ndctl/0032-cxl-add-a-cxl-utility-and-libcxl-library.patch

From 6cd8155dd5a600f1bb435a49ebddc1fae2f60e73 Mon Sep 17 00:00:00 2001
From: Vishal Verma <vishal.l.verma@intel.com>
Date: Thu, 7 Oct 2021 02:21:24 -0600
Subject: [PATCH 032/217] cxl: add a cxl utility and libcxl library

CXL - or Compute eXpress Link - is a new interconnect that extends PCIe
to support a wide range of devices, including cache coherent memory
expanders. As such, these devices can be new sources of 'persistent
memory', and the 'ndctl' umbrella of tools and libraries needs to be able
to interact with them.

Add a new utility and library for managing these CXL memory devices. This
is an initial bring-up for interacting with CXL devices, and only includes
adding the utility and library infrastructure, parsing device information
from sysfs for CXL devices, and providing a 'cxl-list' command to
display this information in JSON formatted output.

Cc: Ben Widawsky <ben.widawsky@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 .clang-format                        |   1 +
 .gitignore                           |   4 +-
 Documentation/cxl/Makefile.am        |  58 +++++
 Documentation/cxl/cxl-list.txt       |  59 +++++
 Documentation/cxl/cxl.txt            |  34 +++
 Documentation/cxl/human-option.txt   |   8 +
 Documentation/cxl/verbose-option.txt |   5 +
 Makefile.am                          |   8 +-
 Makefile.am.in                       |   4 +
 configure.ac                         |   3 +
 cxl/Makefile.am                      |  21 ++
 cxl/builtin.h                        |   8 +
 cxl/cxl.c                            |  96 ++++++++
 cxl/lib/Makefile.am                  |  32 +++
 cxl/lib/libcxl.c                     | 345 +++++++++++++++++++++++++++
 cxl/lib/libcxl.pc.in                 |  11 +
 cxl/lib/libcxl.sym                   |  25 ++
 cxl/lib/private.h                    |  29 +++
 cxl/libcxl.h                         |  55 +++++
 cxl/list.c                           | 121 ++++++++++
 util/filter.c                        |  20 ++
 util/filter.h                        |   2 +
 util/json.c                          |  26 ++
 util/json.h                          |   3 +
 util/main.h                          |   3 +
 25 files changed, 977 insertions(+), 4 deletions(-)
 create mode 100644 Documentation/cxl/Makefile.am
 create mode 100644 Documentation/cxl/cxl-list.txt
 create mode 100644 Documentation/cxl/cxl.txt
 create mode 100644 Documentation/cxl/human-option.txt
 create mode 100644 Documentation/cxl/verbose-option.txt
 create mode 100644 cxl/Makefile.am
 create mode 100644 cxl/builtin.h
 create mode 100644 cxl/cxl.c
 create mode 100644 cxl/lib/Makefile.am
 create mode 100644 cxl/lib/libcxl.c
 create mode 100644 cxl/lib/libcxl.pc.in
 create mode 100644 cxl/lib/libcxl.sym
 create mode 100644 cxl/lib/private.h
 create mode 100644 cxl/libcxl.h
 create mode 100644 cxl/list.c

