I considering for a while to buy proper JTAG in order to use it for some 8-bits AVRs (in this case ATmega2560), however the price and trouble to order it do not approve it usefulness (occasional usage for debug purposes). The second issue is that I use Linux only and using Atmel Studio is out of question.
The first question is related to possibility to DIY some simple and proper JTAG for the purpose.
The second is about proper free software on Linux. Reading somewhere that JTAG protocol for Atmel MCUs is closed is not very promising.
Thank in advance.