iio: ad799x: Fix ad7991/ad7995/ad7999 config setup

The ad7991/ad7995/ad7999 does not have a configuration register like the
other devices that can be written and read. The configuration is written as
part of the conversion sequence.

Fixes: 0f7ddcc1bff1 ("iio:adc:ad799x: Write default config on probe and reset alert status on probe")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Tested-by: Mike Looijmans <mike.looijmans@topic.nl>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c
index e37412da15f5..b99de00e57b8 100644
--- a/drivers/iio/adc/ad799x.c
+++ b/drivers/iio/adc/ad799x.c
@@ -143,9 +143,15 @@ static int ad799x_write_config(struct ad799x_state *st, u16 val)
         case ad7998:
                 return i2c_smbus_write_word_swapped(st->client, AD7998_CONF_REG,
                         val);
-        default:
+        case ad7992:
+        case ad7993:
+        case ad7994:
                 return i2c_smbus_write_byte_data(st->client, AD7998_CONF_REG,
                         val);
+        default:
+                /* Will be written when doing a conversion */
+                st->config = val;
+                return 0;
         }
 }
 
@@ -155,8 +161,13 @@ static int ad799x_read_config(struct ad799x_state *st)
         case ad7997:
         case ad7998:
                 return i2c_smbus_read_word_swapped(st->client, AD7998_CONF_REG);
-        default:
+        case ad7992:
+        case ad7993:
+        case ad7994:
                 return i2c_smbus_read_byte_data(st->client, AD7998_CONF_REG);
+        default:
+                /* No readback support */
+                return st->config;
         }
 }