diff --git a/.clang-format b/.clang-format
index 4e00fff..d2e77d0 100644
--- a/.clang-format
+++ b/.clang-format
@@ -77,6 +77,7 @@ ExperimentalAutoDetectBinPacking: false
 # 		-e 's/\(.*foreach.*\)(.*/\1/' \
 # 	| sort -u)
 ForEachMacros:
+  - 'cxl_memdev_foreach'
   - 'daxctl_dev_foreach'
   - 'daxctl_mapping_foreach'
   - 'daxctl_region_foreach'
diff --git a/.gitignore b/.gitignore
index 53512b2..6a97b92 100644
--- a/.gitignore
+++ b/.gitignore
@@ -16,9 +16,11 @@ Makefile.in
 *.1
 Documentation/daxctl/asciidoc.conf
 Documentation/ndctl/asciidoc.conf
-Documentation/ndctl/attrs.adoc
+Documentation/cxl/asciidoc.conf
 Documentation/daxctl/asciidoctor-extensions.rb
 Documentation/ndctl/asciidoctor-extensions.rb
+Documentation/cxl/asciidoctor-extensions.rb
+Documentation/ndctl/attrs.adoc
 .dirstamp
 daxctl/config.h
 daxctl/daxctl
diff --git a/Documentation/cxl/Makefile.am b/Documentation/cxl/Makefile.am
new file mode 100644
index 0000000..db98dd7
--- /dev/null
+++ b/Documentation/cxl/Makefile.am
@@ -0,0 +1,58 @@
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (C) 2020-2021 Intel Corporation. All rights reserved.
+
+if USE_ASCIIDOCTOR
+
+do_subst = sed -e 's,@Utility@,Cxl,g' -e's,@utility@,cxl,g'
+CONFFILE = asciidoctor-extensions.rb
+asciidoctor-extensions.rb: ../asciidoctor-extensions.rb.in
+	$(AM_V_GEN) $(do_subst) < $< > $@
+
+else
+
+do_subst = sed -e 's,UTILITY,cxl,g'
+CONFFILE = asciidoc.conf
+asciidoc.conf: ../asciidoc.conf.in
+	$(AM_V_GEN) $(do_subst) < $< > $@
+
+endif
+
+man1_MANS = \
+	cxl.1 \
+	cxl-list.1
+
+EXTRA_DIST = $(man1_MANS)
+
+CLEANFILES = $(man1_MANS)
+
+XML_DEPS = \
+	../../version.m4 \
+	../copyright.txt \
+	Makefile \
+	$(CONFFILE)
+
+RM ?= rm -f
+
+if USE_ASCIIDOCTOR
+
+%.1: %.txt $(XML_DEPS)
+	$(AM_V_GEN)$(RM) $@+ $@ && \
+		$(ASCIIDOC) -b manpage -d manpage -acompat-mode \
+		-I. -rasciidoctor-extensions \
+		-amansource=cxl -amanmanual="cxl Manual" \
+		-andctl_version=$(VERSION) -o $@+ $< && \
+		mv $@+ $@
+
+else
+
+%.xml: %.txt $(XML_DEPS)
+	$(AM_V_GEN)$(RM) $@+ $@ && \
+		$(ASCIIDOC) -b docbook -d manpage -f asciidoc.conf \
+		--unsafe -acxl_version=$(VERSION) -o $@+ $< && \
+		mv $@+ $@
+
+%.1: %.xml $(XML_DEPS)
+	$(AM_V_GEN)$(RM) $@ && \
+		$(XMLTO) -o . -m ../manpage-normal.xsl man $<
+
+endif
diff --git a/Documentation/cxl/cxl-list.txt b/Documentation/cxl/cxl-list.txt
new file mode 100644
index 0000000..370d5b8
--- /dev/null
+++ b/Documentation/cxl/cxl-list.txt
@@ -0,0 +1,59 @@
+// SPDX-License-Identifier: GPL-2.0
+
+cxl-list(1)
+===========
+
+NAME
+----
+cxl-list - List CXL capable memory devices, and their attributes in json.
+
+SYNOPSIS
+--------
+[verse]
+'cxl list' [<options>]
+
+Walk the CXL capable device hierarchy in the system and list all device
+instances along with some of their major attributes.
+
+EXAMPLE
+-------
+----
+# cxl list --memdevs
+{
+  "memdev":"mem0",
+  "pmem_size":268435456,
+  "ram_size":0,
+}
+----
+
+OPTIONS
+-------
+-m::
+--memdev=::
+	Specify a cxl memory device name to filter the listing. For example:
+----
+# cxl list --memdev=mem0
+{
+  "memdev":"mem0",
+  "pmem_size":268435456,
+  "ram_size":0,
+}
+----
+
+-M::
+--memdevs::
+	Include CXL memory devices in the listing
+
+-i::
+--idle::
+	Include idle (not enabled / zero-sized) devices in the listing
+
+include::human-option.txt[]
+
+include::verbose-option.txt[]
+
+include::../copyright.txt[]
+
+SEE ALSO
+--------
+linkcxl:ndctl-list[1]
diff --git a/Documentation/cxl/cxl.txt b/Documentation/cxl/cxl.txt
new file mode 100644
index 0000000..41a51c7
--- /dev/null
+++ b/Documentation/cxl/cxl.txt
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0
+
+cxl(1)
+======
+
+NAME
+----
+cxl - Provides enumeration and provisioning commands for CXL platforms
+
+SYNOPSIS
+--------
+[verse]
+'cxl' [--version] [--help] COMMAND [ARGS]
+
+OPTIONS
+-------
+-v::
+--version::
+  Display the version of the 'cxl' utility.
+
+-h::
+--help::
+  Run the 'cxl help' command.
+
+DESCRIPTION
+-----------
+The cxl utility provides enumeration and provisioning commands for
+the CXL devices managed by the Linux kernel.
+
+include::../copyright.txt[]
+
+SEE ALSO
+--------
+linkcxl:ndctl[1]
diff --git a/Documentation/cxl/human-option.txt b/Documentation/cxl/human-option.txt
new file mode 100644
index 0000000..2f4de7a
--- /dev/null
+++ b/Documentation/cxl/human-option.txt
@@ -0,0 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0
+
+-u::
+--human::
+	By default the command will output machine-friendly raw-integer
+	data. Instead, with this flag, numbers representing storage size
+	will be formatted as human readable strings with units, other
+	fields are converted to hexadecimal strings.
diff --git a/Documentation/cxl/verbose-option.txt b/Documentation/cxl/verbose-option.txt
new file mode 100644
index 0000000..cb62c8e
--- /dev/null
+++ b/Documentation/cxl/verbose-option.txt
@@ -0,0 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0
+
+-v::
+--verbose::
+	Emit more debug messages
diff --git a/Makefile.am b/Makefile.am
index 60a1998..428fd40 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,9 +1,9 @@
 include Makefile.am.in
 
