[ndctl PATCH 30/37] cxl/list: Add decoder support

[Dan Williams <dan.j.williams@intel.com>]

Decoder objects exist at each level of a CXL port topology and map a
physical address range a set of interleaved ports at each level of the
hierarchy. Typically end users mostly care about the root-level decoders
which enumerate the potential CXL address space in the system, and the
endpoint decoders that indicate which address ranges a given device
contributes resources. Intermediate switch-level decoders are typically
only useful for debugging decode problems.

$ cxl list -D -d 3.1 -u
{
  "decoder":"decoder3.1",
  "resource":"0x8030000000",
  "size":"512.00 MiB (536.87 MB)",
  "volatile_capable":true
}

Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 .clang-format                    |    1 
 Documentation/cxl/cxl-list.txt   |   18 +++
 Documentation/cxl/lib/libcxl.txt |   70 +++++++++++
 cxl/filter.c                     |  194 ++++++++++++++++++++++++++++++-
 cxl/filter.h                     |    2 
 cxl/json.c                       |   62 ++++++++++
 cxl/json.h                       |    2 
 cxl/lib/libcxl.c                 |  239 +++++++++++++++++++++++++++++++++++---
 cxl/lib/libcxl.sym               |   14 ++
 cxl/lib/private.h                |   31 +++++
 cxl/libcxl.h                     |   28 ++++
 cxl/list.c                       |    9 +
 util/json.h                      |    1 
 13 files changed, 643 insertions(+), 28 deletions(-)

diff --git a/.clang-format b/.clang-format
index 106bc5e25434..16e28ac86959 100644
--- a/.clang-format
+++ b/.clang-format
@@ -80,6 +80,7 @@ ForEachMacros:
   - 'cxl_memdev_foreach'
   - 'cxl_bus_foreach'
   - 'cxl_port_foreach'
+  - 'cxl_decoder_foreach'
   - 'cxl_endpoint_foreach'
   - 'daxctl_dev_foreach'
   - 'daxctl_mapping_foreach'
diff --git a/Documentation/cxl/cxl-list.txt b/Documentation/cxl/cxl-list.txt
index bac27c7b70a1..84872b912975 100644
--- a/Documentation/cxl/cxl-list.txt
+++ b/Documentation/cxl/cxl-list.txt
@@ -5,7 +5,7 @@ cxl-list(1)
 
 NAME
 ----
-cxl-list - List CXL capable memory devices, and their attributes in json.
+cxl-list - List platform CXL objects, and their attributes, in json.
 
 SYNOPSIS
 --------
@@ -29,6 +29,10 @@ The potential top-level array names and their nesting properties are:
 "endpoints":: nest under ports or buses (if ports are not emitted)
 "memdevs":: nest under endpoints or ports (if endpoints are not
    emitted) or buses (if endpoints and ports are not emitted)
+"root decoders":: nest under buses
+"port decoders":: nest under ports, or buses (if ports are not emitted)
+"endpoint decoders":: nest under endpoints, or ports (if endpoints are
+   not emitted) or buses (if endpoints and ports are not emitted)
 
 Filters can by specifed as either a single identidier, a space separated
 quoted string, or a comma separated list. When multiple filter
@@ -254,6 +258,18 @@ OPTIONS
 	Specify CXL endpoint device name(s), or device id(s) to filter
 	the emitted endpoint(s).
 
+-D::
+--decoders::
+	Include decoder objects (CXL Memory decode capability instances
+	in buses, ports, and endpoints) in the listing.
+
+-d::
+--decoder::
+	Specify CXL decoder device name(s), device id(s), or decoder type names
+	to filter the emitted decoder(s). The format for a decoder name is
+	"decoder<port_id>.<instance_id>". The possible decoder type names are
+	"root", "switch", or "endpoint", similar to the port filter syntax.
+
 --debug::
 	If the cxl tool was built with debug enabled, turn on debug
 	messages.
diff --git a/Documentation/cxl/lib/libcxl.txt b/Documentation/cxl/lib/libcxl.txt
index 49edb71b1f97..73af3d03b108 100644
--- a/Documentation/cxl/lib/libcxl.txt
+++ b/Documentation/cxl/lib/libcxl.txt
@@ -179,6 +179,7 @@ struct cxl_bus *cxl_bus_get_first(struct cxl_ctx *ctx);
 struct cxl_bus *cxl_bus_get_next(struct cxl_bus *bus);
 struct cxl_ctx *cxl_bus_get_ctx(struct cxl_bus *bus);
 struct cxl_bus *cxl_memdev_get_bus(struct cxl_memdev *memdev);
+struct cxl_bus *cxl_port_get_bus(struct cxl_port *port);
 struct cxl_bus *cxl_endpoint_get_bus(struct cxl_endpoint *endpoint);
 
 #define cxl_bus_foreach(ctx, bus)                                           \
@@ -215,9 +216,9 @@ struct cxl_port *cxl_bus_get_port(struct cxl_bus *bus);
 struct cxl_port *cxl_port_get_first(struct cxl_port *parent);
 struct cxl_port *cxl_port_get_next(struct cxl_port *port);
 struct cxl_port *cxl_port_get_parent(struct cxl_port *port);
-struct cxl_bus *cxl_port_get_bus(struct cxl_port *port);
 struct cxl_ctx *cxl_port_get_ctx(struct cxl_port *port);
 const char *cxl_port_get_host(struct cxl_port *port);
+struct cxl_port *cxl_decoder_get_port(struct cxl_decoder *decoder);
 
