patch "iio: hid-sensor-trigger: Fix sometimes not powering up the sensor" added to staging-linus

This is a note to let you know that I've just added the patch titled

iio: hid-sensor-trigger: Fix sometimes not powering up the sensor

to my staging git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From: Hans de Goede <[email protected]>
Date: Sat, 14 Apr 2018 17:09:09 +0200
Subject: iio: hid-sensor-trigger: Fix sometimes not powering up the sensor
after resume

hid_sensor_set_power_work() powers the sensors back up after a resume based on the user_requested_state atomic_t.

But hid_sensor_power_state() treats this as a boolean flag, leading to the following problematic scenario:

1) Some app starts using the iio-sensor in buffered / triggered mode, hid_sensor_data_rdy_trigger_set_state(true) gets called, setting user_requested_state to 1.
2) Something directly accesses a _raw value through sysfs, leading to a call to hid_sensor_power_state(true) followed by hid_sensor_power_state(false) call, this sets user_requested_state to 1 followed by setting it to 0.
3) Suspend/resume the machine, hid_sensor_set_power_work() now does NOT power the sensor back up because user_requested_state (wrongly) is 0. Which stops the app using the sensor in buffered mode from receiving any new values.

This commit changes user_requested_state to a counter tracking how many times hid_sensor_power_state(true) was called instead, fixing this.

---
 drivers/iio/common/hid-sensors/hid-sensor-trigger.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

index cfb6588565ba..4905a997a7ec 100644
@@ -178,14 +178,14 @@ int hid_sensor_power_state(struct hid_sensor_common *st, bool state)
 #ifdef CONFIG_PM
 	int ret;
 
-	atomic_set(&st->user_requested_state, state);
-
 	if (atomic_add_unless(&st->runtime_pm_enable, 1, 1))
 		pm_runtime_enable(&st->pdev->dev);
 
-	if (state)
+	if (state) {
+		atomic_inc(&st->user_requested_state);
 		ret = pm_runtime_get_sync(&st->pdev->dev);
-	else {
+	} else {
+		atomic_dec(&st->user_requested_state);
 		pm_runtime_mark_last_busy(&st->pdev->dev);
 		pm_runtime_use_autosuspend(&st->pdev->dev);
 		ret = pm_runtime_put_autosuspend(&st->pdev->dev);

2.17.0