Re: [PATCH] hwmon: (tmp102) Force wait for conversion time for the first valid data

[Guenter Roeck]

On 12/01/2015 06:21 AM, Nishanth Menon wrote:
[ ... ]

Hint about how the patch will look like:

Looks ok (and better).

Guenter

diff --git a/drivers/hwmon/tmp102.c b/drivers/hwmon/tmp102.c
index 65482624ea2c..5289aa0980a8 100644
--- a/drivers/hwmon/tmp102.c
+++ b/drivers/hwmon/tmp102.c
@@ -58,6 +58,7 @@ struct tmp102 {
        u16 config_orig;
        unsigned long last_update;
        int temp[3];
+       bool first_time;
  };

  /* convert left adjusted 13-bit TMP102 register value to milliCelsius */
@@ -93,6 +94,7 @@ static struct tmp102 *tmp102_update_device(struct device *dev)
                                tmp102->temp[i] = tmp102_reg_to_mC(status);
                }
                tmp102->last_update = jiffies;
+               tmp102->first_time = false;
        }
        mutex_unlock(&tmp102->lock);
        return tmp102;
@@ -102,6 +104,12 @@ static int tmp102_read_temp(void *dev, int *temp)
  {
        struct tmp102 *tmp102 = tmp102_update_device(dev);

+       /* Is it too early even to return a conversion? */
+       if (tmp102->first_time) {
+               dev_dbg(dev, "%s: Conversion not ready yet..\n", __func__);
+               return -EAGAIN;
+       }
+
        *temp = tmp102->temp[0];

        return 0;
@@ -114,6 +122,10 @@ static ssize_t tmp102_show_temp(struct device *dev,
        struct sensor_device_attribute *sda = to_sensor_dev_attr(attr);
        struct tmp102 *tmp102 = tmp102_update_device(dev);

+       /* Is it too early even to return a read? */
+       if (tmp102->first_time)
+               return -EAGAIN;
+
        return sprintf(buf, "%d\n", tmp102->temp[sda->index]);
  }

@@ -207,7 +219,9 @@ static int tmp102_probe(struct i2c_client *client,
                status = -ENODEV;
                goto fail_restore_config;
        }
-       tmp102->last_update = jiffies - HZ;
+       tmp102->last_update = jiffies;
+       /* Mark that we are not ready with data until conversion is complete */
+       tmp102->first_time = true;
        mutex_init(&tmp102->lock);

        hwmon_dev = hwmon_device_register_with_groups(dev, client->name,

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