[PATCH] hwmon: (sht4x) Convert update_interval to jiffies in pending data check

[PATCH] hwmon: (sht4x) Convert update_interval to jiffies in pending data check

[Guenter Roeck]

In sht4x_read_values(), the check for whether a pending post-heater
measurement is still fresh compares get_jiffies_64() against
data->heating_complete + data->update_interval. However,
data->heating_complete is stored in jiffies whereas data->update_interval
is stored in milliseconds.

Whenever HZ != 1000, adding data->update_interval directly without
msecs_to_jiffies() mixes incompatible time units. For example, with the
default 2000 ms update_interval, the validity window is inflated to 8
seconds at HZ=250 and 20 seconds at HZ=100 instead of 2 seconds. A read
within that extended window skips triggering a fresh measurement and
instead returns and caches the stale post-heating measurement left in the
sensor's output buffer.

Convert data->update_interval to jiffies using msecs_to_jiffies() when
computing the pending measurement expiration deadline, matching the
next_update calculation right below it.

Reported-by: Sashiko <sashiko-bot@kernel.org>
Fixes: 0eed6fc3d2b9 ("hwmon: (sht4x): add heater support")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
---
 drivers/hwmon/sht4x.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
index 8372b4fc902e..020a523bf863 100644
--- a/drivers/hwmon/sht4x.c
+++ b/drivers/hwmon/sht4x.c
@@ -111,7 +111,9 @@ static int sht4x_read_values(struct sht4x_data *data)
 	}
 
 	if (data->data_pending &&
-	    time_before64(get_jiffies_64(), data->heating_complete + data->update_interval)) {
+	    time_before64(get_jiffies_64(),
+			  data->heating_complete +
+			  msecs_to_jiffies(data->update_interval))) {
 		data->data_pending = false;
 	} else {
 		next_update = data->last_updated +
-- 
2.45.2

Re: [PATCH] hwmon: (sht4x) Convert update_interval to jiffies in pending data check

[sashiko-bot]

> In sht4x_read_values(), the check for whether a pending post-heater
> measurement is still fresh compares get_jiffies_64() against
> data->heating_complete + data->update_interval. However,
> data->heating_complete is stored in jiffies whereas data->update_interval
> is stored in milliseconds.
> 
> Whenever HZ != 1000, adding data->update_interval directly without
> msecs_to_jiffies() mixes incompatible time units. For example, with the
> default 2000 ms update_interval, the validity window is inflated to 8
> seconds at HZ=250 and 20 seconds at HZ=100 instead of 2 seconds. A read
> within that extended window skips triggering a fresh measurement and
> instead returns and caches the stale post-heating measurement left in the
> sensor's output buffer.
> 
> Convert data->update_interval to jiffies using msecs_to_jiffies() when
> computing the pending measurement expiration deadline, matching the
> next_update calculation right below it.
> 
> Reported-by: Sashiko <sashiko-bot@kernel.org>
> Fixes: 0eed6fc3d2b9 ("hwmon: (sht4x): add heater support")
> Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261101014756.1921506-1-linux@roeck-us.net?part=1