[Linux-gpib-general] Patch for linux-gpib GPIO bitbanging driver

[Thomas K. <ele...@gm...>]

Hi,

congratulations on the newest release of linux-gpib - I love that the
bitbanging driver is now included in linux-gpib!

Since 2016 i developed a GPIB-shield for the raspberry pi and a
patch to linux-gpib as driver on my project page (elektronomikon.org).

Marcello helped me with an interrupt-driven design, and his current
version is much more elegant than mine but is missing two features
which imho would warrant looking after:

1, The driver in linux-gpib V4.3.4 is uses the legacy gpio kernel
   interface which is marked deprecated for some time now. The
   raspi_gpib driver uses the GPIO descriptor based interface.
2, My project includes SN75160/161 driver IC's which need three
   extra pins and are unused in the upstream driver.

So i added both changes to the upstream version, which yields the
following file:
https://github.com/elektronomikon/raspi_gpib_driver/blob/master/for_linux-gpib-4.3.4/gpib_bitbang.c

Marcello tested this on his hardware which ran fine.

The use of SN75160/161 is currently en/disabled via a module parameter,
which i think is an acceptable solution. Aa config file switch would be
another possibility, but i dont know how to implement this... Any hints
are appreciated :-)

Patch is attached, please apply.

Greetings,
Thomas Klima