As we mentioned previously, there are several "real-world" users of the debugfs API; can we spot some of them? Well, here's one way: simply search under the kernel source tree's drivers/ directory for files named *debugfs*.c; you might be surprised (I found 114 such files in the 5.4.0 kernel tree!). Let's take a look at a few:
$ cd <kernel-source-tree> ; find drivers/ -iname "*debugfs*.c"
drivers/block/drbd/drbd_debugfs.c
drivers/mmc/core/debugfs.c
drivers/platform/x86/intel_telemetry_debugfs.c
[...]
drivers/infiniband/hw/qib/qib_debugfs.c
drivers/infiniband/hw/hfi1/debugfs.c
[...]
drivers/media/usb/uvc/uvc_debugfs.c
drivers/acpi/debugfs.c
drivers/net/wireless/mediatek/mt76/debugfs.c
[...]
drivers/net/wireless/intel/iwlwifi/mvm/debugfs-vif.c
drivers/net/wimax/i2400m/debugfs.c
drivers/net/ethernet/broadcom/bnxt/bnxt_debugfs.c
drivers/net/ethernet/marvell/mvpp2/mvpp2_debugfs.c
drivers/net/ethernet/mellanox/mlx5/core/debugfs.c
[...]
drivers...
