Have `M-x battery' list all batteries under GNU/Linux

* lisp/battery.el (battery-upower-device): Remove (bug#25559).
(battery--find-linux-sysfs-batteries): New function.
(battery-status-function, battery-linux-sysfs): Use it to list all
batteries, no matter what they're called.

2 files changed, 16 insertions, 12 deletions

diff --git a/etc/NEWS b/etc/NEWS
index 3fdc185af4f..da3c29b1ac5 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -507,6 +507,11 @@ current and the previous or the next line, as before.
 
 * Changes in Specialized Modes and Packages in Emacs 27.1
 
+---
+** On GNU/Linux, `M-x battery' will now list all batteries, no matter
+what they're named, and the `battery-linux-sysfs-regexp' variable has
+been removed.
+
 ** The 'list-processes' command now includes port numbers in the
 network connection information (in addition to the host name).
 
diff --git a/lisp/battery.el b/lisp/battery.el
index 7037d07dcf0..0ef6d37b406 100644
--- a/lisp/battery.el
+++ b/lisp/battery.el
@@ -38,19 +38,21 @@
   :prefix "battery-"
   :group 'hardware)
 
-(defcustom battery-linux-sysfs-regexp "[bB][aA][tT][0-9]?$"
-  "Regexp for folder names to be searched under
-  /sys/class/power_supply/ that contain battery information."
-  :version "26.1"
-  :type 'regexp
-  :group 'battery)
-
 (defcustom battery-upower-device "battery_BAT1"
   "Upower battery device name."
   :version "26.1"
   :type 'string
   :group 'battery)
 
+(defun battery--find-linux-sysfs-batteries ()
+  (let ((dirs nil))
+    (dolist (file (directory-files "/sys/class/power_supply/" t))
+      (when (and (or (file-directory-p file)
+                     (file-symlink-p file))
+                 (file-exists-p (expand-file-name "capacity" file)))
+        (push file dirs)))
+    (nreverse dirs)))
+
 (defcustom battery-status-function
   (cond ((and (eq system-type 'gnu/linux)
               (file-readable-p "/proc/apm"))
@@ -60,8 +62,7 @@
          #'battery-linux-proc-acpi)
         ((and (eq system-type 'gnu/linux)
               (file-directory-p "/sys/class/power_supply/")
-              (directory-files "/sys/class/power_supply/" nil
-                               battery-linux-sysfs-regexp))
+              (battery--find-linux-sysfs-batteries))
          #'battery-linux-sysfs)
         ((and (eq system-type 'berkeley-unix)
               (file-executable-p "/usr/sbin/apm"))
@@ -449,9 +450,7 @@ The following %-sequences are provided:
     ;; available information together.
     (with-temp-buffer
       (dolist (dir (ignore-errors
-                    (directory-files
-                     "/sys/class/power_supply/" t
-                     battery-linux-sysfs-regexp)))
+                     (battery--find-linux-sysfs-batteries)))
         (erase-buffer)
         (ignore-errors (insert-file-contents
                         (expand-file-name "uevent" dir)))