from atsamv.c:663
static const struct command_registration atsamv_exec_command_handlers[] = {
{
.name = "gpnvm",
.handler = samv_handle_gpnvm_command,
.mode = COMMAND_EXEC,
.usage = "[('clr'|'set'|'show') bitnum]",
.help = "Without arguments, shows all bits in the gpnvm "
"register. Otherwise, clears, sets, or shows one "
"General Purpose Non-Volatile Memory (gpnvm) bit.",
},
COMMAND_REGISTRATION_DONE
};