As M92 is based on Freescale i.MX508, it could be useful to know that this SoC has USB Downloader mode for downloading arbitrary code into RAM and executing it.
On recent Kindles (which are using the same SoC) this mode can be enabled with holding of physical key in (re)booting process:
Originally Posted by https://www.mobileread.com/forums/showthread.php?t=169645
To get your kindle touch or k4nt into USB Recovery mode, plug in the USB cable, the press and hold the power switch until the power LED turns off, then press and hold the "Magic Key", then release the power switch, then release the "Magic Key". The "Magic Key" is a special button that is different on each model of kindle, and is used to enter USB Recovery mode.
Kindle Model, Magic Key:
Touch, Home button
K4NT, Five-Way Down button
In this mode device is recognized as NS Blank CODEX
[13973.993075] usb 1-1: new high speed USB device number 11 using ehci_hcd
[13974.108477] usb 1-1: New USB device found, idVendor=15a2, idProduct=0052
[13974.108486] usb 1-1: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[13974.108494] usb 1-1: Product: NS Blank CODEX
[13974.108499] usb 1-1: Manufacturer: Freescale SemiConductor Inc
You can also look at Kindle 4 kernel sources with enabled USB OTG: http://www.christian-hoff.com/
(Kindle 4 is also based on i.MX508).