iio: adc: max1027: Add debugfs register read support

Until now, only write operations were supported. Force two bytes read
operation when reading, which should fit most of the development
purposes. Of course, extended operations like buffered reads on
multiple channels or even temperature + voltage reads will not be read
entirely. Usually, just starting a new operation will work but in any
case a software reset (done through the debufs interface too) will
return the device in a usable state.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
index 214883458582583c1c68949b6cca19ef39a29a82..6cdfe9ef73fc49a325dffa1b0602885798c9bfb6 100644 (file)
--- a/drivers/iio/adc/max1027.c
+++ b/drivers/iio/adc/max1027.c
@@ -309,8 +309,11 @@ static int max1027_debugfs_reg_access(struct iio_dev *indio_dev,
        struct max1027_state *st = iio_priv(indio_dev);
        u8 *val = (u8 *)st->buffer;
 
-       if (readval != NULL)
-               return -EINVAL;
+       if (readval) {
+               int ret = spi_read(st->spi, val, 2);
+               *readval = be16_to_cpu(st->buffer[0]);
+               return ret;
+       }
 
        *val = (u8)writeval;
        return spi_write(st->spi, val, 1);