FAILED: patch "[PATCH] iio: light: isl29028: fix runtime PM reference leak on error paths" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

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 0e30d15b15647df786e60022650613e16dd70645
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107055841-failed-5.15-0e30d15b1564@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

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

From 0e30d15b15647df786e60022650613e16dd70645 Mon Sep 17 00:00:00 2001
From: Fabio Cesari <fabio.cesari@gmail.com>
Date: Thu, 10 Sep 2026 08:24:35 +0200
Subject: [PATCH] iio: light: isl29028: fix runtime PM reference leak on error
 paths

isl29028_read_raw() and isl29028_write_raw() take a runtime PM reference
with pm_runtime_resume_and_get() but return directly on their error
paths without dropping it. The usage count never balances again and the
device stops entering autosuspend for good. In isl29028_read_raw() this
needs a regmap access to fail; in isl29028_write_raw() one rejected
sysfs write is enough, for example

  echo 200 > in_proximity_sampling_frequency

which is outside the [1:100] range and returns -EINVAL with the
reference still held.

Take the reference with PM_RUNTIME_ACQUIRE_AUTOSUSPEND() instead, so it
is released on every return path.

This also stops the return value of pm_runtime_put_autosuspend() from
reaching userspace. That value only says whether the device could be
suspended right away, so -EAGAIN or -EPERM turns a successful access
into a failure, and with CONFIG_PM=n the stub returns -ENOSYS on every
access.

Fixes: 2db5054ac28d ("staging: iio: isl29028: add runtime power management support")
Suggested-by: Joshua Crofts <joshua.crofts1@gmail.com>
Cc: stable@vger.kernel.org
Assisted-by: LLM coccinelle
Signed-off-by: Fabio Cesari <fabio.cesari@gmail.com>
Reviewed-by: Joshua Crofts <joshua.crofts1@gmail.com>
Signed-off-by: Jonathan Cameron <jonathan.cameron@oss.qualcomm.com>
---
 drivers/iio/light/isl29028.c | 33 ++++++++-------------------------
 1 file changed, 8 insertions(+), 25 deletions(-)

diff --git a/drivers/iio/light/isl29028.c b/drivers/iio/light/isl29028.c
index 33deb1726689e..e481ac908fc13 100644
--- a/drivers/iio/light/isl29028.c
+++ b/drivers/iio/light/isl29028.c
@@ -342,8 +342,9 @@ static int isl29028_write_raw(struct iio_dev *indio_dev,
 	struct device *dev = regmap_get_device(chip->regmap);
 	int ret;
 
-	ret = pm_runtime_resume_and_get(dev);
-	if (ret < 0)
+	PM_RUNTIME_ACQUIRE_AUTOSUSPEND(dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
 		return ret;
 
 	mutex_lock(&chip->lock);
@@ -392,14 +393,7 @@ static int isl29028_write_raw(struct iio_dev *indio_dev,
 
 	mutex_unlock(&chip->lock);
 
-	if (ret < 0)
-		return ret;
-
-	ret = pm_runtime_put_autosuspend(dev);
-	if (ret < 0)
-		return ret;
-
-	return 0;
+	return ret;
 }
 
 static int isl29028_read_raw(struct iio_dev *indio_dev,
@@ -408,10 +402,11 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 {
 	struct isl29028_chip *chip = iio_priv(indio_dev);
 	struct device *dev = regmap_get_device(chip->regmap);
-	int ret, pm_ret;
+	int ret;
 
-	ret = pm_runtime_resume_and_get(dev);
-	if (ret < 0)
+	PM_RUNTIME_ACQUIRE_AUTOSUSPEND(dev, pm);
+	ret = PM_RUNTIME_ACQUIRE_ERR(&pm);
+	if (ret)
 		return ret;
 
 	mutex_lock(&chip->lock);
@@ -461,18 +456,6 @@ static int isl29028_read_raw(struct iio_dev *indio_dev,
 
 	mutex_unlock(&chip->lock);
 
-	if (ret < 0)
-		return ret;
-
-	/**
-	 * Preserve the ret variable if the call to
-	 * pm_runtime_put_autosuspend() is successful so the reading
-	 * (if applicable) is returned to user space.
-	 */
-	pm_ret = pm_runtime_put_autosuspend(dev);
-	if (pm_ret < 0)
-		return pm_ret;
-
 	return ret;
 }
 
-- 
2.53.0