Re: [PATCH] [v4]Input: evdev - drop partial events after emptying the buffer

[Aniroop Mathur]

Hello Mr. Torokhov,

Could you please help to update about below patch ?

Thanks,
Aniroop Mathur

On Tue, Jan 5, 2016 at 3:26 AM, Aniroop Mathur <a.mathur@xxxxxxxxxxx> 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 and this in turn reduces
> evdev client reading requests plus saves memory space filled by partial
> events in evdev handler buffer.
> Also, this patch prevents dropping of full packet by evdev client after
> SYN_DROPPED occurs in case last stored event was SYN_REPORT.
> (like after clock change request)
>
> --
> Please ignore v3.
>
> Signed-off-by: Aniroop Mathur <a.mathur@xxxxxxxxxxx>
> ---
>  drivers/input/evdev.c | 53 ++++++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 40 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index e9ae3d5..15b6eb2 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 if partial events need to be dropped */
>         unsigned long *evmasks[EV_CNT];
>         unsigned int bufsize;
>         struct input_event buffer[];
> @@ -156,7 +157,12 @@ static void __evdev_flush_queue(struct evdev_client *client, unsigned int type)
>  static void __evdev_queue_syn_dropped(struct evdev_client *client)
>  {
>         struct input_event ev;
> +       struct input_event *prev_ev;
>         ktime_t time;
> +       unsigned int mask = client->bufsize - 1;
> +
> +       /* Store previous event */
> +       prev_ev = &client->buffer[(client->head - 1) & mask];
>
>         time = client->clk_type == EV_CLK_REAL ?
>                         ktime_get_real() :
> @@ -170,13 +176,33 @@ static void __evdev_queue_syn_dropped(struct evdev_client *client)
>         ev.value = 0;
>
>         client->buffer[client->head++] = ev;
> -       client->head &= client->bufsize - 1;
> +       client->head &= mask;
>
>         if (unlikely(client->head == client->tail)) {
>                 /* drop queue but keep our SYN_DROPPED event */
> -               client->tail = (client->head - 1) & (client->bufsize - 1);
> +               client->tail = (client->head - 1) & mask;
>                 client->packet_head = client->tail;
>         }
> +
> +       /*
> +        * If last packet is NOT fully stored, set drop_pevent to true to
> +        * ignore partial events and if last packet is fully stored, queue
> +        * SYN_REPORT so that clients would not ignore next full packet.
> +        */
> +       if (prev_ev->type != EV_SYN && prev_ev->code != SYN_REPORT) {
> +               client->drop_pevent = true;
> +       } else if (prev_ev->type == EV_SYN && prev_ev->code == SYN_REPORT) {
> +               prev_ev->time = ev.time;
> +               client->buffer[client->head++] = *prev_ev;
> +               client->head &= mask;
> +               client->packet_head = client->head;
> +
> +               /* drop queue but keep our SYN_DROPPED & SYN_REPORT event */
> +               if (unlikely(client->head == client->tail)) {
> +                       client->tail = (client->head - 2) & mask;
> +                       client->packet_head = client->tail;
> +               }
> +       }
>  }
>
>  static void evdev_queue_syn_dropped(struct evdev_client *client)
> @@ -235,18 +261,8 @@ static void __pass_event(struct evdev_client *client,
>         client->head &= client->bufsize - 1;
>
>         if (unlikely(client->head == client->tail)) {
> -               /*
> -                * This effectively "drops" all unconsumed events, leaving
> -                * EV_SYN/SYN_DROPPED plus the newest event in the queue.
> -                */
> -               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->packet_head = client->tail;
> +               __evdev_queue_syn_dropped(client);
>         }
>
>         if (event->type == EV_SYN && event->code == SYN_REPORT) {
> @@ -284,6 +300,17 @@ static void evdev_pass_values(struct evdev_client *client,
>                         wakeup = true;
>                 }
>
> +               /*
> +                * drop partial events of last packet but queue SYN_REPORT
> +                * so that clients would not ignore extra full packet.
> +                */
> +               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
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/