linux-kernel - [PATCH v2 29/31] s2255drv: don't use stack for DMA

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Message-Id: <474df449f4368f552aaa52d7ef77d4500f681bb3.1476179975.git.mchehab@s-opensource.com>
Date:   Tue, 11 Oct 2016 07:09:44 -0300
From:   Mauro Carvalho Chehab <mchehab@...pensource.com>
To:     Linux Media Mailing List <linux-media@...r.kernel.org>
Cc:     Mauro Carvalho Chehab <mchehab@....samsung.com>,
        Mauro Carvalho Chehab <mchehab@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Johannes Stezenbach <js@...uxtv.org>,
        Jiri Kosina <jikos@...nel.org>,
        Patrick Boettcher <patrick.boettcher@...teo.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Michael Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Jörg Otte <jrg.otte@...il.com>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Geunyoung Kim <nenggun.kim@...sung.com>,
        Inki Dae <inki.dae@...sung.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Junghak Sung <jh1009.sung@...sung.com>,
        Wolfram Sang <wsa-dev@...g-engineering.com>,
        Julia Lawall <Julia.Lawall@...6.fr>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>
Subject: [PATCH v2 29/31] s2255drv: don't use stack for DMA

From: Mauro Carvalho Chehab <mchehab@....samsung.com>

The USB control messages require DMA to work. We cannot pass
a stack-allocated buffer, as it is not warranted that the
stack would be into a DMA enabled area.

Signed-off-by: Mauro Carvalho Chehab <mchehab@....samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
---
 drivers/media/usb/s2255/s2255drv.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/s2255/s2255drv.c b/drivers/media/usb/s2255/s2255drv.c
index c3a0e87066eb..f7bb78c1873c 100644
--- a/drivers/media/usb/s2255/s2255drv.c
+++ b/drivers/media/usb/s2255/s2255drv.c
@@ -1901,19 +1901,30 @@ static long s2255_vendor_req(struct s2255_dev *dev, unsigned char Request,
 			     s32 TransferBufferLength, int bOut)
 {
 	int r;
+	unsigned char *buf;
+
+	buf = kmalloc(TransferBufferLength, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
 	if (!bOut) {
 		r = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0),
 				    Request,
 				    USB_TYPE_VENDOR | USB_RECIP_DEVICE |
 				    USB_DIR_IN,
-				    Value, Index, TransferBuffer,
+				    Value, Index, buf,
 				    TransferBufferLength, HZ * 5);
+
+		if (r >= 0)
+			memcpy(TransferBuffer, buf, TransferBufferLength);
 	} else {
+		memcpy(buf, TransferBuffer, TransferBufferLength);
 		r = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0),
 				    Request, USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-				    Value, Index, TransferBuffer,
+				    Value, Index, buf,
 				    TransferBufferLength, HZ * 5);
 	}
+	kfree(buf);
 	return r;
 }
 
-- 
2.7.4