Re: Patch of a new driver for kernel 2.4.x that need review

From: Alan Cox
Date: Thu Jun 23 2005 - 16:59:19 EST

> > + if (check_region(TLCLK_BASE, 8)) {
> > + printk(KERN_ERR
> > + "telclock: I/O region already used by another
> > driver!\n");
> > + return -EBUSY;
> > + } else {
> > + request_region(TLCLK_BASE, 8, "telclock");
> request_region can fail too so you'd better handle that.

check_region() is essentially historical. It used to be that
check_region could fail and request_region did not. Once modules arrived
it becomes possible for drivers to race each other for resources so
request_region now atomically (with respect to itself) checks and if
available allocates a region.

check_region() shouldn't be used except for special cases where you
really want to see a space is free without requesting it. Even then if
you need to do any operation on the space while it is free you need to
request/act/release the region nto check_region for it.


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