DiBcom: protect the I2C bufer access

commit 79fcce3230b140f7675f8529ee53fe2f9644f902 upstream.

This patch protects the I2C buffer access in order to manage concurrent
access. This protection is done using mutex.
Furthermore, for the dib9000, if a pid filtering command is
received during the tuning, this pid filtering command is delayed to
avoid any concurrent access issue.

Cc: Mauro Carvalho Chehab <mchehab@redhat.com>
Cc: Florian Mickler <florian@mickler.org>
Signed-off-by: Olivier Grenie <olivier.grenie@dibcom.fr>
Signed-off-by: Patrick Boettcher <Patrick.Boettcher@dibcom.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

8 files changed, 412 insertions, 67 deletions

diff --git a/drivers/media/dvb/frontends/dib0070.c b/drivers/media/dvb/frontends/dib0070.c
index 1d47d4da7d4..dc1cb17a6ea 100644
--- a/drivers/media/dvb/frontends/dib0070.c
+++ b/drivers/media/dvb/frontends/dib0070.c
@@ -27,6 +27,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/mutex.h>
 
 #include "dvb_frontend.h"
 
@@ -78,10 +79,18 @@ struct dib0070_state {
 	struct i2c_msg msg[2];
 	u8 i2c_write_buffer[3];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
-static uint16_t dib0070_read_reg(struct dib0070_state *state, u8 reg)
+static u16 dib0070_read_reg(struct dib0070_state *state, u8 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	state->i2c_write_buffer[0] = reg;
 
 	memset(state->msg, 0, 2 * sizeof(struct i2c_msg));
@@ -96,13 +105,23 @@ static uint16_t dib0070_read_reg(struct dib0070_state *state, u8 reg)
 
 	if (i2c_transfer(state->i2c, state->msg, 2) != 2) {
 		printk(KERN_WARNING "DiB0070 I2C read failed\n");
-		return 0;
-	}
-	return (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+		ret = 0;
+	} else
+		ret = (state->i2c_read_buffer[0] << 8)
+			| state->i2c_read_buffer[1];
+
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 static int dib0070_write_reg(struct dib0070_state *state, u8 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
 	state->i2c_write_buffer[0] = reg;
 	state->i2c_write_buffer[1] = val >> 8;
 	state->i2c_write_buffer[2] = val & 0xff;
@@ -115,9 +134,12 @@ static int dib0070_write_reg(struct dib0070_state *state, u8 reg, u16 val)
 
 	if (i2c_transfer(state->i2c, state->msg, 1) != 1) {
 		printk(KERN_WARNING "DiB0070 I2C write failed\n");
-		return -EREMOTEIO;
-	}
-	return 0;
+		ret = -EREMOTEIO;
+	} else
+		ret = 0;
+
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 #define HARD_RESET(state) do { \
@@ -734,6 +756,7 @@ struct dvb_frontend *dib0070_attach(struct dvb_frontend *fe, struct i2c_adapter
 	state->cfg = cfg;
 	state->i2c = i2c;
 	state->fe  = fe;
+	mutex_init(&state->i2c_buffer_lock);
 	fe->tuner_priv = state;
 
 	if (dib0070_reset(fe) != 0)
diff --git a/drivers/media/dvb/frontends/dib0090.c b/drivers/media/dvb/frontends/dib0090.c
index c9c935ae41e..b174d1c7858 100644
--- a/drivers/media/dvb/frontends/dib0090.c
+++ b/drivers/media/dvb/frontends/dib0090.c
@@ -27,6 +27,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/mutex.h>
 
 #include "dvb_frontend.h"
 
@@ -196,6 +197,7 @@ struct dib0090_state {
 	struct i2c_msg msg[2];
 	u8 i2c_write_buffer[3];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
 struct dib0090_fw_state {
@@ -208,10 +210,18 @@ struct dib0090_fw_state {
 	struct i2c_msg msg;
 	u8 i2c_write_buffer[2];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
 static u16 dib0090_read_reg(struct dib0090_state *state, u8 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	state->i2c_write_buffer[0] = reg;
 
 	memset(state->msg, 0, 2 * sizeof(struct i2c_msg));
@@ -226,14 +236,24 @@ static u16 dib0090_read_reg(struct dib0090_state *state, u8 reg)
 
 	if (i2c_transfer(state->i2c, state->msg, 2) != 2) {
 		printk(KERN_WARNING "DiB0090 I2C read failed\n");
-		return 0;
-	}
+		ret = 0;
+	} else
+		ret = (state->i2c_read_buffer[0] << 8)
+			| state->i2c_read_buffer[1];
 
-	return (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 static int dib0090_write_reg(struct dib0090_state *state, u32 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
 	state->i2c_write_buffer[0] = reg & 0xff;
 	state->i2c_write_buffer[1] = val >> 8;
 	state->i2c_write_buffer[2] = val & 0xff;
@@ -246,13 +266,23 @@ static int dib0090_write_reg(struct dib0090_state *state, u32 reg, u16 val)
 
 	if (i2c_transfer(state->i2c, state->msg, 1) != 1) {
 		printk(KERN_WARNING "DiB0090 I2C write failed\n");
-		return -EREMOTEIO;
-	}
-	return 0;
+		ret = -EREMOTEIO;
+	} else
+		ret = 0;
+
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 static u16 dib0090_fw_read_reg(struct dib0090_fw_state *state, u8 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	state->i2c_write_buffer[0] = reg;
 
 	memset(&state->msg, 0, sizeof(struct i2c_msg));
@@ -262,13 +292,24 @@ static u16 dib0090_fw_read_reg(struct dib0090_fw_state *state, u8 reg)
 	state->msg.len = 2;
 	if (i2c_transfer(state->i2c, &state->msg, 1) != 1) {
 		printk(KERN_WARNING "DiB0090 I2C read failed\n");
-		return 0;
-	}
-	return (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+		ret = 0;
+	} else
+		ret = (state->i2c_read_buffer[0] << 8)
+			| state->i2c_read_buffer[1];
+
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 static int dib0090_fw_write_reg(struct dib0090_fw_state *state, u8 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
 	state->i2c_write_buffer[0] = val >> 8;
 	state->i2c_write_buffer[1] = val & 0xff;
 
