[bug#28647] [PATCH] services: base: Add file->udev-rule function.

[Maxim Cournoyer <maxim.cournoyer@gmail.com>]

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Hello,

While experimenting with udev rules, I found a need to be able to pass
file-like objects containing udev rules to the udev-service. This patch
implements a `file->udev-rule' method that does just that.


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From 050e96b3325f851f3118de0c881d25796d76049b Mon Sep 17 00:00:00 2001
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Date: Wed, 27 Sep 2017 21:33:25 -0400
Subject: [PATCH] services: base: Add file->udev-rule function.

This function allows passing a file-like object to the udev service.

* gnu/services/base.scm (file->udev-rule): New function.
* doc/guix.texi (Base Services): Document it.
---
 doc/guix.texi         | 15 ++++++++++++---
 gnu/services/base.scm | 17 +++++++++++++++++
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index fff3fbd5f..a073dccb5 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9707,11 +9707,20 @@ Return a service that runs the Guix build daemon according to
 @var{config}.
 @end deffn
 
-@deffn {Scheme Procedure} udev-service [#:udev udev]
+@deffn {Scheme Procedure} udev-service [#:udev @var{eudev} #:rules @code{'()}]
 Run @var{udev}, which populates the @file{/dev} directory dynamically.
+Packages can be included in the @var{rules} list in order to extend the
+udev rules with the definitions found under their
+@file{lib/udev/rules.d} sub-directory.
+
+The functions @code{udev-rules} and @code{file->udev-rules} from
+@code{(gnu services base)} can be used to create rule objects based on a
+string or a file-like object, respectively. Those rule objects can be
+passed to udev-service just like packages.
+
 @end deffn
 
-@deffn {Scheme Procedure} urandom-seed-service @var{#f}
+@deffn {Scheme Procedure} urandom-seed-service
 Save some entropy in @var{%random-seed-file} to seed @file{/dev/urandom}
 when rebooting.
 @end deffn
@@ -9823,7 +9832,7 @@ to add @var{device} to the kernel's entropy pool.  The service will fail if
 @cindex session limits
 @cindex ulimit
 @cindex priority
-@deffn {Scheme Procedure} pam-limits-service [#:limits @var{limits}]
+@deffn {Scheme Procedure} pam-limits-service [#:limits @code{'()}]
 
 Return a service that installs a configuration file for the
 @uref{http://linux-pam.org/Linux-PAM-html/sag-pam_limits.html,
diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 64620a9b0..711167a2f 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -71,6 +71,7 @@
             udev-service-type
             udev-service
             udev-rule
+            file->udev-rule
 
             login-configuration
             login-configuration?
@@ -1628,6 +1629,22 @@ item of @var{packages}."
                          (lambda (port)
                            (display #$contents port)))))))
 
+(define (file->udev-rule file-name file)
+  "Return a directory with a udev rule file FILE-NAME which is a copy of FILE."
+  (computed-file file-name
+                 (with-imported-modules '((guix build utils))
+                   #~(begin
+                       (use-modules (guix build utils))
+
+                       (define rules.d
+                         (string-append #$output "/lib/udev/rules.d"))
+
+                       (define file-copy-dest
+                         (string-append rules.d "/" #$file-name))
+
+                       (mkdir-p rules.d)
+                       (copy-file #$file file-copy-dest)))))
+
 (define kvm-udev-rule
   ;; Return a directory with a udev rule that changes the group of /dev/kvm to
   ;; "kvm" and makes it #o660.  Apparently QEMU-KVM used to ship this rule,
-- 
2.14.1


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Below is an operating-system declaration that makes use of it.


[-- Attachment #4: Sample config using the new method. --]
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;; This is an operating system configuration template
;; for a "desktop" setup without full-blown desktop
;; environments.

(use-modules (gnu)
	     (gnu system nss)
	     (gnu services)
	     (gnu system shadow)	;for user-group
	     (guix download)		;for url-fetch
	     (guix gexp)		;for file-append
	     (guix packages)		;for origin
	     (guix store)		;for %default-substitute-urls
	     (srfi srfi-1))		;for the remove function

(use-service-modules base		;for nscd-service-type
		     desktop
		     networking		;for wicd-service-type
		     ssh)		;for lsh-service

(use-package-modules admin		;for wpa-supplicant
		     ratpoison
		     certs)

(define 51-android-udev.rules
  (let ((version "20170910"))
   (origin
     (method url-fetch)
     (uri (string-append "https://raw.githubusercontent.com/M0Rf30/"
			 "android-udev-rules/" version "/51-android.rules"))
     (sha256
      (base32 "0lmmagpyb6xsq6zcr2w1cyx9qmjqmajkvrdbhjx32gqf1d9is003")))))

(operating-system
  (host-name "apteryx")
  (timezone "America/Montreal")	      ;America/Los_Angeles, Asia/Tokyo
  (locale "en_US.UTF-8")

  ;; Assuming /dev/sdX is the target hard disk, and "my-root"
  ;; is the label of the target root file system.
  (bootloader (bootloader-configuration
	       (bootloader grub-bootloader)
	       (target "/dev/sda")))

  (file-systems (cons (file-system
                        (device "my-root")
                        (title 'label)
                        (mount-point "/")
                        (type "ext4"))
                      %base-file-systems))

  (users (cons (user-account
                (name "maxim")
                (comment "Maxim Cournoyer")
                (group "users")
                (supplementary-groups
		 '("lp"			;for bluetooth
		   "adbusers"		;for adb
		   "wheel" "netdev" "audio" "video"))
                (home-directory "/home/maxim"))
               %base-user-accounts))

  ;; Add plugdev to %base-groups
  (groups (cons (user-group (system? #t) (name "adbusers")) %base-groups))
  
  ;; Add a bunch of window managers; we can choose one at
  ;; the log-in screen with F1.
  (packages (cons* ratpoison
                   nss-certs		;for HTTPS access
                   %base-packages))

  ;; Use the "desktop" services, which include the X11
  ;; log-in service and more.
  (services
   (cons*
    (bluetooth-service #:auto-enable? #t)
    (modify-services %desktop-services
      ;; Add a couple extra substitute servers.
      (guix-service-type config =>
                         (guix-configuration
                          (inherit config)
                          (substitute-urls
                           (cons* "https://bayfront.guixsd.org"
				  "https://berlin.guixsd.org"
                                  %default-substitute-urls))))
      ;; Enable using adb as a simple user with a multitude of devices.
      (udev-service-type
       config =>
       (udev-configuration
      	(inherit config)
      	(rules (cons*
      		(file->udev-rule "51-android-udev.rules" 51-android-udev.rules)
      		(udev-configuration-rules config))))))))

  ;; Allow resolution of '.local' host names with mDNS.
  (name-service-switch %mdns-host-lookup-nss))

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Thanks,

Maxim