linux-kernel - Re: [PATCH V4 09/17] nvdimm/label: Export routine to fetch region information

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Message-ID: <20251217151230.000048c3@huawei.com>
Date: Wed, 17 Dec 2025 15:12:30 +0000
From: Jonathan Cameron <jonathan.cameron@...wei.com>
To: Neeraj Kumar <s.neeraj@...sung.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>
Subject: Re: [PATCH V4 09/17] nvdimm/label: Export routine to fetch region
 information

On Wed, 19 Nov 2025 13:22:47 +0530
Neeraj Kumar <s.neeraj@...sung.com> wrote:

> CXL region information preserved from the LSA needs to be exported for
> use by the CXL driver for CXL region re-creation.
To me it feels like the !nvdimm checks may be excessive in an interface
that makes no sense if NULL is passed in.
Perhaps drop those?

> 
> Signed-off-by: Neeraj Kumar <s.neeraj@...sung.com>
> ---
>  drivers/nvdimm/dimm_devs.c | 18 ++++++++++++++++++
>  include/linux/libnvdimm.h  |  2 ++
>  2 files changed, 20 insertions(+)
> 
> diff --git a/drivers/nvdimm/dimm_devs.c b/drivers/nvdimm/dimm_devs.c
> index 3363a97cc5b5..1474b4e45fcc 100644
> --- a/drivers/nvdimm/dimm_devs.c
> +++ b/drivers/nvdimm/dimm_devs.c
> @@ -280,6 +280,24 @@ void *nvdimm_provider_data(struct nvdimm *nvdimm)
>  }
>  EXPORT_SYMBOL_GPL(nvdimm_provider_data);
>  
> +bool nvdimm_has_cxl_region(struct nvdimm *nvdimm)
> +{
> +	if (!nvdimm)
> +		return false;

Seems a bit odd that this would ever get called on !nvdimm.
Is that protection worth adding?

> +
> +	return nvdimm->is_region_label;
> +}
> +EXPORT_SYMBOL_GPL(nvdimm_has_cxl_region);
> +
> +void *nvdimm_get_cxl_region_param(struct nvdimm *nvdimm)
> +{
> +	if (!nvdimm)

This feels a little more plausible as defense but is this
needed?

> +		return NULL;
> +
> +	return &nvdimm->cxl_region_params;
> +}
> +EXPORT_SYMBOL_GPL(nvdimm_get_cxl_region_param);
> +
>  static ssize_t commands_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> diff --git a/include/linux/libnvdimm.h b/include/linux/libnvdimm.h
> index 07ea2e3f821a..3ffd50ab6ac4 100644
> --- a/include/linux/libnvdimm.h
> +++ b/include/linux/libnvdimm.h
> @@ -330,6 +330,8 @@ int nvdimm_in_overwrite(struct nvdimm *nvdimm);
>  bool is_nvdimm_sync(struct nd_region *nd_region);
>  int nd_region_label_update(struct nd_region *nd_region);
>  int nd_region_label_delete(struct nd_region *nd_region);
> +bool nvdimm_has_cxl_region(struct nvdimm *nvdimm);
> +void *nvdimm_get_cxl_region_param(struct nvdimm *nvdimm);
>  
>  static inline int nvdimm_ctl(struct nvdimm *nvdimm, unsigned int cmd, void *buf,
>  		unsigned int buf_len, int *cmd_rc)