Re: evdev types

[Vojtech P. <vo...@su...>]

On Mon, Apr 22, 2002 at 10:04:54AM +1000, Brad Hards wrote:

> On Wed, 17 Apr 2002 16:27, Brad Hards wrote:
> > On Mon, 15 Apr 2002 23:44, Vojtech Pavlik wrote:
> > <snip>
> >
> > > May I suggest one more change?
> > >
> > > dev->dinfo.bustype to dev->id.bus
> > > dev->devinfo.id_vendor ro dev->id.vendor
> >
> > Mostly done. I kept bustype, because it is more descriptive, and because it
> > helps the assignment operators line up :)
> I have done a similar change to the EVIOCGABS ioctl. It now returns 
> input_absinfo, rather than int[5]. Patches against evtest and 2.4.19-pre7 are 
> attached, including the previous patch (so you only need these ones). Let me 
> know if you'd rather an incremental patch.
> 
> I have commented out the current value element. I am unconvinced that it is an 
> appropriate thing to return from this ioctl.

You need a way to read the initial values of all absolute valuators
before you get any events. You may get none if the valuator doesn't
ever change.

> My tutorial works in stages -
> * finding out things about the event system (EVIOCGVERSION)
> * finding out about the device identity (EVIOCGNAME and EVIOCGID, maybe 
> EVIOCGBUS if it works)

EVIOCGBUS? What's that?

> * finding out about the device features (EVIOCGBIT and EVIOCGABS)

Add EVIOCGKEY, EVIOCGLED and EVIOCGSND to that.

> * getting information from the device (read())
> * sending information to the device (write())
> * modifying the device behaviour (eg EVIOCGREP and EVIOCSREP)
> 
> I think that the first element (now ->curr_value) is a different concept to 
> the programmer compares to the rest of the features identified with 
> EVIOCGABS. 

It's also a value you need before you start reading the events, so it's
handy there.

> If it is important that that value is available before someone does anything 
> to the device, then another ioctl is probably appropriate.

Might work as well.

> PLEASE NOTE:
> I need to know if these patches are going to be accepted and pushed into the 
> main-line kernels, because they affect the documentation. Please let me know 
> ASAP which way you are going to go.

They will.
 

-- 
Vojtech Pavlik
SuSE Labs