linux-kernel - [PATCH v2 18/31] gp8psk: don't do DMA on stack

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Date:   Tue, 11 Oct 2016 07:09:33 -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 18/31] gp8psk: 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/gp8psk.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/gp8psk.c b/drivers/media/usb/dvb-usb/gp8psk.c
index 5d0384dd45b5..fa215ad37f7b 100644
--- a/drivers/media/usb/dvb-usb/gp8psk.c
+++ b/drivers/media/usb/dvb-usb/gp8psk.c
@@ -24,6 +24,10 @@ MODULE_PARM_DESC(debug, "set debugging level (1=info,xfer=2,rc=4 (or-able))." DV
 
 DVB_DEFINE_MOD_OPT_ADAPTER_NR(adapter_nr);
 
+struct gp8psk_state {
+	unsigned char data[80];
+};
+
 static int gp8psk_get_fw_version(struct dvb_usb_device *d, u8 *fw_vers)
 {
 	return (gp8psk_usb_in_op(d, GET_FW_VERS, 0, 0, fw_vers, 6));
@@ -53,17 +57,19 @@ static void gp8psk_info(struct dvb_usb_device *d)
 
 int gp8psk_usb_in_op(struct dvb_usb_device *d, u8 req, u16 value, u16 index, u8 *b, int blen)
 {
+	struct gp8psk_state *st = d->priv;
 	int ret = 0,try = 0;
 
 	if ((ret = mutex_lock_interruptible(&d->usb_mutex)))
 		return ret;
 
 	while (ret >= 0 && ret != blen && try < 3) {
+		memcpy(st->data, b, blen);
 		ret = usb_control_msg(d->udev,
 			usb_rcvctrlpipe(d->udev,0),
 			req,
 			USB_TYPE_VENDOR | USB_DIR_IN,
-			value,index,b,blen,
+			value, index, st->data, blen,
 			2000);
 		deb_info("reading number %d (ret: %d)\n",try,ret);
 		try++;
@@ -86,6 +92,7 @@ int gp8psk_usb_in_op(struct dvb_usb_device *d, u8 req, u16 value, u16 index, u8
 int gp8psk_usb_out_op(struct dvb_usb_device *d, u8 req, u16 value,
 			     u16 index, u8 *b, int blen)
 {
+	struct gp8psk_state *st = d->priv;
 	int ret;
 
 	deb_xfer("out: req. %x, val: %x, ind: %x, buffer: ",req,value,index);
@@ -94,11 +101,12 @@ int gp8psk_usb_out_op(struct dvb_usb_device *d, u8 req, u16 value,
 	if ((ret = mutex_lock_interruptible(&d->usb_mutex)))
 		return ret;
 
+	memcpy(st->data, b, blen);
 	if (usb_control_msg(d->udev,
 			usb_sndctrlpipe(d->udev,0),
 			req,
 			USB_TYPE_VENDOR | USB_DIR_OUT,
-			value,index,b,blen,
+			value,index, st->data, blen,
 			2000) != blen) {
 		warn("usb out operation failed.");
 		ret = -EIO;
@@ -265,6 +273,8 @@ static struct dvb_usb_device_properties gp8psk_properties = {
 	.usb_ctrl = CYPRESS_FX2,
 	.firmware = "dvb-usb-gp8psk-01.fw",
 
+	.size_of_priv = sizeof(struct gp8psk_state),
+
 	.num_adapters = 1,
 	.adapter = {
 		{
-- 
2.7.4