hwmon: Simplify the locking model of two drivers
Many hardware monitoring drivers use two different mutexes, one to
protect their per-device data structure, and one to protect the
access to the device registers. These mutexes are essentially
redundant, as the drivers are transfering values between the device
registers and the data cache, so they almost always end up holding
both mutexes at the same time. Using a single mutex will make the
code more simple and faster.
I am changing only two of the affected drivers here, the authors
of the other affected drivers are welcome to submit similar patches
if they want.
Signed-off-by: Jean Delvare <khali@linux-fr.org>
diff --git a/drivers/hwmon/it87.c b/drivers/hwmon/it87.c
index bb16668..18bb44d 100644
--- a/drivers/hwmon/it87.c
+++ b/drivers/hwmon/it87.c
@@ -221,7 +221,6 @@
struct it87_data {
struct i2c_client client;
struct class_device *class_dev;
- struct mutex lock;
enum chips type;
struct mutex update_lock;
@@ -548,9 +547,10 @@
struct i2c_client *client = to_i2c_client(dev);
struct it87_data *data = i2c_get_clientdata(client);
int val = simple_strtol(buf, NULL, 10);
- u8 reg = it87_read_value(client, IT87_REG_FAN_DIV);
+ u8 reg;
mutex_lock(&data->update_lock);
+ reg = it87_read_value(client, IT87_REG_FAN_DIV);
switch (nr) {
case 0: data->fan_div[nr] = reg & 0x07; break;
case 1: data->fan_div[nr] = (reg >> 3) & 0x07; break;
@@ -949,7 +949,6 @@
}
new_client = &data->client;
- mutex_init(&data->lock);
i2c_set_clientdata(new_client, data);
new_client->addr = isa_address;
new_client->adapter = adapter;
@@ -1127,33 +1126,22 @@
return 0;
}
-/* ISA access must be locked explicitly!
+/* Must be called with data->update_lock held, except during initialization.
We ignore the IT87 BUSY flag at this moment - it could lead to deadlocks,
would slow down the IT87 access and should not be necessary. */
static int it87_read_value(struct i2c_client *client, u8 reg)
{
- struct it87_data *data = i2c_get_clientdata(client);
- int res;
-
- mutex_lock(&data->lock);
outb_p(reg, client->addr + IT87_ADDR_REG_OFFSET);
- res = inb_p(client->addr + IT87_DATA_REG_OFFSET);
- mutex_unlock(&data->lock);
-
- return res;
+ return inb_p(client->addr + IT87_DATA_REG_OFFSET);
}
-/* ISA access must be locked explicitly!
+/* Must be called with data->update_lock held, except during initialization.
We ignore the IT87 BUSY flag at this moment - it could lead to deadlocks,
would slow down the IT87 access and should not be necessary. */
static void it87_write_value(struct i2c_client *client, u8 reg, u8 value)
{
- struct it87_data *data = i2c_get_clientdata(client);
-
- mutex_lock(&data->lock);
outb_p(reg, client->addr + IT87_ADDR_REG_OFFSET);
outb_p(value, client->addr + IT87_DATA_REG_OFFSET);
- mutex_unlock(&data->lock);
}
/* Return 1 if and only if the PWM interface is safe to use */