cxl/test: Add mock version of devm_cxl_add_dport_by_dev()

devm_cxl_add_dport_by_dev() outside of cxl_test is done through PCI
hierarchy. However with cxl_test, it needs to be done through the
platform device hierarchy. Add the mock function for
devm_cxl_add_dport_by_dev().

When cxl_core calls a cxl_core exported function and that function is
mocked by cxl_test, the call chain causes a circular dependency issue. Dan
provided a workaround to avoid this issue. Apply the method to changes from
the late dport allocation changes in order to enable cxl-test.

In cxl_core they are defined with "__" added in front of the function. A
macro is used to define the original function names for when non-test
version of the kernel is built. A bit of macros and typedefs are used to
allow mocking of those functions in cxl_test.

Co-developed-by: Dan Williams <[e-mail]>
Signed-off-by: Dan Williams <[e-mail]>
Reviewed-by: Jonathan Cameron <[e-mail]>
Reviewed-by: Li Ming <[e-mail]>
Tested-by: Alison Schofield <[e-mail]>
Tested-by: Robert Richter <[e-mail]>
Signed-off-by: Dave Jiang <[e-mail]>

drivers/cxl/core/core.h

···
 int cxl_ras_init(void);
 void cxl_ras_exit(void);
 int cxl_gpf_port_setup(struct cxl_dport *dport);
-struct cxl_dport *devm_cxl_add_dport_by_dev(struct cxl_port *port,
-					    struct device *dport_dev);
 
 struct cxl_hdm;
 int cxl_hdm_decode_init(struct cxl_dev_state *cxlds, struct cxl_hdm *cxlhdm,

drivers/cxl/core/pci.c

···
 }
 
 /**
- * devm_cxl_add_dport_by_dev - allocate a dport by the dport device
+ * __devm_cxl_add_dport_by_dev - allocate a dport by dport device
  * @port: cxl_port that hosts the dport
  * @dport_dev: 'struct device' of the dport
  *
  * Returns the allocated dport on success or ERR_PTR() of -errno on error
  */
-struct cxl_dport *devm_cxl_add_dport_by_dev(struct cxl_port *port,
-					    struct device *dport_dev)
+struct cxl_dport *__devm_cxl_add_dport_by_dev(struct cxl_port *port,
+					      struct device *dport_dev)
 {
 	struct cxl_register_map map;
 	struct pci_dev *pdev;
···
 	device_lock_assert(&port->dev);
 	return devm_cxl_add_dport(port, dport_dev, port_num, map.resource);
 }
+EXPORT_SYMBOL_NS_GPL(__devm_cxl_add_dport_by_dev, "CXL");
 
 struct cxl_walk_context {
 	struct pci_bus *bus;

drivers/cxl/cxl.h

···
 			     struct access_coordinate *c2);
 
 bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
+struct cxl_dport *devm_cxl_add_dport_by_dev(struct cxl_port *port,
+					    struct device *dport_dev);
+struct cxl_dport *__devm_cxl_add_dport_by_dev(struct cxl_port *port,
+					      struct device *dport_dev);
 
 /*
  * Unit test builds overrides this to __weak, find the 'strong' version
···
 #endif
 
 u16 cxl_gpf_get_dvsec(struct device *dev);
+
+/*
+ * Declaration for functions that are mocked by cxl_test that are called by
+ * cxl_core. The respective functions are defined as __foo() and called by
+ * cxl_core as foo(). The macros below ensures that those functions would
+ * exist as foo(). See tools/testing/cxl/cxl_core_exports.c and
+ * tools/testing/cxl/exports.h for setting up the mock functions. The dance
+ * is done to avoid a circular dependency where cxl_core calls a function that
+ * ends up being a mock function and goes to * cxl_test where it calls a
+ * cxl_core function.
+ */
+#ifndef CXL_TEST_ENABLE
+#define DECLARE_TESTABLE(x) __##x
+#define devm_cxl_add_dport_by_dev DECLARE_TESTABLE(devm_cxl_add_dport_by_dev)
+#endif
+
 #endif /* __CXL_H__ */

tools/testing/cxl/Kbuild

···
 CXL_CORE_SRC := $(DRIVERS)/cxl/core
 ccflags-y := -I$(srctree)/drivers/cxl/
 ccflags-y += -D__mock=__weak
+ccflags-y += -DCXL_TEST_ENABLE=1
 ccflags-y += -DTRACE_INCLUDE_PATH=$(CXL_CORE_SRC) -I$(srctree)/drivers/cxl/core/
 
 obj-m += cxl_acpi.o

tools/testing/cxl/cxl_core_exports.c

···
 /* Copyright(c) 2022 Intel Corporation. All rights reserved. */
 
 #include "cxl.h"
+#include "exports.h"
 