 ACLOCAL_AMFLAGS = -I m4 ${ACLOCAL_FLAGS}
-SUBDIRS = . daxctl/lib ndctl/lib ndctl daxctl
+SUBDIRS = . cxl/lib daxctl/lib ndctl/lib cxl ndctl daxctl
 if ENABLE_DOCS
-SUBDIRS += Documentation/ndctl Documentation/daxctl
+SUBDIRS += Documentation/ndctl Documentation/daxctl Documentation/cxl
 endif
 SUBDIRS += test
 
@@ -87,4 +87,6 @@ libutil_a_SOURCES = \
 	util/filter.h \
 	util/bitmap.h
 
-nobase_include_HEADERS = daxctl/libdaxctl.h
+nobase_include_HEADERS = \
+	daxctl/libdaxctl.h \
+	cxl/libcxl.h
diff --git a/Makefile.am.in b/Makefile.am.in
index bdceda9..aaeee53 100644
--- a/Makefile.am.in
+++ b/Makefile.am.in
@@ -42,3 +42,7 @@ LIBNDCTL_AGE=19
 LIBDAXCTL_CURRENT=6
 LIBDAXCTL_REVISION=0
 LIBDAXCTL_AGE=5
+
+LIBCXL_CURRENT=1
+LIBCXL_REVISION=0
+LIBCXL_AGE=0
diff --git a/configure.ac b/configure.ac
index dc39dbe..dadae0a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -222,12 +222,15 @@ AC_CONFIG_HEADERS(config.h)
 AC_CONFIG_FILES([
         Makefile
         daxctl/lib/Makefile
+        cxl/lib/Makefile
         ndctl/lib/Makefile
         ndctl/Makefile
         daxctl/Makefile
+        cxl/Makefile
         test/Makefile
         Documentation/ndctl/Makefile
         Documentation/daxctl/Makefile
+        Documentation/cxl/Makefile
 ])
 
