Re: rfc: vmem(9) API/implementation changes

[David Young <dyoung%pobox.com@localhost>]

On Wed, Jul 27, 2011 at 04:58:23PM +0000, Eduardo Horvath wrote:
> On Wed, 27 Jul 2011, David Young wrote:
> 
> > There are a couple of changes to the API that I would like to make.
> > First, I don't think that vmem_addr_t 0 should be reserved for error
> > indications (0 == VMEM_ADDR_NULL), but the API should change from
> > this:
> 
> I'd recommend returning -1 on error.  0 is a valid address, but while -1 
> is a valid address, when do you ever use this interface to allocate 
> something that starts at address -1?  And it gets around all the noxious 
> problems involved in returning data through reference parameters.

I don't know.  Suppose sizeof(vmem_addr_t) == sizeof(uint32_t).  Which
of these cases should fail, and on which statement?

Case A:

     1  vm = vmem_create("test", 0xffffffff, 1, 0, NULL, NULL, NULL, 1,
     2      VM_SLEEP, IPL_NONE);
     3  p = vmem_alloc(vm, 1, VM_SLEEP);

Case B:

     1  vm = vmem_create("test", 0xfffffffe, 2, 0, NULL, NULL, NULL, 1,
     2      VM_SLEEP, IPL_NONE);
     3  p = vmem_alloc(vm, 2, VM_SLEEP);

Case C:

     1  vm = vmem_create("test", 0xfffffffe, 2, 0, NULL, NULL, NULL, 1,
     2      VM_SLEEP, IPL_NONE);
     3  p = vmem_alloc(vm, 1, VM_SLEEP);
     4  q = vmem_alloc(vm, 1, VM_SLEEP);

Dave

-- 
David Young             OJC Technologies
dyoung%ojctech.com@localhost      Urbana, IL * (217) 344-0444 x24