[PATCH 04/15] Introduce POLL_MS for packet frequency

[Peter Hutterer]

On Thu, Jun 09, 2011 at 08:57:25PM +0100, Daniel Stone wrote:
> We expect to be receiving a steady 80 packets/sec (which gives 40
> reports/sec with more than one finger on the pad, as Advanced Gesture
> Mode requires two PS/2 packets per report).  Instead of a random
> scattering of magic 13 and 20ms numbers scattered throughout the driver,
> introduce POLL_MS as 14ms.
> 
> Having this here allows us to call back at a steady frequency to ensure
> that the finger motion remains steady.
> 
> Signed-off-by: Daniel Stone <daniel at fooishbar.org>
> ---
>  src/synaptics.c |    8 +++++---
>  1 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/synaptics.c b/src/synaptics.c
> index caf0528..8a7c6d1 100644
> --- a/src/synaptics.c
> +++ b/src/synaptics.c
> @@ -92,6 +92,8 @@ typedef enum {
>      LEFT_TOP_EDGE = TOP_EDGE | LEFT_EDGE
>  } edge_type;
>  
> +#define POLL_MS 14

please add a comment for this define, the commit message is a good template
here.

also, why 14, not 13? 
13ms * 80 packets/sec is closer to 1 than 14 * 80.

Cheers,
  Peter

> +
>  #define MAX(a, b) (((a)>(b))?(a):(b))
>  #define MIN(a, b) (((a)<(b))?(a):(b))
>  #define TIME_DIFF(a, b) ((int)((a)-(b)))
> @@ -1849,7 +1851,7 @@ ComputeDeltas(SynapticsPrivate *priv, const struct SynapticsHwState *hw,
>  
>      /* to create fluid edge motion, call back 'soon'
>       * even in the absence of new hardware events */
> -    delay = MIN(delay, 13);
> +    delay = MIN(delay, POLL_MS);
>  
>      if (priv->count_packet_finger <= 3) /* min. 3 packets, see get_delta() */
>          goto skip; /* skip the lot */
> @@ -2191,7 +2193,7 @@ HandleScrolling(SynapticsPrivate *priv, struct SynapticsHwState *hw,
>  	double dtime = (hw->millis - HIST(0).millis) / 1000.0;
>  	double ddy = para->coasting_friction * dtime;
>  	priv->autoscroll_y += priv->autoscroll_yspd * dtime;
> -	delay = MIN(delay, 20);
> +	delay = MIN(delay, POLL_MS);
>  	while (priv->autoscroll_y > 1.0) {
>  	    sd->down++;
>  	    priv->autoscroll_y -= 1.0;
> @@ -2212,7 +2214,7 @@ HandleScrolling(SynapticsPrivate *priv, struct SynapticsHwState *hw,
>  	double dtime = (hw->millis - HIST(0).millis) / 1000.0;
>  	double ddx = para->coasting_friction * dtime;
>  	priv->autoscroll_x += priv->autoscroll_xspd * dtime;
> -	delay = MIN(delay, 20);
> +	delay = MIN(delay, POLL_MS);
>  	while (priv->autoscroll_x > 1.0) {
>  	    sd->right++;
>  	    priv->autoscroll_x -= 1.0;
> -- 
> 1.7.5.3