linux-kernel - [PATCH] drm/exynos: Always initialize mapping in exynos_drm_register

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Message-Id: <20210727233656.753002-1-nathan@kernel.org>
Date:   Tue, 27 Jul 2021 16:36:56 -0700
From:   Nathan Chancellor <nathan@...nel.org>
To:     Inki Dae <inki.dae@...sung.com>,
        Joonyoung Shim <jy0922.shim@...sung.com>,
        Seung-Woo Kim <sw0312.kim@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...onical.com>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        clang-built-linux@...glegroups.com,
        Nathan Chancellor <nathan@...nel.org>,
        kernel test robot <lkp@...el.com>
Subject: [PATCH] drm/exynos: Always initialize mapping in exynos_drm_register_dma()

In certain randconfigs, clang warns:

drivers/gpu/drm/exynos/exynos_drm_dma.c:121:19: warning: variable
'mapping' is uninitialized when used here [-Wuninitialized]
                priv->mapping = mapping;
                                ^~~~~~~
drivers/gpu/drm/exynos/exynos_drm_dma.c:111:16: note: initialize the
variable 'mapping' to silence this warning
                void *mapping;
                             ^
                              = NULL
1 warning generated.

This occurs when CONFIG_EXYNOS_IOMMU is enabled and both
CONFIG_ARM_DMA_USE_IOMMU and CONFIG_IOMMU_DMA are disabled, which makes
the code look like

  void *mapping;

  if (0)
    mapping = arm_iommu_create_mapping()
  else if (0)
    mapping = iommu_get_domain_for_dev()

  ...
  priv->mapping = mapping;

Add an else branch that initializes mapping to the -ENODEV error pointer
so that there is no more warning and the driver does not change during
runtime.

Reported-by: kernel test robot <lkp@...el.com>
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/gpu/drm/exynos/exynos_drm_dma.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/exynos/exynos_drm_dma.c b/drivers/gpu/drm/exynos/exynos_drm_dma.c
index 0644936afee2..bf33c3084cb4 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_dma.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_dma.c
@@ -115,6 +115,8 @@ int exynos_drm_register_dma(struct drm_device *drm, struct device *dev,
 				EXYNOS_DEV_ADDR_START, EXYNOS_DEV_ADDR_SIZE);
 		else if (IS_ENABLED(CONFIG_IOMMU_DMA))
 			mapping = iommu_get_domain_for_dev(priv->dma_dev);
+		else
+			mapping = ERR_PTR(-ENODEV);
 
 		if (IS_ERR(mapping))
 			return PTR_ERR(mapping);

base-commit: 7d549995d4e0d99b68e8a7793a0d23da6fc40fe8
-- 
2.32.0.264.g75ae10bc75