Re: parport-arca-9 [was Re: [PARPORT] Re: PARPORT_DEV_EXCL ]

Philip Blundell (
Sat, 26 Sep 1998 18:31:32 +0100

>I just fixed the few drivers that seems to need EXCL access to the port
>(note that parport was misused in such drivers since it was implemented
>the preemt callback that was _only_ returning always 1 specifying that the
>driver was not able to preemt). Such devices was also used to claim the
>port as LURK and so I removed the LURK flag too.

It's perfectly allowable for the preempt function to always fail (though it
ought to be OK to simply provide no preempt function in this case -- the only
reason the drivers in question had one is because lurkers were supposed to
always be preemptable back when that flag had a meaning).

The only restriction is that if your driver isn't preemptable you have to be
sure that it will release the port of its own accord within a finite
timeframe. For example, the QuickCam driver isn't preemptable but it only
claims the port while a frame is actually being captured. You only need the
EXCL flag for devices where this isn't the case.


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This archive was generated by hypermail 2.0b3 on Wed 30 Dec 1998 - 10:18:25 EST