linux-kernel - Re: [PATCH V2 01/20] nvdimm/label: Introduce NDD_CXL

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Message-ID: <1983025922.01757055603347.JavaMail.epsvc@epcpadp1new>
Date: Thu, 4 Sep 2025 18:54:07 +0530
From: Neeraj Kumar <s.neeraj@...sung.com>
To: Dave Jiang <dave.jiang@...el.com>
Cc: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
	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 V2 01/20] nvdimm/label: Introduce NDD_CXL_LABEL flag to
 set cxl label format

On 15/08/25 11:06AM, Dave Jiang wrote:
>
>
>On 8/13/25 6:12 AM, Jonathan Cameron wrote:
>> On Wed, 30 Jul 2025 17:41:50 +0530
>> Neeraj Kumar <s.neeraj@...sung.com> wrote:
>>
>>> Prior to LSA 2.1 version, LSA contain only namespace labels. LSA 2.1
>>> introduced in CXL 2.0 Spec, which contain region label along with
>>> namespace label.
>>>
>>> NDD_LABELING flag is used for namespace. Introduced NDD_CXL_LABEL
>>> flag for region label. Based on these flags nvdimm driver performs
>>> operation on namespace label or region label.
>>>
>>> NDD_CXL_LABEL will be utilized by cxl driver to enable LSA2.1 region
>>> label support
>>>
>>> Accordingly updated label index version
>>>
>>> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
>> Hi Neeraj,
>>
>> A few comments inline.
>>
>>> diff --git a/drivers/nvdimm/label.c b/drivers/nvdimm/label.c
>>> index 04f4a049599a..7a011ee02d79 100644
>>> --- a/drivers/nvdimm/label.c
>>> +++ b/drivers/nvdimm/label.c
>>> @@ -688,11 +688,25 @@ static int nd_label_write_index(struct nvdimm_drvdata *ndd, int index, u32 seq,
>>>  		- (unsigned long) to_namespace_index(ndd, 0);
>>>  	nsindex->labeloff = __cpu_to_le64(offset);
>>>  	nsindex->nslot = __cpu_to_le32(nslot);
>>> -	nsindex->major = __cpu_to_le16(1);
>>> -	if (sizeof_namespace_label(ndd) < 256)
>>> +
>>> +	/* Set LSA Label Index Version */
>>> +	if (ndd->cxl) {
>>> +		/* CXL r3.2 Spec: Table 9-9 Label Index Block Layout */
>>> +		nsindex->major = __cpu_to_le16(2);
>>>  		nsindex->minor = __cpu_to_le16(1);
>>> -	else
>>> -		nsindex->minor = __cpu_to_le16(2);
>>> +	} else {
>>> +		nsindex->major = __cpu_to_le16(1);
>>> +		/*
>>> +		 * NVDIMM Namespace Specification
>>> +		 * Table 2: Namespace Label Index Block Fields
>>> +		 */
>>> +		if (sizeof_namespace_label(ndd) < 256)
>>> +			nsindex->minor = __cpu_to_le16(1);
>>> +		else
>>> +		 /* UEFI Specification 2.7: Label Index Block Definitions */
>>
>> Odd comment alignment. Either put it on the else so
>> 		else /* UEFI 2.7: Label Index Block Defintions */
>>
>> or indent it an extra tab
>>
>> 		else
>> 			/* UEFI 2.7: Label Index Block Definitions */
>> 			
>>> +			nsindex->minor = __cpu_to_le16(2);
>>> +	}
>>> +
>>>  	nsindex->checksum = __cpu_to_le64(0);
>>>  	if (flags & ND_NSINDEX_INIT) {
>>>  		unsigned long *free = (unsigned long *) nsindex->free;
>>
>>> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
>>> index e772aae71843..0a55900842c8 100644
>>> --- a/include/linux/libnvdimm.h
>>> +++ b/include/linux/libnvdimm.h
>>> @@ -44,6 +44,9 @@ enum {
>>>  	/* dimm provider wants synchronous registration by __nvdimm_create() */
>>>  	NDD_REGISTER_SYNC = 8,
>>>
>>> +	/* dimm supports region labels (LSA Format 2.1) */
>>> +	NDD_CXL_LABEL = 9,
>>
>> This enum is 'curious'.  It combined flags from a bunch of different
>> flags fields and some stuff that are nothing to do with flags.
>>
>> Anyhow, putting that aside I'd either rename it to something like
>> NDD_REGION_LABELING (similar to NDD_LABELING that is there for namespace labels
>> or just have it a meaning it is LSA Format 2.1 and drop the fact htat
>> also means region labels are supported.
>
>I agree. I had a conversation with Dan about it where I mentioned calling it CXL to describe LSA 2.1 just doesn't seem quite right. He also offered up something like NDD_REGION_LABELING instead of NDD_CXL_LABEL. So +1 to this comment.
>
>DJ

Sure Dave, I will rename it to NDD_REGION_LABELING in next patch-set

Regards,
Neeraj