 #define cxl_port_foreach(parent, port)                                      \
        for (port = cxl_port_get_first(parent); port != NULL;                \
@@ -284,6 +285,73 @@ int cxl_endpoint_get_id(struct cxl_endpoint *endpoint);
 int cxl_endpoint_is_enabled(struct cxl_endpoint *endpoint);
 ----
 
+DECODERS
+--------
+Decoder objects are associated with the "HDM Decoder Capability"
+published in Port devices and CXL capable PCIe endpoints. The kernel
+additionally models platform firmware described CXL memory ranges (like
+the ACPI CEDT.CFMWS) as static decoder objects. They route System
+Physical Addresses through a port topology to an endpoint decoder that
+does the final translation from SPA to DPA (system-physical-address to
+device-local-physical-address).
+
+=== DECODER: Enumeration
+----
+struct cxl_decoder *cxl_decoder_get_first(struct cxl_port *port);
+struct cxl_decoder *cxl_decoder_get_next(struct cxl_decoder *decoder);
+struct cxl_ctx *cxl_decoder_get_ctx(struct cxl_decoder *decoder);
+
+#define cxl_decoder_foreach(port, decoder)                                  \
+       for (decoder = cxl_decoder_get_first(port); decoder != NULL;         \
+            decoder = cxl_decoder_get_next(decoder))
+----
+The definition of a CXL port in libcxl is an object that hosts one or
+more CXL decoder objects.
+
+=== DECODER: Attributes
+----
+unsigned long long cxl_decoder_get_resource(struct cxl_decoder *decoder);
+unsigned long long cxl_decoder_get_size(struct cxl_decoder *decoder);
+const char *cxl_decoder_get_devname(struct cxl_decoder *decoder);
+int cxl_decoder_get_id(struct cxl_decoder *decoder);
+
+enum cxl_decoder_target_type {
+       CXL_DECODER_TTYPE_UNKNOWN,
+       CXL_DECODER_TTYPE_EXPANDER,
+       CXL_DECODER_TTYPE_ACCELERATOR,
+};
+
+cxl_decoder_get_target_type(struct cxl_decoder *decoder);
+bool cxl_decoder_is_pmem_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_volatile_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_mem_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_accelmem_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_locked(struct cxl_decoder *decoder);
+----
+The kernel protects the enumeration of the physical address layout of
+the system. Without CAP_SYS_ADMIN cxl_decoder_get_resource() returns
+ULLONG_MAX to indicate that the address information was not retrievable.
+Otherwise, cxl_decoder_get_resource() returns the currently programmed
+value of the base of the decoder's decode range. A zero-sized decoder
+indicates a disabled decoder.
+
+Root level decoders only support limited set of memory types in their
+address range. The cxl_decoder_is_<memtype>_capable() helpers identify
+what is supported. Switch level decoders, in contrast are capable of
+routing any memory type, i.e. they just forward along the memory type
+support from their parent port. Endpoint decoders follow the
+capabilities of their host memory device.
+
+The capabilities of a decoder are not to be confused with their type /
+mode.  The type ultimately depends on the endpoint. For example an
+accelerator requires all decoders in its ancestry to be set to
+CXL_DECODER_TTYPE_ACCELERATOR, and conversely plain memory expander
+devices require CXL_DECODER_TTYPE_EXPANDER.
+
+Platform firmware may setup the CXL decode hierarchy before the OS
+boots, and may additionally require that the OS not change the decode
+settings. This property is indicated by the cxl_decoder_is_locked() API.
+
 include::../../copyright.txt[]
 
 SEE ALSO
diff --git a/cxl/filter.c b/cxl/filter.c
index 6dc61a135351..dc052f63d0c5 100644
--- a/cxl/filter.c
+++ b/cxl/filter.c
@@ -171,6 +171,17 @@ util_cxl_endpoint_filter_by_port(struct cxl_endpoint *endpoint,
 	return NULL;
 }
 
+static struct cxl_decoder *
+util_cxl_decoder_filter_by_port(struct cxl_decoder *decoder, const char *ident,
+				enum cxl_port_filter_mode mode)
+{
+	struct cxl_port *port = cxl_decoder_get_port(decoder);
+
+	if (util_cxl_port_filter(port, ident, mode))
+		return decoder;
+	return NULL;
+}
+
 static struct cxl_bus *util_cxl_bus_filter(struct cxl_bus *bus,
 					   const char *__ident)
 {
@@ -233,6 +244,16 @@ static struct cxl_port *util_cxl_port_filter_by_bus(struct cxl_port *port,
 	return NULL;
 }
 
+static struct cxl_decoder *
+util_cxl_decoder_filter_by_bus(struct cxl_decoder *decoder, const char *__ident)
+{
+	struct cxl_port *port = cxl_decoder_get_port(decoder);
+
+	if (!util_cxl_port_filter_by_bus(port, __ident))
+		return NULL;
+	return decoder;
+}
+
 static struct cxl_memdev *
 util_cxl_memdev_serial_filter(struct cxl_memdev *memdev, const char *__serials)
 {
@@ -357,6 +378,49 @@ static struct cxl_port *util_cxl_port_filter_by_memdev(struct cxl_port *port,
 	return NULL;
 }
 
