On Wed, Oct 7, 2020 at 9:23 AM Mark Brown <broonie@xxxxxxxxxx> wrote: > > On Wed, Oct 07, 2020 at 09:19:32AM -0700, Dan Williams wrote: > > On Wed, Oct 7, 2020 at 2:14 AM gregkh@xxxxxxxxxxxxxxxxxxx > > > > "virtual" here means "not real" :) > > > Which of these aux device use cases is not a real device? One of my > > planned usages for this facility is for the NPEM (Native PCIE > > Enclosure Management) mechanism that can appear on any PCIE > > bridge/endpoint. While it is true that the NPEM register set does not > > get its own PCI-b:d:f address on the host bus, it is still > > discoverable by a standard enumeration scheme. It is real auxiliary > > device functionality that can appear on any PCIE device where the > > kernel can now have one common NPEM driver for all instances in the > > topology. > > Some if not all of the SOF cases are entirely software defined by the > firmware downloaded to the audio DSPs. "Software-defined" in the kernel context to me means software Linux kernel developers have control over, so device-mapper devices, other things that show up under /sys/devices/virtual, or /sys/devices/system/memory/. Firmware changing device functionality is more like just-in-time hardware than software-defined. In other words kernel software is not involved in constructing the device functionality.
