linux-kernel - [PATCH 06/26] cxusb: don't do DMA on stack

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Message-Id: <7727b11abd004f683589586082f1b00926d5dade.1475860773.git.mchehab@s-opensource.com>
Date:   Fri,  7 Oct 2016 14:24:16 -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 06/26] cxusb: 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.

Signed-off-by: Mauro Carvalho Chehab <mchehab@...pensource.com>
---
 drivers/media/usb/dvb-usb/cxusb.c | 20 +++++++-------------
 drivers/media/usb/dvb-usb/cxusb.h |  5 +++++
 2 files changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/cxusb.c b/drivers/media/usb/dvb-usb/cxusb.c
index 907ac01ae297..f3615349de52 100644
--- a/drivers/media/usb/dvb-usb/cxusb.c
+++ b/drivers/media/usb/dvb-usb/cxusb.c
@@ -45,9 +45,6 @@
 #include "si2168.h"
 #include "si2157.h"
 
-/* Max transfer size done by I2C transfer functions */
-#define MAX_XFER_SIZE  80
-
 /* debug */
 static int dvb_usb_cxusb_debug;
 module_param_named(debug, dvb_usb_cxusb_debug, int, 0644);
@@ -61,23 +58,20 @@ DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
 static int cxusb_ctrl_msg(struct dvb_usb_device *d,
 			  u8 cmd, u8 *wbuf, int wlen, u8 *rbuf, int rlen)
 {
+	struct cxusb_state *st = d->priv;
 	int wo = (rbuf == NULL || rlen == 0); /* write-only */
-	u8 sndbuf[MAX_XFER_SIZE];
 
-	if (1 + wlen > sizeof(sndbuf)) {
-		warn("i2c wr: len=%d is too big!\n",
-		     wlen);
+	if (1 + wlen > MAX_XFER_SIZE) {
+		warn("i2c wr: len=%d is too big!\n", wlen);
 		return -EOPNOTSUPP;
 	}
 
-	memset(sndbuf, 0, 1+wlen);
-
-	sndbuf[0] = cmd;
-	memcpy(&sndbuf[1], wbuf, wlen);
+	st->data[0] = cmd;
+	memcpy(&st->data[1], wbuf, wlen);
 	if (wo)
-		return dvb_usb_generic_write(d, sndbuf, 1+wlen);
+		return dvb_usb_generic_write(d, st->data, 1 + wlen);
 	else
-		return dvb_usb_generic_rw(d, sndbuf, 1+wlen, rbuf, rlen, 0);
+		return dvb_usb_generic_rw(d, st->data, 1 + wlen, rbuf, rlen, 0);
 }
 
 /* GPIO */
diff --git a/drivers/media/usb/dvb-usb/cxusb.h b/drivers/media/usb/dvb-usb/cxusb.h
index 527ff7905e15..18acda19527a 100644
--- a/drivers/media/usb/dvb-usb/cxusb.h
+++ b/drivers/media/usb/dvb-usb/cxusb.h
@@ -28,10 +28,15 @@
 #define CMD_ANALOG        0x50
 #define CMD_DIGITAL       0x51
 
+/* Max transfer size done by I2C transfer functions */
+#define MAX_XFER_SIZE  80
+
 struct cxusb_state {
 	u8 gpio_write_state[3];
 	struct i2c_client *i2c_client_demod;
 	struct i2c_client *i2c_client_tuner;
+
+	unsigned char data[MAX_XFER_SIZE];
 };
 
 #endif
-- 
2.7.4