Re: evdev types

[Brad H. <bh...@bi...>]

On Wed, 17 Apr 2002 18:21, Vojtech Pavlik wrote:
<snip>
> Not really a 2d bitfield, more like a bunch of 1d bitfields with uneven
> lengths. You pass an argument selecting which one you want and you get
> it. I think EVIOCGBIT is quite OK, because it doesn't really depend on
> the data type ... it just copies a chunk of memory.
>
> What is probably the only wrong w/ the bit arrays is the way they're
> passed through by /proc and hotplug support. And that can be fixed
> without any major pain, because noone is using that on 64-bit systems
> yet.
OK, no issue on 2.4, correct?
This was stuff you added in 2.5?

><snip>
> 	ioctl(fd, EVIOCGBIT(EV_KEY, sizeof(my_buffer)), buffer);
Ah, I think I have it now. For 

ioctl(a, EVIOCGBIT(b, c), d)

a is the file descriptor for the event device you want

b is the type of descriptor bitfield to return
	0 for the type of descriptors that are used
	EV_KEY for the key bitfield
	EV_REL for the relative axes bitfield
	EV_ABS for the absolute axes bitfield
	EV_MSC for the miscellaneous bitfield (not used yet?)
	EV_LED for the bright lights bitfield
	EV_SND for the loud noises bitfield
	EV_REP for the repeat function bitfield (not used yet?)
	EV_FF for the force feedback bitfield

c is the maximum number of bits to return
	If the number of bits available is greater, then you get a warning message

d is a pointer to the memory to put the bitfield

and the return value is the number of bits transfered (if it succeeds) or 
-EFAULT if it fails. The number of bits transferred is the lesser of c, and 
the number of bits for that descriptor type (eg forb == 0, it is EV_MAX,  b 
== EV_KEY, it is KEY_MAX; for b == EV_REL it is REL_MAX, and so on).

OK, my only question now is "how do you get the descriptor bitfield for 
EV_RST?"

Brad