+static struct cxl_decoder *util_cxl_decoder_filter(struct cxl_decoder *decoder,
+						   const char *__ident)
+{
+	struct cxl_port *port = cxl_decoder_get_port(decoder);
+	int pid, did;
+	char *ident, *save;
+	const char *name;
+
+	if (!__ident)
+		return decoder;
+
+	ident = strdup(__ident);
+	if (!ident)
+		return NULL;
+
+	for (name = strtok_r(ident, which_sep(__ident), &save); name;
+	     name = strtok_r(NULL, which_sep(__ident), &save)) {
+		if (strcmp(name, "all") == 0)
+			break;
+
+		if (strcmp(name, "root") == 0 && cxl_port_is_root(port))
+			break;
+		if (strcmp(name, "switch") == 0 && cxl_port_is_switch(port))
+			break;
+		if (strcmp(name, "endpoint") == 0 && cxl_port_is_endpoint(port))
+			break;
+
+		if ((sscanf(name, "%d.%d", &pid, &did) == 2 ||
+		     sscanf(name, "decoder%d.%d", &pid, &did) == 2) &&
+		    cxl_port_get_id(port) == pid &&
+		    cxl_decoder_get_id(decoder) == did)
+			break;
+
+		if (strcmp(name, cxl_decoder_get_devname(decoder)) == 0)
+			break;
+	}
+
+	free(ident);
+	if (name)
+		return decoder;
+	return NULL;
+}
+
 static unsigned long params_to_flags(struct cxl_filter_params *param)
 {
 	unsigned long flags = 0;
@@ -440,15 +504,44 @@ static struct json_object *pick_array(struct json_object *child,
 	return NULL;
 }
 
+static void walk_decoders(struct cxl_port *port, struct cxl_filter_params *p,
+			  struct json_object *jdecoders, unsigned long flags)
+{
+	struct cxl_decoder *decoder;
+
+	cxl_decoder_foreach(port, decoder) {
+		struct json_object *jdecoder;
+
+		if (!p->decoders)
+			continue;
+		if (!util_cxl_decoder_filter(decoder, p->decoder_filter))
+			continue;
+		if (!util_cxl_decoder_filter_by_bus(decoder, p->bus_filter))
+			continue;
+		if (!util_cxl_decoder_filter_by_port(decoder, p->port_filter,
+						     pf_mode(p)))
+			continue;
+		if (!p->idle && cxl_decoder_get_size(decoder) == 0)
+			continue;
+		jdecoder = util_cxl_decoder_to_json(decoder, flags);
+		if (!decoder) {
+			dbg(p, "decoder object allocation failure\n");
+			continue;
+		}
+		json_object_array_add(jdecoders, jdecoder);
+	}
+}
+
 static void walk_endpoints(struct cxl_port *port, struct cxl_filter_params *p,
 			   struct json_object *jeps, struct json_object *jdevs,
-			   unsigned long flags)
+			   struct json_object *jdecoders, unsigned long flags)
 {
 	struct cxl_endpoint *endpoint;
 
 	cxl_endpoint_foreach(port, endpoint) {
 		struct cxl_port *ep_port = cxl_endpoint_get_port(endpoint);
 		const char *devname = cxl_endpoint_get_devname(endpoint);
+		struct json_object *jchilddecoders = NULL;
 		struct json_object *jendpoint = NULL;
 		struct cxl_memdev *memdev;
 
@@ -495,14 +588,31 @@ static void walk_endpoints(struct cxl_port *port, struct cxl_filter_params *p,
 			else
 				json_object_array_add(jdevs, jobj);
 		}
+
+		if (p->decoders && p->endpoints) {
+			jchilddecoders = json_object_new_array();
+			if (!jchilddecoders) {
+				err(p,
+				    "%s: failed to enumerate child decoders\n",
+				    devname);
+				continue;
+			}
+		}
+
+		if (!p->decoders)
+			continue;
+		walk_decoders(cxl_endpoint_get_port(endpoint), p,
+			      pick_array(jchilddecoders, jdecoders), flags);
+		cond_add_put_array_suffix(jendpoint, "decoders", devname,
+					  jchilddecoders);
 	}
 }
 
-static void walk_child_ports(struct cxl_port *parent_port,
-			     struct cxl_filter_params *p,
-			     struct json_object *jports,
-			     struct json_object *jeps,
-			     struct json_object *jdevs, unsigned long flags)
+static void
+walk_child_ports(struct cxl_port *parent_port, struct cxl_filter_params *p,
+		 struct json_object *jports, struct json_object *jportdecoders,
+		 struct json_object *jeps, struct json_object *jepdecoders,
+		 struct json_object *jdevs, unsigned long flags)
 {
 	struct cxl_port *port;
 
@@ -512,6 +622,7 @@ static void walk_child_ports(struct cxl_port *parent_port,
 		struct json_object *jchilddevs = NULL;
 		struct json_object *jchildports = NULL;
 		struct json_object *jchildeps = NULL;
+		struct json_object *jchilddecoders = NULL;
 
 		if (!util_cxl_port_filter_by_memdev(port, p->memdev_filter,
 						    p->serial_filter))
@@ -555,19 +666,37 @@ static void walk_child_ports(struct cxl_port *parent_port,
 					continue;
 				}
 			}
+
+			if (p->decoders) {
+				jchilddecoders = json_object_new_array();
+				if (!jchilddecoders) {
+					err(p,
+					    "%s: failed to enumerate child decoders\n",
+					    devname);
+					continue;
+				}
+			}
 		}
 
 walk_children:
-		if (p->endpoints || p->memdevs)
+		if (p->endpoints || p->memdevs || p->decoders)
 			walk_endpoints(port, p, pick_array(jchildeps, jeps),
-				       pick_array(jchilddevs, jdevs), flags);
+				       pick_array(jchilddevs, jdevs),
+				       pick_array(jchilddecoders, jepdecoders),
+				       flags);
 
