[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>

1 files changed, 25 insertions, 2 deletions

diff --git a/drivers/media/dvb/frontends/dib7000m.c b/drivers/media/dvb/frontends/dib7000m.c
index 79cb1c20df24..dbb76d75c932 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;