linux-kernel - [PATCH v2 11/31] digitv: don't do DMA on stack

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Message-Id: <94cc64233e2cdb8291a6b3a0f03d12880bce27b6.1476179975.git.mchehab@s-opensource.com>
Date:   Tue, 11 Oct 2016 07:09:26 -0300
From:   Mauro Carvalho Chehab <mchehab@...pensource.com>
To:     Linux Media Mailing List <linux-media@...r.kernel.org>
Cc:     Mauro Carvalho Chehab <mchehab@...pensource.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>
Subject: [PATCH v2 11/31] 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@...teo.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
---
 drivers/media/usb/dvb-usb/digitv.c | 20 +++++++++++---------
 drivers/media/usb/dvb-usb/digitv.h |  3 +++
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
index 63134335c994..09f8c28bd4db 100644
--- a/drivers/media/usb/dvb-usb/digitv.c
+++ b/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;
 }
diff --git a/drivers/media/usb/dvb-usb/digitv.h b/drivers/media/usb/dvb-usb/digitv.h
index 908c09f4966b..cf104689bdff 100644
--- a/drivers/media/usb/dvb-usb/digitv.h
+++ b/drivers/media/usb/dvb-usb/digitv.h
@@ -6,6 +6,9 @@
 
 struct digitv_state {
     int is_nxt6000;
+
+    unsigned char sndbuf[7];
+    unsigned char rcvbuf[7];
 };
 
 /* protocol (from usblogging and the SDK:
-- 
2.7.4