+		walk_decoders(port, p,
+			      pick_array(jchilddecoders, jportdecoders), flags);
 		walk_child_ports(port, p, pick_array(jchildports, jports),
+				 pick_array(jchilddecoders, jportdecoders),
 				 pick_array(jchildeps, jeps),
+				 pick_array(jchilddecoders, jepdecoders),
 				 pick_array(jchilddevs, jdevs), flags);
 		cond_add_put_array_suffix(jport, "ports", devname, jchildports);
 		cond_add_put_array_suffix(jport, "endpoints", devname,
 					  jchildeps);
+		cond_add_put_array_suffix(jport, "decoders", devname,
+					  jchilddecoders);
 		cond_add_put_array_suffix(jport, "memdevs", devname,
 					  jchilddevs);
 	}
@@ -578,6 +707,9 @@ int cxl_filter_walk(struct cxl_ctx *ctx, struct cxl_filter_params *p)
 	struct json_object *jdevs = NULL, *jbuses = NULL, *jports = NULL;
 	struct json_object *jplatform = json_object_new_array();
 	unsigned long flags = params_to_flags(p);
+	struct json_object *jportdecoders = NULL;
+	struct json_object *jbusdecoders = NULL;
+	struct json_object *jepdecoders = NULL;
 	struct json_object *janondevs = NULL;
 	struct json_object *jeps = NULL;
 	struct cxl_memdev *memdev;
@@ -609,6 +741,18 @@ int cxl_filter_walk(struct cxl_ctx *ctx, struct cxl_filter_params *p)
 	if (!jdevs)
 		goto err;
 
+	jbusdecoders = json_object_new_array();
+	if (!jbusdecoders)
+		goto err;
+
+	jportdecoders = json_object_new_array();
+	if (!jportdecoders)
+		goto err;
+
+	jepdecoders = json_object_new_array();
+	if (!jepdecoders)
+		goto err;
+
 	dbg(p, "walk memdevs\n");
 	cxl_memdev_foreach(ctx, memdev) {
 		struct json_object *janondev;
@@ -633,6 +777,7 @@ int cxl_filter_walk(struct cxl_ctx *ctx, struct cxl_filter_params *p)
 	dbg(p, "walk buses\n");
 	cxl_bus_foreach(ctx, bus) {
 		struct json_object *jbus = NULL;
+		struct json_object *jchilddecoders = NULL;
 		struct json_object *jchildports = NULL;
 		struct json_object *jchilddevs = NULL;
 		struct json_object *jchildeps = NULL;
@@ -681,15 +826,33 @@ int cxl_filter_walk(struct cxl_ctx *ctx, struct cxl_filter_params *p)
 					continue;
 				}
 			}
+			if (p->decoders) {
+				jchilddecoders = json_object_new_array();
+				if (!jchilddecoders) {
+					err(p,
+					    "%s: failed to enumerate child decoders\n",
+					    devname);
+					continue;
+				}
+			}
+
 		}
 walk_children:
+		dbg(p, "walk decoders\n");
+		walk_decoders(port, p, pick_array(jchilddecoders, jbusdecoders),
+			      flags);
+
 		dbg(p, "walk ports\n");
 		walk_child_ports(port, p, pick_array(jchildports, jports),
+				 pick_array(jchilddecoders, jportdecoders),
 				 pick_array(jchildeps, jeps),
+				 pick_array(jchilddecoders, jepdecoders),
 				 pick_array(jchilddevs, jdevs), flags);
 		cond_add_put_array_suffix(jbus, "ports", devname, jchildports);
 		cond_add_put_array_suffix(jbus, "endpoints", devname,
 					  jchildeps);
+		cond_add_put_array_suffix(jbus, "decoders", devname,
+					  jchilddecoders);
 		cond_add_put_array_suffix(jbus, "memdevs", devname, jchilddevs);
 	}
 
@@ -703,12 +866,24 @@ walk_children:
 		top_level_objs++;
 	if (json_object_array_length(jdevs))
 		top_level_objs++;
+	if (json_object_array_length(jbusdecoders))
+		top_level_objs++;
+	if (json_object_array_length(jportdecoders))
+		top_level_objs++;
+	if (json_object_array_length(jepdecoders))
+		top_level_objs++;
 
 	splice_array(p, janondevs, jplatform, "anon memdevs", top_level_objs > 1);
 	splice_array(p, jbuses, jplatform, "buses", top_level_objs > 1);
 	splice_array(p, jports, jplatform, "ports", top_level_objs > 1);
 	splice_array(p, jeps, jplatform, "endpoints", top_level_objs > 1);
 	splice_array(p, jdevs, jplatform, "memdevs", top_level_objs > 1);
+	splice_array(p, jbusdecoders, jplatform, "root decoders",
+		     top_level_objs > 1);
+	splice_array(p, jportdecoders, jplatform, "port decoders",
+		     top_level_objs > 1);
+	splice_array(p, jepdecoders, jplatform, "endpoint decoders",
+		     top_level_objs > 1);
 
 	util_display_json_array(stdout, jplatform, flags);
 
@@ -719,6 +894,9 @@ err:
 	json_object_put(jports);
 	json_object_put(jeps);
 	json_object_put(jdevs);
+	json_object_put(jbusdecoders);
+	json_object_put(jportdecoders);
+	json_object_put(jepdecoders);
 	json_object_put(jplatform);
 	return -ENOMEM;
 }
diff --git a/cxl/filter.h b/cxl/filter.h
index bbd341c71721..5d7bf45f3301 100644
--- a/cxl/filter.h
+++ b/cxl/filter.h
@@ -12,8 +12,10 @@ struct cxl_filter_params {
 	const char *bus_filter;
 	const char *port_filter;
 	const char *endpoint_filter;
+	const char *decoder_filter;
 	bool single;
 	bool endpoints;
+	bool decoders;
 	bool memdevs;
 	bool ports;
 	bool buses;
diff --git a/cxl/json.c b/cxl/json.c
index 51918d65f671..548bc52f2d16 100644
--- a/cxl/json.c
+++ b/cxl/json.c
@@ -262,6 +262,68 @@ struct json_object *util_cxl_bus_to_json(struct cxl_bus *bus,
 	return jbus;
 }
 
