[lkml]   [2006]   [Nov]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH] usb: generic calibration support

On 11/17/06, Holger Schurig <> wrote:
> > sorry, but i have to give you a big NACK on that one:
> Hehe, I actually anticipated this NACK :-)
> > - no more modparam: it should be per-device sysfs attributes
> > (swap_xy is basically only for touchkitusb compatibility and
> > shoud be converted to per-device sysfs attribute as well. i
> > just never got to do it)
> That would be okay for me.

Actually I think having module parameter is OK as long as we have
comlementing device attribute. Then user has an option to either
specify default value for the parameter at load/boot time or fiddle
with an individual device.

> > - calibration can be handled in userspace just fine
> Yes it can, and that is the most convinging argument against my
> patch.
> However, user-space calibration often sucks. For example, in X11
> the calibration values are stored in /etc/X11/xorg.conf, so a
> calibration program has to parse & write that file. And I've
> seen binary-only-calibration programs from vendors
> use /etc/X11/XF86Config, which doesn't exist here. Anyway, once
> you've calibrated you have to restart X-Windows, so you need to
> terminate all running X applications just because of a silly
> re-calibration. Not nice.

I believe tslib handles this.

> A calibration at kernel level (may it be input level or driver
> level) doesn't have this problem. I can make the level
> persistent via udev, modules.conf or other means. Even when I
> have a frame-buffer based calibration utility, the calibration
> would be OK for X11 or GTK/DirectFB as well.
> For me, this speaks against "Calibration is purely a user-space
> problem".
> > - even for in-kernel it's in the wrong place. there are other
> > devices that report raw absolute it would belong to
> > the input layer
> Suppose I have a graphics tabled and a touchscreen connected at
> the same time. Can I distinguish this easily at the input layer
> level?
> I can very easily distinguish this at the device driver level.
> After all, the individual calibration parameters are a property
> of this individual device.

Yes, but evdev is the interface between input layer and userspace. If
we ever implement in-kernel calibration I think we'll add
recalibrate() method to input device structure and have EVIOCSABS
ioctl handler call it. But I'd look at tslib first. I believe Qt,
Xserver, etc support it.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2006-11-17 15:19    [W:0.050 / U:8.964 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site