Similar to https://askubuntu.com/questions/760196/why-is-enps-in-stead-of-eth-whats-the-meaning-of-enps
But what f# stands for in enp#s#f# interface name format?
Wiki states only this, not mentioning f:
Adapters in the specified PCI slot, with slot index number on the adapter enp<PCI slot>s<card index no>, similar here https://www.freedesktop.org/wiki/Software/systemd/PredictableNetworkInterfaceNames/
The f is for "function indexes".
en = ethernet
p# = PCI bus number
s# = slot number
f# = function index
Added some resources: libvirt.org has a good explanation
waste.org says this about "f":
All devices have at least 1 function, function #0. There are 8 possible functions per device, numbered 0-7. Any device that has more than 1 function is called a multi-function device. Multi-function devices, such as a combination modem+soundcard will usually have 2 uniquely addressable functions, numbered 0 and 1.
The function leads to the vendor and device id:
Every function of a device has 256 eight-bit registers. Registers 0-3F are defined by the PCI specification and provide a wealth of information about the particular function. Registers 40-FF are vendor defined and control the properties of the function itself. Without vendor specific documentation, these registers should probably be left untouched.
- Registers 0 and 1 are defined by the PCI spec as being the vendor ID. The vendor ID is a 16bit value.
- Registers 2 and 3 are the device ID
From pbhj's link in comments it leads to the source code:
Line 264+:
if (sscanf(sysname, "%x:%x:%x.%u", &domain, &bus, &slot, &func) != 4)
return -ENOENT;
if (naming_scheme_has(NAMING_NPAR_ARI) &&
is_pci_ari_enabled(names->pcidev))
/* ARI devices support up to 256 functions on a single device ("slot"), and interpret the
* traditional 5-bit slot and 3-bit function number as a single 8-bit function number,
* where the slot makes up the upper 5 bits. /
func += slot 8;