+struct json_object *util_cxl_decoder_to_json(struct cxl_decoder *decoder,
+					     unsigned long flags)
+{
+	const char *devname = cxl_decoder_get_devname(decoder);
+	struct cxl_port *port = cxl_decoder_get_port(decoder);
+	struct json_object *jdecoder, *jobj;
+	u64 val;
+
+	jdecoder = json_object_new_object();
+	if (!jdecoder)
+		return NULL;
+
+	jobj = json_object_new_string(devname);
+	if (jobj)
+		json_object_object_add(jdecoder, "decoder", jobj);
+
+	val = cxl_decoder_get_resource(decoder);
+	if (val < ULLONG_MAX) {
+		jobj = util_json_object_hex(val, flags);
+		if (jobj)
+			json_object_object_add(jdecoder, "resource", jobj);
+	}
+
+	val = cxl_decoder_get_size(decoder);
+	if (val < ULLONG_MAX) {
+		jobj = util_json_object_size(val, flags);
+		if (jobj)
+			json_object_object_add(jdecoder, "size", jobj);
+	}
+
+	if (val == 0) {
+		jobj = json_object_new_string("disabled");
+		if (jobj)
+			json_object_object_add(jdecoder, "state", jobj);
+	}
+
+	if (cxl_port_is_root(port) && cxl_decoder_is_mem_capable(decoder)) {
+		if (cxl_decoder_is_pmem_capable(decoder)) {
+			jobj = json_object_new_boolean(true);
+			if (jobj)
+				json_object_object_add(jdecoder, "pmem_capable",
+						       jobj);
+		}
+		if (cxl_decoder_is_volatile_capable(decoder)) {
+			jobj = json_object_new_boolean(true);
+			if (jobj)
+				json_object_object_add(
+					jdecoder, "volatile_capable", jobj);
+		}
+	}
+
+	if (cxl_port_is_root(port) &&
+	    cxl_decoder_is_accelmem_capable(decoder)) {
+		jobj = json_object_new_boolean(true);
+		if (jobj)
+			json_object_object_add(jdecoder, "accelmem_capable",
+					       jobj);
+	}
+
+	return jdecoder;
+}
+
 static struct json_object *__util_cxl_port_to_json(struct cxl_port *port,
 						   const char *name_key,
 						   unsigned long flags)
diff --git a/cxl/json.h b/cxl/json.h
index 8f45190f67e5..fcca2e6e9cb6 100644
--- a/cxl/json.h
+++ b/cxl/json.h
@@ -13,4 +13,6 @@ struct json_object *util_cxl_port_to_json(struct cxl_port *port,
 					  unsigned long flags);
 struct json_object *util_cxl_endpoint_to_json(struct cxl_endpoint *endpoint,
 					      unsigned long flags);
+struct json_object *util_cxl_decoder_to_json(struct cxl_decoder *decoder,
+					     unsigned long flags);
 #endif /* __CXL_UTIL_JSON_H__ */
diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
index 2fdaf71bb837..5e3092364e4a 100644
--- a/cxl/lib/libcxl.c
+++ b/cxl/lib/libcxl.c
@@ -63,16 +63,26 @@ static void free_memdev(struct cxl_memdev *memdev, struct list_head *head)
 	free(memdev->firmware_version);
 	free(memdev->dev_buf);
 	free(memdev->dev_path);
-	free(memdev->host);
+	free(memdev->host_path);
 	free(memdev);
 }
 
+static void free_decoder(struct cxl_decoder *decoder, struct list_head *head)
+{
+	if (head)
+		list_del_from(head, &decoder->list);
+	free(decoder->dev_buf);
+	free(decoder->dev_path);
+	free(decoder);
+}
+
 static void free_port(struct cxl_port *port, struct list_head *head);
 static void free_endpoint(struct cxl_endpoint *endpoint, struct list_head *head);
 static void __free_port(struct cxl_port *port, struct list_head *head)
 {
 	struct cxl_port *child, *_c;
 	struct cxl_endpoint *endpoint, *_e;
+	struct cxl_decoder *decoder, *_d;
 
 	if (head)
 		list_del_from(head, &port->list);
@@ -80,6 +90,8 @@ static void __free_port(struct cxl_port *port, struct list_head *head)
 		free_port(child, &port->child_ports);
 	list_for_each_safe(&port->endpoints, endpoint, _e, port.list)
 		free_endpoint(endpoint, &port->endpoints);
+	list_for_each_safe(&port->decoders, decoder, _d, list)
+		free_decoder(decoder, &port->decoders);
 	kmod_module_unref(port->module);
 	free(port->dev_buf);
 	free(port->dev_path);
@@ -298,9 +310,9 @@ static void *add_cxl_memdev(void *parent, int id, const char *cxlmem_base)
 	char *path = calloc(1, strlen(cxlmem_base) + 100);
 	struct cxl_ctx *ctx = parent;
 	struct cxl_memdev *memdev, *memdev_dup;
-	char *host, *rpath = NULL;
 	char buf[SYSFS_ATTR_SIZE];
 	struct stat st;
+	char *host;
 
 	if (!path)
 		return NULL;
@@ -358,21 +370,13 @@ static void *add_cxl_memdev(void *parent, int id, const char *cxlmem_base)
 	if (!memdev->dev_path)
 		goto err_read;
 
