linux-kernel - [PATCH] mtd: maps: fix -Wvoid-pointer-to-enum-cast warning

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Date:   Tue, 15 Aug 2023 21:11:12 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Linus Walleij <linus.walleij@...aro.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Richard Weinberger <richard@....at>,
        Vignesh Raghavendra <vigneshr@...com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>
Cc:     linux-arm-kernel@...ts.infradead.org,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] mtd: maps: fix -Wvoid-pointer-to-enum-cast warning

When building with clang 18 I see the following warning:
|       drivers/mtd/maps/physmap-versatile.c:209:25: warning: cast to smaller
|               integer type 'enum versatile_flashprot' from 'const void *' [-Wvoid-pointer-to-enum-cast]
|         209 |                 versatile_flashprot = (enum versatile_flashprot)devid->data;

This is due to the fact that `devid->data` is a void* while `enum
versatile_flashprot` has the size of an int. This leads to truncation
and possible data loss.

Link: https://github.com/ClangBuiltLinux/linux/issues/1910
Reported-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: There is likely no data loss occurring here due to the fact that
`enum versatile_flashprot` has only a few enumerated fields, none of
which are large enough to cause data loss. Nonetheless, this patch helps
towards the goal of eventually enabling this warning for more builds.

Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
 drivers/mtd/maps/physmap-versatile.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/maps/physmap-versatile.c b/drivers/mtd/maps/physmap-versatile.c
index a1b8b7b25f88..d65cf8833771 100644
--- a/drivers/mtd/maps/physmap-versatile.c
+++ b/drivers/mtd/maps/physmap-versatile.c
@@ -206,7 +206,7 @@ int of_flash_probe_versatile(struct platform_device *pdev,
 		if (!sysnp)
 			return -ENODEV;
 
-		versatile_flashprot = (enum versatile_flashprot)devid->data;
+		versatile_flashprot = (uintptr_t)devid->data;
 		rmap = syscon_node_to_regmap(sysnp);
 		of_node_put(sysnp);
 		if (IS_ERR(rmap))

---
base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
change-id: 20230815-void-drivers-mtd-maps-physmap-versatile-2270fe7fdf16

Best regards,
--
Justin Stitt <justinstitt@...gle.com>