platform/x86/intel/pmt/telemetry: Add API to retrieve telemetry regions by feature

Introduce a new API, intel_pmt_get_regions_by_feature(), that gathers
telemetry regions based on a provided capability flag. This API enables
retrieval of regions with various capabilities (for example, RMID-based
telemetry) and provides a unified interface for accessing them. Resource
management is handled via reference counting using
intel_pmt_put_feature_group().

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20250703022832.1302928-15-david.e.box@linux.intel.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>

drivers/platform/x86/intel/pmt/telemetry.c

@@ -9,16 +9,21 @@
  */
 
 #include <linux/auxiliary_bus.h>
+#include <linux/bitops.h>
+#include <linux/cleanup.h>
+#include <linux/err.h>
 #include <linux/intel_pmt_features.h>
 #include <linux/intel_vsec.h>
 #include <linux/kernel.h>
 #include <linux/kref.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/overflow.h>
 #include <linux/pci.h>
 #include <linux/slab.h>
 #include <linux/types.h>
 #include <linux/uaccess.h>
-#include <linux/overflow.h>
+#include <linux/xarray.h>
 
 #include "class.h"
 
@@ -209,6 +214,87 @@ unlock:
 }
 EXPORT_SYMBOL_NS_GPL(pmt_telem_get_endpoint_info, "INTEL_PMT_TELEMETRY");
 
+static int pmt_copy_region(struct telemetry_region *region,
+			   struct intel_pmt_entry *entry)
+{
+
+	struct oobmsm_plat_info *plat_info;
+
+	plat_info = intel_vsec_get_mapping(entry->ep->pcidev);
+	if (IS_ERR(plat_info))
+		return PTR_ERR(plat_info);
+
+	region->plat_info = *plat_info;
+	region->guid = entry->guid;
+	region->addr = entry->ep->base;
+	region->size = entry->size;
+	region->num_rmids = entry->num_rmids;
+
+	return 0;
+}
+
+static void pmt_feature_group_release(struct kref *kref)
+{
+	struct pmt_feature_group *feature_group;
+
+	feature_group = container_of(kref, struct pmt_feature_group, kref);
+	kfree(feature_group);
+}
+
+struct pmt_feature_group *intel_pmt_get_regions_by_feature(enum pmt_feature_id id)
+{
+	struct pmt_feature_group *feature_group __free(kfree) = NULL;
+	struct telemetry_region *region;
+	struct intel_pmt_entry *entry;
+	unsigned long idx;
+	int count = 0;
+	size_t size;
+
+	if (!pmt_feature_id_is_valid(id))
+		return ERR_PTR(-EINVAL);
+
+	guard(mutex)(&ep_lock);
+	xa_for_each(&telem_array, idx, entry) {
+		if (entry->feature_flags & BIT(id))
+			count++;
+	}
+
+	if (!count)
+		return ERR_PTR(-ENOENT);
+
+	size = struct_size(feature_group, regions, count);
+	feature_group = kzalloc(size, GFP_KERNEL);
+	if (!feature_group)
+		return ERR_PTR(-ENOMEM);
+
+	feature_group->count = count;
+
+	region = feature_group->regions;
+	xa_for_each(&telem_array, idx, entry) {
+		int ret;
+
+		if (!(entry->feature_flags & BIT(id)))
+			continue;
+
+		ret = pmt_copy_region(region, entry);
+		if (ret)
+			return ERR_PTR(ret);
+
+		region++;
+	}
+
+	kref_init(&feature_group->kref);
+
+	return no_free_ptr(feature_group);
+}
+EXPORT_SYMBOL(intel_pmt_get_regions_by_feature);
+
+void intel_pmt_put_feature_group(struct pmt_feature_group *feature_group)
+{
+	kref_put(&feature_group->kref, pmt_feature_group_release);
+}
+EXPORT_SYMBOL(intel_pmt_put_feature_group);
+
 int pmt_telem_read(struct telem_endpoint *ep, u32 id, u64 *data, u32 count)
 {
 	u32 offset, size;
@@ -353,3 +439,4 @@ MODULE_AUTHOR("David E. Box <david.e.box@linux.intel.com>");
 MODULE_DESCRIPTION("Intel PMT Telemetry driver");
 MODULE_LICENSE("GPL v2");
 MODULE_IMPORT_NS("INTEL_PMT");
+MODULE_IMPORT_NS("INTEL_VSEC");

include/linux/intel_vsec.h

@@ -4,6 +4,7 @@
 
 #include <linux/auxiliary_bus.h>
 #include <linux/bits.h>
+#include <linux/err.h>
 #include <linux/intel_pmt_features.h>
 
 /*
@@ -218,4 +219,21 @@ static inline struct oobmsm_plat_info *intel_vsec_get_mapping(struct pci_dev *pd
 	return ERR_PTR(-ENODEV);
 }
 #endif
+
+#if IS_ENABLED(CONFIG_INTEL_PMT_TELEMETRY)
+struct pmt_feature_group *
+intel_pmt_get_regions_by_feature(enum pmt_feature_id id);
+
+void intel_pmt_put_feature_group(struct pmt_feature_group *feature_group);
+#else
+static inline struct pmt_feature_group *
+intel_pmt_get_regions_by_feature(enum pmt_feature_id id)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline void
+intel_pmt_put_feature_group(struct pmt_feature_group *feature_group) {}
+#endif
+
 #endif