[PATCH] iio: adc: stm32: fix null pointer on defer_probe error

[Olivier Moysan]

dev_err_probe() calls __device_set_deferred_probe_reason()
on -EPROBE_DEFER error.
If device pointer to driver core private structure is not initialized,
a null pointer error occurs.
This pointer is set too late on iio_device_register() call, for iio device.
So use parent device instead for dev_err_probe() call.

Fixes: 0e346b2cfa85 ("iio: adc: stm32-adc: add vrefint calibration support")

Signed-off-by: Olivier Moysan <olivier.moysan at foss.st.com>
---
 drivers/iio/adc/stm32-adc.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
index 7f1fb36c747c..14c7c9d390e8 100644
--- a/drivers/iio/adc/stm32-adc.c
+++ b/drivers/iio/adc/stm32-adc.c
@@ -217,6 +217,7 @@ struct stm32_adc_cfg {
 
 /**
  * struct stm32_adc - private data of each ADC IIO instance
+ * dev:			parent device
  * @common:		reference to ADC block common data
  * @offset:		ADC instance register offset in ADC block
  * @cfg:		compatible configuration data
@@ -243,6 +244,7 @@ struct stm32_adc_cfg {
  * @int_ch:		internal channel indexes array
  */
 struct stm32_adc {
+	struct device		*dev;
 	struct stm32_adc_common	*common;
 	u32			offset;
 	const struct stm32_adc_cfg	*cfg;
@@ -1986,8 +1988,7 @@ static int stm32_adc_populate_int_ch(struct iio_dev *indio_dev, const char *ch_n
 			/* Get calibration data for vrefint channel */
 			ret = nvmem_cell_read_u16(&indio_dev->dev, "vrefint", &vrefint);
 			if (ret && ret != -ENOENT) {
-				return dev_err_probe(&indio_dev->dev, ret,
-						     "nvmem access error\n");
+				return dev_err_probe(adc->dev, ret, "nvmem access error\n");
 			}
 			if (ret == -ENOENT)
 				dev_dbg(&indio_dev->dev, "vrefint calibration not found\n");
@@ -2221,6 +2222,7 @@ static int stm32_adc_probe(struct platform_device *pdev)
 	init_completion(&adc->completion);
 	adc->cfg = (const struct stm32_adc_cfg *)
 		of_match_device(dev->driver->of_match_table, dev)->data;
+	adc->dev = &pdev->dev;
 
 	indio_dev->name = dev_name(&pdev->dev);
 	indio_dev->dev.of_node = pdev->dev.of_node;
-- 
2.17.1