 /* Exporting of cxl_core symbols that are only used by cxl_test */
 EXPORT_SYMBOL_NS_GPL(cxl_num_decoders_committed, "CXL");
+
+cxl_add_dport_by_dev_fn _devm_cxl_add_dport_by_dev =
+	__devm_cxl_add_dport_by_dev;
+EXPORT_SYMBOL_NS_GPL(_devm_cxl_add_dport_by_dev, "CXL");
+
+struct cxl_dport *devm_cxl_add_dport_by_dev(struct cxl_port *port,
+					    struct device *dport_dev)
+{
+	return _devm_cxl_add_dport_by_dev(port, dport_dev);
+}
+EXPORT_SYMBOL_NS_GPL(devm_cxl_add_dport_by_dev, "CXL");

tools/testing/cxl/exports.h

···
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright(c) 2025 Intel Corporation */
+#ifndef __MOCK_CXL_EXPORTS_H_
+#define __MOCK_CXL_EXPORTS_H_
+
+typedef struct cxl_dport *(*cxl_add_dport_by_dev_fn)(struct cxl_port *port,
+							  struct device *dport_dev);
+extern cxl_add_dport_by_dev_fn _devm_cxl_add_dport_by_dev;
+
+#endif

tools/testing/cxl/test/cxl.c

···
 	return __mock_cxl_decoders_setup(port);
 }
 
-static int mock_cxl_port_enumerate_dports(struct cxl_port *port)
+static int get_port_array(struct cxl_port *port,
+			  struct platform_device ***port_array,
+			  int *port_array_size)
 {
 	struct platform_device **array;
-	int i, array_size;
+	int array_size;
 
 	if (port->depth == 1) {
 		if (is_multi_bridge(port->uport_dev)) {
···
 		return -ENXIO;
 	}
 
+	*port_array = array;
+	*port_array_size = array_size;
+
+	return 0;
+}
+
+static int mock_cxl_port_enumerate_dports(struct cxl_port *port)
+{
+	struct platform_device **array;
+	int i, array_size;
+	int rc;
+
+	rc = get_port_array(port, &array, &array_size);
+	if (rc)
+		return rc;
+
 	for (i = 0; i < array_size; i++) {
 		struct platform_device *pdev = array[i];
 		struct cxl_dport *dport;
···
 	}
 
 	return 0;
+}
+
+static struct cxl_dport *mock_cxl_add_dport_by_dev(struct cxl_port *port,
+						   struct device *dport_dev)
+{
+	struct platform_device **array;
+	int rc, i, array_size;
+
+	rc = get_port_array(port, &array, &array_size);
+	if (rc)
+		return ERR_PTR(rc);
+
+	for (i = 0; i < array_size; i++) {
+		struct platform_device *pdev = array[i];
+
+		if (pdev->dev.parent != port->uport_dev) {
+			dev_dbg(&port->dev, "%s: mismatch parent %s\n",
+				dev_name(port->uport_dev),
+				dev_name(pdev->dev.parent));
+			continue;
+		}
+
+		if (&pdev->dev != dport_dev)
+			continue;
+
+		return devm_cxl_add_dport(port, &pdev->dev, pdev->id,
+					  CXL_RESOURCE_NONE);
+	}
+
+	return ERR_PTR(-ENODEV);
 }
 
 /*
···
 	.devm_cxl_endpoint_decoders_setup = mock_cxl_endpoint_decoders_setup,
 	.devm_cxl_port_enumerate_dports = mock_cxl_port_enumerate_dports,
 	.cxl_endpoint_parse_cdat = mock_cxl_endpoint_parse_cdat,
+	.devm_cxl_add_dport_by_dev = mock_cxl_add_dport_by_dev,
 	.list = LIST_HEAD_INIT(cxl_mock_ops.list),
 };
 

tools/testing/cxl/test/mock.c

···
 #include <cxlmem.h>
 #include <cxlpci.h>
 #include "mock.h"
+#include "../exports.h"
 
 static LIST_HEAD(mock);
+
+static struct cxl_dport *
+redirect_devm_cxl_add_dport_by_dev(struct cxl_port *port,
+				   struct device *dport_dev);
 
 void register_cxl_mock_ops(struct cxl_mock_ops *ops)
 {
 	list_add_rcu(&ops->list, &mock);
+	_devm_cxl_add_dport_by_dev = redirect_devm_cxl_add_dport_by_dev;
 }
 EXPORT_SYMBOL_GPL(register_cxl_mock_ops);
 
···
 
 void unregister_cxl_mock_ops(struct cxl_mock_ops *ops)
 {
+	_devm_cxl_add_dport_by_dev = __devm_cxl_add_dport_by_dev;
 	list_del_rcu(&ops->list);
 	synchronize_srcu(&cxl_mock_srcu);
 }
···
 	put_cxl_mock_ops(index);
 }
 EXPORT_SYMBOL_NS_GPL(__wrap_cxl_dport_init_ras_reporting, "CXL");
+
+struct cxl_dport *redirect_devm_cxl_add_dport_by_dev(struct cxl_port *port,
+						     struct device *dport_dev)
+{
+	int index;
+	struct cxl_mock_ops *ops = get_cxl_mock_ops(&index);
+	struct cxl_dport *dport;
+
+	if (ops && ops->is_mock_port(port->uport_dev))
+		dport = ops->devm_cxl_add_dport_by_dev(port, dport_dev);
+	else
+		dport = __devm_cxl_add_dport_by_dev(port, dport_dev);
+	put_cxl_mock_ops(index);
+
+	return dport;
+}
 
 MODULE_LICENSE("GPL v2");
 MODULE_DESCRIPTION("cxl_test: emulation module");

tools/testing/cxl/test/mock.h

···
 	int (*devm_cxl_switch_port_decoders_setup)(struct cxl_port *port);
 	int (*devm_cxl_endpoint_decoders_setup)(struct cxl_port *port);
 	void (*cxl_endpoint_parse_cdat)(struct cxl_port *port);
+	struct cxl_dport *(*devm_cxl_add_dport_by_dev)(struct cxl_port *port,
+						       struct device *dport_dev);
 };
 
 void register_cxl_mock_ops(struct cxl_mock_ops *ops);