[coreboot] [PATCH] unavailable resources

Myles Watson mylesgw at gmail.com
Fri Jun 4 18:49:45 CEST 2010

On Fri, Jun 4, 2010 at 10:41 AM, Stefan Reinauer <stepan at coresystems.de> wrote:
> On 6/4/10 6:36 PM, Myles Watson wrote:
>>               if (!(res->flags & IORESOURCE_FIXED))
>>                       continue;
>> ...
>>               /* Is it already outside the limits? */
>> -             if (((res->base + res->size -1) < lim->base) || (res->base > lim->limit))
>> +             if (((res->base + res->size -1) < lim->base) || (res->base > lim->limit)) {
>> +                     printk(BIOS_ERR, "%s: Resources not available.\n", dev_path(dev));
>>                       continue;
>> +             }
>> This code only is executed for fixed resources.  If they are outside
>> of the limits it's a good thing.  I don't think there should be an
>> error message.
> Why is that good? (can we add that explanation to the code as a comment?)
Sure.  I guess since I wrote it I'm not a good judge of clarifying comments.

Here's the big picture:

You start with a full address space
You constrain what the allocator can use by subtracting fixed resources

And a completely contrived example:
 - take I/O 0x0000-0xffff
 - let's imagine that 0x400-420, 0x40-0x80, and 0xf000-0xf800 are
fixed resources (the allocator can't use that space)
First pass, the allocator chooses to use 0x420-0xffff (larger than 0x0-0x400)
Second pass, the allocator does nothing because 0x40-0x80 is already
outside the limits
Third pass, the allocator chooses to use 0x420-0xf800 (larger than

I'd love it if you'd add some clarifying comments.


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