linux-kernel - [PATCH 1/2] virtio_pci_modern: type-safe io accessors

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Date:	Sun, 15 Feb 2015 06:31:16 +0100
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	virtualization@...ts.linux-foundation.org
Subject: [PATCH 1/2] virtio_pci_modern: type-safe io accessors

The spec is very clear on this:

4.1.3.1 Driver Requirements: PCI Device Layout

The driver MUST access each field using the “natural” access method,
i.e. 32-bit accesses for 32-bit fields, 16-bit accesses for 16-bit
fields and 8-bit accesses for 8-bit fields.

Add type-safe wrappers to prevent access with incorrect width.

Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
 drivers/virtio/virtio_pci_modern.c | 37 +++++++++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/drivers/virtio/virtio_pci_modern.c b/drivers/virtio/virtio_pci_modern.c
index 2aa38e5..4e73ef7 100644
--- a/drivers/virtio/virtio_pci_modern.c
+++ b/drivers/virtio/virtio_pci_modern.c
@@ -20,6 +20,43 @@
 #define VIRTIO_PCI_NO_LEGACY
 #include "virtio_pci_common.h"
 
+/*
+ * Type-safe wrappers for io accesses.
+ * Use these to enforce at compile time the following spec requirement:
+ *
+ * The driver MUST access each field using the “natural” access
+ * method, i.e. 32-bit accesses for 32-bit fields, 16-bit accesses
+ * for 16-bit fields and 8-bit accesses for 8-bit fields.
+ */
+static inline u8 vp_ioread8(u8 __iomem *addr)
+{
+	return ioread8(addr);
+}
+static inline u16 vp_ioread16 (u16 __iomem *addr)
+{
+	return ioread16(addr);
+}
+
+static inline u32 vp_ioread32(u32 __iomem *addr)
+{
+	return ioread32(addr);
+}
+
+static inline void vp_iowrite8(u8 value, u8 __iomem *addr)
+{
+	iowrite8(value, addr);
+}
+
+static inline void vp_iowrite16(u16 value, u16 __iomem *addr)
+{
+	iowrite16(value, addr);
+}
+
+static inline void vp_iowrite32(u32 value, u32 __iomem *addr)
+{
+	iowrite16(value, addr);
+}
+
 static void __iomem *map_capability(struct pci_dev *dev, int off,
 				    size_t minlen,
 				    u32 align,
-- 
MST

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