[realusername]

As I'm working in this area, I can say that the biggest problem isn't binary only drivers but spotty mainline support of core features (provided that we're talking about Android phones, not iPhones or old Windows mobile stuff)

[RossBencina]

From where you're standing, what does the path to improving mainline support of core features look like? Aside from sheer volume of work are there other major challenges or opportunities? In the past I've hacked around adding stuff to Armbian kernels, but navigating a path to mainline seemed like a whole other job.

[realusername]

It really depends of your device but some SOC have very poor mainline support and are essentially living in a forked repo with nothing sent to lkml, others have partial support in mainline but with some of the core features being broken.

Drivers can also be partially implemented / buggy depending on the device. (And I'm not talking about closed source stuff, even things like usb or touch screen drivers).

I would say that the major blocker is that nobody really cares about these devices and the task itself to mainline them is gigantic.

Most SOC have 3 or maybe 4 contributors maximum and the phonedev kernel mailing list gets a new patch only every 2 days. The whole phone mainlining community is probably less than 60 people.