Re: Arm drivers: are device tree descriptions required for every device?

[Matthew Widup <widupmm%proton.me@localhost>]

------- Original Message -------
On Tuesday, April 11th, 2023 at 12:33 AM, Jason Thorpe <thorpej%me.com@localhost> wrote:

> > Yes, every device must exist in the device tree (and of course have a relevant point of connection).
> 
> 
> This is not a true statement.

You are correct.  I was not thkining about it in the right way.  Really either each device, or all of the buses each device announces its presence to.

<snip>

> Devices that are connected to busses that have a "native" discovery protocol (USB and PCI are the canonical examples) do NOT need to be described by the device tree; in the case of PCI, they might have nodes in the device tree if there is a need to convey some platform-specific information about them (and such devices are almost certainly at some fixed location in the bus topology).
> 
> Yes, devices that are not on a self-describing bus need to be in some sort of device tree (whether that's Device Tree: The Breakfast Cereal or ACPI) in order to be enumerated; legacy mechanisms that have been used for decades are being ignored here since this discussion is in the context of the ARM port.

Thank you for the clarification.  You can probably tell I only really know "PC" hardware before there was PCI.