linux-kernel - [PATCH v2] rust: helpers: Remove volatile qualifier from io helpers

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Message-ID: <20250412005341.157150-1-fujita.tomonori@gmail.com>
Date: Sat, 12 Apr 2025 09:53:41 +0900
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: rust-for-linux@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	linux-um@...ts.infradead.org,
	richard@....at,
	anton.ivanov@...bridgegreys.com,
	johannes@...solutions.net,
	geert@...ux-m68k.org,
	logang@...tatee.com,
	sbates@...thlin.com,
	dakr@...nel.org,
	dinguyen@...nel.org,
	miguel.ojeda.sandonis@...il.com,
	arnd@...db.de
Subject: [PATCH v2] rust: helpers: Remove volatile qualifier from io helpers

Remove the `volatile` qualifier used with __iomem in helper functions
in io.c. These helper functions are just wrappers around the
corresponding accessors so they are unnecessary.

This fixes the following UML build error with CONFIG_RUST enabled:

In file included from /home/fujita/git/linux-rust/rust/helpers/helpers.c:19:
/home/fujita/git/linux-rust/rust/helpers/io.c:12:10: error: passing 'volatile void *' to parameter of type 'void *' discards qualifiers [-Werror,-Wincompatible-pointer-types-discards-qualifiers]
   12 |         iounmap(addr);
      |                 ^~~~
/home/fujita/git/linux-rust/arch/um/include/asm/io.h:19:42: note: passing argument to parameter 'addr' here
   19 | static inline void iounmap(void __iomem *addr)
      |                                          ^
1 error generated.

Fixes: ce30d94e6855 ("rust: add `io::{Io, IoRaw}` base types")
Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
---
v2:
- remove all the volatile in io helpers instead of aligning UML's iounmap() with other
v1: https://lore.kernel.org/lkml/20250409061129.136788-1-fujita.tomonori@gmail.com/
---
 rust/helpers/io.c | 34 +++++++++++++++++-----------------
 1 file changed, 17 insertions(+), 17 deletions(-)

diff --git a/rust/helpers/io.c b/rust/helpers/io.c
index 4c2401ccd720..15ea187c5466 100644
--- a/rust/helpers/io.c
+++ b/rust/helpers/io.c
@@ -7,94 +7,94 @@ void __iomem *rust_helper_ioremap(phys_addr_t offset, size_t size)
 	return ioremap(offset, size);
 }
 
-void rust_helper_iounmap(volatile void __iomem *addr)
+void rust_helper_iounmap(void __iomem *addr)
 {
 	iounmap(addr);
 }
 
-u8 rust_helper_readb(const volatile void __iomem *addr)
+u8 rust_helper_readb(const void __iomem *addr)
 {
 	return readb(addr);
 }
 
-u16 rust_helper_readw(const volatile void __iomem *addr)
+u16 rust_helper_readw(const void __iomem *addr)
 {
 	return readw(addr);
 }
 
-u32 rust_helper_readl(const volatile void __iomem *addr)
+u32 rust_helper_readl(const void __iomem *addr)
 {
 	return readl(addr);
 }
 
 #ifdef CONFIG_64BIT
-u64 rust_helper_readq(const volatile void __iomem *addr)
+u64 rust_helper_readq(const void __iomem *addr)
 {
 	return readq(addr);
 }
 #endif
 
-void rust_helper_writeb(u8 value, volatile void __iomem *addr)
+void rust_helper_writeb(u8 value, void __iomem *addr)
 {
 	writeb(value, addr);
 }
 
-void rust_helper_writew(u16 value, volatile void __iomem *addr)
+void rust_helper_writew(u16 value, void __iomem *addr)
 {
 	writew(value, addr);
 }
 
-void rust_helper_writel(u32 value, volatile void __iomem *addr)
+void rust_helper_writel(u32 value, void __iomem *addr)
 {
 	writel(value, addr);
 }
 
 #ifdef CONFIG_64BIT
-void rust_helper_writeq(u64 value, volatile void __iomem *addr)
+void rust_helper_writeq(u64 value, void __iomem *addr)
 {
 	writeq(value, addr);
 }
 #endif
 
-u8 rust_helper_readb_relaxed(const volatile void __iomem *addr)
+u8 rust_helper_readb_relaxed(const void __iomem *addr)
 {
 	return readb_relaxed(addr);
 }
 
-u16 rust_helper_readw_relaxed(const volatile void __iomem *addr)
+u16 rust_helper_readw_relaxed(const void __iomem *addr)
 {
 	return readw_relaxed(addr);
 }
 
-u32 rust_helper_readl_relaxed(const volatile void __iomem *addr)
+u32 rust_helper_readl_relaxed(const void __iomem *addr)
 {
 	return readl_relaxed(addr);
 }
 
 #ifdef CONFIG_64BIT
-u64 rust_helper_readq_relaxed(const volatile void __iomem *addr)
+u64 rust_helper_readq_relaxed(const void __iomem *addr)
 {
 	return readq_relaxed(addr);
 }
 #endif
 
-void rust_helper_writeb_relaxed(u8 value, volatile void __iomem *addr)
+void rust_helper_writeb_relaxed(u8 value, void __iomem *addr)
 {
 	writeb_relaxed(value, addr);
 }
 
-void rust_helper_writew_relaxed(u16 value, volatile void __iomem *addr)
+void rust_helper_writew_relaxed(u16 value, void __iomem *addr)
 {
 	writew_relaxed(value, addr);
 }
 
-void rust_helper_writel_relaxed(u32 value, volatile void __iomem *addr)
+void rust_helper_writel_relaxed(u32 value, void __iomem *addr)
 {
 	writel_relaxed(value, addr);
 }
 
 #ifdef CONFIG_64BIT
-void rust_helper_writeq_relaxed(u64 value, volatile void __iomem *addr)
+void rust_helper_writeq_relaxed(u64 value, void __iomem *addr)
 {
 	writeq_relaxed(value, addr);
 }

base-commit: c59026c0570a2a97ce2e7d5ae5e9c48fc841542b
-- 
2.43.0