AVR uno Burn bootloader uses variable with name protocol that is not defined in boards.txt nor platform.txt

[jantje]

I'm not sure wether this is a problem in the avr platform, a documentation issue, a misunderstanding on my part or something else.
So please bear with me.

I tried to implement the burn bootloader functionality as described in:
https://arduino.github.io/arduino-cli/latest/platform-specification/#burn-bootloader

The documentation described this as a 2 step activity and I fail to reproduce the Arduino IDE created erase command for the avr uno board for platform version 1.8.3

The platform.txt file on my system contains the following erase pattern

tools.avrdude.erase.pattern="{cmd.path}" "-C{config.path}" {erase.verbose} -p{build.mcu} -c{protocol} {program.extra_params} -e -Ulock:w:{bootloader.unlock_bits}:m -Uefuse:w:{bootloader.extended_fuses}:m -Uhfuse:w:{bootloader.high_fuses}:m -Ulfuse:w:{bootloader.low_fuses}:m

As you can see, this command contains {protocol}. The same can be found in the github repository here
https://github.com/arduino/ArduinoCore-avr/blob/master/platform.txt#L117

However I do not find where protocol is defined.
When I run the burn bootloader command in the arduino IDE I see protocol resolves to stk500v2. There are several references to stk500v2 in platform.txt boards.txt and programmers.txt but none that I can confidently map.

Can you please advice how to resolve protocol properly?
Thanks

[jantje]

Looking at this a bit further in the command line I see the same problem with program.extra_params
It looks as if the info comes from the programmers.txt for the key avrisp.

avrisp.name=AVR ISP
avrisp.communication=serial
avrisp.protocol=stk500v1
avrisp.program.protocol=stk500v1
avrisp.program.tool=avrdude
avrisp.program.extra_params=-P{serial.port}

[jantje]

I found the missing link.
Apparently the programmer selected in the gui is used for "uploading using programmer" but also for "burn bootloader"

[jantje]

Reading the platform.txt section I would propose to add the dependency of platform.txt to the burn bootloader section.
The upload using external programmer already makes the dependency clear.