@@ -118,15 +118,10 @@ 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;
@@ -144,6 +139,21 @@ 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;
@@ -153,8 +163,15 @@ 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]));
}
This is a note to let you know that I have just added a patch titled [media] dib8000: make 32 bits read atomic to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.18. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From a6720170eda6aad7a3c8f7656f66516df68028a3 Mon Sep 17 00:00:00 2001 From: Mauro Carvalho Chehab <m.chehab@samsung.com> Date: Fri, 13 Dec 2013 10:35:03 -0300 Subject: [media] 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: Kamal Mostafa <kamal@canonical.com> --- drivers/media/dvb-frontends/dib8000.c | 33 +++++++++++++++++++++++++-------- 1 file changed, 25 insertions(+), 8 deletions(-) -- 1.8.3.2