Since GCC 10, the compiler defaults to -fno-common, thus variables with
multiple tentative definitions result in linker errors.
We've (me and @MrMoDDoM) extern-ed the shared variables to fix the issue.
Also, when I implemented ISR sharing, somehow I forgot about a function
which was shared as well, so I fixed that mistake and added a couple of
comments on how shared function calls work.
Another buffer used for store card->reader traffic is added, so that card->reader traffic sniffing can start right after the reader->Card trafic sniffing finished.
(cherry picked from commit e074fcc)
Federico Cerutti
Fabian
chenzitai
Georg
Timo Kasper
Simon Küppers