From 746375524bb6a93bc3ef7a3c2e8c916bfdfcb0b2 Mon Sep 17 00:00:00 2001 From: Nathan Chancellor Date: Thu, 10 Apr 2025 10:43:08 -0700 Subject: [PATCH] drm/sysfb: efidrm: Avoid clang -Wsometimes-uninitialized in efidrm_device_create() Clang warns (or errors with CONFIG_WERROR=y): drivers/gpu/drm/sysfb/efidrm.c:353:11: error: variable 'screen_base' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized] 353 | else if (mem_flags & EFI_MEMORY_WB) | ^~~~~~~~~~~~~~~~~~~~~~~~~ drivers/gpu/drm/sysfb/efidrm.c:356:7: note: uninitialized use occurs here 356 | if (!screen_base) | ^~~~~~~~~~~ drivers/gpu/drm/sysfb/efidrm.c:353:7: note: remove the 'if' if its condition is always true 353 | else if (mem_flags & EFI_MEMORY_WB) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 354 | screen_base = devm_memremap(&pdev->dev, mem->start, resource_size(mem), drivers/gpu/drm/sysfb/efidrm.c:261:27: note: initialize the variable 'screen_base' to silence this warning 261 | void __iomem *screen_base; | ^ | = NULL efidrm_get_mem_flags() can only return a mask that has at least one of the tested values set so the else case is impossible but clang's static analysis runs before inlining so it cannot know that. Initialize screen_base to NULL and add a defensive error message in case mem_flags were ever returned without one of the four valid values. Fixes: 32ae90c66fb6 ("drm/sysfb: Add efidrm for EFI displays") Reviewed-by: Thomas Zimmermann Signed-off-by: Nathan Chancellor Signed-off-by: Thomas Zimmermann Link: https://lore.kernel.org/r/20250410-efidrm-avoid-uninit-screen_info-warning-v2-1-b79646f58c24@kernel.org --- drivers/gpu/drm/sysfb/efidrm.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/sysfb/efidrm.c b/drivers/gpu/drm/sysfb/efidrm.c index af90064a4c04..3cfd5d2cbf48 100644 --- a/drivers/gpu/drm/sysfb/efidrm.c +++ b/drivers/gpu/drm/sysfb/efidrm.c @@ -258,7 +258,7 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv, struct drm_sysfb_device *sysfb; struct drm_device *dev; struct resource *mem = NULL; - void __iomem *screen_base; + void __iomem *screen_base = NULL; struct drm_plane *primary_plane; struct drm_crtc *crtc; struct drm_encoder *encoder; @@ -353,6 +353,8 @@ static struct efidrm_device *efidrm_device_create(struct drm_driver *drv, else if (mem_flags & EFI_MEMORY_WB) screen_base = devm_memremap(&pdev->dev, mem->start, resource_size(mem), MEMREMAP_WB); + else + drm_err(dev, "invalid mem_flags: 0x%llx\n", mem_flags); if (!screen_base) return ERR_PTR(-ENOMEM); iosys_map_set_vaddr_iomem(&sysfb->fb_addr, screen_base); -- 2.25.1