@Alessandro-Floris the link you're following is for the Omega 1, which is based on OpenWRT. The Omega 2 makes use of LEDE, which is a branch/fork of OpenWRT. Ergo, you need to use the LEDE toolchain. Searching this forum should reveal some light on the matter.
@Luciano-S @WereCatf told here that the devs of the Omega2 forgot to enable CONFIG_DEVMEM in the newer firmware. The last working one is 0.1.6 b137
So my guess is that it is fixed in the next release if it is indeed just a forgotten flag.
@Costas-Costas the approach chosen by Kit and now Travis won't work on standard firmware until the /dev/mem issue is fixed.
Yes, one of the many reasons that I am holding off upgrading the code to Omega2
The other main constraint (other than time availability) is that the endianess differs on the Omega1 and Omega2 and I need to check out the places where this is significant in the code (I know of at least one place)
Surprised to hear that removing the sigaddset doesn't work for you - it seems to do so for me. I will have a closer look and get back to you as and when I find anything.
Thanks for the info on how you are building - this implies that the extra memory usage for new-gpio is down to the extra code functionality