[OpenOCD-devel] Bitbang extension: Override bitbang_exchange

[Lucas V. H. <luc...@gm...>]

Hello, this is my first post here, so please forgive me if I miss something.

I was writing a remote-bitbang-like implementation using an ESP8266 as a
JTAG-TCP or SWD-TCP bridge. I got it to work with a STM32F030F4P6 as target
and SWD as transport. Using pure bitbang made it awfully slow, disabling
naggle madi it better but not enough.

I then had the idea to move the code for bitbang_exchange to the ESP, and
it got a lot better (under 15s program and boot, about 3s step over or run
to breakpoint).

For that I added a bitbang_interface.exchange function pointer, checked for
null pointer in bitbang_exchange, and redirected the call if the pointer
was not-null. This makes me concerned about other bitbang drivers drivers,
though...

Questions:
- Is this redirection desired at all for the OpenOCD project?
- Is it safe to presume uninitialized structure fields (i.e. the exchange
function pointer) are implicitly zero?

If it is not safe then I'll need to fix all other bitbang-based drivers
(initialize exchange to null) before I submit a patch to gerrit.

Regards.
--
Lucas Vinicius Hartmann

Dizem que se você rodar o CD do Windows ao contrário ele mostra uma
mensagem demoníaca... Mas isso nem é o pior, se você rodar ele normal ele
instala o Windows!