Re: btattach: auto triggering at boot time by Linux distributions

["Jérôme de Bretagne" <jerome.debretagne@gmail.com>]

Hi Marcel,

> the real evolution would be that we get a serial bus (as discussed a
> few weeks ago) which then the UART kernel drivers can enumerate its
> devices on.

I've read this discussion, thanks for the pointer, and I've seen the
latest patch set proposal from Rob Herring reusing the existing serio
bus. 

If I understood correctly, you would like to stop exposing /dev/ttyX
for Bluetooth UART drivers in the long run. Would it mean that the
user-space btattach will then be deprecated and the firmware loading
will be moved into the kernel itself? Or another approach instead?

> Until then, you need an userspace part that triggers btattach with
> the right hardware id on the right /dev/ttySx device node as soon as
> it becomes available. So that means udev rules.

Great, I will investigate the udev rules direction.

>  However the problem is and always has been to figure out what
> hardware is behind what /dev/ttySx. If you are lucky it is part of
> ACPI tables or DT. If you are unlucky you need a DT overlay or
> hardcode it.

I faced that precise limitation when I was trying to find out what was
the chipset ACPI ID on the ThinkPad 8 tablet, to guess which btattach
parameter to use. And I don't remember finding it in the ACPI tables :(

I fear I will have to hardcode it to get started, and then investigate
the usage of a DT overlay in a second step.

Regards,
Jérôme