diff --git a/Makefile.dkms b/Makefile.dkms
new file mode 100644
index 0000000..3a06762
--- /dev/null
+++ b/Makefile.dkms
@@ -0,0 +1,24 @@
+modname := bbswitch
+DKMS := dkms
+modver := $(shell awk -F'"' '/define *BBSWITCH_VERSION/{print $$2}' < bbswitch.c)
+
+# directory in which generated files are stored
+DKMS_DEST := /usr/src/$(modname)-$(modver)
+
+all: install
+
+src_install:
+	mkdir -p '$(DKMS_DEST)'
+	cp Makefile bbswitch.c '$(DKMS_DEST)'
+	sed 's/#MODULE_VERSION#/$(modver)/' dkms/dkms.conf > '$(DKMS_DEST)/dkms.conf'
+
+build: src_install
+	$(DKMS) build 'bbswitch/$(modver)'
+
+install: build
+	$(DKMS) install 'bbswitch/$(modver)'
+
+uninstall:
+	$(DKMS) remove bbswitch/$(modver) --all
+
+.PHONY: all src_install build install uninstall
diff --git a/NEWS b/NEWS
index 2f08c50..335e37e 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,11 @@
+Version 0.4.2 - 26 April 2012
+
+* Fixed a documentation error on unload_state.
+* Added Makefile.dkms and documentation for easier installation using DKMS.
+* Make /proc/acpi/bbswitch world-writable
+* Fix NULL pointer dereference when reporting a failure during ACPI method
+  evaluation.
+
 Version 0.4.1 - 16 January 2012
 
 * Corrected a small error that yielded an confusing error message "The discrete
diff --git a/README.md b/README.md
index 5376608..17bef18 100644
--- a/README.md
+++ b/README.md
@@ -38,10 +38,16 @@ information.
 DKMS support
 ------------
 
-Change `#MODULE_VERSION#` to the current version of bbswitch. Copy the
-Makefile, C source and dkms.conf file to `/usr/src/bbswitch-VERSION/` (replace
-VERSION with the current version of bbswitch which has been inserted for
-`#MODULE_VERSION#`.
+If you have DKMS installed, you can install bbswitch in such a way that it
+survives kernel upgrades. It is recommended to remove older versions of bbswitch
+by running `dkms remove bbswitch/OLDVERSION --all` as root. To install the new
+version, simply run:
+
+    # make -f Makefile.dkms
+
+To uninstall it, run:
+
+    # make -f Makefile.dkms uninstall
 
 Usage
 -----
@@ -74,7 +80,7 @@ The module has some options that control the behavior on loading and unloading:
 `load_state` and `unload_state`. Valid values are `-1`, `0` and `1` meaning "do
 not change the card state", "turn the card off" and "turn the card on"
 respectively. For example, if you want to have `bbswitch` disable the card
-immediately when loading the module while disabling the card on unload, load the
+immediately when loading the module while enabling the card on unload, load the
 module with:
 
     # modprobe bbswitch load_state=0 unload_state=1
diff --git a/bbswitch.c b/bbswitch.c
index 269ceed..ca79e0d 100644
--- a/bbswitch.c
+++ b/bbswitch.c
@@ -16,10 +16,12 @@
 #include <linux/suspend.h>
 #include <linux/seq_file.h>
 
+#define BBSWITCH_VERSION "0.4.2"
+
 MODULE_LICENSE("GPL");
 MODULE_DESCRIPTION("Toggle the discrete graphics card");
 MODULE_AUTHOR("Peter Lekensteyn <lekensteyn@gmail.com>");
-MODULE_VERSION("0.4.1");
+MODULE_VERSION(BBSWITCH_VERSION);
 
 enum {
     CARD_UNCHANGED = -1,
@@ -69,12 +71,11 @@ static struct notifier_block nb;
 /* whether the card was off before suspend or not; on: 0, off: 1 */
 int dis_before_suspend_disabled;
 
-static char *buffer_to_string(const char buffer[], char *target) {
+static char *buffer_to_string(const char *buffer, size_t n, char *target) {
     int i;
-    for (i=0; i<sizeof(buffer); i++) {
-        sprintf(target + i * 5, "%02X,", buffer[i]);
+    for (i=0; i<n; i++) {
+        snprintf(target + i * 5, 5 * (n - i), "0x%02X,", buffer ? buffer[i] & 0xFF : 0);
     }
-    target[sizeof(buffer) * 5] = '\0';
     return target;
 }
 
@@ -110,12 +111,13 @@ static int acpi_call_dsm(acpi_handle handle, const char muid[16], int revid,
 
     err = acpi_evaluate_object(handle, "_DSM", &input, &output);
     if (err) {
-        char tmp[5 * max(sizeof(muid), sizeof(args))];
+        char muid_str[5 * 16];
+        char args_str[5 * 4];
 
-        printk(KERN_WARNING "bbswitch: failed to evaluate _DSM {%s} %X %X"
+        printk(KERN_WARNING "bbswitch: failed to evaluate _DSM {%s} 0x%X 0x%X"
             " {%s}: %s\n",
-            buffer_to_string(muid, tmp), revid, func,
-            buffer_to_string(args, tmp), acpi_format_exception(err));
+            buffer_to_string(muid, 16, muid_str), revid, func,
+            buffer_to_string(args,  4, args_str), acpi_format_exception(err));
         return err;
     }
 
@@ -330,6 +332,8 @@ static int __init bbswitch_init(void) {
     struct pci_dev *pdev = NULL;
     acpi_handle igd_handle = NULL;
 
+    printk(KERN_INFO "bbswitch: version %s\n", BBSWITCH_VERSION);
+
     while ((pdev = pci_get_device(PCI_ANY_ID, PCI_ANY_ID, pdev)) != NULL) {
         struct acpi_buffer buf = { ACPI_ALLOCATE_BUFFER, NULL };
         acpi_handle handle;
@@ -386,7 +390,7 @@ static int __init bbswitch_init(void) {
         }
     }
 
-    acpi_entry = proc_create("bbswitch", 0660, acpi_root_dir, &bbswitch_fops);
+    acpi_entry = proc_create("bbswitch", 0664, acpi_root_dir, &bbswitch_fops);
     if (acpi_entry == NULL) {
         printk(KERN_ERR "bbswitch: Couldn't create proc entry\n");
         return -ENOMEM;