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SubjectRe: [PATCH v3 05/20] Input: Send events one packet at a time
On Sat, Sep 01, 2012 at 09:47:00PM +0200, Henrik Rydberg wrote:
> On heavy event loads, such as a multitouch driver, the irqsoff latency
> can be as high as 250 us. By accumulating a frame worth of data
> before passing it on, the latency can be dramatically reduced. As a
> side effect, the special EV_SYN handling can be removed, since the
> frame is now atomic.
>
> This patch adds the events() handler callback and uses it if it
> exists. The latency is improved by 50 us even without the callback.
>
> Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
> ---
> drivers/input/input.c | 176 +++++++++++++++++++++++++++++++++++---------------
> include/linux/input.h | 24 ++++++-
> 2 files changed, 144 insertions(+), 56 deletions(-)
>
> diff --git a/drivers/input/input.c b/drivers/input/input.c
> index a57c4a5..5b66b2f 100644
> --- a/drivers/input/input.c
> +++ b/drivers/input/input.c
> @@ -47,6 +47,8 @@ static DEFINE_MUTEX(input_mutex);
>
> static struct input_handler *input_table[8];
>
> +static const struct input_value input_value_sync = { EV_SYN, SYN_REPORT, 1 };
> +
> static inline int is_event_supported(unsigned int code,
> unsigned long *bm, unsigned int max)
> {
> @@ -90,46 +92,81 @@ static void input_stop_autorepeat(struct input_dev *dev)
> * filtered out, through all open handles. This function is called with
> * dev->event_lock held and interrupts disabled.
> */
> -static void input_pass_event(struct input_dev *dev,
> - unsigned int type, unsigned int code, int value)
> +static unsigned int input_to_handler(struct input_handle *handle,
> + struct input_value *vals, unsigned int count)
> {
> - struct input_handler *handler;
> - struct input_handle *handle;
> + struct input_handler *handler = handle->handler;
> + struct input_value *end = vals;
> + struct input_value *v;
>
> - rcu_read_lock();
> + for (v = vals; v != vals + count; v++) {
> + if (handler->filter &&
> + handler->filter(handle, v->type, v->code, v->value))
> + continue;
> + if (end != v)
> + *end = *v;
> + end++;
> + }
>
> - handle = rcu_dereference(dev->grab);
> - if (handle)
> - handle->handler->event(handle, type, code, value);
> - else {
> - bool filtered = false;
> + count = end - vals;
> + if (!count)
> + return 0;
>
> - list_for_each_entry_rcu(handle, &dev->h_list, d_node) {
> - if (!handle->open)
> - continue;
> + if (handler->events)
> + handler->events(handle, vals, count);
> + else
> + for (v = vals; v != end; v++)
> + handler->event(handle, v->type, v->code, v->value);

Filter handlers do not typically have ->event() methods, that's the
reason for reported panic.

Thanks.

--
Dmitry


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