kernel/media-DiBcom-protect-the-I2C-bufer-access.patch

From: Patrick Boettcher <Patrick.Boettcher@dibcom.fr>
Date: Wed, 3 Aug 2011 15:08:21 +0000 (-0300)
Subject: [media] DiBcom: protect the I2C bufer access
X-Git-Tag: next-20110927~67^2~4^2~225
X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Fnext%2Flinux-next.git;a=commitdiff_plain;h=79fcce3230b140f7675f8529ee53fe2f9644f902

[media] DiBcom: protect the I2C bufer access

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>
Cc: stable@kernel.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>
---

diff --git a/drivers/media/dvb/frontends/dib0070.c b/drivers/media/dvb/frontends/dib0070.c
index 1d47d4d..dc1cb17 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 c9c935a..b174d1c 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 79cb1c2..dbb76d7 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 a64a538..4eb9c2b 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;
 
 	/* FIXME: make sure the dev.parent field is initialized, or else
 	   request_firmware() will hit an OOPS (this should be moved somewhere
diff --git a/drivers/media/dvb/frontends/dib8000.c b/drivers/media/dvb/frontends/dib8000.c
index 7d2ea11..fe284d5 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 a085588..b931074 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 dc5d17a..774d507 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 f031165..5e01147 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,