@@ -279,9 +320,12 @@ static int dib0090_fw_write_reg(struct dib0090_fw_state *state, u8 reg, u16 val)
 	state->msg.len = 2;
 	if (i2c_transfer(state->i2c, &state->msg, 1) != 1) {
 		printk(KERN_WARNING "DiB0090 I2C write failed\n");
-		return -EREMOTEIO;
-	}
-	return 0;
+		ret = -EREMOTEIO;
+	} else
+		ret = 0;
+
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 #define HARD_RESET(state) do {  if (cfg->reset) {  if (cfg->sleep) cfg->sleep(fe, 0); msleep(10);  cfg->reset(fe, 1); msleep(10);  cfg->reset(fe, 0); msleep(10);  }  } while (0)
@@ -2440,6 +2484,7 @@ struct dvb_frontend *dib0090_register(struct dvb_frontend *fe, struct i2c_adapte
 	st->config = config;
 	st->i2c = i2c;
 	st->fe = fe;
+	mutex_init(&st->i2c_buffer_lock);
 	fe->tuner_priv = st;
 
 	if (config->wbd == NULL)
@@ -2471,6 +2516,7 @@ struct dvb_frontend *dib0090_fw_register(struct dvb_frontend *fe, struct i2c_ada
 	st->config = config;
 	st->i2c = i2c;
 	st->fe = fe;
+	mutex_init(&st->i2c_buffer_lock);
 	fe->tuner_priv = st;
 
 	if (dib0090_fw_reset_digital(fe, st->config) != 0)
diff --git a/drivers/media/dvb/frontends/dib7000m.c b/drivers/media/dvb/frontends/dib7000m.c
index 79cb1c20df2..dbb76d75c93 100644
--- a/drivers/media/dvb/frontends/dib7000m.c
+++ b/drivers/media/dvb/frontends/dib7000m.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/mutex.h>
 
 #include "dvb_frontend.h"
 
@@ -55,6 +56,7 @@ struct dib7000m_state {
 	struct i2c_msg msg[2];
 	u8 i2c_write_buffer[4];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
 enum dib7000m_power_mode {
@@ -69,6 +71,13 @@ enum dib7000m_power_mode {
 
 static u16 dib7000m_read_word(struct dib7000m_state *state, u16 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	state->i2c_write_buffer[0] = (reg >> 8) | 0x80;
 	state->i2c_write_buffer[1] = reg & 0xff;
 
@@ -85,11 +94,21 @@ static u16 dib7000m_read_word(struct dib7000m_state *state, u16 reg)
 	if (i2c_transfer(state->i2c_adap, state->msg, 2) != 2)
 		dprintk("i2c read error on %d",reg);
 
-	return (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	ret = (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	mutex_unlock(&state->i2c_buffer_lock);
+
+	return ret;
 }
 
 static int dib7000m_write_word(struct dib7000m_state *state, u16 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
 	state->i2c_write_buffer[0] = (reg >> 8) & 0xff;
 	state->i2c_write_buffer[1] = reg & 0xff;
 	state->i2c_write_buffer[2] = (val >> 8) & 0xff;
@@ -101,7 +120,10 @@ static int dib7000m_write_word(struct dib7000m_state *state, u16 reg, u16 val)
 	state->msg[0].buf = state->i2c_write_buffer;
 	state->msg[0].len = 4;
 
-	return i2c_transfer(state->i2c_adap, state->msg, 1) != 1 ? -EREMOTEIO : 0;
+	ret = (i2c_transfer(state->i2c_adap, state->msg, 1) != 1 ?
+			-EREMOTEIO : 0);
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 static void dib7000m_write_tab(struct dib7000m_state *state, u16 *buf)
 {
@@ -1385,6 +1407,7 @@ struct dvb_frontend * dib7000m_attach(struct i2c_adapter *i2c_adap, u8 i2c_addr,
 	demod                   = &st->demod;
 	demod->demodulator_priv = st;
 	memcpy(&st->demod.ops, &dib7000m_ops, sizeof(struct dvb_frontend_ops));
+	mutex_init(&st->i2c_buffer_lock);
 
 	st->timf_default = cfg->bw->timf;
 
diff --git a/drivers/media/dvb/frontends/dib7000p.c b/drivers/media/dvb/frontends/dib7000p.c
index 0c9f40c2a25..292bc19746b 100644
--- a/drivers/media/dvb/frontends/dib7000p.c
+++ b/drivers/media/dvb/frontends/dib7000p.c
@@ -10,6 +10,7 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/mutex.h>
 
 #include "dvb_math.h"
 #include "dvb_frontend.h"
@@ -68,6 +69,7 @@ struct dib7000p_state {
 	struct i2c_msg msg[2];
 	u8 i2c_write_buffer[4];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
 enum dib7000p_power_mode {
@@ -81,6 +83,13 @@ static int dib7090_set_diversity_in(struct dvb_frontend *fe, int onoff);
 
 static u16 dib7000p_read_word(struct dib7000p_state *state, u16 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	state->i2c_write_buffer[0] = reg >> 8;
 	state->i2c_write_buffer[1] = reg & 0xff;
 
@@ -97,11 +106,20 @@ static u16 dib7000p_read_word(struct dib7000p_state *state, u16 reg)
 	if (i2c_transfer(state->i2c_adap, state->msg, 2) != 2)
 		dprintk("i2c read error on %d", reg);
 
