Subject: [bug#30355] [PATCH] services: agetty: Make tty optional and add agetty instance to base services.

From: Danny Milosavljevic <[email-masked]>
Date: Mon, 5 Feb 2018 09:15:53 +0100

* gnu/system/install.scm (agetty-default-service): Delete variable.
(beaglebone-black-installation-os): Do not specify tty.
(a20-olinuxino-lime-installation-os): Do not specify tty.
(a20-olinuxino-lime2-emmc-installation-os): Do not specify tty.
(a20-olinuxino-micro-installation-os): Do not specify tty.
(banana-pi-m2-ultra-installation-os): Do not specify tty.
(nintendo-nes-classic-edition-installation-os): Do not specify tty.
(embedded-installation-os): Move agetty-service instantiation to...
* gnu/services/base.scm (%base-services): ...here.
(default-serial-port): New variable.
(agetty-shepherd-service): Make tty optional, default to the above.
* doc/guix.texi (agetty-configuration): Update "tty" documentation.
---
 doc/guix.texi          | 15 +++++++++-
 gnu/services/base.scm  | 77 ++++++++++++++++++++++++++++++++++++++++----------
 gnu/system/install.scm | 37 ++++++++----------------
 3 files changed, 88 insertions(+), 41 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 2b27a675c..4e5d9e33f 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9621,7 +9621,20 @@ man page for more information.
 
 @item @code{tty}
 The name of the console this agetty runs on, as a string---e.g.,
-@code{"ttyS0"}. This argument is mandatory.
+@code{"ttyS0"}. This argument is optional, it will default to
+a reasonable default serial port used by Linux.
+
+For this, if there is a value for an option "agetty.tty" in the Linux
+command line, agetty will extract the device name of the serial port
+from it and use that.
+
+If not and if there is a value for an option "console" with a tty in
+the Linux command line, agetty will extract the device name of the
+serial port from it and use that.
+
+In both cases, agetty will leave the other serial device settings
+(baud rate etc) alone - in the hope that Linux pinned them to the
+correct values.
 
 @item @code{baud-rate} (default: @code{#f})
 A string containing a comma-separated list of one or more baud rates, in
diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index 8e30bcd34..8e740bf6c 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -817,7 +817,7 @@ the message of the day, among other things."
   agetty-configuration?
   (agetty           agetty-configuration-agetty   ;<package>
                     (default util-linux))
-  (tty              agetty-configuration-tty)     ;string
+  (tty              agetty-configuration-tty)     ;string | #f
   (term             agetty-term                   ;string | #f
                     (default #f))
   (baud-rate        agetty-baud-rate              ;string | #f
@@ -890,6 +890,42 @@ the message of the day, among other things."
 ;;;                 (default #f))
   )
 
+(define (default-serial-port)
+  "Return a gexp that determines a reasonable default serial port
+to use as the tty.  This is primarily useful for headless systems."
+  #~(begin
+      ;; console=device,options
+      ;; device: can be tty0, ttyS0, lp0, ttyUSB0 (serial).
+      ;; options: BBBBPNF. P n|o|e, N number of bits,
+      ;; F flow control (r RTS)
+      (use-modules (gnu build linux-boot))
+      (let* ((not-comma (char-set-complement (char-set #\,)))
+             (command (linux-command-line))
+             (agetty-specs (find-long-options "agetty.tty" command))
+             (console-specs (filter (lambda (spec)
+                                     (not (or
+                                            (string-prefix? "tty0" spec)
+                                            (string-prefix? "tty1" spec)
+                                            (string-prefix? "tty2" spec)
+                                            (string-prefix? "tty3" spec)
+                                            (string-prefix? "tty4" spec)
+                                            (string-prefix? "tty5" spec)
+                                            (string-prefix? "tty6" spec)
+                                            (string-prefix? "tty7" spec)
+                                            (string-prefix? "tty8" spec)
+                                            (string-prefix? "tty9" spec))))
+                                   (filter
+                                     (lambda (spec)
+                                       (string-prefix? "tty" spec))
+                                     (find-long-options "console" command))))
+             (specs (append agetty-specs console-specs))
+             (spec (if (null? specs)
+                      #f
+                      (car specs))))
+        (and spec
+             ;; Extract device name.
+             (car (string-tokenize spec not-comma))))))
+
 (define agetty-shepherd-service
   (match-lambda
     (($ <agetty-configuration> agetty tty term baud-rate auto-login
@@ -901,7 +937,7 @@ the message of the day, among other things."
      (list
        (shepherd-service
          (documentation "Run agetty on a tty.")
-         (provision (list (symbol-append 'term- (string->symbol tty))))
+         (provision (list (symbol-append 'term- (string->symbol (or tty "auto")))))
 
          ;; Since the login prompt shows the host name, wait for the 'host-name'
          ;; service to be done.  Also wait for udev essentially so that the tty
@@ -946,6 +982,9 @@ the message of the day, among other things."
                                         ('always "--local-line=always")
                                         ('never "-local-line=never")))
                                  #~())
+                          #$@(if tty
+                                 #~()
+                                 #~("--keep-baud"))
                           #$@(if extract-baud?
                                  #~("--extract-baud")
                                  #~())
@@ -1009,7 +1048,7 @@ the message of the day, among other things."
                           #$@(if login-pause?
                                  #~("--login-pause")
                                  #~())
-                          #$tty
+                          #$(or tty (default-serial-port))
                           #$@(if baud-rate
                                  #~(#$baud-rate)
                                  #~())
@@ -1058,18 +1097,21 @@ the tty to run, among other things."
        ;; text is not lost in the middle of kernel messages (XXX).
        (requirement '(user-processes host-name udev))
 
