Re: [avrdude-dev] support for bitbanging GPIO lines through /sys/class/gpio

[Joerg Wunsch]

As Radoslav Kolev wrote:

> Ivan implemented an AVR programmer in Perl to use his Bifferboard
> GPIO lines to program an AVR. I suggested that it would be better to
> add this as part of avrdude to reuse all the MCU definitions. Biff
> expressed an interest and I decided to do it as an exercise during
> the weekend. So currently there are 2-5 potential users :).

Probably enough. ;-)

> I don't know if it will be possible to automatically
> detect this though. Usually for embedded systems you cross-compile
> so testing about sysfs-gpio support in the kernel of the system
> doing the build is not of much use.

Right, you'd have to detect this for the target system.

> Probably a better approach would be to provide a
> configure option or something to enable/disable this programmer if
> needed.

That's fine with me.  There are already some examples for --enable/
--disable switches in the existing configure.ac file.

> How is this usually handled for other similar cases in avrdude?

There are currently no cross-compilation switches available.  libusb
is auto-probed, but that assumes the target system matches the build
system.  We should probably allow for an override to disable the
positive result from the autoprobing (the target system might not have
libusb installed while the host system does).

> This uses nothing more than file open/read/write/close functions so
> it should build on all platforms. If you try to use it and the
> expected /sys/class/gpio directory is not there it will exit with an
> error.

OK, anyway, it doesn't make sense to compile dead code if it's sure
the target system won't have any use for it, so I'd prefer having it
as a separate --enable option.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)