Hi William,
On Fri, Feb 12, 2021 at 09:13:41PM +0900, William Breathitt Gray wrote:
> This patch introduces a character device interface for the Counter
> subsystem. Device data is exposed through standard character device read
> operations. Device data is gathered when a Counter event is pushed by
> the respective Counter device driver. Configuration is handled via ioctl
> operations on the respective Counter character device node.
.....
> +/**
> + * counter_push_event - queue event for userspace reading
> + * @counter: pointer to Counter structure
> + * @event: triggered event
> + * @channel: event channel
> + *
> + * Note: If no one is watching for the respective event, it is silently
> + * discarded.
> + */
> +void counter_push_event(struct counter_device *const counter, const u8 event,
> + const u8 channel)
> +{
> + struct counter_event ev = {0};
> + unsigned int copied = 0;
> + unsigned long flags;
> + struct counter_event_node *event_node;
> + struct counter_comp_node *comp_node;
> +
> + ev.timestamp = ktime_get_ns();
> + ev.watch.event = event;
> + ev.watch.channel = channel;
> +
> + /* Could be in an interrupt context, so use a raw spin lock */
> + raw_spin_lock_irqsave(&counter->events_list_lock, flags);
> +
> + /* Search for event in the list */
> + list_for_each_entry(event_node, &counter->events_list, l)
> + if (event_node->event == event &&
> + event_node->channel == channel)
> + break;
> +
> + /* If event is not in the list */
> + if (&event_node->l == &counter->events_list)
> + goto exit_early;
To cover my "interrupt-counter" use case, I added following line here to
convert the tail drop fifo to the head drop fifo:
+ list_for_each_entry(comp_node, &event_node->comp_list, l)
+ to_copy += sizeof(ev);
+
+ while (kfifo_avail(&counter->events) < to_copy)
+ kfifo_skip(&counter->events);
May be it make sense to make it optional and integrate in to you patches
before it goes mainline?
Regards,
Oleksij
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