-	return (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	ret = (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 static int dib7000p_write_word(struct dib7000p_state *state, u16 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
 	state->i2c_write_buffer[0] = (reg >> 8) & 0xff;
 	state->i2c_write_buffer[1] = reg & 0xff;
 	state->i2c_write_buffer[2] = (val >> 8) & 0xff;
@@ -113,7 +131,10 @@ static int dib7000p_write_word(struct dib7000p_state *state, u16 reg, u16 val)
 	state->msg[0].buf = state->i2c_write_buffer;
 	state->msg[0].len = 4;
 
-	return i2c_transfer(state->i2c_adap, state->msg, 1) != 1 ? -EREMOTEIO : 0;
+	ret = (i2c_transfer(state->i2c_adap, state->msg, 1) != 1 ?
+			-EREMOTEIO : 0);
+	mutex_unlock(&state->i2c_buffer_lock);
+	return ret;
 }
 
 static void dib7000p_write_tab(struct dib7000p_state *state, u16 * buf)
@@ -1646,6 +1667,7 @@ int dib7000p_i2c_enumeration(struct i2c_adapter *i2c, int no_of_demods, u8 defau
 		return -ENOMEM;
 
 	dpst->i2c_adap = i2c;
+	mutex_init(&dpst->i2c_buffer_lock);
 
 	for (k = no_of_demods - 1; k >= 0; k--) {
 		dpst->cfg = cfg[k];
@@ -2324,6 +2346,7 @@ struct dvb_frontend *dib7000p_attach(struct i2c_adapter *i2c_adap, u8 i2c_addr,
 	demod = &st->demod;
 	demod->demodulator_priv = st;
 	memcpy(&st->demod.ops, &dib7000p_ops, sizeof(struct dvb_frontend_ops));
+	mutex_init(&st->i2c_buffer_lock);
 
 	dib7000p_write_word(st, 1287, 0x0003);	/* sram lead in, rdy */
 
@@ -2333,8 +2356,9 @@ struct dvb_frontend *dib7000p_attach(struct i2c_adapter *i2c_adap, u8 i2c_addr,
 	st->version = dib7000p_read_word(st, 897);
 
 	/* FIXME: make sure the dev.parent field is initialized, or else
-		request_firmware() will hit an OOPS (this should be moved somewhere
-		more common) */
+	   request_firmware() will hit an OOPS (this should be moved somewhere
+	   more common) */
+	st->i2c_master.gated_tuner_i2c_adap.dev.parent = i2c_adap->dev.parent;
 
 	dibx000_init_i2c_master(&st->i2c_master, DIB7000P, st->i2c_adap, st->i2c_addr);
 
diff --git a/drivers/media/dvb/frontends/dib8000.c b/drivers/media/dvb/frontends/dib8000.c
index 7d2ea112ae2..fe284d5292f 100644
--- a/drivers/media/dvb/frontends/dib8000.c
+++ b/drivers/media/dvb/frontends/dib8000.c
@@ -10,6 +10,8 @@
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/i2c.h>
+#include <linux/mutex.h>
+
 #include "dvb_math.h"
 
 #include "dvb_frontend.h"
@@ -37,6 +39,7 @@ struct i2c_device {
 	u8 addr;
 	u8 *i2c_write_buffer;
 	u8 *i2c_read_buffer;
+	struct mutex *i2c_buffer_lock;
 };
 
 struct dib8000_state {
@@ -77,6 +80,7 @@ struct dib8000_state {
 	struct i2c_msg msg[2];
 	u8 i2c_write_buffer[4];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
 enum dib8000_power_mode {
@@ -86,24 +90,39 @@ enum dib8000_power_mode {
 
 static u16 dib8000_i2c_read16(struct i2c_device *i2c, u16 reg)
 {
+	u16 ret;
 	struct i2c_msg msg[2] = {
-		{.addr = i2c->addr >> 1, .flags = 0,
-			.buf = i2c->i2c_write_buffer, .len = 2},
-		{.addr = i2c->addr >> 1, .flags = I2C_M_RD,
-			.buf = i2c->i2c_read_buffer, .len = 2},
+		{.addr = i2c->addr >> 1, .flags = 0, .len = 2},
+		{.addr = i2c->addr >> 1, .flags = I2C_M_RD, .len = 2},
 	};
 
+	if (mutex_lock_interruptible(i2c->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
+	msg[0].buf    = i2c->i2c_write_buffer;
 	msg[0].buf[0] = reg >> 8;
 	msg[0].buf[1] = reg & 0xff;
+	msg[1].buf    = i2c->i2c_read_buffer;
 
 	if (i2c_transfer(i2c->adap, msg, 2) != 2)
 		dprintk("i2c read error on %d", reg);
 
-	return (msg[1].buf[0] << 8) | msg[1].buf[1];
+	ret = (msg[1].buf[0] << 8) | msg[1].buf[1];
+	mutex_unlock(i2c->i2c_buffer_lock);
+	return ret;
 }
 
 static u16 dib8000_read_word(struct dib8000_state *state, u16 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	state->i2c_write_buffer[0] = reg >> 8;
 	state->i2c_write_buffer[1] = reg & 0xff;
 
@@ -120,7 +139,10 @@ static u16 dib8000_read_word(struct dib8000_state *state, u16 reg)
 	if (i2c_transfer(state->i2c.adap, state->msg, 2) != 2)
 		dprintk("i2c read error on %d", reg);
 
-	return (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	ret = (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+	mutex_unlock(&state->i2c_buffer_lock);
+
+	return ret;
 }
 
 static u32 dib8000_read32(struct dib8000_state *state, u16 reg)
@@ -135,22 +157,35 @@ static u32 dib8000_read32(struct dib8000_state *state, u16 reg)
 
 static int dib8000_i2c_write16(struct i2c_device *i2c, u16 reg, u16 val)
 {
-	struct i2c_msg msg = {.addr = i2c->addr >> 1, .flags = 0,
-		.buf = i2c->i2c_write_buffer, .len = 4};
+	struct i2c_msg msg = {.addr = i2c->addr >> 1, .flags = 0, .len = 4};
 	int ret = 0;
 
