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SubjectRe: [Q] devicetree overlays
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On 07.08.20 16:17, Sven Van Asbroeck wrote:

Hi,

> I believe you're asking: "how do I associate device tree nodes to
> devices on a dynamically discoverable bus such as USB or PCI" right ?
>
> I believe that already exists. You can describe the _expected_ pci or
> usb topology in the
> devicetree. If a device gets detected in a spot on the bus described
> in the tree, that
> snippet will be automatically associated with this device.
>
> How to for usb:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/usb/usb-device.txt?h=v5.8
>
> How to for pci:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/devicetree/bindings/pci/pci.txt?h=v5.8

Thanks, that looks good.

But I've still got another problem: how can I use DT along w/ ACPI ?

The scenario goes like this:

* machine boots and probes normally w/ ACPI
* device is detected via USB, PCI, DMI, etc -> driver gets active
* driver loads (or carries) a DT snippet
* devices on the bus are instantiated via this DT snippet

(driver could also be some udev vodoo)

Example a:

* generic usb i2c dongle w/ some i2c devices attached behind it
* config (or DT snippet) somewhere in the FS

Example b:

* x86 board driver (eg. apu2/3/4), probed via DMI
* just instantiates a bunch of generic drivers and wires up
devices (gpio, leds, keys, ...)


Do you think we can already do that ?
Otherwise, what has to be done to achieve that ?


--mtx

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Enrico Weigelt, metux IT consult
Free software and Linux embedded engineering
info@metux.net -- +49-151-27565287

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