linux-kernel - Re: [PATCH V3 13/20] cxl/mem: Refactor cxl pmem region auto-assembling

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Message-ID: <1983025922.01763020202072.JavaMail.epsvc@epcpadp1new>
Date: Thu, 13 Nov 2025 12:57:09 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: Dave Jiang <dave.jiang@...el.com>
Cc: linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, gost.dev@...sung.com,
	a.manzanares@...sung.com, vishak.g@...sung.com, neeraj.kernel@...il.com,
	cpgs@...sung.com
Subject: Re: [PATCH V3 13/20] cxl/mem: Refactor cxl pmem region
 auto-assembling

On 12/11/25 08:55AM, Dave Jiang wrote:
>
>

<snip>

>> During cxl_pci_probe() we call devm_cxl_add_memdev(struct cxl_memdev_ops *ops)
>> where function pointer as ops gets registered which gets called in cxl_mem_probe()
>> using cxlmd->ops->probe()
>>
>> The probe callback runs after the port topology is successfully attached for
>> the given memdev.
>>
>> So to use this infra we have to pass cxl_region_discovery() as ops parameter
>> of devm_cxl_add_memdev() getting called from cxl_pci_probe().
>>  
>> In this patch-set cxl_region_discovery() signature is different from cxlmd->ops->probe()
>>
>>    {{{
>>     void cxl_region_discovery(struct cxl_port *port)
>>     {
>>             device_for_each_child(&port->dev, NULL, discover_region);
>>     }
>>
>>     struct cxl_memdev_ops {
>>             int (*probe)(struct cxl_memdev *cxlmd);
>>     };
>>    }}}
>>
>> Even after changing the signature of cxl_region_discovery() as per cxlmd->ops->probe()
>> may create problem as when the ops->probe() fails, then it will halts the probe sequence
>> of cxl_pci_probe()
>>
>> It is because discover_region() may fail if two memdevs are participating into one region
>
>While discover_region() may fail, the return value is ignored. The current code disregards failures from device_for_each_child(). And also above, cxl_region_discovery() returns void. So I don't follow how ops->probe() would fail if we ignore errors from discover_region().
>
>DJ

Hi Dave,

Yes, you are correct. We can just change signature of cxl_region_discovery() as per
cxlmd->ops->probe(), anyway we are ignoring errors from discover_region().
With this change we can directly register cxl_region_discovery() with
devm_cxl_add_memdev(struct cxl_memdev_ops *ops) during pci_probe() using Dan's Infra.

I will use this new infra for region auto-assembling and share the v4 series shortly.


Regards,
Neeraj