Re: [RFC PATCH 0/3] UART slave device bus

[Marcel Holtmann <marcel@holtmann.org>]

Hi Linus,

>> 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.
> 
>> 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