Hi Linus,

quoted

Currently, devices attached via a UART are not well supported in the
kernel. The problem is the device support is done in tty line disciplines,
various platform drivers to handle some sideband, and in userspace with
utilities such as hciattach.

Freaking *awesome* Rob, this really really needs to happen.
I'm very happy that you're driving this.

quoted

This is functional with minimal testing using the loopback driver and
pl011 (w/o DMA) UART under QEMU (modified to add a DT node for the slave
device). It still needs lots of work and polish.

I have Bluetooth (HCI) over UART on the Nomadik and Ux500,
both with DMA support for the PL011 too. So I hope to be able
to utilize this.

(The HCI transport is then used for GPS, FM radio and whatnot
but that is another issue.)

that is something we can already solve via regmap. We have started work on Intel LnP which also includes a FM radio chip where registers/interrupts are exposed via HCI commands/events. So fundamentally the Bluetooth HCI device would expose the GPS and FM radio nodes via regmap.

Regards

Marcel