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

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Message-ID: <20230815-void-drivers-mtd-nand-raw-vf610_nfc-v1-1-7cc65314c56c@google.com>
Date:   Tue, 15 Aug 2023 20:58:47 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Stefan Agner <stefan@...er.ch>,
        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-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] mtd: rawnand: fix -Wvoid-pointer-to-enum-cast warning

When building with clang 18 I see the following warning:
|       drivers/mtd/nand/raw/vf610_nfc.c:853:17: warning: cast to smaller integer
|               type 'enum vf610_nfc_variant' from 'const void *' [-Wvoid-pointer-to-enum-cast]
|         853 |         nfc->variant = (enum vf610_nfc_variant)of_id->data;

This is due to the fact that `of_id->data` is a void* while `enum
vf610_nfc_variant` 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 actually occurring here due to the
fact that `enum vf610_nfc_variant` only has a few fields which are not
nearly large enough to cause data loss. This patch helps towards the
goal of eventually enabling this warning.

Also, should we use `unsigned long` here instead of `uintptr_t`? I've
seen maintainers request both and I'm flipping a coin here.
---
 drivers/mtd/nand/raw/vf610_nfc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/vf610_nfc.c b/drivers/mtd/nand/raw/vf610_nfc.c
index 86522048e271..11d996dc655d 100644
--- a/drivers/mtd/nand/raw/vf610_nfc.c
+++ b/drivers/mtd/nand/raw/vf610_nfc.c
@@ -850,7 +850,7 @@ static int vf610_nfc_probe(struct platform_device *pdev)
 		goto err_disable_clk;
 	}
 
-	nfc->variant = (enum vf610_nfc_variant)of_id->data;
+	nfc->variant = (uintptr_t)of_id->data;
 
 	for_each_available_child_of_node(nfc->dev->of_node, child) {
 		if (of_device_is_compatible(child, "fsl,vf610-nfc-nandcs")) {

---
base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
change-id: 20230815-void-drivers-mtd-nand-raw-vf610_nfc-6c358f424b8a

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