linux-kernel - [PATCH] power: vexpress: fix -Wvoid-pointer-to-enum-cast warning

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Message-ID: <20230814-void-drivers-power-reset-vexpress-poweroff-v1-1-c3d9b0107e5d@google.com>
Date:   Mon, 14 Aug 2023 22:21:51 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Sebastian Reichel <sre@...nel.org>,
        Liviu Dudau <liviu.dudau@....com>,
        Sudeep Holla <sudeep.holla@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>
Cc:     linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] power: vexpress: fix -Wvoid-pointer-to-enum-cast warning

When building with clang 18 I see the following warning:
|       drivers/power/reset/vexpress-poweroff.c:124:10: warning: cast to smaller integer type 'enum vexpress_reset_func' from 'const void *' [-Wvoid-pointer-to-enum-cast]
|         124 |         switch ((enum vexpress_reset_func)match->data) {

This is due to the fact that `match->data` is a void* while `enum vexpress_reset_func`
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: In this case, it seems unlikely that any data loss is occurring
since `enum vexpress_reset_func` only has a few fields enumerated from 0.
---
 drivers/power/reset/vexpress-poweroff.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/power/reset/vexpress-poweroff.c b/drivers/power/reset/vexpress-poweroff.c
index 447ffdacddf9..17064d7b19f6 100644
--- a/drivers/power/reset/vexpress-poweroff.c
+++ b/drivers/power/reset/vexpress-poweroff.c
@@ -121,7 +121,7 @@ static int vexpress_reset_probe(struct platform_device *pdev)
 		return PTR_ERR(regmap);
 	dev_set_drvdata(&pdev->dev, regmap);
 
-	switch ((enum vexpress_reset_func)match->data) {
+	switch ((uintptr_t)match->data) {
 	case FUNC_SHUTDOWN:
 		vexpress_power_off_device = &pdev->dev;
 		pm_power_off = vexpress_power_off;

---
base-commit: 2ccdd1b13c591d306f0401d98dedc4bdcd02b421
change-id: 20230814-void-drivers-power-reset-vexpress-poweroff-ca762488cf1f

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