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[PATCH v2 13/31] dtt200u-fe: don't do DMA on stack

From Mauro Carvalho Chehab <mchehab@s-opensource.com>
Newsgroups linux.kernel
Subject [PATCH v2 13/31] dtt200u-fe: don't do DMA on stack
Date 2016-10-11 12:20 +0200
Message-ID <sr2kb-5sy-53@gated-at.bofh.it> (permalink)
References <sr2k9-5sy-3@gated-at.bofh.it>
Organization linux.* mail to news gateway

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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@s-opensource.com>
---
 drivers/media/usb/dvb-usb/dtt200u-fe.c | 95 +++++++++++++++++++++++-----------
 1 file changed, 65 insertions(+), 30 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/dtt200u-fe.c b/drivers/media/usb/dvb-usb/dtt200u-fe.c
index 9bb15f7b48db..7f7f64be6353 100644
--- a/drivers/media/usb/dvb-usb/dtt200u-fe.c
+++ b/drivers/media/usb/dvb-usb/dtt200u-fe.c
@@ -18,17 +18,22 @@ struct dtt200u_fe_state {
 
 	struct dtv_frontend_properties fep;
 	struct dvb_frontend frontend;
+
+	unsigned char data[80];
+	struct mutex data_mutex;
 };
 
 static int dtt200u_fe_read_status(struct dvb_frontend *fe,
 				  enum fe_status *stat)
 {
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
-	u8 st = GET_TUNE_STATUS, b[3];
 
-	dvb_usb_generic_rw(state->d,&st,1,b,3,0);
+	mutex_lock(&state->data_mutex);
+	state->data[0] = GET_TUNE_STATUS;
 
-	switch (b[0]) {
+	dvb_usb_generic_rw(state->d, state->data, 1, state->data, 3, 0);
+
+	switch (state->data[0]) {
 		case 0x01:
 			*stat = FE_HAS_SIGNAL | FE_HAS_CARRIER |
 				FE_HAS_VITERBI | FE_HAS_SYNC | FE_HAS_LOCK;
@@ -41,51 +46,75 @@ static int dtt200u_fe_read_status(struct dvb_frontend *fe,
 			*stat = 0;
 			break;
 	}
+	mutex_unlock(&state->data_mutex);
 	return 0;
 }
 
 static int dtt200u_fe_read_ber(struct dvb_frontend* fe, u32 *ber)
 {
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
-	u8 bw = GET_VIT_ERR_CNT,b[3];
-	dvb_usb_generic_rw(state->d,&bw,1,b,3,0);
-	*ber = (b[0] << 16) | (b[1] << 8) | b[2];
+
+	mutex_lock(&state->data_mutex);
+	state->data[0] = GET_VIT_ERR_CNT;
+
+	dvb_usb_generic_rw(state->d, state->data, 1, state->data, 3, 0);
+	*ber = (state->data[0] << 16) | (state->data[1] << 8) | state->data[2];
+
+	mutex_unlock(&state->data_mutex);
 	return 0;
 }
 
 static int dtt200u_fe_read_unc_blocks(struct dvb_frontend* fe, u32 *unc)
 {
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
-	u8 bw = GET_RS_UNCOR_BLK_CNT,b[2];
 
-	dvb_usb_generic_rw(state->d,&bw,1,b,2,0);
-	*unc = (b[0] << 8) | b[1];
-	return 0;
+	mutex_lock(&state->data_mutex);
+	state->data[0] = GET_RS_UNCOR_BLK_CNT;
+
+	dvb_usb_generic_rw(state->d, state->data, 1, state->data, 2, 0);
+
+	mutex_unlock(&state->data_mutex);
+	return ret;
 }
 
 static int dtt200u_fe_read_signal_strength(struct dvb_frontend* fe, u16 *strength)
 {
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
-	u8 bw = GET_AGC, b;
-	dvb_usb_generic_rw(state->d,&bw,1,&b,1,0);
-	*strength = (b << 8) | b;
-	return 0;
+
+	mutex_lock(&state->data_mutex);
+	state->data[0] = GET_AGC;
+
+	dvb_usb_generic_rw(state->d, state->data, 1, state->data, 1, 0);
+
+	mutex_unlock(&state->data_mutex);
+	return ret;
 }
 
 static int dtt200u_fe_read_snr(struct dvb_frontend* fe, u16 *snr)
 {
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
-	u8 bw = GET_SNR,br;
-	dvb_usb_generic_rw(state->d,&bw,1,&br,1,0);
-	*snr = ~((br << 8) | br);
-	return 0;
+
+	mutex_lock(&state->data_mutex);
+	state->data[0] = GET_SNR;
+
+	dvb_usb_generic_rw(state->d, state->data, 1, state->data, 1, 0);
+
+	mutex_unlock(&state->data_mutex);
+	return ret;
 }
 
