On 3/15/06, taha siddiqi <tawushafeez@xxxxxxxxx> wrote:
> Hi....
> I am trying to read data from my laptop's (thinkpad R51) parallel port
> (similar to the example in Linux Device Drivers 3rd Edition).
> But, everytime i am reading the data it always comes to be 0xFF(255) ....
> I even tried the following loop in my write function (struct file_operations)
> while(count--){
> printk("writing %x\n", *ptr);
> out(*(ptr++), port);
> wmb();
> printk("reading data : %x\n", inb(port));
> }
> but the debug message in log shows something like
> writing 116
> reading 255
> writing 78
> reading 255
> ...
> ...
There are different modes for Parallel Port (AFAIR like
bi-directional, EPP or so, just google for it) which you have to
configure to bi-directional in your board bios setup (its by-default
not configured as bi-directional). So you are only able to read the
data not able to write and all your write operations does nothing.
CMIIW
I hope this helps.
--
Fawad Lateef
--
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