-	rpath = realpath(cxlmem_base, NULL);
-	if (!rpath)
+	memdev->host_path = realpath(cxlmem_base, NULL);
+	if (!memdev->host_path)
 		goto err_read;
-	host = strrchr(rpath, '/');
-	if (host) {
-		host[0] = '\0';
-		host = strrchr(rpath, '/');
-	}
+	host = strrchr(memdev->host_path, '/');
 	if (!host)
 		goto err_read;
-	memdev->host = strdup(host + 1);
-	if (!memdev->host)
-		goto err_read;
-	free(rpath);
-	rpath = NULL;
+	host[0] = '\0';
 
 	sprintf(path, "%s/firmware_version", cxlmem_base);
 	if (sysfs_read_attr(ctx, path, buf) < 0)
@@ -404,8 +408,8 @@ static void *add_cxl_memdev(void *parent, int id, const char *cxlmem_base)
 	free(memdev->firmware_version);
 	free(memdev->dev_buf);
 	free(memdev->dev_path);
+	free(memdev->host_path);
 	free(memdev);
-	free(rpath);
  err_dev:
 	free(path);
 	return NULL;
@@ -463,7 +467,7 @@ CXL_EXPORT const char *cxl_memdev_get_devname(struct cxl_memdev *memdev)
 
 CXL_EXPORT const char *cxl_memdev_get_host(struct cxl_memdev *memdev)
 {
-	return memdev->host;
+	return devpath_to_devname(memdev->host_path);
 }
 
 CXL_EXPORT struct cxl_bus *cxl_memdev_get_bus(struct cxl_memdev *memdev)
@@ -679,9 +683,11 @@ static int cxl_port_init(struct cxl_port *port, struct cxl_port *parent_port,
 	port->ctx = ctx;
 	port->type = type;
 	port->parent = parent_port;
+	port->type = type;
 
 	list_head_init(&port->child_ports);
 	list_head_init(&port->endpoints);
+	list_head_init(&port->decoders);
 
 	port->dev_path = strdup(cxlport_base);
 	if (!port->dev_path)
@@ -842,6 +848,207 @@ cxl_endpoint_get_memdev(struct cxl_endpoint *endpoint)
 	return NULL;
 }
 
