On Mon, Jan 04, 2016 at 09:58:48PM +0530, Aniroop Mathur wrote:
> This patch introduces concept to drop partial events in evdev handler
> itself after emptying the buffer which are dropped by all evdev
> clients in userspace after SYN_DROPPED occurs.
> This in turn saves space of partial events in evdev handler buffer
> and reduces evdev client reading requests.
>
> Signed-off-by: Aniroop Mathur <a.mathur@xxxxxxxxxxx>
> ---
> drivers/input/evdev.c | 56 ++++++++++++++++++++++++++++++++++++++++++---------
> 1 file changed, 47 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index e9ae3d5..0a5ead8 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -58,6 +58,7 @@ struct evdev_client {
> struct list_head node;
> unsigned int clk_type;
> bool revoked;
> + bool drop_pevent; /* specifies whether partial events need to be dropped */
> unsigned long *evmasks[EV_CNT];
> unsigned int bufsize;
> struct input_event buffer[];
> @@ -192,6 +193,7 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
> {
> unsigned long flags;
> unsigned int clk_type;
> + struct input_event ev;
>
> switch (clkid) {
>
> @@ -218,8 +220,26 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
> spin_lock_irqsave(&client->buffer_lock, flags);
>
> if (client->head != client->tail) {
> - client->packet_head = client->head = client->tail;
> +
> + /* Store previous event */
> + client->head--;
> + client->head &= client->bufsize - 1;
> + ev = client->buffer[client->head];
> +
> + client->packet_head = client->head = client->tail = 0;
> __evdev_queue_syn_dropped(client);
> +
> + /*
> + * If last packet is fully stored, queue SYN_REPORT
> + * so that clients do not ignore next full packet.
> + * And if last packet is NOT fully stored,
> + * set drop_pevent to true to ignore partial events.
> + */
> + if (ev.type == EV_SYN && ev.code == SYN_REPORT) {
> + ev.time = client->buffer[client->head - 1].time;
if client->head happens to be 0, your index won't be what it should be :)
you need the &= here and again after the next line:
> + client->buffer[client->head++] = ev;
> + } else if (ev.type != EV_SYN && ev.code != SYN_REPORT)
> + client->drop_pevent = true;
> }
>
> spin_unlock_irqrestore(&client->buffer_lock, flags);
> @@ -236,17 +256,27 @@ static void __pass_event(struct evdev_client *client,
>
> if (unlikely(client->head == client->tail)) {
> /*
> - * This effectively "drops" all unconsumed events, leaving
> - * EV_SYN/SYN_DROPPED plus the newest event in the queue.
> + * This effectively "drops" all unconsumed events, storing
> + * EV_SYN/SYN_DROPPED and the newest event in the queue but
> + * only if it is EV_SYN/SYN_REPORT so that clients can read
> + * the next full event packet. And set drop_pevent to true
> + * if last event packet is not stored completely in buffer
> + * to ignore upcoming partial events.
> */
> - client->tail = (client->head - 2) & (client->bufsize - 1);
>
> - client->buffer[client->tail].time = event->time;
> - client->buffer[client->tail].type = EV_SYN;
> - client->buffer[client->tail].code = SYN_DROPPED;
> - client->buffer[client->tail].value = 0;
> + client->tail = client->head = client->packet_head;
>
> - client->packet_head = client->tail;
> + client->buffer[client->head].time = event->time;
> + client->buffer[client->head].type = EV_SYN;
> + client->buffer[client->head].code = SYN_DROPPED;
> + client->buffer[client->head].value = 0;
> + client->head = (client->head + 1) & (client->bufsize -1);
> +
> + if (event->type == EV_SYN && event->code == SYN_REPORT) {
> + client->buffer[client->head++] = *event;
> + client->head &= client->bufsize - 1;
> + } else if (event->type != EV_SYN && event->code != SYN_REPORT)
> + client->drop_pevent = true;
given that this condition is almost exactly the same as above, you should
share the code. you should also look into checking whether this can be moved
to __evdev_queue_syn_dropped() anyway, it seems like it can with little
effort.
The protocol itself looks correct now though.
Cheers,
Peter
> }
>
> if (event->type == EV_SYN && event->code == SYN_REPORT) {
> @@ -284,6 +314,14 @@ static void evdev_pass_values(struct evdev_client *client,
> wakeup = true;
> }
>
> + /* drop partial events of last packet but queue SYN_REPORT */
> + if (client->drop_pevent) {
> + if (v->type == EV_SYN && v->code == SYN_REPORT)
> + client->drop_pevent = false;
> + else
> + continue;
> + }
> +
> event.type = v->type;
> event.code = v->code;
> event.value = v->value;
> --
> 2.6.2
>
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