+	if (mutex_lock_interruptible(i2c->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
+	msg.buf    = i2c->i2c_write_buffer;
 	msg.buf[0] = (reg >> 8) & 0xff;
 	msg.buf[1] = reg & 0xff;
 	msg.buf[2] = (val >> 8) & 0xff;
 	msg.buf[3] = val & 0xff;
 
 	ret = i2c_transfer(i2c->adap, &msg, 1) != 1 ? -EREMOTEIO : 0;
+	mutex_unlock(i2c->i2c_buffer_lock);
 
 	return ret;
 }
 
 static int dib8000_write_word(struct dib8000_state *state, u16 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
 	state->i2c_write_buffer[0] = (reg >> 8) & 0xff;
 	state->i2c_write_buffer[1] = reg & 0xff;
 	state->i2c_write_buffer[2] = (val >> 8) & 0xff;
@@ -162,7 +197,11 @@ static int dib8000_write_word(struct dib8000_state *state, u16 reg, u16 val)
 	state->msg[0].buf = state->i2c_write_buffer;
 	state->msg[0].len = 4;
 
-	return i2c_transfer(state->i2c.adap, state->msg, 1) != 1 ? -EREMOTEIO : 0;
+	ret = (i2c_transfer(state->i2c.adap, state->msg, 1) != 1 ?
+			-EREMOTEIO : 0);
+	mutex_unlock(&state->i2c_buffer_lock);
+
+	return ret;
 }
 
 static const s16 coeff_2k_sb_1seg_dqpsk[8] = {
@@ -2434,8 +2473,15 @@ int dib8000_i2c_enumeration(struct i2c_adapter *host, int no_of_demods, u8 defau
 	if (!client.i2c_read_buffer) {
 		dprintk("%s: not enough memory", __func__);
 		ret = -ENOMEM;
-		goto error_memory;
+		goto error_memory_read;
+	}
+	client.i2c_buffer_lock = kzalloc(sizeof(struct mutex), GFP_KERNEL);
+	if (!client.i2c_buffer_lock) {
+		dprintk("%s: not enough memory", __func__);
+		ret = -ENOMEM;
+		goto error_memory_lock;
 	}
+	mutex_init(client.i2c_buffer_lock);
 
 	for (k = no_of_demods - 1; k >= 0; k--) {
 		/* designated i2c address */
@@ -2476,8 +2522,10 @@ int dib8000_i2c_enumeration(struct i2c_adapter *host, int no_of_demods, u8 defau
 	}
 
 error:
+	kfree(client.i2c_buffer_lock);
+error_memory_lock:
 	kfree(client.i2c_read_buffer);
-error_memory:
+error_memory_read:
 	kfree(client.i2c_write_buffer);
 
 	return ret;
@@ -2581,6 +2629,8 @@ struct dvb_frontend *dib8000_attach(struct i2c_adapter *i2c_adap, u8 i2c_addr, s
 	state->i2c.addr = i2c_addr;
 	state->i2c.i2c_write_buffer = state->i2c_write_buffer;
 	state->i2c.i2c_read_buffer = state->i2c_read_buffer;
+	mutex_init(&state->i2c_buffer_lock);
+	state->i2c.i2c_buffer_lock = &state->i2c_buffer_lock;
 	state->gpio_val = cfg->gpio_val;
 	state->gpio_dir = cfg->gpio_dir;
 
diff --git a/drivers/media/dvb/frontends/dib9000.c b/drivers/media/dvb/frontends/dib9000.c
index a0855883b5c..b931074a952 100644
--- a/drivers/media/dvb/frontends/dib9000.c
+++ b/drivers/media/dvb/frontends/dib9000.c
@@ -38,6 +38,15 @@ struct i2c_device {
 #define DibInitLock(lock) mutex_init(lock)
 #define DibFreeLock(lock)
 
+struct dib9000_pid_ctrl {
+#define DIB9000_PID_FILTER_CTRL 0
+#define DIB9000_PID_FILTER      1
+	u8 cmd;
+	u8 id;
+	u16 pid;
+	u8 onoff;
+};
+
 struct dib9000_state {
 	struct i2c_device i2c;
 
@@ -99,6 +108,10 @@ struct dib9000_state {
 	struct i2c_msg msg[2];
 	u8 i2c_write_buffer[255];
 	u8 i2c_read_buffer[255];
+	DIB_LOCK demod_lock;
+	u8 get_frontend_internal;
+	struct dib9000_pid_ctrl pid_ctrl[10];
+	s8 pid_ctrl_index; /* -1: empty list; -2: do not use the list */
 };
 
 static const u32 fe_info[44] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
@@ -1743,19 +1756,56 @@ EXPORT_SYMBOL(dib9000_set_gpio);
 int dib9000_fw_pid_filter_ctrl(struct dvb_frontend *fe, u8 onoff)
 {
 	struct dib9000_state *state = fe->demodulator_priv;
-	u16 val = dib9000_read_word(state, 294 + 1) & 0xffef;
+	u16 val;
+	int ret;
+
+	if ((state->pid_ctrl_index != -2) && (state->pid_ctrl_index < 9)) {
+		/* postpone the pid filtering cmd */
+		dprintk("pid filter cmd postpone");
+		state->pid_ctrl_index++;
+		state->pid_ctrl[state->pid_ctrl_index].cmd = DIB9000_PID_FILTER_CTRL;
+		state->pid_ctrl[state->pid_ctrl_index].onoff = onoff;
+		return 0;
+	}
+
+	DibAcquireLock(&state->demod_lock);
+
+	val = dib9000_read_word(state, 294 + 1) & 0xffef;
 	val |= (onoff & 0x1) << 4;
 
