Re: [PATCH] cxl/region: Fix logic for finding a free cxl decoder

[Zijun Hu <zijun_hu@icloud.com>]

On 2024/9/4 04:14, Alison Schofield wrote:
> On Tue, Sep 03, 2024 at 08:41:44PM +0800, Zijun Hu wrote:
>> From: Zijun Hu <quic_zijuhu@quicinc.com>
>>
>> match_free_decoder()'s logic for finding a free cxl decoder depends on
>> a prerequisite that all child decoders are sorted by ID in ascending order
>> but the prerequisite may not be guaranteed, fix by finding a free cxl
>> decoder with minimal ID.
> 
> After reading the 'Closes' tag below I have a better understanding of
> why you may be doing this, but I don't want to have to jump to that
> Link. Can you describe here examples of when the ordered allocation
> may not be guaranteed, and the impact when that happens.
> 

thank you for code review.
let me try to do it.

> This includes a change to device_for_each_child() which I see mentioned
> in the Closes tag discussion too. Is that required for this fix?
>

yes, device_for_each_child() is better than device_find_child() to
correct logic for finding a free cxl decoder.
> It's feeling like the fix and api update are comingled. Please clarify.
> 

actually, there are two concerns as shown below:

concern A: device_find_child() modifies caller's match data.
concern B: weird logic for finding a free cxl decoder

this patch focuses on concern B, and it also solve concern A in passing.

the following exclusive patch only solves concern A.
https://lore.kernel.org/all/20240905-const_dfc_prepare-v4-1-4180e1d5a244@quicinc.com/

either will solve concern A i care about.

> Thanks,
> Alison
> 
>>