Re: USB input ati_remote autorepeat problem

[Marko Macek]

Vojtech Pavlik wrote:
> On Tue, Jun 27, 2006 at 02:46:39PM -0700, Nish Aravamudan wrote:
>   
> > On 6/27/06, Marko Macek <Marko.Macek@xxxxxxx> wrote:
> >     
> > > Hello!
> > >
> > > I have problems with autorepeat in ati_remote (drivers/usb/input) driver
> > > in "recent" kernels: all keys start repeating immediately without some
> > > delay.
> > >
> > > This makes some things, like changing the channel prev/next or toggling
> > > fullscreen, etc... impossible/hard.
> > >
> > > The problem seems to be related to FILTER_TIME and HZ=250 (which I
> > > forgot to change).
> > >
> > > FILTER_TIME is defined to HZ / 20, and since 250 is not divisible by 20,
> > > the time will be too short to ignore enough events.
> > >
> > > Defining FILTER_TIME to HZ / 20 + 1 seems to fix things, but I'm not
> > > sure if there are any bad side effects.
> > >       
> > Can you try just defining it to msecs_to_jiffies(50)? That should
> > handle the various HZ cases just fine.
> >     
>  
> Indeed, that would be thr right solution. Even better would be to 
>
> 	#define	FILTER_TIME	50	/* 50 msec */
>
> and later use
>
> 	msecs_to_jiffies(FILTER_TIME)
>
> in the code.
There is still a problem (reproducible in HZ=100, at least), because 
msec_to_jiffies

#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ)
       return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ);

Calculates 5 ticks for 50ms, which might seem to be correct, but it 
really isn't,  since 5 ticks can happen in as little as 40 (+eps) ms.

I wonder if this usage of msec_to_jiffies is correct (seems wrong to me).

A working (but not clean) patch might look like this:

--- linux-2.6.17.orig/drivers/usb/input/ati_remote.c    2006-06-29 21:18:15.000000000 +0200

+++ linux-2.6.17/drivers/usb/input/ati_remote.c    2006-07-02 20:10:17.000000000 +0200

@@ -155,9 +155,8 @@

 * events. The hardware generates 5 events for the first keypress

 * and we have to take this into account for an accurate repeat

 * behaviour.

- * (HZ / 20) == 50 ms and works well for me.

 */

-#define FILTER_TIME (HZ / 20)

+#define FILTER_TIME 51 /* msec */



struct ati_remote {

    struct input_dev *idev;

@@ -470,7 +469,7 @@

        /* Filter duplicate events which happen "too close" together. */

        if ((ati_remote->old_data[0] == data[1]) &&

            (ati_remote->old_data[1] == data[2]) &&

-            time_before(jiffies, ati_remote->old_jiffies + FILTER_TIME)) {

+            time_before(jiffies, ati_remote->old_jiffies + msecs_to_jiffies(FILTER_TIME))) {

            ati_remote->repeat_count++;

        } else {

            ati_remote->repeat_count = 0;


Some googling reveals that an old patch used HZ >> 4 (HZ / 16) instead 
of HZ / 20;

Perhaps using msec_to_jiffies(50) + 1 would be the correct fix?

   Mark

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