 	dprintk("PID filter enabled %d", onoff);
-	return dib9000_write_word(state, 294 + 1, val);
+	ret = dib9000_write_word(state, 294 + 1, val);
+	DibReleaseLock(&state->demod_lock);
+	return ret;
+
 }
 EXPORT_SYMBOL(dib9000_fw_pid_filter_ctrl);
 
 int dib9000_fw_pid_filter(struct dvb_frontend *fe, u8 id, u16 pid, u8 onoff)
 {
 	struct dib9000_state *state = fe->demodulator_priv;
+	int ret;
+
+	if (state->pid_ctrl_index != -2) {
+		/* postpone the pid filtering cmd */
+		dprintk("pid filter postpone");
+		if (state->pid_ctrl_index < 9) {
+			state->pid_ctrl_index++;
+			state->pid_ctrl[state->pid_ctrl_index].cmd = DIB9000_PID_FILTER;
+			state->pid_ctrl[state->pid_ctrl_index].id = id;
+			state->pid_ctrl[state->pid_ctrl_index].pid = pid;
+			state->pid_ctrl[state->pid_ctrl_index].onoff = onoff;
+		} else
+			dprintk("can not add any more pid ctrl cmd");
+		return 0;
+	}
+
+	DibAcquireLock(&state->demod_lock);
 	dprintk("Index %x, PID %d, OnOff %d", id, pid, onoff);
-	return dib9000_write_word(state, 300 + 1 + id, onoff ? (1 << 13) | pid : 0);
+	ret = dib9000_write_word(state, 300 + 1 + id,
+			onoff ? (1 << 13) | pid : 0);
+	DibReleaseLock(&state->demod_lock);
+	return ret;
 }
 EXPORT_SYMBOL(dib9000_fw_pid_filter);
 
@@ -1778,6 +1828,7 @@ static void dib9000_release(struct dvb_frontend *demod)
 	DibFreeLock(&state->platform.risc.mbx_lock);
 	DibFreeLock(&state->platform.risc.mem_lock);
 	DibFreeLock(&state->platform.risc.mem_mbx_lock);
+	DibFreeLock(&state->demod_lock);
 	dibx000_exit_i2c_master(&st->i2c_master);
 
 	i2c_del_adapter(&st->tuner_adap);
@@ -1795,14 +1846,19 @@ static int dib9000_sleep(struct dvb_frontend *fe)
 {
 	struct dib9000_state *state = fe->demodulator_priv;
 	u8 index_frontend;
-	int ret;
+	int ret = 0;
 
+	DibAcquireLock(&state->demod_lock);
 	for (index_frontend = 1; (index_frontend < MAX_NUMBER_OF_FRONTENDS) && (state->fe[index_frontend] != NULL); index_frontend++) {
 		ret = state->fe[index_frontend]->ops.sleep(state->fe[index_frontend]);
 		if (ret < 0)
-			return ret;
+			goto error;
 	}
-	return dib9000_mbx_send(state, OUT_MSG_FE_SLEEP, NULL, 0);
+	ret = dib9000_mbx_send(state, OUT_MSG_FE_SLEEP, NULL, 0);
+
+error:
+	DibReleaseLock(&state->demod_lock);
+	return ret;
 }
 
 static int dib9000_fe_get_tune_settings(struct dvb_frontend *fe, struct dvb_frontend_tune_settings *tune)
@@ -1816,7 +1872,10 @@ static int dib9000_get_frontend(struct dvb_frontend *fe, struct dvb_frontend_par
 	struct dib9000_state *state = fe->demodulator_priv;
 	u8 index_frontend, sub_index_frontend;
 	fe_status_t stat;
-	int ret;
+	int ret = 0;
+
+	if (state->get_frontend_internal == 0)
+		DibAcquireLock(&state->demod_lock);
 
 	for (index_frontend = 1; (index_frontend < MAX_NUMBER_OF_FRONTENDS) && (state->fe[index_frontend] != NULL); index_frontend++) {
 		state->fe[index_frontend]->ops.read_status(state->fe[index_frontend], &stat);
@@ -1846,14 +1905,15 @@ static int dib9000_get_frontend(struct dvb_frontend *fe, struct dvb_frontend_par
 					    state->fe[index_frontend]->dtv_property_cache.rolloff;
 				}
 			}
-			return 0;
+			ret = 0;
+			goto return_value;
 		}
 	}
 
 	/* get the channel from master chip */
 	ret = dib9000_fw_get_channel(fe, fep);
 	if (ret != 0)
-		return ret;
+		goto return_value;
 
 	/* synchronize the cache with the other frontends */
 	for (index_frontend = 1; (index_frontend < MAX_NUMBER_OF_FRONTENDS) && (state->fe[index_frontend] != NULL); index_frontend++) {
@@ -1866,8 +1926,12 @@ static int dib9000_get_frontend(struct dvb_frontend *fe, struct dvb_frontend_par
 		state->fe[index_frontend]->dtv_property_cache.code_rate_LP = fe->dtv_property_cache.code_rate_LP;
 		state->fe[index_frontend]->dtv_property_cache.rolloff = fe->dtv_property_cache.rolloff;
 	}
+	ret = 0;
 
-	return 0;
+return_value:
+	if (state->get_frontend_internal == 0)
+		DibReleaseLock(&state->demod_lock);
+	return ret;
 }
 
 static int dib9000_set_tune_state(struct dvb_frontend *fe, enum frontend_tune_state tune_state)
@@ -1912,6 +1976,10 @@ static int dib9000_set_frontend(struct dvb_frontend *fe, struct dvb_frontend_par
 		dprintk("dib9000: must specify bandwidth ");
 		return 0;
 	}
+
+	state->pid_ctrl_index = -1; /* postpone the pid filtering cmd */
+	DibAcquireLock(&state->demod_lock);
+
 	fe->dtv_property_cache.delivery_system = SYS_DVBT;
 
