linux-kernel - [PATCH 05/26] cinergyT2-fe: don't do DMA on stack

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Date:   Fri,  7 Oct 2016 14:24:15 -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 05/26] cinergyT2-fe: 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/cinergyT2-fe.c | 45 ++++++++++++++++----------------
 1 file changed, 23 insertions(+), 22 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/cinergyT2-fe.c b/drivers/media/usb/dvb-usb/cinergyT2-fe.c
index fd8edcb56e61..03ba66ef1f28 100644
--- a/drivers/media/usb/dvb-usb/cinergyT2-fe.c
+++ b/drivers/media/usb/dvb-usb/cinergyT2-fe.c
@@ -139,6 +139,9 @@ static uint16_t compute_tps(struct dtv_frontend_properties *op)
 struct cinergyt2_fe_state {
 	struct dvb_frontend fe;
 	struct dvb_usb_device *d;
+
+	unsigned char data[64];
+
 	struct dvbt_get_status_msg status;
 };
 
@@ -146,28 +149,28 @@ static int cinergyt2_fe_read_status(struct dvb_frontend *fe,
 				    enum fe_status *status)
 {
 	struct cinergyt2_fe_state *state = fe->demodulator_priv;
-	struct dvbt_get_status_msg result;
-	u8 cmd[] = { CINERGYT2_EP1_GET_TUNER_STATUS };
 	int ret;
 
-	ret = dvb_usb_generic_rw(state->d, cmd, sizeof(cmd), (u8 *)&result,
-			sizeof(result), 0);
+	state->data[0] = CINERGYT2_EP1_GET_TUNER_STATUS;
+
+	ret = dvb_usb_generic_rw(state->d, state->data, 1,
+				 state->data, sizeof(state->status), 0);
 	if (ret < 0)
 		return ret;
 
-	state->status = result;
+	memcpy(&state->status, state->data, sizeof(state->status));
 
 	*status = 0;
 
-	if (0xffff - le16_to_cpu(result.gain) > 30)
+	if (0xffff - le16_to_cpu(state->status.gain) > 30)
 		*status |= FE_HAS_SIGNAL;
-	if (result.lock_bits & (1 << 6))
+	if (state->status.lock_bits & (1 << 6))
 		*status |= FE_HAS_LOCK;
-	if (result.lock_bits & (1 << 5))
+	if (state->status.lock_bits & (1 << 5))
 		*status |= FE_HAS_SYNC;
-	if (result.lock_bits & (1 << 4))
+	if (state->status.lock_bits & (1 << 4))
 		*status |= FE_HAS_CARRIER;
-	if (result.lock_bits & (1 << 1))
+	if (state->status.lock_bits & (1 << 1))
 		*status |= FE_HAS_VITERBI;
 
 	if ((*status & (FE_HAS_CARRIER | FE_HAS_VITERBI | FE_HAS_SYNC)) !=
@@ -232,31 +235,29 @@ static int cinergyt2_fe_set_frontend(struct dvb_frontend *fe)
 {
 	struct dtv_frontend_properties *fep = &fe->dtv_property_cache;
 	struct cinergyt2_fe_state *state = fe->demodulator_priv;
-	struct dvbt_set_parameters_msg param;
-	char result[2];
+	struct dvbt_set_parameters_msg *param = (void *)state->data;
 	int err;
 
-	param.cmd = CINERGYT2_EP1_SET_TUNER_PARAMETERS;
-	param.tps = cpu_to_le16(compute_tps(fep));
-	param.freq = cpu_to_le32(fep->frequency / 1000);
-	param.flags = 0;
+	param->cmd = CINERGYT2_EP1_SET_TUNER_PARAMETERS;
+	param->tps = cpu_to_le16(compute_tps(fep));
+	param->freq = cpu_to_le32(fep->frequency / 1000);
+	param->flags = 0;
 
 	switch (fep->bandwidth_hz) {
 	default:
 	case 8000000:
-		param.bandwidth = 8;
+		param->bandwidth = 8;
 		break;
 	case 7000000:
-		param.bandwidth = 7;
+		param->bandwidth = 7;
 		break;
 	case 6000000:
-		param.bandwidth = 6;
+		param->bandwidth = 6;
 		break;
 	}
 
-	err = dvb_usb_generic_rw(state->d,
-			(char *)&param, sizeof(param),
-			result, sizeof(result), 0);
+	err = dvb_usb_generic_rw(state->d, state->data, sizeof(*param),
+				 state->data, 2, 0);
 	if (err < 0)
 		err("cinergyt2_fe_set_frontend() Failed! err=%d\n", err);
 
-- 
2.7.4