It is all fixed now. I repaired my kindle touch using the serial port. I did NOT restore my backup copy of the root partition (mmcblk0p1). That means that if you "slightly" break your startup scripts, you can boot to diag mode and repair them. In my case, I made a backup copy of the script before I changed it, but without a backup you could still manually edit out your damaging changes.
A complication was that I had to reset a boot counter manually. The file /var/local/upstart/lab126_gui.restarts had the value "2" in it. I did "echo 0 > /var/local/upstart/lab126_gui.restarts" to reset the boot counter. [Thanks for the suggestion, nueva!]
I had also cleaned up my USB drive from an export in diags (a bit too thoroughly). I had deleted an xml file needed to exit diags mode. I was able to force normal boot mode with the idme command, and I got my desktop back. I tried diags again, but it still could not exit. I replaced the missing xml file from a backup copy to the diags usb export drive, then exited properly. All is well now, and I can exit diags correctly without forcing it with the idme command.
I will [maybe] do a video like seaniko7 did for the k3, where I intentionally damage my scripts so it gets stuck in the "Repair Needed" screen at bootup. Then I will repair it WITHOUT a root partition backup copy. (After the holiday rush). EDIT: Now that the cover is back on my Kindle Touch, going through all this again just for a video seems like it would consume a lot of time that I would rather spend developing new code, so I may postpone this until I *accidentally* brick my touch again.
I plan to do another thing that seaniko7 did for his own personal use -- add usbserial to my startup scripts, exept that my version will be conditional on a trigger file (ENABLE_USBSERIAL). That should allow doing all this repair stuff over usbserial (not usbnet) instead of using a serial cable.
If that works, a packaged USBSERIAL hack would be an excellent add-on for all kindles (conditional on the trigger file, like how NiLuJe's USBNET works), as a safety precaution for "easy" debricking without opening the kindle.
Last edited by geekmaster; 12-28-2011 at 12:16 AM.