 	/* set the master status */
@@ -1974,13 +2042,18 @@ static int dib9000_set_frontend(struct dvb_frontend *fe, struct dvb_frontend_par
 	/* check the tune result */
 	if (exit_condition == 1) {	/* tune failed */
 		dprintk("tune failed");
+		DibReleaseLock(&state->demod_lock);
+		/* tune failed; put all the pid filtering cmd to junk */
+		state->pid_ctrl_index = -1;
 		return 0;
 	}
 
 	dprintk("tune success on frontend%i", index_frontend_success);
 
 	/* synchronize all the channel cache */
+	state->get_frontend_internal = 1;
 	dib9000_get_frontend(state->fe[0], fep);
+	state->get_frontend_internal = 0;
 
 	/* retune the other frontends with the found channel */
 	channel_status.status = CHANNEL_STATUS_PARAMETERS_SET;
@@ -2025,6 +2098,28 @@ static int dib9000_set_frontend(struct dvb_frontend *fe, struct dvb_frontend_par
 	/* turn off the diversity for the last frontend */
 	dib9000_fw_set_diversity_in(state->fe[index_frontend - 1], 0);
 
+	DibReleaseLock(&state->demod_lock);
+	if (state->pid_ctrl_index >= 0) {
+		u8 index_pid_filter_cmd;
+		u8 pid_ctrl_index = state->pid_ctrl_index;
+
+		state->pid_ctrl_index = -2;
+		for (index_pid_filter_cmd = 0;
+				index_pid_filter_cmd <= pid_ctrl_index;
+				index_pid_filter_cmd++) {
+			if (state->pid_ctrl[index_pid_filter_cmd].cmd == DIB9000_PID_FILTER_CTRL)
+				dib9000_fw_pid_filter_ctrl(state->fe[0],
+						state->pid_ctrl[index_pid_filter_cmd].onoff);
+			else if (state->pid_ctrl[index_pid_filter_cmd].cmd == DIB9000_PID_FILTER)
+				dib9000_fw_pid_filter(state->fe[0],
+						state->pid_ctrl[index_pid_filter_cmd].id,
+						state->pid_ctrl[index_pid_filter_cmd].pid,
+						state->pid_ctrl[index_pid_filter_cmd].onoff);
+		}
+	}
+	/* do not postpone any more the pid filtering */
+	state->pid_ctrl_index = -2;
+
 	return 0;
 }
 
@@ -2041,6 +2136,7 @@ static int dib9000_read_status(struct dvb_frontend *fe, fe_status_t * stat)
 	u8 index_frontend;
 	u16 lock = 0, lock_slave = 0;
 
+	DibAcquireLock(&state->demod_lock);
 	for (index_frontend = 1; (index_frontend < MAX_NUMBER_OF_FRONTENDS) && (state->fe[index_frontend] != NULL); index_frontend++)
 		lock_slave |= dib9000_read_lock(state->fe[index_frontend]);
 
@@ -2059,6 +2155,8 @@ static int dib9000_read_status(struct dvb_frontend *fe, fe_status_t * stat)
 	if ((lock & 0x0008) || (lock_slave & 0x0008))
 		*stat |= FE_HAS_LOCK;
 
+	DibReleaseLock(&state->demod_lock);
+
 	return 0;
 }
 
@@ -2066,10 +2164,14 @@ static int dib9000_read_ber(struct dvb_frontend *fe, u32 * ber)
 {
 	struct dib9000_state *state = fe->demodulator_priv;
 	u16 *c;
+	int ret = 0;
 
+	DibAcquireLock(&state->demod_lock);
 	DibAcquireLock(&state->platform.risc.mem_mbx_lock);
-	if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0)
-		return -EIO;
+	if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0) {
+		ret = -EIO;
+		goto error;
+	}
 	dib9000_risc_mem_read(state, FE_MM_R_FE_MONITOR,
 			state->i2c_read_buffer, 16 * 2);
 	DibReleaseLock(&state->platform.risc.mem_mbx_lock);
@@ -2077,7 +2179,10 @@ static int dib9000_read_ber(struct dvb_frontend *fe, u32 * ber)
 	c = (u16 *)state->i2c_read_buffer;
 
 	*ber = c[10] << 16 | c[11];
-	return 0;
+
+error:
+	DibReleaseLock(&state->demod_lock);
+	return ret;
 }
 
 static int dib9000_read_signal_strength(struct dvb_frontend *fe, u16 * strength)
@@ -2086,7 +2191,9 @@ static int dib9000_read_signal_strength(struct dvb_frontend *fe, u16 * strength)
 	u8 index_frontend;
 	u16 *c = (u16 *)state->i2c_read_buffer;
 	u16 val;
+	int ret = 0;
 
+	DibAcquireLock(&state->demod_lock);
 	*strength = 0;
 	for (index_frontend = 1; (index_frontend < MAX_NUMBER_OF_FRONTENDS) && (state->fe[index_frontend] != NULL); index_frontend++) {
 		state->fe[index_frontend]->ops.read_signal_strength(state->fe[index_frontend], &val);
@@ -2097,8 +2204,10 @@ static int dib9000_read_signal_strength(struct dvb_frontend *fe, u16 * strength)
 	}
 
 	DibAcquireLock(&state->platform.risc.mem_mbx_lock);
-	if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0)
-		return -EIO;
+	if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0) {
+		ret = -EIO;
+		goto error;
+	}
 	dib9000_risc_mem_read(state, FE_MM_R_FE_MONITOR, (u8 *) c, 16 * 2);
 	DibReleaseLock(&state->platform.risc.mem_mbx_lock);
 
