Update README.md

README.md

@@ -19,38 +19,89 @@ In another place one user threw in an udev rule which would disable write-cache
 
 I dug into the intricacies of udev and found a method to only target USB storage devices.
 
-* Documentation on https://wiki.archlinux.org/title/udev
+* Documentation for https://wiki.archlinux.org/title/udev
 
-The final rule
+The rule has gotten a major overhaul and now consist of the rule, a config file and a script
 
+### The rule **/etc/udev/rules.d/99-usb-sync.rules**
 ```
 # rule to disable write cache for usb storage
 # requires hdparm to be installed
-ACTION=="add|change", KERNEL=="sd[a-z]", ENV{ID_USB_TYPE}=="disk", RUN+="/usr/bin/hdparm -W 0 /dev/%k"
+ACTION=="add|change", KERNEL=="sd[a-z]", ENV{ID_USB_TYPE}=="disk", RUN+="/usr/bin/hdparm -W 0 /dev/%K"
+
 #
 # the following rules is introduced with kernel 6.2
 # https://docs.kernel.org/admin-guide/abi-testing.html#abi-sys-class-bdi-bdi-strict-limit
 # https://docs.kernel.org/admin-guide/abi-testing.html#abi-sys-class-bdi-bdi-max-ratio
 # https://docs.kernel.org/admin-guide/abi-testing.html#abi-sys-class-bdi-bdi-max-bytes
-ACTION=="add|change", KERNEL=="sd[a-z]", ENV{ID_USB_TYPE}=="disk", RUN+="/usr/bin/echo 1 > /sys/block/%k/bdi/strict_limit",  RUN+="/usr/bin/echo 50 > /sys/block/%k/bdi/max_ratio", RUN+="/usr/bin/echo 16777216 > /sys/block/%k/bdi/max_bytes"
+ACTION=="add|change", KERNEL=="sd[a-z]", ENV{ID_USB_TYPE}=="disk", RUN+="/usr/bin/udev-usb-sync %k"
+```
+### The config **/etc/usb-dev-sync/udev-usb-sync.conf**
+```
+# default values 
+#use_tweaks=1
+#max_bytes=16777216
+#max_ratio=50
+#strict_limit=1
+```
+### The script **/usr/bin/udev-usb-sync**
+```
+#!/usr/bin/bash
+#
+# script to tweak USB storage device filesystem sync
+#
+# sources /etc/usb-dev-sync/usb-dev-sync.conf
+#
+
+use_tweaks=1
+max_bytes=16777216
+max_ration=50
+strict_limit=1
+
+# read user config
+source /etc/udev-usb-sync/udev-usb-sync.conf
+
+if [[ "$use_tweaks" = 0 ]]; then
+        exit 0
+fi
+
+if [[ -z "$1" ]]; then
+        exit 1
+fi
+
+echo "$max_bytes" > "/sys/block/$1/bdi/max_bytes"
+echo "$max_ration" > "/sys/block/$1/bdi/max_ratio"
+echo "$strict_limit" > "/sys/block/$1/bdi/strict_limit"
 ```
 
-The rule activates on
+The rule activates when udev detects 
 
 * add or change
 * kernel event for disk devices **sd[a-z]**
-* only if the device environment **ID_USB_TYPE==‘disk’**
-* execute **hdparm -W 0 /dev/%K**
+* only if the device environment **ID_USB_TYPE=='disk'**
+* run 
+  - **hdparm -W 0 /dev/%k** (disable write cache if supported)
+  - **udev-usb-sync %k**
+    - applies defaults
+    - read config and apply user values
+    - if use_tweaks=0 the script exits
+    - if use_tweaks=1 the applies the values (default or config)
 
-Create a file in **/etc/udev/rules.d/99-usb-sync.rules** and paste above content into the file and save it.
+Create a file in **/etc/udev/rules.d/99-usb-sync.rules** and paste the rule into it.
+Create a file in **/etc/udev-usb-sync/udev-usb-sync.conf** and paste the default values.
+Create a file in **/usr/bin/udev-usb-sync** and paste the script content.
 
 Install **hdparm** package.
 
     sudo pacman -Syu hdparm
 
-Then plug an usb device - open in your file manager - copy a huge amount of file data to the device - when the copy is done - click eject in the file manager - note how quick the device is ejected.
+Reload udev
 
-For those preferring the package manager, I have created a [PKGBUILD](./PKGBUILD) which will pull the hdparm dependency upon installation. The same PKGBUILD can found within AUR (Arch User Repository) at https://aur.archlinux.org/packages/udev-usb-sync
+    sudo udevadm control --reload
+
+Then plug an usb device - open in your file manager - copy a huge amout of files to the device - when the copy is done - click eject in the file manager - note how quick the device is ejected.
+
+For those preferring the package manager, I have created a [PKGBUILD][1] which will pull the **hdparm** dependency upon installation.
 
     pamac build udev-usb-sync