HIDIOCKM[GS]DIRECT ioctls for the USB HID driver [PSARC/2009/329 FastTrack timeout 06/10/2009]

[Aaron Zang]

Hi James,


James Carlson wrote:
> Garrett D'Amore - sun microsystems writes:
>   
>> To solve the above problem, two new HID ioctls are introduced:
>>     
>
> Two questions:
>
>   - How do these ioctls solve the problem?  Who will issue the ioctls
>     and under what conditions?  What happens if they're not used (if,
>     for example, something kills the Xorg server)?
>
>   

First, Xorg will open the hid devices upon startup. So the input goes to 
Xorg.
While switching back to console, Xorg is in charge of issuing the ioctls 
to switch input
to console since only Xorg has the context of which devices it keeps 
opening.

If something kills the Xorg server, the opened files will be closed, so 
the input will
automatically directed to the internal stream again.

>   - Why not just send copies of the input to all open streams?
>     Wouldn't that be simpler?
>
>   

If we send the input to both the internal and external streams, when you 
are on console
again no matter by switching back or Xorg exits, all the input 
characters typed under
X will be shown on console, that would be messy.

Hope it answers your questions.

Regards,
Aaron