xiaoxiang781216 commented on code in PR #19596:
URL: https://github.com/apache/nuttx/pull/19596#discussion_r3697653883
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drivers/sensors/sensor.c:
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@@ -1177,12 +1248,40 @@ static int sensor_poll(FAR struct file *filep,
fds->priv = filep;
if (lower->ops->fetch)
{
- /* Always return POLLIN for fetch only sensor: the data is read
- * from the device on demand by sensor_read(), so there is never
- * anything to wait for.
+ /* A fetch() only sensor is read from the device on demand, so it
+ * is always ready unless this subscriber asked for a rate, in
+ * which case it becomes ready once per interval and
+ * sensor_fetch_worker() is what wakes the poll.
+ */
+
+#ifdef CONFIG_SCHED_LPWORK
+ if (user->state.interval == UINT32_MAX)
+ {
+ eventset |= POLLIN;
+ }
+ else
+ {
+ uint64_t now = sensor_get_timestamp();
+ uint64_t elapsed = now - user->fetched;
+
+ if (elapsed >= user->state.interval)
+ {
+ user->fetched = now;
+ eventset |= POLLIN;
+ }
+ else
+ {
+ work_queue(LPWORK, &user->work, sensor_fetch_worker, user,
Review Comment:
should we avoid the work queue? the benefit from fetch is avoiding the work
or thread.
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