linux-kernel - [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn

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Message-Id: <20180225172236.29650-6-malat@debian.org>
Date:   Sun, 25 Feb 2018 18:22:20 +0100
From:   Mathieu Malaterre <malat@...ian.org>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Jiri Slaby <jslaby@...e.com>, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, Mathieu Malaterre <malat@...ian.org>
Subject: [PATCH 05/21] powerpc: Avoid comparison of unsigned long >= 0 in pfn_valid

Rewrite comparison since all values compared are of type `unsigned long`.

Fix a warning (treated as error in W=1):

  CC      arch/powerpc/kernel/irq.o
In file included from ./include/linux/bug.h:5:0,
                 from ./include/linux/cpumask.h:13,
                 from ./include/linux/smp.h:13,
                 from ./include/linux/kernel_stat.h:5,
                 from arch/powerpc/kernel/irq.c:35:
./include/linux/dma-mapping.h: In function ‘dma_map_resource’:
./arch/powerpc/include/asm/page.h:129:32: error: comparison of unsigned expression >= 0 is always true [-Werror=type-limits]
 #define pfn_valid(pfn)  ((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr)
                                ^
Suggested-by: Segher Boessenkool <segher@...nel.crashing.org>
Signed-off-by: Mathieu Malaterre <malat@...ian.org>
---
 arch/powerpc/include/asm/page.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/page.h b/arch/powerpc/include/asm/page.h
index 8da5d4c1cab2..19dea64e7ed2 100644
--- a/arch/powerpc/include/asm/page.h
+++ b/arch/powerpc/include/asm/page.h
@@ -126,7 +126,8 @@ extern long long virt_phys_offset;
 
 #ifdef CONFIG_FLATMEM
 #define ARCH_PFN_OFFSET		((unsigned long)(MEMORY_START >> PAGE_SHIFT))
-#define pfn_valid(pfn)		((pfn) >= ARCH_PFN_OFFSET && (pfn) < max_mapnr)
+#define pfn_valid(pfn) \
+		(((pfn) - ARCH_PFN_OFFSET) < (max_mapnr - ARCH_PFN_OFFSET))
 #endif
 
 #define virt_to_pfn(kaddr)	(__pa(kaddr) >> PAGE_SHIFT)
-- 
2.11.0