[PATCH] unavailable resources

[Stefan Reinauer]

See patch

[Myles Watson]

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.

Thanks,
Myles

[Stefan Reinauer]

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?)

[Myles Watson]

On Fri, Jun 4, 2010 at 10:41 AM, Stefan Reinauer  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
0xf800-0xffff.

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

Thanks,
Myles