On Tue, Feb 9, 2021 at 12:25 AM Enrico Weigelt, metux IT consult <info@xxxxxxxxx> wrote: > > Hello folks, > > here's an RFC for using compiled-in dtb's for initializing board devices > that can't be probed via bus'es or firmware. > > Use cases are boards with non-oftree firmware (ACPI, etc) where certain > platform devices can't be directly enumerated via firmware. Traditionally > we had to write board specific drivers that check for board identification > (DMI strings, etc), then initialize the actual devices and their links > (eg. gpio<->leds/buttons, ...). Often this can be expressed just by DT. In ACPI we support DT compatible strings, and we support overlays for a long time. Would it work for you? > This patch queue does a bunch of preparations in oftree code, so we can > support multiple fully independent DT's (not using DT overlays). And then > adds a generic driver parses compiled-in fdt blobs, checks for mathing > DMI strings and initializes the devices. As an example, the last patch > adds an alternative implementation for the PC engines APU2/3/4 board > family based on device tree. Sounds weird, but let's see... > The approach can be easily be extended to other kinds of composite devices, > eg. PCI cards or USB dongles. What do you mean? PCI and USB are self-enumerated. What's wrong with them? > Yet some drawbacks of the current implementation: > > * individual FDT's can't be modularized yet (IMHO, we don't have DMI-based > modprobing anyways) What?! https://lwn.net/Articles/233385/ `git grep -n 'MODULE_DEVICE_TABLE(dmi'` > * can't reconfigure or attach to devices outside the individual DT's > (eg. probed by PCI, etc) -- With Best Regards, Andy Shevchenko
