Patch "[media] cxusb: Use a dma capable buffer also for reading" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

[media] cxusb: Use a dma capable buffer also for reading

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cxusb-use-a-dma-capable-buffer-also-for-reading.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: =?UTF-8?q?Stefan=20Br=C3=BCns?= <[email protected]>
Date: Sun, 5 Feb 2017 12:57:59 -0200
Subject: [media] cxusb: Use a dma capable buffer also for reading
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From: Stefan Brüns <[email protected]>

commit 3f190e3aec212fc8c61e202c51400afa7384d4bc upstream.

Commit 17ce039b4e54 ("[media] cxusb: don't do DMA on stack") added a kmalloc'ed bounce buffer for writes, but missed to do the same for reads. As the read only happens after the write is finished, we can reuse the same buffer.

As dvb_usb_generic_rw handles a read length of 0 by itself, avoid calling it using the dvb_usb_generic_read wrapper function.

---
 drivers/media/usb/dvb-usb/cxusb.c |   15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

@@ -59,23 +59,24 @@ static int cxusb_ctrl_msg(struct dvb_usb
 			  u8 cmd, u8 *wbuf, int wlen, u8 *rbuf, int rlen)
 {
 	struct cxusb_state *st = d->priv;
-	int ret, wo;
+	int ret;
 
 	if (1 + wlen > MAX_XFER_SIZE) {
 		warn("i2c wr: len=%d is too big!\n", wlen);
 		return -EOPNOTSUPP;
 	}
 
-	wo = (rbuf == NULL || rlen == 0); /* write-only */
+	if (rlen > MAX_XFER_SIZE) {
+		warn("i2c rd: len=%d is too big!\n", rlen);
+		return -EOPNOTSUPP;
+	}
 
 	mutex_lock(&d->data_mutex);
 	st->data[0] = cmd;
 	memcpy(&st->data[1], wbuf, wlen);
-	if (wo)
-		ret = dvb_usb_generic_write(d, st->data, 1 + wlen);
-	else
-		ret = dvb_usb_generic_rw(d, st->data, 1 + wlen,
-					 rbuf, rlen, 0);
+	ret = dvb_usb_generic_rw(d, st->data, 1 + wlen, st->data, rlen, 0);
+	if (!ret && rbuf && rlen)
+		memcpy(rbuf, st->data, rlen);
 
 	mutex_unlock(&d->data_mutex);
 	return ret;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/dvb-usb-firmware-don-t-do-dma-on-stack.patch queue-4.9/cxusb-use-a-dma-capable-buffer-also-for-reading.patch