On Thu, Aug 12, 2010 at 8:24 AM, Russell King - ARM Linux
<linux@xxxxxxxxxxxxxxxx> wrote:
> On Wed, Aug 11, 2010 at 05:31:00PM -0700, Erik Gilling wrote:
>> >> + if (!request_mem_region(r->start, (r->end - r->start) + 1,
>> >> + dev_name(&pdev->dev))) {
>> >> + ret = -EBUSY;
>> >> + goto err0;
>> >> + }
>> >
>> > I believe the platform bus does this for you already by calling
>> > insert_resource() on all the platform bus ranges. See if /proc/iomem
>> > is any different with or without this call to verify.
>>
>> You're right. Didn't realize this
>
> There is a big difference between what the platform bus does and what
> drivers do.
>
> The platform bus adds the resources to the resource tree as they stand
> without marking them _busy_. This means that they can be sub-divided
> and other resources registered within their range.
>
> request_mem_region() adds resources to the resource tree marking them
> busy, detecting overlapping resources and indicating whether two
> drivers are trying to claim the same resource region. In other words,
> it's a preventative measure against two device drivers accessing the
> same region.
>
> You're absolutely right to do what you're doing above, please continue
> to do so.
>
Thanks for the explanation. I'll add it back in.
Cheers,
Erik
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