+static void *add_cxl_decoder(void *parent, int id, const char *cxldecoder_base)
+{
+	const char *devname = devpath_to_devname(cxldecoder_base);
+	char *path = calloc(1, strlen(cxldecoder_base) + 100);
+	struct cxl_decoder *decoder, *decoder_dup;
+	struct cxl_port *port = parent;
+	struct cxl_ctx *ctx = cxl_port_get_ctx(port);
+	char buf[SYSFS_ATTR_SIZE];
+	size_t i;
+
+	dbg(ctx, "%s: base: \'%s\'\n", devname, cxldecoder_base);
+
+	if (!path)
+		return NULL;
+
+	decoder = calloc(1, sizeof(*decoder));
+	if (!decoder)
+		goto err;
+
+	decoder->id = id;
+	decoder->ctx = ctx;
+	decoder->port = port;
+
+	decoder->dev_path = strdup(cxldecoder_base);
+	if (!decoder->dev_path)
+		goto err;
+
+	decoder->dev_buf = calloc(1, strlen(cxldecoder_base) + 50);
+	if (!decoder->dev_buf)
+		goto err;
+	decoder->buf_len = strlen(cxldecoder_base) + 50;
+
+	sprintf(path, "%s/start", cxldecoder_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		decoder->start = ULLONG_MAX;
+	else
+		decoder->start = strtoull(buf, NULL, 0);
+
+	sprintf(path, "%s/size", cxldecoder_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		decoder->size = ULLONG_MAX;
+	else
+		decoder->size = strtoull(buf, NULL, 0);
+
+	switch (port->type) {
+	case CXL_PORT_SWITCH:
+	case CXL_PORT_ENDPOINT:
+		decoder->pmem_capable = true;
+		decoder->volatile_capable = true;
+		decoder->mem_capable = true;
+		decoder->accelmem_capable = true;
+		sprintf(path, "%s/locked", cxldecoder_base);
+		if (sysfs_read_attr(ctx, path, buf) == 0)
+			decoder->locked = !!strtoul(buf, NULL, 0);
+		sprintf(path, "%s/target_type", cxldecoder_base);
+		if (sysfs_read_attr(ctx, path, buf) == 0) {
+			if (strcmp(buf, "accelerator") == 0)
+				decoder->target_type =
+					CXL_DECODER_TTYPE_ACCELERATOR;
+			if (strcmp(buf, "expander") == 0)
+				decoder->target_type =
+					CXL_DECODER_TTYPE_EXPANDER;
+		}
+		break;
+	case CXL_PORT_ROOT: {
+		struct cxl_decoder_flag {
+			char *name;
+			bool *flag;
+		} flags[] = {
+			{ "cap_type2", &decoder->accelmem_capable },
+			{ "cap_type3", &decoder->mem_capable },
+			{ "cap_ram", &decoder->volatile_capable },
+			{ "cap_pmem", &decoder->pmem_capable },
+			{ "locked", &decoder->locked },
+		};
+
+		for (i = 0; i < ARRAY_SIZE(flags); i++) {
+			struct cxl_decoder_flag *flag = &flags[i];
+
+			sprintf(path, "%s/%s", cxldecoder_base, flag->name);
+			if (sysfs_read_attr(ctx, path, buf) == 0)
+				*(flag->flag) = !!strtoul(buf, NULL, 0);
+		}
+		break;
+	}
+	}
+
+	cxl_decoder_foreach(port, decoder_dup)
+		if (decoder_dup->id == decoder->id) {
+			free_decoder(decoder, NULL);
+			return decoder_dup;
+		}
+
+	list_add(&port->decoders, &decoder->list);
+
+	return decoder;
+err:
+	free(decoder->dev_path);
+	free(decoder->dev_buf);
+	free(decoder);
+	free(path);
+	return NULL;
+}
+
+static void cxl_decoders_init(struct cxl_port *port)
+{
+	struct cxl_ctx *ctx = cxl_port_get_ctx(port);
+	char *decoder_fmt;
+
+	if (port->decoders_init)
+		return;
+
+	if (asprintf(&decoder_fmt, "decoder%d.", cxl_port_get_id(port)) < 0) {
+		err(ctx, "%s: failed to add decoder(s)\n",
+		    cxl_port_get_devname(port));
+		return;
+	}
+
+	port->decoders_init = 1;
+
+	sysfs_device_parse(ctx, port->dev_path, decoder_fmt, port,
+			   add_cxl_decoder);
+
+	free(decoder_fmt);
+}
+
+CXL_EXPORT struct cxl_decoder *cxl_decoder_get_first(struct cxl_port *port)
+{
+	cxl_decoders_init(port);
+
+	return list_top(&port->decoders, struct cxl_decoder, list);
+}
+
+CXL_EXPORT struct cxl_decoder *cxl_decoder_get_next(struct cxl_decoder *decoder)
+{
+	struct cxl_port *port = decoder->port;
+
+	return list_next(&port->decoders, decoder, list);
+}
+
+CXL_EXPORT struct cxl_ctx *cxl_decoder_get_ctx(struct cxl_decoder *decoder)
+{
+	return decoder->ctx;
+}
+
+CXL_EXPORT int cxl_decoder_get_id(struct cxl_decoder *decoder)
+{
+	return decoder->id;
+}
+
+CXL_EXPORT struct cxl_port *cxl_decoder_get_port(struct cxl_decoder *decoder)
+{
+	return decoder->port;
+}
+
+CXL_EXPORT unsigned long long cxl_decoder_get_resource(struct cxl_decoder *decoder)
+{
+	return decoder->start;
+}
+
+CXL_EXPORT unsigned long long cxl_decoder_get_size(struct cxl_decoder *decoder)
+{
+	return decoder->size;
+}
+
+CXL_EXPORT enum cxl_decoder_target_type
+cxl_decoder_get_target_type(struct cxl_decoder *decoder)
+{
+	return decoder->target_type;
+}
+
+CXL_EXPORT bool cxl_decoder_is_pmem_capable(struct cxl_decoder *decoder)
+{
+	return decoder->pmem_capable;
+}
+
+CXL_EXPORT bool cxl_decoder_is_volatile_capable(struct cxl_decoder *decoder)
+{
+	return decoder->volatile_capable;
+}
+
+CXL_EXPORT bool cxl_decoder_is_mem_capable(struct cxl_decoder *decoder)
+{
+	return decoder->mem_capable;
+}
+
+CXL_EXPORT bool cxl_decoder_is_accelmem_capable(struct cxl_decoder *decoder)
+{
+	return decoder->accelmem_capable;
+}
+
+CXL_EXPORT bool cxl_decoder_is_locked(struct cxl_decoder *decoder)
+{
+	return decoder->locked;
+}
+
+CXL_EXPORT const char *cxl_decoder_get_devname(struct cxl_decoder *decoder)
+{
+	return devpath_to_devname(decoder->dev_path);
+}
+
 static void *add_cxl_port(void *parent, int id, const char *cxlport_base)
 {
 	const char *devname = devpath_to_devname(cxlport_base);
diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
index f235e99e3bf0..22babb760f23 100644
--- a/cxl/lib/libcxl.sym
+++ b/cxl/lib/libcxl.sym
@@ -117,4 +117,18 @@ global:
 	cxl_memdev_get_bus;
 	cxl_memdev_disable_invalidate;
 	cxl_memdev_enable;
+	cxl_decoder_get_first;
+	cxl_decoder_get_next;
+	cxl_decoder_get_ctx;
+	cxl_decoder_get_id;
+	cxl_decoder_get_port;
+	cxl_decoder_get_resource;
+	cxl_decoder_get_size;
+	cxl_decoder_get_devname;
+	cxl_decoder_get_target_type;
+	cxl_decoder_is_pmem_capable;
+	cxl_decoder_is_volatile_capable;
+	cxl_decoder_is_mem_capable;
+	cxl_decoder_is_accelmem_capable;
+	cxl_decoder_is_locked;
 } LIBCXL_1;
diff --git a/cxl/lib/private.h b/cxl/lib/private.h
index c00bb3600138..1743a244877a 100644
--- a/cxl/lib/private.h
+++ b/cxl/lib/private.h
@@ -23,7 +23,7 @@ struct cxl_memdev {
 	int numa_node;
 	void *dev_buf;
 	size_t buf_len;
-	char *host;
+	char *host_path;
 	char *dev_path;
 	char *firmware_version;
 	struct cxl_ctx *ctx;
@@ -52,6 +52,7 @@ struct cxl_port {
 	char *uport;
 	int ports_init;
 	int endpoints_init;
+	int decoders_init;
 	struct cxl_ctx *ctx;
 	struct cxl_bus *bus;
 	enum cxl_port_type type;
@@ -60,6 +61,7 @@ struct cxl_port {
 	struct list_node list;
 	struct list_head child_ports;
 	struct list_head endpoints;
+	struct list_head decoders;
 };
 
 struct cxl_bus {
@@ -71,6 +73,33 @@ struct cxl_endpoint {
 	struct cxl_memdev *memdev;
 };
 
