[PATCH v3] staging: iio: adc: ad7192: disable burnout currents on misconfig

[<alexandru.ardelean@analog.com>]

From: Alexandru Ardelean <alexandru.ardelean@analog.com>

The burnout currents can be enabled only if buffer is enabled
and CHOP is disabled.

So, if neither of these conditions are met, then
we should disable the burnout currents in the driver as well,
and warn the user.

This change doesn't fix anything.
The burnout currents simply won't work if CHOP is enabled
or buffer is disabled.
The intent is to provide the user with some feedback
instead of silently not working inside the chip.

Signed-off-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
---

Changes v2 -> v3:
  * fixed "dev_warn(dev," ==> "dev_warn(&st->sd.spi->dev,"
    `dev` does not exist
  * moved the warning as part of an else case ; patch is
    simpler and `pdata` is const which fails

 drivers/staging/iio/adc/ad7192.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/iio/adc/ad7192.c b/drivers/staging/iio/adc/ad7192.c
index d11c6de9c777..aebbc3b58194 100644
--- a/drivers/staging/iio/adc/ad7192.c
+++ b/drivers/staging/iio/adc/ad7192.c
@@ -291,8 +291,12 @@ static int ad7192_setup(struct ad7192_state *st,
 	if (pdata->unipolar_en)
 		st->conf |= AD7192_CONF_UNIPOLAR;
 
-	if (pdata->burnout_curr_en)
+	if (pdata->burnout_curr_en && pdata->buf_en && !pdata->chop_en) {
 		st->conf |= AD7192_CONF_BURN;
+	} else {
+		dev_warn(&st->sd.spi->dev,
+			 "Can't enable burnout currents: see CHOP or buffer\n");
+	}
 
 	ret = ad_sd_write_reg(&st->sd, AD7192_REG_MODE, 3, st->mode);
 	if (ret)
-- 
2.14.1