Touchpad and i8042

Touchpad and i8042

[Mircea Bardac]

Hi all,

I've noticed a weird behaviour when monitoring roughly the number of 
interrupts fired. The number of interrupts for "i8042" increase dramatically 
when I move the pointer using the touchpad.

I've only used "watch cat /proc/interrupts".

dramatically = ~800 interrupts
for only moving the finger from the top to the bottom of the touchpad.

I'm using kernel 2.6.21.1, don't know if this happened before - I noticed it 
now.

The interrupts only appear on touchpad usage, not on standby.

I think it is a synaptics touchpad, but I'm not really sure (how could I find 
out?)

Does anyone have an explanation for this? I've seen the "appletouch" problem 
problem on the linuxpowertop.org site but I don't know if they're related.


If any other info is needed, let me know.

Mircea

Re: Touchpad and i8042

[Matthew Garrett]

On Sat, May 19, 2007 at 06:28:08PM +0300, Mircea Bardac wrote:

> I've noticed a weird behaviour when monitoring roughly the number of 
> interrupts fired. The number of interrupts for "i8042" increase dramatically 
> when I move the pointer using the touchpad.

The touchpad is attached to an i8042. When you touch it, it sends data 
and generates interrupts. That's perfectly normal.

-- 
Matthew Garrett | mjg59@srcf.ucam.org

Re: Touchpad and i8042

[Dmitry Torokhov]

On Saturday 19 May 2007 11:42, Matthew Garrett wrote:
> On Sat, May 19, 2007 at 06:28:08PM +0300, Mircea Bardac wrote:
> 
> > I've noticed a weird behaviour when monitoring roughly the number of 
> > interrupts fired. The number of interrupts for "i8042" increase dramatically 
> > when I move the pointer using the touchpad.
> 
> The touchpad is attached to an i8042. When you touch it, it sends data 
> and generates interrupts. That's perfectly normal.

Yep. With Synaptics touchpad that by default has 80 pps @ 6 bytes per
packet you should be getting ~480 interrupts per second.

-- 
Dmitry