Public bug reported:
Ubuntu Release: Ubuntu 26.04.1 LTS (Resolute, arm64)
Package: linux-raspi / linux-modules-7.0.0-1021-raspi (7.0.0-1021.21)
[ Impact ]
On Raspberry Pi 400 (CID: 202010-28327) running Ubuntu 26.04 LTS (resolute
arm64), the on-board wireless interface fails to initialize completely under
kernel 7.0.0-1021.21-raspi. Checkbox certification test
com.canonical.certification::wireless/detect fails with "No devices detected by
udev".
[ Root Cause ]
In Linux 7.0, the brcmfmac driver modularized vendor firmware support (cyw,
wcc, bca). When probing the Raspberry Pi 400's BCM4345/9 chip (F1 signature
0x15294345), brcmfmac.ko calls request_module("brcmfmac-cyw").
In 7.0.0-1019.19-raspi, linux-modules-7.0.0-1019-raspi included:
/lib/modules/7.0.0-1019-raspi/kernel/drivers/net/wireless/broadcom/brcm80211/brcmfmac/cyw/brcmfmac-cyw.ko.zst
In 7.0.0-1021.21-raspi, brcmfmac-cyw.ko.zst was omitted from linux-
modules-7.0.0-1021-raspi. As a result, the request fails with error 256:
text
[ 3.648342] kernel: brcmfmac: F1 signature read @0x18000000=0x15294345
[ 3.651068] kernel: brcmfmac: brcmf_fw_alloc_request: using
brcm/brcmfmac43456-sdio for chip BCM4345/9
[ 3.654230] kernel: usbcore: registered new interface driver brcmfmac
[ 3.829825] kernel: brcmfmac: brcmf_fwvid_request_module: mod=cyw: failed 256
[ 3.829942] kernel: ieee80211 phy0: brcmf_attach: brcmf_fwvid_attach failed
[ 3.846028] kernel: brcmfmac: brcmf_sdio_firmware_callback: brcmf_attach
failed
Because brcmf_attach fails, no wireless interface (wlan0) is created.
[ Test Plan ]
1. On an RPi 400 (or RPi with BCM43455/BCM43456 SDIO Wi-Fi) running Ubuntu
26.04 LTS, boot linux-image-7.0.0-1021-raspi.
2. Inspect dmesg | grep brcmfmac.
3. Check ip link or run checkbox-cli run
com.canonical.certification::wireless/detect.
4. With the fix, brcmfmac-cyw.ko is present in linux-modules-*-raspi, loads
successfully, wlan0 appears, and wireless/detect passes (as verified on
7.0.0-1019.19-raspi).
[ Where Problems Could Occur ]
Packaging brcmfmac-cyw.ko restores the modular Cypress driver vendor plugin as
intended by upstream kernel 7.0; regression risk is minimal because it restores
known working behavior from 7.0.0-1019.19.
** Affects: linux-raspi (Ubuntu)
Importance: Undecided
Status: New
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https://bugs.launchpad.net/bugs/2168469
Title:
[SRU][Regression] linux-raspi 7.0.0-1021.21 drops brcmfmac-cyw.ko,
breaking Wi-Fi on RPi 400
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