linux-kernel - [PATCH] agp: define proper stubs for empty helpers

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Date:   Mon, 20 Sep 2021 14:17:19 +0200
From:   Arnd Bergmann <arnd@...nel.org>
To:     linux-fbdev@...r.kernel.org,
        "James E.J. Bottomley" <James.Bottomley@...senPartnership.com>,
        Helge Deller <deller@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     dri-devel@...ts.freedesktop.org, Arnd Bergmann <arnd@...db.de>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, sparclinux@...r.kernel.org
Subject: [PATCH] agp: define proper stubs for empty helpers

From: Arnd Bergmann <arnd@...db.de>

The empty unmap_page_from_agp() macro causes a warning when
building with 'make W=1' on a couple of architectures:

drivers/char/agp/generic.c: In function 'agp_generic_destroy_page':
drivers/char/agp/generic.c:1265:28: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
 1265 |   unmap_page_from_agp(page);

Change the definitions to a 'do { } while (0)' construct to
make these more reliable.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 arch/parisc/include/asm/agp.h  | 4 ++--
 arch/powerpc/include/asm/agp.h | 4 ++--
 arch/sparc/include/asm/agp.h   | 6 +++---
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/arch/parisc/include/asm/agp.h b/arch/parisc/include/asm/agp.h
index cb04470e63d0..14ae54cfd368 100644
--- a/arch/parisc/include/asm/agp.h
+++ b/arch/parisc/include/asm/agp.h
@@ -8,8 +8,8 @@
  *
  */
 
-#define map_page_into_agp(page)		/* nothing */
-#define unmap_page_from_agp(page)	/* nothing */
+#define map_page_into_agp(page)		do { } while (0)
+#define unmap_page_from_agp(page)	do { } while (0)
 #define flush_agp_cache()		mb()
 
 /* GATT allocation. Returns/accepts GATT kernel virtual address. */
diff --git a/arch/powerpc/include/asm/agp.h b/arch/powerpc/include/asm/agp.h
index b29b1186f819..6b6485c988dd 100644
--- a/arch/powerpc/include/asm/agp.h
+++ b/arch/powerpc/include/asm/agp.h
@@ -5,8 +5,8 @@
 
 #include <asm/io.h>
 
-#define map_page_into_agp(page)
-#define unmap_page_from_agp(page)
+#define map_page_into_agp(page) do {} while (0)
+#define unmap_page_from_agp(page) do {} while (0)
 #define flush_agp_cache() mb()
 
 /* GATT allocation. Returns/accepts GATT kernel virtual address. */
diff --git a/arch/sparc/include/asm/agp.h b/arch/sparc/include/asm/agp.h
index efe0d6a12e5a..2d0ff84cee3f 100644
--- a/arch/sparc/include/asm/agp.h
+++ b/arch/sparc/include/asm/agp.h
@@ -4,9 +4,9 @@
 
 /* dummy for now */
 
-#define map_page_into_agp(page)
-#define unmap_page_from_agp(page)
-#define flush_agp_cache() mb()
+#define map_page_into_agp(page)		do { } while (0)
+#define unmap_page_from_agp(page)	do { } while (0)
+#define flush_agp_cache()		mb()
 
 /* GATT allocation. Returns/accepts GATT kernel virtual address. */
 #define alloc_gatt_pages(order)		\
-- 
2.29.2