linux-kernel - Re: [PATCH] zd1211rw: Use DMA-aware buffer for usb transfer

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Date:	Fri, 16 May 2008 17:27:05 +0900 (JST)
From:	Atsushi Nemoto <anemo@....ocn.ne.jp>
To:	linville@...driver.com
Cc:	dsd@...too.org, kune@...ne-taler.de,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] zd1211rw: Use DMA-aware buffer for usb transfer

On Thu, 15 May 2008 15:16:47 -0400, "John W. Linville" <linville@...driver.com> wrote:
> This looks like a reasonable fix to me.  I would prefer to see a
> comment in the code indicating why you are reusing the "p" buffer
> instead of simply using "ret" directly.  Also, I think the style
> suggestion by Michael Buesch would make the code appear more idiomatic
> as well.

OK, revised.  Thank you for review.

------------------------------------------------------
Subject: [PATCH] zd1211rw: Use DMA-aware buffer for usb transfer
From: Atsushi Nemoto <anemo@....ocn.ne.jp>

The zd1211rw driver uses unaligned stack buffer for USB control
message.  But it might cause stack corruption on non-coherent
platform, such as MIPS.  Use DMA-aware buffers for USB transfer.

Signed-off-by: Atsushi Nemoto <anemo@....ocn.ne.jp>
---
 drivers/net/wireless/zd1211rw/zd_usb.c |   23 +++++++++++++++++------
 1 files changed, 17 insertions(+), 6 deletions(-)

diff --git a/drivers/net/wireless/zd1211rw/zd_usb.c b/drivers/net/wireless/zd1211rw/zd_usb.c
index 12e24f0..f9a9a5d 100644
--- a/drivers/net/wireless/zd1211rw/zd_usb.c
+++ b/drivers/net/wireless/zd1211rw/zd_usb.c
@@ -169,10 +169,11 @@ static int upload_code(struct usb_device *udev,
 	if (flags & REBOOT) {
 		u8 ret;
 
+		/* Use "DMA-aware" buffer. */
 		r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
 			USB_REQ_FIRMWARE_CONFIRM,
 			USB_DIR_IN | USB_TYPE_VENDOR,
-			0, 0, &ret, sizeof(ret), 5000 /* ms */);
+			0, 0, p, sizeof(ret), 5000 /* ms */);
 		if (r != sizeof(ret)) {
 			dev_err(&udev->dev,
 				"control request firmeware confirmation failed."
@@ -181,6 +182,7 @@ static int upload_code(struct usb_device *udev,
 				r = -ENODEV;
 			goto error;
 		}
+		ret = p[0];
 		if (ret & 0x80) {
 			dev_err(&udev->dev,
 				"Internal error while downloading."
@@ -312,22 +314,31 @@ int zd_usb_read_fw(struct zd_usb *usb, zd_addr_t addr, u8 *data, u16 len)
 {
 	int r;
 	struct usb_device *udev = zd_usb_to_usbdev(usb);
+	u8 *buf;
 
+	/* Use "DMA-aware" buffer. */
+	buf = kmalloc(len, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
 	r = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
 		USB_REQ_FIRMWARE_READ_DATA, USB_DIR_IN | 0x40, addr, 0,
-		data, len, 5000);
+		buf, len, 5000);
 	if (r < 0) {
 		dev_err(&udev->dev,
 			"read over firmware interface failed: %d\n", r);
-		return r;
+		goto exit;
 	} else if (r != len) {
 		dev_err(&udev->dev,
 			"incomplete read over firmware interface: %d/%d\n",
 			r, len);
-		return -EIO;
+		r = -EIO;
+		goto exit;
 	}
-
-	return 0;
+	r = 0;
+	memcpy(data, buf, len);
+exit:
+	kfree(buf);
+	return r;
 }
 
 #define urb_dev(urb) (&(urb)->dev->dev)
--
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