@@ -2107,7 +2216,10 @@ static int dib9000_read_signal_strength(struct dvb_frontend *fe, u16 * strength)
 		*strength = 65535;
 	else
 		*strength += val;
-	return 0;
+
+error:
+	DibReleaseLock(&state->demod_lock);
+	return ret;
 }
 
 static u32 dib9000_get_snr(struct dvb_frontend *fe)
@@ -2151,6 +2263,7 @@ static int dib9000_read_snr(struct dvb_frontend *fe, u16 * snr)
 	u8 index_frontend;
 	u32 snr_master;
 
+	DibAcquireLock(&state->demod_lock);
 	snr_master = dib9000_get_snr(fe);
 	for (index_frontend = 1; (index_frontend < MAX_NUMBER_OF_FRONTENDS) && (state->fe[index_frontend] != NULL); index_frontend++)
 		snr_master += dib9000_get_snr(state->fe[index_frontend]);
@@ -2161,6 +2274,8 @@ static int dib9000_read_snr(struct dvb_frontend *fe, u16 * snr)
 	} else
 		*snr = 0;
 
+	DibReleaseLock(&state->demod_lock);
+
 	return 0;
 }
 
@@ -2168,15 +2283,22 @@ static int dib9000_read_unc_blocks(struct dvb_frontend *fe, u32 * unc)
 {
 	struct dib9000_state *state = fe->demodulator_priv;
 	u16 *c = (u16 *)state->i2c_read_buffer;
+	int ret = 0;
 
+	DibAcquireLock(&state->demod_lock);
 	DibAcquireLock(&state->platform.risc.mem_mbx_lock);
-	if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0)
-		return -EIO;
+	if (dib9000_fw_memmbx_sync(state, FE_SYNC_CHANNEL) < 0) {
+		ret = -EIO;
+		goto error;
+	}
 	dib9000_risc_mem_read(state, FE_MM_R_FE_MONITOR, (u8 *) c, 16 * 2);
 	DibReleaseLock(&state->platform.risc.mem_mbx_lock);
 
 	*unc = c[12];
-	return 0;
+
+error:
+	DibReleaseLock(&state->demod_lock);
+	return ret;
 }
 
 int dib9000_i2c_enumeration(struct i2c_adapter *i2c, int no_of_demods, u8 default_addr, u8 first_addr)
@@ -2322,6 +2444,10 @@ struct dvb_frontend *dib9000_attach(struct i2c_adapter *i2c_adap, u8 i2c_addr, c
 	DibInitLock(&st->platform.risc.mbx_lock);
 	DibInitLock(&st->platform.risc.mem_lock);
 	DibInitLock(&st->platform.risc.mem_mbx_lock);
+	DibInitLock(&st->demod_lock);
+	st->get_frontend_internal = 0;
+
+	st->pid_ctrl_index = -2;
 
 	st->fe[0] = fe;
 	fe->demodulator_priv = st;
diff --git a/drivers/media/dvb/frontends/dibx000_common.c b/drivers/media/dvb/frontends/dibx000_common.c
index dc5d17a6757..774d507b66c 100644
--- a/drivers/media/dvb/frontends/dibx000_common.c
+++ b/drivers/media/dvb/frontends/dibx000_common.c
@@ -1,4 +1,5 @@
 #include <linux/i2c.h>
+#include <linux/mutex.h>
 
 #include "dibx000_common.h"
 
@@ -10,6 +11,13 @@ MODULE_PARM_DESC(debug, "turn on debugging (default: 0)");
 
 static int dibx000_write_word(struct dibx000_i2c_master *mst, u16 reg, u16 val)
 {
+	int ret;
+
+	if (mutex_lock_interruptible(&mst->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
 	mst->i2c_write_buffer[0] = (reg >> 8) & 0xff;
 	mst->i2c_write_buffer[1] = reg & 0xff;
 	mst->i2c_write_buffer[2] = (val >> 8) & 0xff;
@@ -21,11 +29,21 @@ static int dibx000_write_word(struct dibx000_i2c_master *mst, u16 reg, u16 val)
 	mst->msg[0].buf = mst->i2c_write_buffer;
 	mst->msg[0].len = 4;
 
-	return i2c_transfer(mst->i2c_adap, mst->msg, 1) != 1 ? -EREMOTEIO : 0;
+	ret = i2c_transfer(mst->i2c_adap, mst->msg, 1) != 1 ? -EREMOTEIO : 0;
+	mutex_unlock(&mst->i2c_buffer_lock);
+
+	return ret;
 }
 
 static u16 dibx000_read_word(struct dibx000_i2c_master *mst, u16 reg)
 {
+	u16 ret;
+
+	if (mutex_lock_interruptible(&mst->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return 0;
+	}
+
 	mst->i2c_write_buffer[0] = reg >> 8;
 	mst->i2c_write_buffer[1] = reg & 0xff;
 
@@ -42,7 +60,10 @@ static u16 dibx000_read_word(struct dibx000_i2c_master *mst, u16 reg)
 	if (i2c_transfer(mst->i2c_adap, mst->msg, 2) != 2)
 		dprintk("i2c read error on %d", reg);
 
-	return (mst->i2c_read_buffer[0] << 8) | mst->i2c_read_buffer[1];
+	ret = (mst->i2c_read_buffer[0] << 8) | mst->i2c_read_buffer[1];
+	mutex_unlock(&mst->i2c_buffer_lock);
+
+	return ret;
 }
 
 static int dibx000_is_i2c_done(struct dibx000_i2c_master *mst)
@@ -257,6 +278,7 @@ static int dibx000_i2c_gated_gpio67_xfer(struct i2c_adapter *i2c_adap,
 					struct i2c_msg msg[], int num)
 {
 	struct dibx000_i2c_master *mst = i2c_get_adapdata(i2c_adap);
+	int ret;
 
 	if (num > 32) {
 		dprintk("%s: too much I2C message to be transmitted (%i).\
@@ -264,10 +286,15 @@ static int dibx000_i2c_gated_gpio67_xfer(struct i2c_adapter *i2c_adap,
 		return -ENOMEM;
 	}
 
