Subject: FAILED: patch "[PATCH] iio: adc: max1363: sign-extend bipolar differential channel" failed to apply to 5.15-stable tree
To: congnt264@gmail.com,andriy.shevchenko@intel.com,jonathan.cameron@oss.qualcomm.com
Cc: <stable@vger.kernel.org>
From: <gregkh@linuxfoundation.org>
Date: Tue, 06 Oct 2026 09:44:25 +0200
Message-ID: <2026100625-specimen-axis-124d@gregkh>
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The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 91908c0a78baddc8572aa3ab69e62ee2eb496ba4
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '2026100625-specimen-axis-124d@gregkh' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Possible dependencies:


thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 91908c0a78baddc8572aa3ab69e62ee2eb496ba4 Mon Sep 17 00:00:00 2001
From: Cong Nguyen <congnt264@gmail.com>
Date: Mon, 10 Aug 2026 23:44:46 +0700
Subject: [PATCH] iio: adc: max1363: sign-extend bipolar differential channel
 reads

MAX1363 differential channels are bipolar, but max1363_read_single_chan()
masks the raw value to the ADC resolution without sign-extending it.
Negative differential readings are therefore reported to userspace as
large positive values (e.g. -1 as 4095 on a 12-bit part).

Sign-extend the masked value from the resolution bit for differential
channels. Single-ended channels are unipolar and are left unchanged.

Fixes: d1325cf45077 ("Staging: IIO: max1363 ADC driver")
Cc: stable@vger.kernel.org
Assisted-by: Claude:claude-opus-4
Signed-off-by: Cong Nguyen <congnt264@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>

diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c
index 65a2d92bb112..629c53af6472 100644
--- a/drivers/iio/adc/max1363.c
+++ b/drivers/iio/adc/max1363.c
@@ -404,6 +404,14 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
 
 		data = rxbuf[0];
 	}
+
+	/*
+	 * Differential channels are bipolar and the device returns the sample
+	 * in two's complement, so sign-extend it from the resolution bit.
+	 */
+	if (chan->differential)
+		data = sign_extend32(data, st->chip_info->bits - 1);
+
 	*val = data;
 
 	return 0;