Fix Clang 22 warnings by KonstaT · Pull Request #7299 · raspberrypi/linux

KonstaT · 2026-04-02T16:17:41Z

This patch set fixes build warnings with Clang. These issues were observed when compiling code merged from this repository as part of Android kernel which is compiled using Clang 22 and CONFIG_WERROR=y set.

I also reproduced that these issues are present and resolved with this patch set when compiling the kernel from this repository (rpi-6.18.y branch) with Clang 22 both cross-compiling on Ubuntu host as well as natively on Raspberry Pi 5 using Raspberry Pi OS.

# Install Raspberry Pi OS (2025-12-04-raspios-trixie-arm64.img.xz) and update
$ sudo apt update
$ sudo apt full-upgrade

# Install build dependecies (https://www.raspberrypi.com/documentation/computers/linux_kernel.html#natively-build-a-kernel)
$ sudo apt install bc bison flex libssl-dev make

# Install Clang 22 (https://apt.llvm.org/)
$ wget https://apt.llvm.org/llvm.sh
$ chmod +x llvm.sh
$ sudo ./llvm.sh 22

# Download kernel source code (shallow clone to save time)
$ git clone https://github.com/raspberrypi/linux -b rpi-6.18.y --depth=1
$ cd linux

# Compile using Clang 22 with CONFIG_WERROR=y set
$ export LLVM=-22 CC=clang-22 KERNEL=kernel_2712
$ make bcm2712_defconfig
$ scripts/config --file .config --set-val CONFIG_WERROR y
$ make Image.gz modules dtbs -j$(nproc)

Also fixed minor issue that SND_PIMIDI and SND_PISOUND_MICRO should rather select CRC8 than depend on it. This likely works here as some other drivers already selects CRC8. I generally don't compile the Android kernel with SND_PISOUND_MICRO enabled but it doesn't get set in defconfig as there's also no CRC8 set otherwise.

6by9 · 2026-04-07T14:23:28Z

I agree with "fixup! drm/vc4: Assign 32 overlay planes to writeback only"

I'll leave others to review the remaining patches.

popcornmix · 2026-04-09T14:54:27Z

These all look fine, although I'd like @pelwell to check the PIO_ORIGIN_ANY one (which I suspect is fine).

pelwell · 2026-04-09T17:14:26Z

The PIO_ORIGIN_ANY change is going to need more thought by me, but I'm happy to merge the others now if you split it into a separate PR.

* Fixes build with Clang. drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c:1513:3: error: variable 'chan_flags_all' is uninitialized when used here [-Werror,-Wuninitialized] 1513 | chan_flags_all |= dw->chan_flags[i]; | ^~~~~~~~~~~~~~ drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c:1502:25: note: initialize the variable 'chan_flags_all' to silence this warning 1502 | uint32_t chan_flags_all; | ^ | = 0 1 error generated.

* Fixes build with Clang. drivers/gpu/drm/vc4/vc4_plane.c:2799:2: error: variable 'txp_crtc' is used uninitialized whenever 'for' loop exits because its condition is false [-Werror,-Wsometimes-uninitialized] 2799 | drm_for_each_crtc(crtc, drm) { | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/drm/drm_crtc.h:1312:2: note: expanded from macro 'drm_for_each_crtc' 1312 | list_for_each_entry(crtc, &(dev)->mode_config.crtc_list, head) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ include/linux/list.h:783:7: note: expanded from macro 'list_for_each_entry' 783 | !list_entry_is_head(pos, head, member); \ | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/vc4/vc4_plane.c:2809:20: note: uninitialized use occurs here 2809 | drm_crtc_mask(txp_crtc); | ^~~~~~~~ drivers/gpu/drm/vc4/vc4_plane.c:2799:2: note: remove the condition if it is always true 2799 | drm_for_each_crtc(crtc, drm) { | ^ include/drm/drm_crtc.h:1312:2: note: expanded from macro 'drm_for_each_crtc' 1312 | list_for_each_entry(crtc, &(dev)->mode_config.crtc_list, head) | ^ include/linux/list.h:783:7: note: expanded from macro 'list_for_each_entry' 783 | !list_entry_is_head(pos, head, member); \ | ^ drivers/gpu/drm/vc4/vc4_plane.c:2796:27: note: initialize the variable 'txp_crtc' to silence this warning 2796 | struct drm_crtc *txp_crtc; | ^ | = NULL 1 error generated.

* Fixes build with Clang. drivers/net/wireless/broadcom/brcm80211/brcmfmac/common.c:461:10: error: array index 18 is past the end of the array (that has type 'u8[1]' (aka 'unsigned char[1]')) [-Werror,-Warray-bounds] 461 | setbit(eventmask_msg->mask, BRCMF_E_ULP); | ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ drivers/net/wireless/broadcom/brcm80211/brcmfmac/../include/brcmu_utils.h:37:30: note: expanded from macro 'setbit' 37 | #define setbit(a, i) (((u8 *)a)[(i)/NBBY] |= 1<<((i)%NBBY)) | ^ ~~~~~~~~ drivers/net/wireless/broadcom/brcm80211/brcmfmac/fweh.h:313:2: note: array 'mask' declared here 313 | u8 mask[1]; | ^ 1 error generated.

