Re: USB IR receivers and evdev

On Tue, Feb 13, 2007 at 11:44:35PM +0200, Ville Syrjälä wrote:

> > I poked around in what meager uinput doc I could find. It is not clear
> > if events fed into uinput appear on their own evdev device or if they
> > get merged into another stream.

uinput is designed to allow for creation of virtual input devices
controlled from userspace, indistinguishable from the real thing by
applications.

> A quick look at the code suggests that using write() + UI_DEV_CREATE 
> ioctl you can register an input device (which should appear as 
> /dev/input/eventX via udev). However it looks like you need a daemon 
> process per device since there is no 'add new device' ioctl and it uses 
> struct file to identify the device.

You need a new open() for each new device, not a separate process.

> > For sure there are two different styles of doing this:
> > 1) ir driver sends raw ir codes to user space, user space maps, sends
> > back via uinput
> > 2) load mapping table into driver and have driver directly generate evdev events
> 
> Maybe this could use the firmware loader.

Yes, both can work. 1) Generates more latency 2) Requires processing
done in the kernel

Latency probably isn't a big issue with IR (which is slow anyway), and I
don't know how complex the processing of the IR signals is.

> > Most IR units function as a blaster too, so the events have to go back
> > the other way too.

You currently can't send EV_KEY events in the other than usual direction
through the input core. But if there is a need, a way can be found to
implement that functionality.

-- 
Vojtech Pavlik
Director SuSE Labs

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