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authorMauro Carvalho Chehab <m.chehab@samsung.com>2013-12-13 10:35:03 -0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-02-13 13:48:02 -0800
commit549ac1ac8cf1e7c696501ed8e53956f6c64b217e (patch)
tree298b9df3a50701f03510ec9a6d0b1a3e710fd203
parent8bed1b8f616b58441801d0f0fb277099b467c055 (diff)
downloadlinaro-lsk-549ac1ac8cf1e7c696501ed8e53956f6c64b217e.tar.gz
dib8000: make 32 bits read atomic
commit 5ac64ba12aca3bef18e61c866583155a3bbf81c4 upstream. As the dvb-frontend kthread can be called anytime, it can race with some get status ioctl. So, it seems better to avoid one to race with the other while reading a 32 bits register. I can't see any other reason for having a mutex there at I2C, except to provide such kind of protection, as the I2C core already has a mutex to protect I2C transfers. Note: instead of this approach, it could eventually remove the dib8000 specific mutex for it, and either group the 4 ops into one xfer or to manually control the I2C mutex. The main advantage of the current approach is that the changes are smaller and more puntual. Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com> Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com> Acked-by: Patrick Boettcher <pboettcher@kernellabs.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/media/dvb-frontends/dib8000.c33
1 files changed, 25 insertions, 8 deletions
diff --git a/drivers/media/dvb-frontends/dib8000.c b/drivers/media/dvb-frontends/dib8000.c
index a54182dd0e9..67e96557fd3 100644
--- a/drivers/media/dvb-frontends/dib8000.c
+++ b/drivers/media/dvb-frontends/dib8000.c
@@ -157,15 +157,10 @@ static u16 dib8000_i2c_read16(struct i2c_device *i2c, u16 reg)
return ret;
}
-static u16 dib8000_read_word(struct dib8000_state *state, u16 reg)
+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;
@@ -183,6 +178,21 @@ static u16 dib8000_read_word(struct dib8000_state *state, u16 reg)
dprintk("i2c read error on %d", reg);
ret = (state->i2c_read_buffer[0] << 8) | state->i2c_read_buffer[1];
+
+ 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;
+ }
+
+ ret = __dib8000_read_word(state, reg);
+
mutex_unlock(&state->i2c_buffer_lock);
return ret;
@@ -192,8 +202,15 @@ static u32 dib8000_read32(struct dib8000_state *state, u16 reg)
{
u16 rw[2];
- rw[0] = dib8000_read_word(state, reg + 0);
- rw[1] = dib8000_read_word(state, reg + 1);
+ if (mutex_lock_interruptible(&state->i2c_buffer_lock) < 0) {
+ dprintk("could not acquire lock");
+ return 0;
+ }
+
+ rw[0] = __dib8000_read_word(state, reg + 0);
+ rw[1] = __dib8000_read_word(state, reg + 1);
+
+ mutex_unlock(&state->i2c_buffer_lock);
return ((rw[0] << 16) | (rw[1]));
}