edid-override: Document process to fix edid

edid-override.md

@@ -41,10 +41,29 @@ Linux provides direct access to the EDID data as a file, per display output of t
 
 To remove the YUV mode, the EDID may be transformed to a human readable format, edited and transformed back by an appropriate tool, or the data may be edited directly with a hex editor.
 
-More information on this is TBD.
+cros-chameleon is one such python tool that transforms edid data to human readable json and back.
+
+```
+git clone https://github.com/rpavlik/cros-chameleon.git
+~/cros-chameleon/edid2json.py /sys/class/drm/card0-HDMI-A-1/edid > edid.json
+```
+Now in edid.json the YUV modes have to be disabled. The Direkt-Tek WVR2 for example contains these modes:
+```
+"YCbCr 4:2:2": true,
+"YCbCr 4:4:4": true
+```
+Switch those to false
+```
+"YCbCr 4:2:2": false,
+"YCbCr 4:4:4": false
+```
+and convert the fixed json back to edid data:
+```
+~/cros-chameleon/json2edid.py edid.json override.edid
+```
 
 #### Overriding the EDID
 
-Place the edid in /lib/firmware/edid/, for example `/lib/firmware/edid/override.edid`.
+Place the edid in /lib/firmware/edid/, for example `/lib/firmware/edid/override.edid`. You may need to regenerate your initramfs to include the firmware files.
 
-Append `drm.edid_firmware=HDMI-A-1:edid/override.edid` to your kernel command line. Replace HDMI-A-1 with the appropriate output name found in `/sys/class/drm/card*-*`
+Append `drm.edid_firmware=HDMI-A-1:edid/override.edid` to your kernel command line. Replace HDMI-A-1 with the appropriate output name found in `/sys/class/drm/card*-*`.