-       (start  #~(make-forkexec-constructor
-                  (list #$(file-append mingetty "/sbin/mingetty")
-                        "--noclear" #$tty
-                        #$@(if auto-login
-                               #~("--autologin" #$auto-login)
-                               #~())
-                        #$@(if login-program
-                               #~("--loginprog" #$login-program)
-                               #~())
-                        #$@(if login-pause?
-                               #~("--loginpause")
-                               #~()))))
+       (start  #~(let ((tty #$(default-serial-port)))
+                   (if tty
+                       (make-forkexec-constructor
+                        (list #$(file-append mingetty "/sbin/mingetty")
+                              "--noclear" #$tty
+                              #$@(if auto-login
+                                     #~("--autologin" #$auto-login)
+                                     #~())
+                              #$@(if login-program
+                                     #~("--loginprog" #$login-program)
+                                     #~())
+                              #$@(if login-pause?
+                                     #~("--loginpause")
+                                     #~())))
+                       (const #f)))) ; never start.
        (stop   #~(make-kill-destructor)))))))
 
 (define mingetty-service-type
@@ -2012,6 +2054,11 @@ This service is not part of @var{%base-services}."
                         (cons tty %default-console-font))
                       '("tty1" "tty2" "tty3" "tty4" "tty5" "tty6")))
 
+        (agetty-service (agetty-configuration
+                         (extra-options '("-L")) ; no carrier detect
+                         (term "vt100")
+                         (tty #f))) ; automatic
+
         (mingetty-service (mingetty-configuration
                            (tty "tty1")))
         (mingetty-service (mingetty-configuration
diff --git a/gnu/system/install.scm b/gnu/system/install.scm
index e4b2e8237..db06b7a52 100644
--- a/gnu/system/install.scm
+++ b/gnu/system/install.scm
@@ -381,19 +381,10 @@ You have been warned.  Thanks for being so brave.\x1b[0m
                      nvi                          ;:wq!
                      %base-packages))))
 
-(define* (agetty-default-service #:optional (tty "ttyS0"))
-  "Return an agetty-service on the given TTY"
-  (agetty-service (agetty-configuration
-                   (extra-options '("-L"))
-                   (baud-rate "115200")
-                   (term "vt100")
-                   (tty tty))))
-
-(define* (embedded-installation-os bootloader bootloader-target tty
+(define* (embedded-installation-os bootloader bootloader-target
                                    #:key (extra-modules '()))
   "Return an installation os for embedded systems.
 The initrd gets the extra modules EXTRA-MODULES.
-A getty is provided on TTY.
 The bootloader BOOTLOADER is installed to BOOTLOADER-TARGET."
   (operating-system
     (inherit installation-os)
@@ -404,43 +395,39 @@ The bootloader BOOTLOADER is installed to BOOTLOADER-TARGET."
     (initrd (lambda (fs . rest)
               (apply base-initrd fs
                      #:extra-modules extra-modules
-                     rest)))
-    (services (cons* (agetty-default-service tty)
-                     (operating-system-user-services installation-os)))))
+                     rest)))))
 
 (define beaglebone-black-installation-os
   (embedded-installation-os u-boot-beaglebone-black-bootloader
                             "/dev/sda"
-                            "ttyO0"
                             #:extra-modules
                             ;; This module is required to mount the sd card.
                             '("omap_hsmmc")))
 
-
 (define a20-olinuxino-lime-installation-os
   (embedded-installation-os u-boot-a20-olinuxino-lime-bootloader
-                            "/dev/mmcblk0" ; SD card storage
-                            "ttyS0"))
+                            ;; SD card storage
+                            "/dev/mmcblk0"))
 
 (define a20-olinuxino-lime2-emmc-installation-os
   (embedded-installation-os u-boot-a20-olinuxino-lime2-bootloader
-                            "/dev/mmcblk1" ; eMMC storage
-                            "ttyS0"))
+                            ;; eMMC storage
+                            "/dev/mmcblk1"))
 
 (define a20-olinuxino-micro-installation-os
   (embedded-installation-os u-boot-a20-olinuxino-micro-bootloader
-                            "/dev/mmcblk0" ; SD card storage
-                            "ttyS0"))
+                            ;; SD card storage
+                            "/dev/mmcblk0"))
 
 (define banana-pi-m2-ultra-installation-os
   (embedded-installation-os u-boot-banana-pi-m2-ultra-bootloader
-                            "/dev/mmcblk1" ; eMMC storage
-                            "ttyS0"))
+                            ;; eMMC storage
+                            "/dev/mmcblk1"))
 
 (define nintendo-nes-classic-edition-installation-os
   (embedded-installation-os u-boot-nintendo-nes-classic-edition-bootloader
-                            "/dev/mmcblk0" ; SD card (solder it yourself)
-                            "ttyS0"))
+                            ;; SD card storage (solder it yourself)
+                            "/dev/mmcblk0"))
 
 ;; Return the default os here so 'guix system' can consume it directly.
 installation-os