[PATCH] thermal: qcom-spmi-adc-tm5: fix all temperature reads failing with -EINVAL

[PATCH] thermal: qcom-spmi-adc-tm5: fix all temperature reads failing with -EINVAL

[Paul Hollinsky]

adc_tm5_get_temp() rejects any iio_read_channel_processed() return value
that is not IIO_VAL_INT. Since commit bb21ee31f575 ("iio: Fix
iio_multiply_value use in iio_read_channel_processed_scale"),
iio_read_channel_processed() returns 0 on success, per its documented
contract, instead of passing through the value type from the underlying
read.

Since IIO_VAL_INT is 1, every successful read now takes the error path,
so get_temp() returns -EINVAL unconditionally and every ADC-TM5 thermal
zone is dead: with no valid temperature readings the core cannot
evaluate trip points. Observed on a SC7180 Trogdor Chromebook (Lenovo
IdeaPad Duet 3 / wormdingler), where the charger and skin-temp zones
report an error on every read.

The check no longer serves its original defensive purpose either: since
commit 05f958d003c9 ("iio: Improve iio_read_channel_processed_scale()
precision"), fractional value types are folded into the integer result
by iio_multiply_value() inside the IIO core, so the return value carries
no information beyond success or failure. Just drop the check and rely
on the ret < 0 test above it.

qcom-spmi-adc-tm5 is the only iio_read_channel_processed() consumer in
tree still testing the return value this way.

Fixes: bb21ee31f575 ("iio: Fix iio_multiply_value use in iio_read_channel_processed_scale")
Cc: stable@vger.kernel.org # 6.18+
Signed-off-by: Paul Hollinsky <phollinsky@holtechnik.com>
---
 drivers/thermal/qcom/qcom-spmi-adc-tm5.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/drivers/thermal/qcom/qcom-spmi-adc-tm5.c b/drivers/thermal/qcom/qcom-spmi-adc-tm5.c
index bb6222c8cc5f..af72db6299cd 100644
--- a/drivers/thermal/qcom/qcom-spmi-adc-tm5.c
+++ b/drivers/thermal/qcom/qcom-spmi-adc-tm5.c
@@ -369,9 +369,6 @@ static int adc_tm5_get_temp(struct thermal_zone_device *tz, int *temp)
 	if (ret < 0)
 		return ret;
 
-	if (ret != IIO_VAL_INT)
-		return -EINVAL;
-
 	return 0;
 }
 
-- 
2.55.0