linux-kernel - [PATCH 5.18 141/181] iio: afe: rescale: Fix boolean logic bug

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Date:   Mon, 27 Jun 2022 13:21:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Liam Beguin <liambeguin@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Peter Rosin <peda@...ntia.se>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 5.18 141/181] iio: afe: rescale: Fix boolean logic bug

From: Linus Walleij <linus.walleij@...aro.org>

commit 9decacd8b3a432316d61c4366f302e63384cb08d upstream.

When introducing support for processed channels I needed
to invert the expression:

  if (!iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) ||
      !iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE))
        dev_err(dev, "source channel does not support raw/scale\n");

To the inverse, meaning detect when we can usse raw+scale
rather than when we can not. This was the result:

  if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) ||
      iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE))
       dev_info(dev, "using raw+scale source channel\n");

Ooops. Spot the error. Yep old George Boole came up and bit me.
That should be an &&.

The current code "mostly works" because we have not run into
systems supporting only raw but not scale or only scale but not
raw, and I doubt there are few using the rescaler on anything
such, but let's fix the logic.

Cc: Liam Beguin <liambeguin@...il.com>
Cc: stable@...r.kernel.org
Fixes: 53ebee949980 ("iio: afe: iio-rescale: Support processed channels")
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Reviewed-by: Liam Beguin <liambeguin@...il.com>
Acked-by: Peter Rosin <peda@...ntia.se>
Link: https://lore.kernel.org/r/20220524075448.140238-1-linus.walleij@linaro.org
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/iio/afe/iio-rescale.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/afe/iio-rescale.c
+++ b/drivers/iio/afe/iio-rescale.c
@@ -278,7 +278,7 @@ static int rescale_configure_channel(str
 	chan->ext_info = rescale->ext_info;
 	chan->type = rescale->cfg->type;
 
-	if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) ||
+	if (iio_channel_has_info(schan, IIO_CHAN_INFO_RAW) &&
 	    iio_channel_has_info(schan, IIO_CHAN_INFO_SCALE)) {
 		dev_info(dev, "using raw+scale source channel\n");
 	} else if (iio_channel_has_info(schan, IIO_CHAN_INFO_PROCESSED)) {