 static int dtt200u_fe_init(struct dvb_frontend* fe)
 {
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
-	u8 b = SET_INIT;
-	return dvb_usb_generic_write(state->d,&b,1);
+	int ret;
+
+	mutex_lock(&state->data_mutex);
+	state->data[0] = SET_INIT;
+
+	ret = dvb_usb_generic_write(state->d, state->data, 1);
+	mutex_unlock(&state->data_mutex);
+
+	return ret;
 }
 
 static int dtt200u_fe_sleep(struct dvb_frontend* fe)
@@ -106,29 +135,34 @@ static int dtt200u_fe_set_frontend(struct dvb_frontend *fe)
 	struct dtv_frontend_properties *fep = &fe->dtv_property_cache;
 	struct dtt200u_fe_state *state = fe->demodulator_priv;
 	u16 freq = fep->frequency / 250000;
-	u8 bwbuf[2] = { SET_BANDWIDTH, 0 },freqbuf[3] = { SET_RF_FREQ, 0, 0 };
 
+	mutex_lock(&state->data_mutex);
+	state->data[0] = SET_BANDWIDTH;
 	switch (fep->bandwidth_hz) {
 	case 8000000:
-		bwbuf[1] = 8;
+		state->data[1] = 8;
 		break;
 	case 7000000:
-		bwbuf[1] = 7;
+		state->data[1] = 7;
 		break;
 	case 6000000:
-		bwbuf[1] = 6;
+		state->data[1] = 6;
 		break;
 	default:
-		return -EINVAL;
+		ret = -EINVAL;
+		goto ret;
 	}
 
-	dvb_usb_generic_write(state->d,bwbuf,2);
+	dvb_usb_generic_write(state->d, state->data, 2);
 
-	freqbuf[1] = freq & 0xff;
-	freqbuf[2] = (freq >> 8) & 0xff;
-	dvb_usb_generic_write(state->d,freqbuf,3);
+	state->data[0] = SET_RF_FREQ;
+	state->data[1] = freq & 0xff;
+	state->data[2] = (freq >> 8) & 0xff;
+	dvb_usb_generic_write(state->d, state->data, 3);
 
-	return 0;
+ret:
+	mutex_unlock(&state->data_mutex);
+	return ret;
 }
 
 static int dtt200u_fe_get_frontend(struct dvb_frontend* fe,
@@ -160,6 +194,7 @@ struct dvb_frontend* dtt200u_fe_attach(struct dvb_usb_device *d)
 	deb_info("attaching frontend dtt200u\n");
 
 	state->d = d;
+	mutex_init(&state->data_mutex);
 
 	memcpy(&state->frontend.ops,&dtt200u_fe_ops,sizeof(struct dvb_frontend_ops));
 	state->frontend.demodulator_priv = state;
-- 
2.7.4

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[PATCH v2 00/31]  Don't use stack for DMA transers on media usb drivers Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 04/31] cinergyT2-fe: cache stats at cinergyt2_fe_read_status() Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 05/31] cinergyT2-fe: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 29/31] s2255drv: don't use stack for DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 26/31] dw2102: return error if su3000_power_ctrl() fails Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 30/31] stk-webcam: don't use stack for DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 28/31] cpia2_usb: don't use stack for DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
    Re: [PATCH v2 28/31] cpia2_usb: don't use stack for DMA  Kosuke Tatsukawa <tatsu@ab.jp.nec.com> - 2016-10-12 01:00 +0200
      [PATCH v2 .1 28/31] cpia2_usb: don't use stack for DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-12 04:20 +0200
      Re: [PATCH v2 28/31] cpia2_usb: don't use stack for DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-12 04:20 +0200
  [PATCH v2 01/31] af9005: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 15/31] dtt200u: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 24/31] dvb-usb: warn if return value for USB read/write routines is not checked Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 02/31] cinergyT2-core: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 07/31] dib0700: be sure that dib0700_ctrl_rd() users can do DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 11/31] digitv: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 17/31] dtv5100: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 25/31] nova-t-usb2: handle error code on RC query Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 18/31] gp8psk: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 20/31] nova-t-usb2: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 31/31] flexcop-usb: don't use stack for DMA Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 22/31] pctv452e: don't call BUG_ON() on non-fatal error Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 10/31] dibusb: handle error code on RC query Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 27/31] digitv: handle error code on RC query Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 16/31] dtt200u: handle USB control message errors Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 13/31] dtt200u-fe: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 21/31] pctv452e: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 19/31] gp8psk: don't go past the buffer size Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 12/31] dtt200u-fe: don't keep waiting for lock at set_frontend() Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 08/31] dib0700_core: don't use stack on I2C reads Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200
  [PATCH v2 06/31] cxusb: don't do DMA on stack Mauro Carvalho Chehab <mchehab@s-opensource.com> - 2016-10-11 12:20 +0200

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