I've just had a look at the DragonBox Pyra. It looks like it's going to use a PowerVR GPU (i.e. no FOSS drivers).
Can you clarify how a mainline kernel can be run on such a device? I assume PowerVR are written only for specific kernel versions (e.g. in the same way GPU drivers are written specifically for Android's Linux kernel 3.4)
That's true. My plan was to run the Pyra without 3D acceleration, as I will use it just as a minilaptop for maps, chat and ssh. AFAIK, the Vivante chip included in Pyra has a usable free driver, which is what matters most for my usecase.
PowerVR is also said to be working on a free driver [1]. This might do the trick.
Generally, GPUs are the showstopper in ARM architectures. Otherwise, it is possible to run not only a mainline linux kernel, but a deblobbed one (linux-libre). I do this on a Chromebook C201 [2]. Note you don't even need CPU firmware, as it is the case with Intel.
Can you clarify how a mainline kernel can be run on such a device? I assume PowerVR are written only for specific kernel versions (e.g. in the same way GPU drivers are written specifically for Android's Linux kernel 3.4)