iio: mma8452: avoid switching to active because of config change

[cascardo/linux.git] / drivers / iio / accel / mma8452.c

diff --git a/drivers/iio/accel/mma8452.c b/drivers/iio/accel/mma8452.c
index 17d72bc..9c4a84a 100644 (file)
--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -393,24 +393,47 @@ static int mma8452_active(struct mma8452_data *data)
                                         data->ctrl_reg1);
 }
 
+/* returns >0 if active, 0 if in standby and <0 on error */
+static int mma8452_is_active(struct mma8452_data *data)
+{
+       int reg;
+
+       reg = i2c_smbus_read_byte_data(data->client, MMA8452_CTRL_REG1);
+       if (reg < 0)
+               return reg;
+
+       return reg & MMA8452_CTRL_ACTIVE;
+}
+
 static int mma8452_change_config(struct mma8452_data *data, u8 reg, u8 val)
 {
        int ret;
+       int is_active;
 
        mutex_lock(&data->lock);
 
-       /* config can only be changed when in standby */
-       ret = mma8452_standby(data);
-       if (ret < 0)
+       is_active = mma8452_is_active(data);
+       if (is_active < 0) {
+               ret = is_active;
                goto fail;
+       }
+
+       /* config can only be changed when in standby */
+       if (is_active > 0) {
+               ret = mma8452_standby(data);
+               if (ret < 0)
+                       goto fail;
+       }
 
        ret = i2c_smbus_write_byte_data(data->client, reg, val);
        if (ret < 0)
                goto fail;
 
-       ret = mma8452_active(data);
-       if (ret < 0)
-               goto fail;
+       if (is_active > 0) {
+               ret = mma8452_active(data);
+               if (ret < 0)
+                       goto fail;
+       }
 
        ret = 0;
 fail: