Hello, On Fri, 26 Apr 2024 11:51:41 +0200 Luca Ceresoli <luca.ceresoli@xxxxxxxxxxx> wrote: [...] > We described 2 use cases we are working on at Bootlin. > > One use case is for the LAN966x, a classic SoC that can be however be > started in "endpoint mode", i.e. with the CPU cores deactivated and a > PCI endpoint that allows an external CPU to access all the peripherals > over PCIe. In practice the whole SoC would be used as a peripheral chip > providing lots of devices for another SoC where the OS runs. This use > case has been described by Rob Herring and Lizhi Hou at LPC 2023 [4][5]. > > The other use case, which was discussed in more detail, is for an > industrial product under development by a Bootlin customer, which is a > regular, self-standing embedded Linux system with a connector allowing > to connect an add-on with additional peripherals. The add-on > peripherals are on I2C, MIPI DSI and potentially other non-discoverable > busses (there are also peripherals on natively hot-pluggable busses > such as USB and Ethernet, but by their nature they don't need special > work). > > For both use cases (and perhaps others we are unaware of) runtime > loading/unloading DT overlays appears as the most fitting technique. > Except it is not yet ready for real usage. > > For it to work, we highlighted 3 main areas in need of work in the > Linux kernel: > > 1. how to describe the connector and the add-ons in device tree > (bindings etc) -- only relevant for the 2nd use case > 2. implementation of DT overlays for adding/removing the add-on > peripherals > 3. fixing issues with various subsystems and drivers that don't react > well on device removal Quick update: I just sent a series with a proposal covering items 1 and 2: https://lore.kernel.org/all/20240510-hotplug-drm-bridge-v2-0-ec32f2c66d56@xxxxxxxxxxx/ Luca -- Luca Ceresoli, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
