Re: [PATCH 1/8] cxl: Add helper function to retrieve a feature entry

[Alison Schofield]

On Thu, Feb 27, 2025 at 10:38:08PM +0000, shiju.jose@xxxxxxxxxx wrote:
> From: Shiju Jose <shiju.jose@xxxxxxxxxx>
> 
> Add helper function to retrieve a feature entry from the supported
> features list, if supported.
> 
> Signed-off-by: Shiju Jose <shiju.jose@xxxxxxxxxx>
> ---
>  drivers/cxl/core/core.h     |  2 ++
>  drivers/cxl/core/features.c | 20 ++++++++++++++++++++
>  2 files changed, 22 insertions(+)
> 
> diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h
> index 3d3b00835446..6c83f6f18122 100644
> --- a/drivers/cxl/core/core.h
> +++ b/drivers/cxl/core/core.h
> @@ -120,6 +120,8 @@ int cxl_port_get_switch_dport_bandwidth(struct cxl_port *port,
>  int cxl_gpf_port_setup(struct device *dport_dev, struct cxl_port *port);
>  
>  #ifdef CONFIG_CXL_FEATURES
> +struct cxl_feat_entry *cxl_get_feature_entry(struct cxl_dev_state *cxlds,
> +					     const uuid_t *feat_uuid);
>  size_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
>  		       enum cxl_get_feat_selection selection,
>  		       void *feat_out, size_t feat_out_size, u16 offset,
> diff --git a/drivers/cxl/core/features.c b/drivers/cxl/core/features.c
> index 048ba4fc3538..c822fb4a8c33 100644
> --- a/drivers/cxl/core/features.c
> +++ b/drivers/cxl/core/features.c
> @@ -203,6 +203,26 @@ int devm_cxl_setup_features(struct cxl_dev_state *cxlds)
>  }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_setup_features, "CXL");
>  
> +struct cxl_feat_entry *cxl_get_feature_entry(struct cxl_dev_state *cxlds,
> +					     const uuid_t *feat_uuid)
> +{
> +	struct cxl_features_state *cxlfs = to_cxlfs(cxlds);
> +	struct cxl_feat_entry *feat_entry;
> +	int count;
> +
> +	/*
> +	 * Retrieve the feature entry from the supported features list,
> +	 * if the feature is supported.
> +	 */
> +	feat_entry = cxlfs->entries->ent;

Do we need some NULL checking here on cxlfs, entries


> +	for (count = 0; count < cxlfs->entries->num_features; count++, feat_entry++) {

Was num_features previously validated? 

> +		if (uuid_equal(&feat_entry->uuid, feat_uuid))
> +			return feat_entry;
> +	}
> +
> +	return ERR_PTR(-ENOENT);

Why not just return NULL?


> +}
> +
>  size_t cxl_get_feature(struct cxl_mailbox *cxl_mbox, const uuid_t *feat_uuid,
>  		       enum cxl_get_feat_selection selection,
>  		       void *feat_out, size_t feat_out_size, u16 offset,
> -- 
> 2.43.0
>