #t)))))
+         (respawn? #f)
+         (one-shot? #t))))
+
+(define uvesafb-service-type
+  (service-type
+   (name 'uvesafb)
+   (extensions
+    (list (service-extension shepherd-root-service-type
+                             uvesafb-shepherd-service)))
+   (default-value #t)))
+
+(define %uvesafb-service
+  (service uvesafb-service-type))
+
 (define %installation-services
   ;; List of services of the installation system.
   (let ((motd (plain-file "motd" "
@@ -408,7 +445,13 @@ Access documentation at any time by pressing Alt-F2.\x1b[0m
                    (list bare-bones-os
                          glibc-utf8-locales
                          texinfo
-                         (canonical-package guile-2.2))))))
+                         (canonical-package guile-2.2)))
+
+          ;; Machines without Kernel Mode Setting (those with many old and
+          ;; current AMD GPUs, SiS GPUs, ...) need uvesafb to show the GUI
+          ;; installer.  Some may also need a kernel parameter like nomodeset
+          ;; or vga=793, but we leave that for the user to specify in GRUB.
+          %uvesafb-service)))
 
 (define %issue
   ;; Greeting.
-- 
2.26.0