at76c50x-usb: clean up DMA on stack

Cleanup dma on stack issues:

- no DMA on stack
- cleanup unclear endianness issue

Corrected version of Oliver Neukum's original patch for at76_usb.
Signed-off-by: Jason Andryuk <jandryuk@gmail.com>
Signed-off-by: Kalle Valo <kalle.valo@iki.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

drivers/net/wireless/at76c50x-usb.c

@@ -580,18 +580,25 @@ static int at76_remap(struct usb_device *udev)
 static int at76_get_op_mode(struct usb_device *udev)
 {
 	int ret;
-	u8 op_mode;
+	u8 saved;
+	u8 *op_mode;
 
+	op_mode = kmalloc(1, GFP_NOIO);
+	if (!op_mode)
+		return -ENOMEM;
 	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0), 0x33,
 			      USB_TYPE_VENDOR | USB_DIR_IN |
-			      USB_RECIP_INTERFACE, 0x01, 0, &op_mode, 1,
+			      USB_RECIP_INTERFACE, 0x01, 0, op_mode, 1,
 			      USB_CTRL_GET_TIMEOUT);
+	saved = *op_mode;
+	kfree(op_mode);
+
 	if (ret < 0)
 		return ret;
 	else if (ret < 1)
 		return -EIO;
 	else
-		return op_mode;
+		return saved;
 }
 
 /* Load a block of the second ("external") part of the firmware */
@@ -704,21 +711,25 @@ static inline int at76_get_mib(struct usb_device *udev, u16 mib, void *buf,
 /* Return positive number for status, negative for an error */
 static inline int at76_get_cmd_status(struct usb_device *udev, u8 cmd)
 {
-	u8 stat_buf[40];
+	u8 *stat_buf;
 	int ret;
 
+	stat_buf = kmalloc(40, GFP_NOIO);
+	if (!stat_buf)
+		return -ENOMEM;
+
 	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0), 0x22,
 			USB_TYPE_VENDOR | USB_DIR_IN |
 			USB_RECIP_INTERFACE, cmd, 0, stat_buf,
-			      sizeof(stat_buf), USB_CTRL_GET_TIMEOUT);
-	if (ret < 0)
-		return ret;
+			40, USB_CTRL_GET_TIMEOUT);
+	if (ret >= 0)
+		ret = stat_buf[5];
+	kfree(stat_buf);
 
-	return stat_buf[5];
+	return ret;
 }
 
 #define MAKE_CMD_CASE(c) case (c): return #c
-
 static const char *at76_get_cmd_string(u8 cmd_status)
 {
 	switch (cmd_status) {
@@ -735,7 +746,7 @@ static const char *at76_get_cmd_string(u8 cmd_status)
 	return "UNKNOWN";
 }
 
-static int at76_set_card_command(struct usb_device *udev, int cmd, void *buf,
+static int at76_set_card_command(struct usb_device *udev, u8 cmd, void *buf,
 				 int buf_size)
 {
 	int ret;