linux-kernel - Re: One problem in reassign pci bus number?

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Date:	Thu, 3 May 2012 20:15:29 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Richard Yang <weiyang@...ux.vnet.ibm.com>
Cc:	Wei Yang <weiyang.kernel@...il.com>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: One problem in reassign pci bus number?

On Thu, May 3, 2012 at 7:47 PM, Richard Yang <weiyang@...ux.vnet.ibm.com> wrote:
> On Thu, May 03, 2012 at 01:33:17AM -0700, Yinghai Lu wrote:
>>On Wed, May 2, 2012 at 11:54 PM, Richard Yang
>><weiyang@...ux.vnet.ibm.com> wrote:
>>> On Wed, Apr 25, 2012 at 09:28:19AM -0700, Yinghai Lu wrote:
>>>>On Wed, Apr 25, 2012 at 2:47 AM, Wei Yang <weiyang.kernel@...il.com> wrote:
>>>>>> busn_alloc patchset should address your concern.
>>>>>>
>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/yinghai/linux-yinghai.git
>>>>>> for-pci-busn-alloc
>>>
>>> For some functions, such as probe_resource() would you mind add some
>>> comments?  Such as explain the parameter usage.
>>> That would help for reading the function.
>>
>>I updated for-pci-busn-alloc branch with updating of probe_resource()...
>>and removing bus->secondary and subordinate.
>>
> You mean you remove the bus->secondary field?
> So the pci_bus->number hold the bus number?
> I think this is a huge work.
>>Please check if you can understand it ...
>>
>>http://git.kernel.org/?p=linux/kernel/git/yinghai/linux-yinghai.git;a=commitdiff;h=7de8df57b223d54af95ffe67f8da2dd39a265971
> Some question:
>
> +static resource_size_t __find_res_top_free_size(struct resource *res,
> +                                                int skip_nr)
> +{
> +       resource_size_t n_size;
> +       struct resource tmp_res;
> +
> +       */
> +        *   find out free number below res->end that we can use.
> +        *      res->start to res->start + skip_nr - 1 can not be used.
> +        */
> +       n_size = resource_size(res);
> +       if (n_size <= skip_nr)
> +               return 0;
> +
> +       n_size -= skip_nr;
> +       memset(&tmp_res, 0, sizeof(struct resource));
> +       while (n_size > 0) {
> +               int ret;
> +
> +               ret = __allocate_resource(res, &tmp_res, n_size,
> +                       res->end - n_size + skip_nr, res->end,
> +                       1, NULL, NULL, false);
> +               if (ret == 0) {
> +                       __release_resource(&tmp_res);
> +                       break;
> +               }
> +               n_size--;
> +       }
> +
> +       return n_size;
> +}
> So this is trying to find out the biggest free space of res?
> On the right side?
>
> For example we have , res like
>   90-150
>        105-140
> The __find_res_top_free_size() will return 10 instead of 15.
> So this is the design decision to find the right side free resouce not
> the left side?

 __find_res_top_free_size()  is called by probe_resource().

probe_resource will return [91-104].

Thanks

Yinghai
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