rtl8187: use DMA-aware buffers with usb_control_msg

Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/net/wireless/rtl818x/rtl8187.h b/drivers/net/wireless/rtl818x/rtl8187.h
index 9718f61..edeff82 100644
--- a/drivers/net/wireless/rtl818x/rtl8187.h
+++ b/drivers/net/wireless/rtl818x/rtl8187.h
@@ -120,6 +120,12 @@
 		__le64 buf;
 		struct sk_buff_head queue;
 	} b_tx_status; /* This queue is used by both -b and non-b devices */
+	struct mutex io_mutex;
+	union {
+		u8 bits8;
+		__le16 bits16;
+		__le32 bits32;
+	} *io_dmabuf;
 };
 
 void rtl8187_write_phy(struct ieee80211_hw *dev, u8 addr, u32 data);
@@ -129,10 +135,14 @@
 {
 	u8 val;
 
+	mutex_lock(&priv->io_mutex);
 	usb_control_msg(priv->udev, usb_rcvctrlpipe(priv->udev, 0),
 			RTL8187_REQ_GET_REG, RTL8187_REQT_READ,
-			(unsigned long)addr, idx & 0x03, &val,
-			sizeof(val), HZ / 2);
+			(unsigned long)addr, idx & 0x03,
+			&priv->io_dmabuf->bits8, sizeof(val), HZ / 2);
+
+	val = priv->io_dmabuf->bits8;
+	mutex_unlock(&priv->io_mutex);
 
 	return val;
 }
@@ -147,10 +157,14 @@
 {
 	__le16 val;
 
+	mutex_lock(&priv->io_mutex);
 	usb_control_msg(priv->udev, usb_rcvctrlpipe(priv->udev, 0),
 			RTL8187_REQ_GET_REG, RTL8187_REQT_READ,
-			(unsigned long)addr, idx & 0x03, &val,
-			sizeof(val), HZ / 2);
+			(unsigned long)addr, idx & 0x03,
+			&priv->io_dmabuf->bits16, sizeof(val), HZ / 2);
+
+	val = priv->io_dmabuf->bits16;
+	mutex_unlock(&priv->io_mutex);
 
 	return le16_to_cpu(val);
 }
@@ -165,10 +179,14 @@
 {
 	__le32 val;
 
+	mutex_lock(&priv->io_mutex);
 	usb_control_msg(priv->udev, usb_rcvctrlpipe(priv->udev, 0),
 			RTL8187_REQ_GET_REG, RTL8187_REQT_READ,
-			(unsigned long)addr, idx & 0x03, &val,
-			sizeof(val), HZ / 2);
+			(unsigned long)addr, idx & 0x03,
+			&priv->io_dmabuf->bits32, sizeof(val), HZ / 2);
+
+	val = priv->io_dmabuf->bits32;
+	mutex_unlock(&priv->io_mutex);
 
 	return le32_to_cpu(val);
 }
@@ -181,10 +199,15 @@
 static inline void rtl818x_iowrite8_idx(struct rtl8187_priv *priv,
 					u8 *addr, u8 val, u8 idx)
 {
+	mutex_lock(&priv->io_mutex);
+
+	priv->io_dmabuf->bits8 = val;
 	usb_control_msg(priv->udev, usb_sndctrlpipe(priv->udev, 0),
 			RTL8187_REQ_SET_REG, RTL8187_REQT_WRITE,
-			(unsigned long)addr, idx & 0x03, &val,
-			sizeof(val), HZ / 2);
+			(unsigned long)addr, idx & 0x03,
+			&priv->io_dmabuf->bits8, sizeof(val), HZ / 2);
+
+	mutex_unlock(&priv->io_mutex);
 }
 
 static inline void rtl818x_iowrite8(struct rtl8187_priv *priv, u8 *addr, u8 val)
@@ -195,12 +218,15 @@
 static inline void rtl818x_iowrite16_idx(struct rtl8187_priv *priv,
 					 __le16 *addr, u16 val, u8 idx)
 {
-	__le16 buf = cpu_to_le16(val);
+	mutex_lock(&priv->io_mutex);
 
+	priv->io_dmabuf->bits16 = cpu_to_le16(val);
 	usb_control_msg(priv->udev, usb_sndctrlpipe(priv->udev, 0),
 			RTL8187_REQ_SET_REG, RTL8187_REQT_WRITE,
-			(unsigned long)addr, idx & 0x03, &buf, sizeof(buf),
-			HZ / 2);
+			(unsigned long)addr, idx & 0x03,
+			&priv->io_dmabuf->bits16, sizeof(val), HZ / 2);
+
+	mutex_unlock(&priv->io_mutex);
 }
 
 static inline void rtl818x_iowrite16(struct rtl8187_priv *priv, __le16 *addr,
@@ -212,12 +238,15 @@
 static inline void rtl818x_iowrite32_idx(struct rtl8187_priv *priv,
 					 __le32 *addr, u32 val, u8 idx)
 {
-	__le32 buf = cpu_to_le32(val);
+	mutex_lock(&priv->io_mutex);
 
+	priv->io_dmabuf->bits32 = cpu_to_le32(val);
 	usb_control_msg(priv->udev, usb_sndctrlpipe(priv->udev, 0),
 			RTL8187_REQ_SET_REG, RTL8187_REQT_WRITE,
-			(unsigned long)addr, idx & 0x03, &buf, sizeof(buf),
-			HZ / 2);
+			(unsigned long)addr, idx & 0x03,
+			&priv->io_dmabuf->bits32, sizeof(val), HZ / 2);
+
+	mutex_unlock(&priv->io_mutex);
 }
 
 static inline void rtl818x_iowrite32(struct rtl8187_priv *priv, __le32 *addr,