linux-kernel - [PATCH 1/6] [media] a800: get rid of on-stack dma buffers

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Date:	Mon, 21 Mar 2011 19:33:41 +0100
From:	Florian Mickler <florian@...kler.org>
To:	mchehab@...radead.org
Cc:	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
	js@...uxtv.org, tskd2@...oo.co.jp, liplianin@...by,
	g.marco@...enet.de, aet@...terburn.org, pb@...uxtv.org,
	mkrufky@...uxtv.org, nick@...k-andrew.net, max@...eto.com,
	janne-dvb@...nau.be, Florian Mickler <florian@...kler.org>
Subject: [PATCH 1/6] [media] a800: get rid of on-stack dma buffers

usb_control_msg initiates (and waits for completion of) a dma transfer using
the supplied buffer. That buffer thus has to be seperately allocated on
the heap.

In lib/dma_debug.c the function check_for_stack even warns about it:
	WARNING: at lib/dma-debug.c:866 check_for_stack

Note: This change is tested to compile only, as I don't have the hardware.

Signed-off-by: Florian Mickler <florian@...kler.org>
---
 drivers/media/dvb/dvb-usb/a800.c |   17 +++++++++++++----
 1 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/drivers/media/dvb/dvb-usb/a800.c b/drivers/media/dvb/dvb-usb/a800.c
index 53b93a4..fe2366b 100644
--- a/drivers/media/dvb/dvb-usb/a800.c
+++ b/drivers/media/dvb/dvb-usb/a800.c
@@ -78,17 +78,26 @@ static struct rc_map_table rc_map_a800_table[] = {
 
 static int a800_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
 {
-	u8 key[5];
+	int ret;
+	u8 *key = kmalloc(5, GFP_KERNEL);
+	if (!key)
+		return -ENOMEM;
+
 	if (usb_control_msg(d->udev,usb_rcvctrlpipe(d->udev,0),
 				0x04, USB_TYPE_VENDOR | USB_DIR_IN, 0, 0, key, 5,
-				2000) != 5)
-		return -ENODEV;
+				2000) != 5) {
+		ret = -ENODEV;
+		goto out;
+	}
 
 	/* call the universal NEC remote processor, to find out the key's state and event */
 	dvb_usb_nec_rc_key_to_event(d,key,event,state);
 	if (key[0] != 0)
 		deb_rc("key: %x %x %x %x %x\n",key[0],key[1],key[2],key[3],key[4]);
-	return 0;
+	ret = 0;
+out:
+	kfree(key);
+	return ret;
 }
 
 /* USB Driver stuff */
-- 
1.7.4.1

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