How do I make Xglamo read directly from the touchscreen?

Holger Freyther zecke at
Thu Jan 8 19:42:22 CET 2009

On Thursday 08 January 2009 16:58:32 Andy Green wrote:
> Somebody in the thread at some point said:
> | 	1.) Get the code upstream into the linux kernel
> We feel showing it can remove the need for tslib gives us a story that
> gives a better chance upstream.

I think one can imagine that this will work. But what about actually sending 
the idea + patch set to the linux input device list? I think it makes sense to 
check if the people maintaining the linux input framework would be willing to 
have and maintain code that is doing that.

> | that goal, we walk into the other direction.
> We went in the direction of resolving a longstanding problem for users,
> GTA02 touchscreen was unusable until this was done.
> There's no point to repeat the cycle of "shoulda done it in tslib"
> because that's out of scope for me and nobody else took action.

I don't know what is wrong... I highlighted a migration path. If you don't 
want to do this, fine.  Just to repeat what I said:

If _one_ wants to migrate away from a working user-space infrastructure one 
should have:
	1.) The in kernel code upstream or at least the idea accepted

	2.) Developer tools (like ts_print, ts_test, ts_print_raw) to ease future 
bring up of touchscreen devices...

	3.) Fix the fallouts (e.g. getting X and XCalibrate working again)

I don't see any circle here, and I think this list is pretty constructive. The 
challenge is not to get touchscreen of _one_ device working but the amount of 
resources required to bring up the next touchscreen device... this is where 
modules, developers tools come to play. I'm not emotionally attached to tslib 
but currently there are things that are easy with tslib and hard with the in 
kernel approach.

How to test the touchscreen:
Kernel: cat device... spitting out things but no numbers
tslib: ts_print and ts_print_raw with nice output

How to calibrate the touchscreen:
Kernel: Aeehh... find the Determinate yourself solve the equations
tslib: ts_calibrate

How to change the number of samples you work on:
Kernel: Change the board file, recompile, reboot
tslib: edit ts.conf

Tools support:
Kernel: No tool knows about /sys/bus/i2c/devices/I/m/lost/here/a, /b, c..
tslib: Tools know about /etc/ts.conf

I just highlight what is missing in your story, if you want to push the 
migration you should offer the same features as tslib or convince people why 
these are not needed... I'm willing to help you migrating but it starts with 
1st) convincing people maintaining the linux input device system that this is 
a good idea (otherwise we will end up with GTA06 and have 100 "feature 
patches" because we do clever things that upstream does not understand... and 
this will be a nightmare for everyone involved).


PS: Yes the values you have found GTA0X are great and are an improvement, what 
about the time needed for the next touchscreen? roundtrips?...

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