…nk-up * Fixes build with Clang. drivers/pci/controller/pcie-brcmstb.c:1595:3: error: variable 'clkreq_cntl' is uninitialized when used here [-Werror,-Wuninitialized] 1595 | clkreq_cntl |= PCIE_MISC_HARD_PCIE_HARD_DEBUG_CLKREQ_DEBUG_ENABLE_MASK; | ^~~~~~~~~~~ drivers/pci/controller/pcie-brcmstb.c:1578:17: note: initialize the variable 'clkreq_cntl' to silence this warning 1578 | u32 clkreq_cntl; | ^ | = 0 1 error generated.

* Change SND_PIMIDI and SND_PISOUND_MICRO to select CRC8 instead of depend on it. * Fixes build with Clang. sound/drivers/upisnd/upisnd_codec.c:741:6: error: variable 'ret' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] 741 | if (adau->clk_src != ADAU1961_CLK_SRC_MCLK) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ sound/drivers/upisnd/upisnd_codec.c:744:9: note: uninitialized use occurs here 744 | return ret; | ^~~ sound/drivers/upisnd/upisnd_codec.c:741:2: note: remove the 'if' if its condition is always true 741 | if (adau->clk_src != ADAU1961_CLK_SRC_MCLK) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 742 | ret = snd_soc_dapm_add_routes(dapm, &adau1961_dapm_pll_route, 1); sound/drivers/upisnd/upisnd_codec.c:739:9: note: initialize the variable 'ret' to silence this warning 739 | int ret; | ^ | = 0 1 error generated.

* Fixes build with Clang. sound/soc/bcm/hifiberry_studio_dac8x.c:770:41: error: equality comparison with extraneous parentheses [-Werror,-Wparentheses-equality] 770 | if ((priv->card_info.card_clk_options == 0x02)) { | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~ sound/soc/bcm/hifiberry_studio_dac8x.c:770:41: note: remove extraneous parentheses around the comparison to silence this warning 770 | if ((priv->card_info.card_clk_options == 0x02)) { | ~ ^ ~ sound/soc/bcm/hifiberry_studio_dac8x.c:770:41: note: use '=' to turn this equality comparison into an assignment 770 | if ((priv->card_info.card_clk_options == 0x02)) { | ^~ | = 1 error generated.

KonstaT · 2026-04-09T18:10:12Z

Done. Split the PIO_ORIGIN_ANY change to #7309.

RP1_PIO_ORIGIN_ANY is defined elsewhere as ((uint16_t)(~0)).
https://github.com/raspberrypi/linux/blob/rpi-6.18.y/include/uapi/misc/rp1_pio_if.h#L16

Not familiar with the code so not sure why PIO_ORIGIN_ANY is defined here as ((uint)(~0)).

Would
#define PIO_ORIGIN_ANY RP1_PIO_ORIGIN_ANY
actually be more clear if it's fine otherwise?

KonstaT · 2026-04-10T13:23:12Z

Thanks for the merge!

Couple of follow up questions.

At what point do you generally start merging the sublevel releases (i.e. 6.18.y in this case) instead of rebasing Raspberry Pi specific patches on top? It's a bit tedious for downstream maintainer, that's all. E.g. in my case I'm merging this with AOSP common kernel source with few additional patches on top (few less now thanks to this :)).
Could you consider adding a build target to CI that uses Clang compiler to avoid similar problems in the future? Clang diagnostics seems to be better at picking up possible issues.

popcornmix · 2026-04-10T13:26:44Z

when the kernel reaches apt. Probably within the next few weeks.

KonstaT mentioned this pull request Apr 2, 2026

Enable CONFIG_RUST support (for dkms bcachefs) #7289

Open

popcornmix force-pushed the rpi-6.18.y branch from 21da81b to 5558a45 Compare April 8, 2026 13:43

KonstaT force-pushed the rpi-6.18.y-clang branch from cc6a4fb to 2033fd9 Compare April 9, 2026 07:29

KonstaT added 6 commits April 9, 2026 20:58

KonstaT force-pushed the rpi-6.18.y-clang branch from 2033fd9 to e166a8c Compare April 9, 2026 17:59

KonstaT mentioned this pull request Apr 9, 2026

Fix Clang 22 warnings part 2 #7309

Closed

pelwell merged commit eb7cf94 into raspberrypi:rpi-6.18.y Apr 10, 2026
11 of 12 checks passed

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Fix Clang 22 warnings#7299

Fix Clang 22 warnings#7299
pelwell merged 6 commits intoraspberrypi:rpi-6.18.yfrom
KonstaT:rpi-6.18.y-clang

KonstaT commented Apr 2, 2026 •

edited

Loading

Uh oh!

6by9 commented Apr 7, 2026

Uh oh!

popcornmix commented Apr 9, 2026

Uh oh!

pelwell commented Apr 9, 2026

Uh oh!

KonstaT commented Apr 9, 2026 •

edited

Loading

Uh oh!

Uh oh!

KonstaT commented Apr 10, 2026

Uh oh!

popcornmix commented Apr 10, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

Conversation

KonstaT commented Apr 2, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

6by9 commented Apr 7, 2026

Uh oh!

popcornmix commented Apr 9, 2026

Uh oh!

pelwell commented Apr 9, 2026

Uh oh!

KonstaT commented Apr 9, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

Uh oh!

KonstaT commented Apr 10, 2026

Uh oh!

popcornmix commented Apr 10, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

KonstaT commented Apr 2, 2026 •

edited

Loading

KonstaT commented Apr 9, 2026 •

edited

Loading