-	memset(mst->msg, 0, sizeof(struct i2c_msg) * (2 + num));
-
 	dibx000_i2c_select_interface(mst, DIBX000_I2C_INTERFACE_GPIO_6_7);
 
+	if (mutex_lock_interruptible(&mst->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+
+	memset(mst->msg, 0, sizeof(struct i2c_msg) * (2 + num));
+
 	/* open the gate */
 	dibx000_i2c_gate_ctrl(mst, &mst->i2c_write_buffer[0], msg[0].addr, 1);
 	mst->msg[0].addr = mst->i2c_addr;
@@ -282,7 +309,11 @@ static int dibx000_i2c_gated_gpio67_xfer(struct i2c_adapter *i2c_adap,
 	mst->msg[num + 1].buf = &mst->i2c_write_buffer[4];
 	mst->msg[num + 1].len = 4;
 
-	return i2c_transfer(mst->i2c_adap, mst->msg, 2 + num) == 2 + num ? num : -EIO;
+	ret = (i2c_transfer(mst->i2c_adap, mst->msg, 2 + num) == 2 + num ?
+			num : -EIO);
+
+	mutex_unlock(&mst->i2c_buffer_lock);
+	return ret;
 }
 
 static struct i2c_algorithm dibx000_i2c_gated_gpio67_algo = {
@@ -294,6 +325,7 @@ static int dibx000_i2c_gated_tuner_xfer(struct i2c_adapter *i2c_adap,
 					struct i2c_msg msg[], int num)
 {
 	struct dibx000_i2c_master *mst = i2c_get_adapdata(i2c_adap);
+	int ret;
 
 	if (num > 32) {
 		dprintk("%s: too much I2C message to be transmitted (%i).\
@@ -301,10 +333,14 @@ static int dibx000_i2c_gated_tuner_xfer(struct i2c_adapter *i2c_adap,
 		return -ENOMEM;
 	}
 
-	memset(mst->msg, 0, sizeof(struct i2c_msg) * (2 + num));
-
 	dibx000_i2c_select_interface(mst, DIBX000_I2C_INTERFACE_TUNER);
 
+	if (mutex_lock_interruptible(&mst->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+	memset(mst->msg, 0, sizeof(struct i2c_msg) * (2 + num));
+
 	/* open the gate */
 	dibx000_i2c_gate_ctrl(mst, &mst->i2c_write_buffer[0], msg[0].addr, 1);
 	mst->msg[0].addr = mst->i2c_addr;
@@ -319,7 +355,10 @@ static int dibx000_i2c_gated_tuner_xfer(struct i2c_adapter *i2c_adap,
 	mst->msg[num + 1].buf = &mst->i2c_write_buffer[4];
 	mst->msg[num + 1].len = 4;
 
-	return i2c_transfer(mst->i2c_adap, mst->msg, 2 + num) == 2 + num ? num : -EIO;
+	ret = (i2c_transfer(mst->i2c_adap, mst->msg, 2 + num) == 2 + num ?
+			num : -EIO);
+	mutex_unlock(&mst->i2c_buffer_lock);
+	return ret;
 }
 
 static struct i2c_algorithm dibx000_i2c_gated_tuner_algo = {
@@ -390,8 +429,18 @@ static int i2c_adapter_init(struct i2c_adapter *i2c_adap,
 int dibx000_init_i2c_master(struct dibx000_i2c_master *mst, u16 device_rev,
 				struct i2c_adapter *i2c_adap, u8 i2c_addr)
 {
-	u8 tx[4];
-	struct i2c_msg m = {.addr = i2c_addr >> 1,.buf = tx,.len = 4 };
+	int ret;
+
+	mutex_init(&mst->i2c_buffer_lock);
+	if (mutex_lock_interruptible(&mst->i2c_buffer_lock) < 0) {
+		dprintk("could not acquire lock");
+		return -EINVAL;
+	}
+	memset(mst->msg, 0, sizeof(struct i2c_msg));
+	mst->msg[0].addr = i2c_addr >> 1;
+	mst->msg[0].flags = 0;
+	mst->msg[0].buf = mst->i2c_write_buffer;
+	mst->msg[0].len = 4;
 
 	mst->device_rev = device_rev;
 	mst->i2c_adap = i2c_adap;
@@ -431,9 +480,12 @@ int dibx000_init_i2c_master(struct dibx000_i2c_master *mst, u16 device_rev,
 				"DiBX000: could not initialize the master i2c_adapter\n");
 
 	/* initialize the i2c-master by closing the gate */
-	dibx000_i2c_gate_ctrl(mst, tx, 0, 0);
+	dibx000_i2c_gate_ctrl(mst, mst->i2c_write_buffer, 0, 0);
+
+	ret = (i2c_transfer(i2c_adap, mst->msg, 1) == 1);
+	mutex_unlock(&mst->i2c_buffer_lock);
 
-	return i2c_transfer(i2c_adap, &m, 1) == 1;
+	return ret;
 }
 
 EXPORT_SYMBOL(dibx000_init_i2c_master);
diff --git a/drivers/media/dvb/frontends/dibx000_common.h b/drivers/media/dvb/frontends/dibx000_common.h
index f031165c045..5e011474be4 100644
--- a/drivers/media/dvb/frontends/dibx000_common.h
+++ b/drivers/media/dvb/frontends/dibx000_common.h
@@ -33,6 +33,7 @@ struct dibx000_i2c_master {
 	struct i2c_msg msg[34];
 	u8 i2c_write_buffer[8];
 	u8 i2c_read_buffer[2];
+	struct mutex i2c_buffer_lock;
 };
 
 extern int dibx000_init_i2c_master(struct dibx000_i2c_master *mst,