Re: [Lcd4linux-devel] WRAP platform and LCD4Linux

[Luis.F.Correia <Lui...@se...>]

Hi! 

> -----Original Message-----
> From: Stefan Krister [mailto:ste...@cr...] 
> Sent: Thursday, August 17, 2006 12:47 PM
> To: lcd4linux devel
> Subject: Re: [Lcd4linux-devel] WRAP platform and LCD4Linux
> 
> Hi Luis,
> 
> Luis.F.Correia schrieb am 17.08.2006 11:07:
> >
> > It reports 74mA to the USB hub.
> 
> That seems to be O.K.
> 
> > Ok, this would be a good project, I think. I can help you with the 
> > GPIO think, but only for 2.4 kernels. Still interested?
> 
> Fine! *eg*
> 
> Yes sure I am. To my knowledge for now - there are only 
> outb() neccesary to put data on the GPIOs. And before using 
> the GPIO there has a) to switch off the "LPC" behaviour of 
> the J2 and to b) set in- or out-direction of the GPIO pins. 
> All that is done by outb().
> 
> I found 2 examples from other WRAP users doing some stuff 
> (switches and some optocoupled relais):
> 
> http://wiki.voyage.hk/dokuwiki/doku.php?id=wrap_switches
> http://list.voyage.hk/pipermail/voyage-linux/2006-June/000969.html
> 
> I found there code is handy for the a) part. And there is no 
> special kernel issue.

Yes it is, an outb() must be done by root and in systems with the
grsecurity patches (Bering uClibc) it won't work from a userspace
application.

Even so, a simple kernel module mimicing the parport behaviuor
should be more then enough.

I'm going to explian in further detail what this means, from lcd4linux
point of view, there is a parport device. But instead of loading 
parport, you load the wrap-gpio module. This solves the hardware issue
of using those pins as GPIO.

Then the LCD module itself is another issue. But one step at a time.

> 
> MfG
> 
> Stefan

Thanks for the links, they will help me building the required kernel module.


Luis Correia   
Bering uClibc Team Member

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