* [9fans] why is /dev/mousein exclusive use?
@ 2012-12-10 16:36 Richard Miller
2012-12-10 16:38 ` erik quanstrom
2012-12-10 16:48 ` Anthony Martin
0 siblings, 2 replies; 6+ messages in thread
From: Richard Miller @ 2012-12-10 16:36 UTC (permalink / raw)
To: 9fans
Is there a good reason to forbid multiple processes to open
the mousein device? I can't think what trouble it could cause
(writes have to be atomic anyway because the driver will only
parse a complete input), and it makes it awkward to debug
a new mouse driver if a usb mouse is already (or has ever been)
connected.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] why is /dev/mousein exclusive use?
2012-12-10 16:36 [9fans] why is /dev/mousein exclusive use? Richard Miller
@ 2012-12-10 16:38 ` erik quanstrom
2012-12-10 17:47 ` lucio
2012-12-11 15:30 ` Richard Miller
2012-12-10 16:48 ` Anthony Martin
1 sibling, 2 replies; 6+ messages in thread
From: erik quanstrom @ 2012-12-10 16:38 UTC (permalink / raw)
To: 9fans
On Mon Dec 10 11:37:12 EST 2012, 9fans@hamnavoe.com wrote:
> Is there a good reason to forbid multiple processes to open
> the mousein device? I can't think what trouble it could cause
> (writes have to be atomic anyway because the driver will only
> parse a complete input), and it makes it awkward to debug
> a new mouse driver if a usb mouse is already (or has ever been)
> connected.
can't think of any. one can already attach 2 mice to a pc,
one ps/2, and one usb. it works fine.
- erik
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] why is /dev/mousein exclusive use?
2012-12-10 16:36 [9fans] why is /dev/mousein exclusive use? Richard Miller
2012-12-10 16:38 ` erik quanstrom
@ 2012-12-10 16:48 ` Anthony Martin
1 sibling, 0 replies; 6+ messages in thread
From: Anthony Martin @ 2012-12-10 16:48 UTC (permalink / raw)
To: Fans of the OS Plan 9 from Bell Labs
Richard Miller <9fans@hamnavoe.com> once said:
> Is there a good reason to forbid multiple processes to open
> the mousein device? I can't think what trouble it could cause
> (writes have to be atomic anyway because the driver will only
> parse a complete input), and it makes it awkward to debug
> a new mouse driver if a usb mouse is already (or has ever been)
> connected.
IIRC, this restriction was removed in 9front.
Anthony
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] why is /dev/mousein exclusive use?
2012-12-10 16:38 ` erik quanstrom
@ 2012-12-10 17:47 ` lucio
2012-12-11 15:30 ` Richard Miller
1 sibling, 0 replies; 6+ messages in thread
From: lucio @ 2012-12-10 17:47 UTC (permalink / raw)
To: 9fans
> can't think of any. one can already attach 2 mice to a pc,
> one ps/2, and one usb. it works fine.
I second that, I've had a ps2 mouse and a serial trackball working
side by side.
++L
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] why is /dev/mousein exclusive use?
2012-12-10 16:38 ` erik quanstrom
2012-12-10 17:47 ` lucio
@ 2012-12-11 15:30 ` Richard Miller
2012-12-11 15:45 ` erik quanstrom
1 sibling, 1 reply; 6+ messages in thread
From: Richard Miller @ 2012-12-11 15:30 UTC (permalink / raw)
To: 9fans
No objections having been raised, I've submitted a patch
(mousein-non-exclusive) to remove this restriction.
Next, the same question about /dev/kbin - does that need to be
exclusive open? I think not. Slightly more complicated, because
kbin can receive a pair of inputs (escape + scancode) and pass them
one at a time to the kbd driver. But that is already a potential bug,
not prevented by exclusive open - usbd can start driver processes for
two usb keyboards, multiplexing their inputs through one fd to kbin,
and on a multiprocessor the escapes might be incorrectly interleaved.
My proposal is to remove the exclusive open, and instead put a qlock
around the loop which sends codes from kbin to kbd.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [9fans] why is /dev/mousein exclusive use?
2012-12-11 15:30 ` Richard Miller
@ 2012-12-11 15:45 ` erik quanstrom
0 siblings, 0 replies; 6+ messages in thread
From: erik quanstrom @ 2012-12-11 15:45 UTC (permalink / raw)
To: 9fans
> My proposal is to remove the exclusive open, and instead put a qlock
> around the loop which sends codes from kbin to kbd.
or, keep a small structure, perhaps in the channel to keep
track of these things. there's also a limitation where the same
kbmap gets applied to all keyboards.
- erik
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2012-12-11 15:45 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
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2012-12-10 16:36 [9fans] why is /dev/mousein exclusive use? Richard Miller
2012-12-10 16:38 ` erik quanstrom
2012-12-10 17:47 ` lucio
2012-12-11 15:30 ` Richard Miller
2012-12-11 15:45 ` erik quanstrom
2012-12-10 16:48 ` Anthony Martin
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