Subject: [PATCH v7 3/6] linux-boot: Load kernel modules only when the hardware is present.

From: Danny Milosavljevic <[email-masked]>
Date: Fri, 2 Mar 2018 16:34:05 +0100

* gnu/build/linux-boot.scm (boot-system): Load kernel modules only when
the hardware is present.
(lookup-module): Delete procedure.
* gnu/system/linux-initrd.scm (raw-initrd): Add imports.
---
 gnu/build/linux-boot.scm    | 42 +++++++++++++++++++++++++++++++++++-------
 gnu/system/linux-initrd.scm |  4 +++-
 2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/gnu/build/linux-boot.scm b/gnu/build/linux-boot.scm
index 18d87260a..1b16f267a 100644
--- a/gnu/build/linux-boot.scm
+++ b/gnu/build/linux-boot.scm
@@ -469,9 +469,31 @@ upon error."
              mounts)
         "ext4"))
 
-  (define (lookup-module name)
-    (string-append linux-module-directory "/"
-                   (ensure-dot-ko name)))
+  (define (load-kernel-modules)
+    "Examine /sys/devices to find out which modules to load and load them."
+    (define enter?
+      (const #t))
+    (define (down! path stat result)
+     ;; Note: modprobe mutates the tree starting with path.
+     (let ((modalias-name (string-append path "/modalias")))
+       (if (file-exists? modalias-name)
+           (let ((modalias
+                 (string-trim-right (call-with-input-file modalias-name
+                                                          read-string)
+                                    #\newline)))
+             (system* "/sbin/modprobe" "-q" "--" modalias))))
+       #t)
+    (define up
+      (const #t))
+    (define skip
+      (const #t))
+    (define leaf
+      (const #t))
+    (define (error name stat errno result)
+      (format (current-error-port) "warning: ~a: ~a~%"
+              name (strerror errno))
+      result)
+    (file-system-fold enter? leaf down! up skip error #t "/sys/devices"))
 
   (display "Welcome, this is GNU's early boot Guile.\n")
   (display "Use '--repl' for an initrd REPL.\n\n")
@@ -486,10 +508,16 @@ upon error."
        (when (member "--repl" args)
          (start-repl))
 
-       (display "loading kernel modules...\n")
-       (for-each (cut load-linux-module* <>
-                      #:lookup-module lookup-module)
-                 (map lookup-module linux-modules))
+       (let* ((kernel-release
+               (utsname:release (uname)))
+              (directory
+               (string-append linux-module-directory "/lib/modules/"
+                              kernel-release))
+              (old-umask (umask #o022)))
+         (make-static-device-nodes directory)
+         (umask old-umask))
+
+       (load-kernel-modules)
 
        (when qemu-guest-networking?
          (unless (configure-qemu-networking)
diff --git a/gnu/system/linux-initrd.scm b/gnu/system/linux-initrd.scm
index e7f97bb88..b50d3ff80 100644
--- a/gnu/system/linux-initrd.scm
+++ b/gnu/system/linux-initrd.scm
@@ -208,7 +208,9 @@ upon error."
                       ;; this info via gexps.
                       ((gnu build file-systems)
                        #:select (find-partition-by-luks-uuid))
-                      (rnrs bytevectors))
+                      (rnrs bytevectors)
+                      (ice-9 ftw)
+                      (ice-9 rdelim))
 
          (with-output-to-port (%make-void-port "w")
            (lambda ()