[media] digitv: don't do DMA on stack

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.
Reviewed-by: Patrick Boettcher <patrick.boettcher@posteo.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>

drivers/media/usb/dvb-usb/digitv.c

@@ -28,20 +28,22 @@ DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
 static int digitv_ctrl_msg(struct dvb_usb_device *d,
 		u8 cmd, u8 vv, u8 *wbuf, int wlen, u8 *rbuf, int rlen)
 {
+	struct digitv_state *st = d->priv;
 	int wo = (rbuf == NULL || rlen == 0); /* write-only */
-	u8 sndbuf[7],rcvbuf[7];
-	memset(sndbuf,0,7); memset(rcvbuf,0,7);
 
-	sndbuf[0] = cmd;
-	sndbuf[1] = vv;
-	sndbuf[2] = wo ? wlen : rlen;
+	memset(st->sndbuf, 0, 7);
+	memset(st->rcvbuf, 0, 7);
+
+	st->sndbuf[0] = cmd;
+	st->sndbuf[1] = vv;
+	st->sndbuf[2] = wo ? wlen : rlen;
 
 	if (wo) {
-		memcpy(&sndbuf[3],wbuf,wlen);
-		dvb_usb_generic_write(d,sndbuf,7);
+		memcpy(&st->sndbuf[3], wbuf, wlen);
+		dvb_usb_generic_write(d, st->sndbuf, 7);
 	} else {
-		dvb_usb_generic_rw(d,sndbuf,7,rcvbuf,7,10);
-		memcpy(rbuf,&rcvbuf[3],rlen);
+		dvb_usb_generic_rw(d, st->sndbuf, 7, st->rcvbuf, 7, 10);
+		memcpy(rbuf, &st->rcvbuf[3], rlen);
 	}
 	return 0;
 }

drivers/media/usb/dvb-usb/digitv.h

@@ -5,7 +5,10 @@
 #include "dvb-usb.h"
 
 struct digitv_state {
-    int is_nxt6000;
+	int is_nxt6000;
+
+	unsigned char sndbuf[7];
+	unsigned char rcvbuf[7];
 };
 
 /* protocol (from usblogging and the SDK: