Raspberry Pi 4 doesn't show a wireless interface - what drivers are required?

Question

I have a raspberry pi 4 running Raspbian Buster. I'll be the first to admit this particular instalation is non-standard. It's been upgraded a version or two and was definitely active on my pi-3 if not my pi-2 as well. By that I mean I've popped the SD card from one and put it in the next, fixing the boot loader where necessary. So its possible probable that I don't have a few packages that are now shipped as standard with Raspbian.

For the first time I'm trying to get wireless working. At the moment I don't have a wireless interface listed when I type ip link. I suspect this is a simple matter of drivers, but am at a loss to find exactly what I need to install to get the wifi card to recognise.

For completeness here's the output of lsmod:

Module                  Size  Used by
bnep                   20480  2
hci_uart               40960  1
btbcm                  16384  1 hci_uart
serdev                 20480  1 hci_uart
bluetooth             389120  24 hci_uart,bnep,btbcm
ecdh_generic           28672  1 bluetooth
sg                     28672  0
brcmfmac              311296  0
vc4                   176128  0
brcmutil               16384  1 brcmfmac
sha256_generic         20480  0
cfg80211              614400  1 brcmfmac
v3d                    61440  0
drm_kms_helper        184320  1 vc4
rfkill                 28672  4 bluetooth,cfg80211
gpu_sched              28672  1 v3d
raspberrypi_hwmon      16384  0
hwmon                  16384  1 raspberrypi_hwmon
drm                   442368  5 v3d,vc4,gpu_sched,drm_kms_helper
bcm2835_codec          36864  0
bcm2835_v4l2           45056  0
v4l2_mem2mem           24576  1 bcm2835_codec
drm_panel_orientation_quirks    16384  1 drm
bcm2835_mmal_vchiq     32768  2 bcm2835_codec,bcm2835_v4l2
v4l2_common            16384  1 bcm2835_v4l2
videobuf2_vmalloc      16384  1 bcm2835_v4l2
videobuf2_dma_contig    20480  1 bcm2835_codec
snd_soc_core          192512  1 vc4
snd_bcm2835            24576  1
videobuf2_memops       16384  2 videobuf2_dma_contig,videobuf2_vmalloc
snd_compress           20480  1 snd_soc_core
videobuf2_v4l2         24576  3 bcm2835_codec,bcm2835_v4l2,v4l2_mem2mem
snd_pcm_dmaengine      16384  1 snd_soc_core
snd_pcm               102400  4 vc4,snd_pcm_dmaengine,snd_bcm2835,snd_soc_core
videobuf2_common       45056  4 bcm2835_codec,bcm2835_v4l2,v4l2_mem2mem,videobuf2_v4l2
syscopyarea            16384  1 drm_kms_helper
sysfillrect            16384  1 drm_kms_helper
snd_timer              32768  1 snd_pcm
sysimgblt              16384  1 drm_kms_helper
fb_sys_fops            16384  1 drm_kms_helper
snd                    73728  7 snd_compress,snd_timer,snd_bcm2835,snd_soc_core,snd_pcm
videodev              200704  6 bcm2835_codec,v4l2_common,videobuf2_common,bcm2835_v4l2,v4l2_mem2mem,videobuf2_v4l2
media                  36864  3 bcm2835_codec,videodev,v4l2_mem2mem
vc_sm_cma              36864  1 bcm2835_mmal_vchiq
rpivid_mem             16384  0
uio_pdrv_genirq        16384  0
fixed                  16384  0
uio                    20480  1 uio_pdrv_genirq
ip_tables              24576  0
x_tables               32768  1 ip_tables
ipv6                  450560  46

Could anyone point me in the right direction of what I may be missing?

---

For completeness, the accepted answer led me to believe the required drivers are there, but there's a different problem. Here's the output from journalctl for future reference.

journalctl -b | grep brcmfmac

May 06 22:36:14 mercury kernel: brcmfmac: F1 signature read @0x18000000=0x15264345
May 06 22:36:14 mercury kernel: brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
May 06 22:36:14 mercury kernel: usbcore: registered new interface driver brcmfmac
May 06 22:36:15 mercury kernel: brcmfmac: brcmf_sdio_htclk: HT Avail timeout (1000000): clkctl 0x50
May 06 22:36:16 mercury kernel: brcmfmac: brcmf_sdio_htclk: HT Avail timeout (1000000): clkctl 0x50

Answer 1

On a Raspberry Pi 4 only Raspbian Buster is running out of the box. On a Buster installation you will find the firmware with:

rpi ~$ apt list *raspberrypi*
Listing... Done
libraspberrypi-bin/testing,now 1.20200212-1 armhf [installed]
libraspberrypi-dev/testing,now 1.20200212-1 armhf [installed]
libraspberrypi-doc/testing,now 1.20200212-1 armhf [installed]
libraspberrypi0/testing,now 1.20200212-1 armhf [installed]
raspberrypi-archive-keyring/testing 2016.10.31 all
raspberrypi-artwork/testing 20150921 all
raspberrypi-bootloader/testing,now 1.20200212-1 armhf [installed]
raspberrypi-kernel-headers/testing 1.20200212-1 armhf
raspberrypi-kernel/testing,now 1.20200212-1 armhf [installed]
raspberrypi-net-mods/testing,now 1.3.0 all [installed]
raspberrypi-sys-mods/testing,now 20191105 armhf [installed]
raspberrypi-ui-mods/testing 1.20200218 all

addressed with:

rpi ~$ cat /etc/apt/sources.list.d/raspi.list
deb http://archive.raspberrypi.org/debian/ buster main
# Uncomment line below then 'apt-get update' to enable 'apt-get source'
#deb-src http://archive.raspberrypi.org/debian/ buster main

It may help you to identify where to look for overlays. From the journal I find for the WiFi driver brcmfmac:

rpi ~$ journalctl -b | grep brcmfmac
May 05 22:46:12 raspberrypi kernel: brcmfmac: F1 signature read @0x18000000=0x15264345
May 05 22:46:12 raspberrypi kernel: brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
May 05 22:46:12 raspberrypi kernel: usbcore: registered new interface driver brcmfmac
May 05 22:46:12 raspberrypi kernel: brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43455-sdio for chip BCM4345/6
May 05 22:46:12 raspberrypi kernel: brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM4345/6 wl0: Mar  2 2020 23:30:41 version 7.45.202 (r724630 CY) FWID 01-72f6ece2
May 05 22:46:15 raspberrypi kernel: brcmfmac: power management disabled
May 05 23:14:13 raspberrypi kernel: brcmfmac: power management disabled

The most important here seems to be
Firmware: BCM4345/6 wl0: Mar 2 2020 23:30:41 version 7.45.202 (r724630 CY) FWID 01-72f6ece2

The package containing the driver I find with:

rpi ~$ apt search bcm4345
Sorting... Done
Full Text Search... Done
firmware-brcm80211/testing,now 1:20190114-1+rpt6 all [installed]
  Binary firmware for Broadcom/Cypress 802.11 wireless cards

Now its up to you to make it running on your system ;-)

UPDATE:
And yes, Philip was able to make it running on his system as he wrote in a comment:

there's a comment here about this error being caused by corrupt driver files. I downloaded a fresh copy of the driver for brcmfmac43455 from from here and everything worked fine.