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

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