Hi Anoroop,
On Wed, Oct 05, 2016 at 12:42:56AM +0530, Aniroop Mathur wrote:
> If last event dropped in the old queue was EV_SYN/SYN_REPORT, then lets
> generate EV_SYN/SYN_REPORT immediately after queing EV_SYN/SYN_DROPPED
> so that clients would not ignore next valid full packet events.
>
> Signed-off-by: Aniroop Mathur <a.mathur@xxxxxxxxxxx>
>
> Difference from v8:
> Added check for handling EVIOCG[type] ioctl for queue empty case
> ---
> drivers/input/evdev.c | 52 ++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 39 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/input/evdev.c b/drivers/input/evdev.c
> index e9ae3d5..69407ff 100644
> --- a/drivers/input/evdev.c
> +++ b/drivers/input/evdev.c
> @@ -156,7 +156,12 @@ 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 *last_ev;
> ktime_t time;
> + unsigned int mask = client->bufsize - 1;
> +
> + /* capture last event stored in the buffer */
> + last_ev = &client->buffer[(client->head - 1) & mask];
I am uneasy with this "looking back" into the queue. How can we be sure
that we are looking at the right event? As far as I can tell we do not
know if that event has been consumed or not.
>
> time = client->clk_type == EV_CLK_REAL ?
> ktime_get_real() :
> @@ -170,13 +175,28 @@ 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 was completely stored, then queue SYN_REPORT
> + * so that clients would not ignore next valid full packet
> + */
> + if (last_ev->type == EV_SYN && last_ev->code == SYN_REPORT) {
> + last_ev->time = ev.time;
> + client->buffer[client->head++] = *last_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;
> + }
> }
>
> static void evdev_queue_syn_dropped(struct evdev_client *client)
> @@ -218,7 +238,7 @@ 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;
> + client->packet_head = client->tail = client->head;
> __evdev_queue_syn_dropped(client);
> }
>
> @@ -231,22 +251,24 @@ static int evdev_set_clk_type(struct evdev_client *client, unsigned int clkid)
> static void __pass_event(struct evdev_client *client,
> const struct input_event *event)
> {
> + unsigned int mask = client->bufsize - 1;
> +
> client->buffer[client->head++] = *event;
> - client->head &= client->bufsize - 1;
> + client->head &= mask;
>
> if (unlikely(client->head == client->tail)) {
> /*
> * This effectively "drops" all unconsumed events, leaving
> - * EV_SYN/SYN_DROPPED plus the newest event in the queue.
> + * EV_SYN/SYN_DROPPED, EV_SYN/SYN_REPORT (if required) and
> + * 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->head = (client->head - 1) & mask;
> + client->packet_head = client->tail = client->head;
> + __evdev_queue_syn_dropped(client);
>
> - client->packet_head = client->tail;
> + client->buffer[client->head++] = *event;
> + client->head &= mask;
> + /* No need to check for buffer overflow as it just occurred */
> }
>
> if (event->type == EV_SYN && event->code == SYN_REPORT) {
> @@ -920,6 +942,7 @@ static int evdev_handle_get_val(struct evdev_client *client,
> int ret;
> unsigned long *mem;
> size_t len;
> + bool is_queue_empty;
>
> len = BITS_TO_LONGS(maxbit) * sizeof(unsigned long);
> mem = kmalloc(len, GFP_KERNEL);
> @@ -933,12 +956,15 @@ static int evdev_handle_get_val(struct evdev_client *client,
>
> spin_unlock(&dev->event_lock);
>
> + if (client->head == client->tail)
> + is_queue_empty = true;
> +
> __evdev_flush_queue(client, type);
>
> spin_unlock_irq(&client->buffer_lock);
>
> ret = bits_to_user(mem, maxbit, maxlen, p, compat);
> - if (ret < 0)
> + if (ret < 0 && !is_queue_empty)
> evdev_queue_syn_dropped(client);
>
> kfree(mem);
> --
> 2.6.2
>
Thanks.
--
Dmitry
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