linux-kernel - [PATCH] net: nixge: fix -Wvoid-pointer-to-enum-cast warning

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Message-ID: <20230815-void-drivers-net-ethernet-ni-nixge-v1-1-f096a6e43038@google.com>
Date:   Tue, 15 Aug 2023 20:50:13 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] net: nixge: fix -Wvoid-pointer-to-enum-cast warning

When building with clang 18 I see the following warning:
|       drivers/net/ethernet/ni/nixge.c:1273:12: warning: cast to smaller integer
|               type 'enum nixge_version' from 'const void *' [-Wvoid-pointer-to-enum-cast]
|        1273 |         version = (enum nixge_version)of_id->data;

This is due to the fact that `of_id->data` is a void* while `enum nixge_version`
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 since `enum nixge_version`
has only a few fields which aren't nearly large enough to cause data
loss. However, this patch still works towards the goal of enabling this
warning for more builds by reducing noise.
---
 drivers/net/ethernet/ni/nixge.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ni/nixge.c b/drivers/net/ethernet/ni/nixge.c
index 0fd156286d4d..105977804e6a 100644
--- a/drivers/net/ethernet/ni/nixge.c
+++ b/drivers/net/ethernet/ni/nixge.c
@@ -1270,7 +1270,7 @@ static int nixge_of_get_resources(struct platform_device *pdev)
 	if (!of_id)
 		return -ENODEV;
 
-	version = (enum nixge_version)of_id->data;
+	version = (uintptr_t)of_id->data;
 	if (version <= NIXGE_V2)
 		priv->dma_regs = devm_platform_get_and_ioremap_resource(pdev, 0, NULL);
 	else

---
base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
change-id: 20230815-void-drivers-net-ethernet-ni-nixge-37b465831af0

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