platform/x86/intel/vsec: Add device links to enforce dependencies

New Intel VSEC features will have dependencies on other features, requiring
certain supplier drivers to be probed before their consumers. To enforce
this dependency ordering, introduce device links using device_link_add(),
ensuring that suppliers are fully registered before consumers are probed.

- Add device link tracking by storing supplier devices and tracking their
  state.
- Implement intel_vsec_link_devices() to establish links between suppliers
  and consumers based on feature dependencies.
- Add get_consumer_dependencies() to retrieve supplier-consumer
  relationships.
- Modify feature registration logic:
  * Consumers now check that all required suppliers are registered before
    being initialized.
  * suppliers_ready() verifies that all required supplier devices are
    available.
- Prevent potential null consumer name issue in sysfs:
  - Use dev_set_name() when creating auxiliary devices to ensure a
    unique, non-null consumer name.
- Update intel_vsec_pci_probe() to loop up to the number of possible
  features or when all devices are registered, whichever comes first.
- Introduce VSEC_CAP_UNUSED to prevent sub-features (registered via
  exported APIs) from being mistakenly linked.

Signed-off-by: David E. Box <david.e.box@linux.intel.com>
Link: https://lore.kernel.org/r/20250703022832.1302928-5-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>

1 files changed, 23 insertions, 5 deletions

diff --git a/include/linux/intel_vsec.h b/include/linux/intel_vsec.h
index bc95821f1bfb..71067afaca99 100644
--- a/include/linux/intel_vsec.h
+++ b/include/linux/intel_vsec.h
@@ -5,11 +5,18 @@
 #include <linux/auxiliary_bus.h>
 #include <linux/bits.h>
 
-#define VSEC_CAP_TELEMETRY	BIT(0)
-#define VSEC_CAP_WATCHER	BIT(1)
-#define VSEC_CAP_CRASHLOG	BIT(2)
-#define VSEC_CAP_SDSI		BIT(3)
-#define VSEC_CAP_TPMI		BIT(4)
+/*
+ * VSEC_CAP_UNUSED is reserved. It exists to prevent zero initialized
+ * intel_vsec devices from being automatically set to a known
+ * capability with ID 0
+ */
+#define VSEC_CAP_UNUSED		BIT(0)
+#define VSEC_CAP_TELEMETRY	BIT(1)
+#define VSEC_CAP_WATCHER	BIT(2)
+#define VSEC_CAP_CRASHLOG	BIT(3)
+#define VSEC_CAP_SDSI		BIT(4)
+#define VSEC_CAP_TPMI		BIT(5)
+#define VSEC_FEATURE_COUNT	6
 
 /* Intel DVSEC offsets */
 #define INTEL_DVSEC_ENTRIES		0xA
@@ -81,22 +88,31 @@ struct pmt_callbacks {
 	int (*read_telem)(struct pci_dev *pdev, u32 guid, u64 *data, loff_t off, u32 count);
 };
 
+struct vsec_feature_dependency {
+	unsigned long feature;
+	unsigned long supplier_bitmap;
+};
+
 /**
  * struct intel_vsec_platform_info - Platform specific data
  * @parent:    parent device in the auxbus chain
  * @headers:   list of headers to define the PMT client devices to create
+ * @deps:      array of feature dependencies
  * @priv_data: private data, usable by parent devices, currently a callback
  * @caps:      bitmask of PMT capabilities for the given headers
  * @quirks:    bitmask of VSEC device quirks
  * @base_addr: allow a base address to be specified (rather than derived)
+ * @num_deps:  Count feature dependencies
  */
 struct intel_vsec_platform_info {
 	struct device *parent;
 	struct intel_vsec_header **headers;
+	const struct vsec_feature_dependency *deps;
 	void *priv_data;
 	unsigned long caps;
 	unsigned long quirks;
 	u64 base_addr;
+	int num_deps;
 };
 
 /**
@@ -110,6 +126,7 @@ struct intel_vsec_platform_info {
  * @priv_data:     any private data needed
  * @quirks:        specified quirks
  * @base_addr:     base address of entries (if specified)
+ * @cap_id:        the enumerated id of the vsec feature
  */
 struct intel_vsec_device {
 	struct auxiliary_device auxdev;
@@ -122,6 +139,7 @@ struct intel_vsec_device {
 	size_t priv_data_size;
 	unsigned long quirks;
 	u64 base_addr;
+	unsigned long cap_id;
 };
 
 int intel_vsec_add_aux(struct pci_dev *pdev, struct device *parent,