adc: ads1x1x: improve behaviour during i2c errors

Fixes #61401

The ADS1x1x driver has a bad habit of assuming i2c operations will
always suceed - this fixes the two worse cases in the code I could
identify (there may yet be more).

* During initial ADC setup, if either of the two I2C operations
  (read or write) fails, raise the error immediately to the caller
  rather than letting it fall through to the acquisition thread.

  This ensures that we only ever attempt to give a result that was
  definitely connected to our attempt to start the capture.

* If the acquisition thread encounters an I2C error, raise the error
  but do not terminate the aquisition thread.  This ensures the
  application can attempt to fix the condition that caused the I2C
  error and try again.

Signed-off-by: Chris Collins <[email protected]>

Author: kuroneko

drivers/adc/adc_ads1x1x.c

@@ -185,12 +185,16 @@ static int ads1x1x_start_conversion(const struct device *dev)
 {
 	/* send start sampling command */
 	uint16_t config;
+	int ret;
 
-	ads1x1x_read_reg(dev, ADS1X1X_REG_CONFIG, &config);
+	ret = ads1x1x_read_reg(dev, ADS1X1X_REG_CONFIG, &config);
+	if (ret != 0) {
+		return ret;
+	}
 	config |= ADS1X1X_CONFIG_OS;
-	ads1x1x_write_reg(dev, ADS1X1X_REG_CONFIG, config);
+	ret = ads1x1x_write_reg(dev, ADS1X1X_REG_CONFIG, config);
 
-	return 0;
+	return ret;
 }
 
 static inline int ads1x1x_acq_time_to_dr(const struct device *dev, uint16_t acq_time)
@@ -458,11 +462,19 @@ static void adc_context_update_buffer_pointer(struct adc_context *ctx, bool repe
 static void adc_context_start_sampling(struct adc_context *ctx)
 {
 	struct ads1x1x_data *data = CONTAINER_OF(ctx, struct ads1x1x_data, ctx);
+	int ret;
 
 	data->repeat_buffer = data->buffer;
 
-	ads1x1x_start_conversion(data->dev);
-
+	ret = ads1x1x_start_conversion(data->dev);
+	if (ret != 0) {
+		/* if we fail to complete the I2C operations to start
+		 * sampling, return an immediate error (likely -EIO) rather
+		 * than handing it off to the acquisition thread.
+		 */
+		adc_context_complete(ctx, ret);
+		return;
+	}
 	k_sem_give(&data->acq_sem);
 }
 
@@ -537,7 +549,7 @@ static void ads1x1x_acquisition_thread(const struct device *dev)
 		if (rc != 0) {
 			LOG_ERR("failed to get ready status (err %d)", rc);
 			adc_context_complete(&data->ctx, rc);
-			break;
+			continue;
 		}
 
 		ads1x1x_adc_perform_read(dev);