API for libgpiod has changed in v2

[jasonKercher]

Here are the steps I follow to reproduce the issue:

1. Have libgpiod version >= 2
2. Attempt to compile linuxcnc v 2.9.2

This is what I expected to happen:

Build succeeds

This is what happened instead:

In file included from hal/drivers/hal_gpio.c:39:
hal/drivers/hal_gpio.c:188:50: error: invalid application of ‘sizeof’ to incomplete type ‘struct gpiod_line_bulk’
  188 |             (*ptr)[c].bulk = rtapi_kmalloc(sizeof(*(*ptr)[c].bulk), RTAPI_GFP_KERNEL);

...along with lots of warnings for implicit declarations of functions (due to API change).

It worked properly before this:

libgpiod version <= 1.6.4

Information about my hardware and software:

• I am using Manjaro. I know that is not officially supported, but we do keep a working linuxcnc package over there.
  Manjaro is part of the Arch Linux family, so we always have the bleeding edge latest software. I imagine this will not be an issue on Debian for some time.
• Linux Kernel Version 6.1.66
• Linux CNC v2.9.2

[andypugh]

This was something that I knew was coming, and that I don't really know how to solve.

libgpiod is a mess, for example libgpiod2 is still v1.6, not 2.

There are no packages in Debian for libgpiod v2, with the new API, so I decided this was a problem that can be kicked down the road until at least after Trixie (which still has v1.6) https://packages.debian.org/search?suite=trixie&searchon=names&keywords=libgpiod

There is probably something horribly messy that can be done with conditional compilation, or a wrapper API.

I am not even 100% sure that libgpiod has a 1:1 mapping between v1.x and v2.x functions.

The libgpiod developers were keen that I should code for v2, but with no packages available from Debian, how would our users get it? We can host the packages on our own repository, but that isn't a fix for folk installing LinuxCNC from the main Debian mirrors.

[FabioLolix]

Hello, on the AUR making a pkgbuild for libgpiod v1.6.4 installed in /opt/libgpiod-1.6.4 (or something similar) so it doesn't conflicts with the system's one isn't a problem

How I could pass that to autogen.sh or ./configure ?

[andypugh]

As I knew this was coming somewhere down the line, ./configure does set an environment variable containing the version:
https://github.com/LinuxCNC/linuxcnc/blob/master/src/configure.ac#L535
Currently it is only used to detect the presence of the library:
https://github.com/LinuxCNC/linuxcnc/blob/master/src/Makefile#L1006
But I suppose, in theory, it could be used to compile a completely different source file into the same module (with the same Linuxcnc-side API)

[FabioLolix]

btw https://github.com/pikvm/ustreamer updated to build with libgpiod 2.0.x while also working with the older version seems, the 2 relevant commits:

• pikvm/ustreamer@d9b5f2b
• pikvm/ustreamer@4d92dc6