+struct cxl_target {
+	struct list_node list;
+	struct cxl_decoder *decoder;
+	char *dev_path;
+	int id, position;
+};
+
+struct cxl_decoder {
+	struct cxl_port *port;
+	struct list_node list;
+	struct cxl_ctx *ctx;
+	u64 start;
+	u64 size;
+	void *dev_buf;
+	size_t buf_len;
+	char *dev_path;
+	int nr_targets;
+	int id;
+	bool pmem_capable;
+	bool volatile_capable;
+	bool mem_capable;
+	bool accelmem_capable;
+	bool locked;
+	enum cxl_decoder_target_type target_type;
+	struct list_head targets;
+};
+
 enum cxl_cmd_query_status {
 	CXL_CMD_QUERY_NOT_RUN = 0,
 	CXL_CMD_QUERY_OK,
diff --git a/cxl/libcxl.h b/cxl/libcxl.h
index 53f68dde2770..439ed9305397 100644
--- a/cxl/libcxl.h
+++ b/cxl/libcxl.h
@@ -98,6 +98,34 @@ bool cxl_port_hosts_memdev(struct cxl_port *port, struct cxl_memdev *memdev);
 	for (port = cxl_port_get_first(parent); port != NULL;                  \
 	     port = cxl_port_get_next(port))
 
+struct cxl_decoder;
+struct cxl_decoder *cxl_decoder_get_first(struct cxl_port *port);
+struct cxl_decoder *cxl_decoder_get_next(struct cxl_decoder *decoder);
+unsigned long long cxl_decoder_get_resource(struct cxl_decoder *decoder);
+unsigned long long cxl_decoder_get_size(struct cxl_decoder *decoder);
+const char *cxl_decoder_get_devname(struct cxl_decoder *decoder);
+struct cxl_ctx *cxl_decoder_get_ctx(struct cxl_decoder *decoder);
+int cxl_decoder_get_id(struct cxl_decoder *decoder);
+struct cxl_port *cxl_decoder_get_port(struct cxl_decoder *decoder);
+
+enum cxl_decoder_target_type {
+	CXL_DECODER_TTYPE_UNKNOWN,
+	CXL_DECODER_TTYPE_EXPANDER,
+	CXL_DECODER_TTYPE_ACCELERATOR,
+};
+
+enum cxl_decoder_target_type
+cxl_decoder_get_target_type(struct cxl_decoder *decoder);
+bool cxl_decoder_is_pmem_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_volatile_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_mem_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_accelmem_capable(struct cxl_decoder *decoder);
+bool cxl_decoder_is_locked(struct cxl_decoder *decoder);
+
+#define cxl_decoder_foreach(port, decoder)                                     \
+	for (decoder = cxl_decoder_get_first(port); decoder != NULL;           \
+	     decoder = cxl_decoder_get_next(decoder))
+
 struct cxl_endpoint;
 struct cxl_endpoint *cxl_endpoint_get_first(struct cxl_port *parent);
 struct cxl_endpoint *cxl_endpoint_get_next(struct cxl_endpoint *endpoint);
diff --git a/cxl/list.c b/cxl/list.c
index b15e01ce40f6..d70192a8cecf 100644
--- a/cxl/list.c
+++ b/cxl/list.c
@@ -36,6 +36,11 @@ static const struct option options[] = {
 		   "filter by CXL endpoint device name(s)"),
 	OPT_BOOLEAN('E', "endpoints", &param.endpoints,
 		    "include CXL endpoint info"),
+	OPT_STRING('d', "decoder", &param.decoder_filter,
+		   "decoder device name",
+		   "filter by CXL decoder device name(s) / class"),
+	OPT_BOOLEAN('D', "decoders", &param.decoders,
+		    "include CXL decoder info"),
 	OPT_BOOLEAN('i', "idle", &param.idle, "include disabled devices"),
 	OPT_BOOLEAN('u', "human", &param.human,
 		    "use human friendly number formats "),
@@ -50,7 +55,7 @@ static const struct option options[] = {
 static int num_list_flags(void)
 {
 	return !!param.memdevs + !!param.buses + !!param.ports +
-	       !!param.endpoints;
+	       !!param.endpoints + !!param.decoders;
 }
 
 int cmd_list(int argc, const char **argv, struct cxl_ctx *ctx)
@@ -82,6 +87,8 @@ int cmd_list(int argc, const char **argv, struct cxl_ctx *ctx)
 			param.ports = true;
 		if (param.endpoint_filter)
 			param.endpoints = true;
+		if (param.decoder_filter)
+			param.decoders = true;
 		if (num_list_flags() == 0) {
 			/*
 			 * TODO: We likely want to list regions by default if
diff --git a/util/json.h b/util/json.h
index 061f0d423158..e026df1e1519 100644
--- a/util/json.h
+++ b/util/json.h
@@ -18,6 +18,7 @@ enum util_json_flags {
 	UTIL_JSON_FIRMWARE	= (1 << 8),
 	UTIL_JSON_DAX_MAPPINGS	= (1 << 9),
 	UTIL_JSON_HEALTH	= (1 << 10),
+	UTIL_JSON_TARGETS	= (1 << 11),
 };
 
 void util_display_json_array(FILE *f_out, struct json_object *jarray,