linux-kernel - [PATCH] soc: renesas: rmobile-sysc: fix -Wvoid-pointer-to-enum-cast warning

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Message-ID: <20230814-void-drivers-soc-renesas-rmobile-sysc-v1-1-6648dfd854de@google.com>
Date:   Mon, 14 Aug 2023 22:11:28 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Magnus Damm <magnus.damm@...il.com>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>
Cc:     linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        llvm@...ts.linux.dev, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] soc: renesas: rmobile-sysc: fix -Wvoid-pointer-to-enum-cast warning

When building with clang 18 I see the following warning:
|      drivers/soc/renesas/rmobile-sysc.c:193:22: warning: cast to smaller integer
|               type 'enum pd_types' from 'const void *' [-Wvoid-pointer-to-enum-cast]
|        193 |                 add_special_pd(np, (enum pd_types)id->data);

This is due to the fact that `id->data` is a void* and `enum pd_types`
has the size of an integer. This cast from pointer-width to int-width
causes truncation and possible data loss. Instead, cast to `uintptr_t`
which has the same width as void*.

Link: https://github.com/ClangBuiltLinux/linux/issues/1910
Reported-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Note: It should be noted that there is likely no data loss occurring in
this case since the enum only has a few fields. The narrowing cast from
pointer to int will not lose any data.
---
 drivers/soc/renesas/rmobile-sysc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/soc/renesas/rmobile-sysc.c b/drivers/soc/renesas/rmobile-sysc.c
index 912daadaa10d..0b77f37787d5 100644
--- a/drivers/soc/renesas/rmobile-sysc.c
+++ b/drivers/soc/renesas/rmobile-sysc.c
@@ -190,7 +190,7 @@ static void __init get_special_pds(void)
 
 	/* PM domains containing other special devices */
 	for_each_matching_node_and_match(np, special_ids, &id)
-		add_special_pd(np, (enum pd_types)id->data);
+		add_special_pd(np, (uintptr_t)id->data);
 }
 
 static void __init put_special_pds(void)

---
base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
change-id: 20230814-void-drivers-soc-renesas-rmobile-sysc-98150a2571cc

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