 AC_OUTPUT
diff --git a/cxl/Makefile.am b/cxl/Makefile.am
new file mode 100644
index 0000000..98606b9
--- /dev/null
+++ b/cxl/Makefile.am
@@ -0,0 +1,21 @@
+include $(top_srcdir)/Makefile.am.in
+
+bin_PROGRAMS = cxl
+
+DISTCLEANFILES = config.h
+BUILT_SOURCES = config.h
+config.h: $(srcdir)/Makefile.am
+	$(AM_V_GEN) echo "/* Autogenerated by cxl/Makefile.am */" >$@
+
+cxl_SOURCES =\
+		cxl.c \
+		list.c \
+		../util/json.c \
+		builtin.h
+
+cxl_LDADD =\
+	lib/libcxl.la \
+	../libutil.a \
+	$(UUID_LIBS) \
+	$(KMOD_LIBS) \
+	$(JSON_LIBS)
diff --git a/cxl/builtin.h b/cxl/builtin.h
new file mode 100644
index 0000000..3797f98
--- /dev/null
+++ b/cxl/builtin.h
@@ -0,0 +1,8 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2020-2021 Intel Corporation. All rights reserved. */
+#ifndef _CXL_BUILTIN_H_
+#define _CXL_BUILTIN_H_
+
+struct cxl_ctx;
+int cmd_list(int argc, const char **argv, struct cxl_ctx *ctx);
+#endif /* _CXL_BUILTIN_H_ */
diff --git a/cxl/cxl.c b/cxl/cxl.c
new file mode 100644
index 0000000..a7725f8
--- /dev/null
+++ b/cxl/cxl.c
@@ -0,0 +1,96 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2020-2021 Intel Corporation. All rights reserved. */
+/* Copyright (C) 2005 Andreas Ericsson. All rights reserved. */
+
+/* originally copied from perf and git */
+
+#include <stdio.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <cxl/libcxl.h>
+#include <util/parse-options.h>
+#include <ccan/array_size/array_size.h>
+
+#include <util/strbuf.h>
+#include <util/util.h>
+#include <util/main.h>
+#include <cxl/builtin.h>
+
+const char cxl_usage_string[] = "cxl [--version] [--help] COMMAND [ARGS]";
+const char cxl_more_info_string[] =
+	"See 'cxl help COMMAND' for more information on a specific command.\n"
+	" cxl --list-cmds to see all available commands";
+
+static int cmd_version(int argc, const char **argv, struct cxl_ctx *ctx)
+{
+	printf("%s\n", VERSION);
+	return 0;
+}
+
+static int cmd_help(int argc, const char **argv, struct cxl_ctx *ctx)
+{
+	const char * const builtin_help_subcommands[] = {
+		"list",
+		NULL,
+	};
+	struct option builtin_help_options[] = {
+		OPT_END(),
+	};
+	const char *builtin_help_usage[] = {
+		"cxl help [command]",
+		NULL
+	};
+
+	argc = parse_options_subcommand(argc, argv, builtin_help_options,
+			builtin_help_subcommands, builtin_help_usage, 0);
+
+	if (!argv[0]) {
+		printf("\n usage: %s\n\n", cxl_usage_string);
+		printf("\n %s\n\n", cxl_more_info_string);
+		return 0;
+	}
+
+	return help_show_man_page(argv[0], "cxl", "CXL_MAN_VIEWER");
+}
+
+static struct cmd_struct commands[] = {
+	{ "version", .c_fn = cmd_version },
+	{ "list", .c_fn = cmd_list },
+	{ "help", .c_fn = cmd_help },
+};
+
+int main(int argc, const char **argv)
+{
+	struct cxl_ctx *ctx;
+	int rc;
+
+	/* Look for flags.. */
+	argv++;
+	argc--;
+	main_handle_options(&argv, &argc, cxl_usage_string, commands,
+			ARRAY_SIZE(commands));
+
+	if (argc > 0) {
+		if (!prefixcmp(argv[0], "--"))
+			argv[0] += 2;
+	} else {
+		/* The user didn't specify a command; give them help */
+		printf("\n usage: %s\n\n", cxl_usage_string);
+		printf("\n %s\n\n", cxl_more_info_string);
+		goto out;
+	}
+
+	rc = cxl_new(&ctx);
+	if (rc)
+		goto out;
+	main_handle_internal_command(argc, argv, ctx, commands,
+			ARRAY_SIZE(commands), PROG_CXL);
+	cxl_unref(ctx);
+	fprintf(stderr, "Unknown command: '%s'\n", argv[0]);
+out:
+	return 1;
+}
diff --git a/cxl/lib/Makefile.am b/cxl/lib/Makefile.am
new file mode 100644
index 0000000..277f0cd
--- /dev/null
+++ b/cxl/lib/Makefile.am
@@ -0,0 +1,32 @@
+include $(top_srcdir)/Makefile.am.in
+
+%.pc: %.pc.in Makefile
+	$(SED_PROCESS)
+
+pkginclude_HEADERS = ../libcxl.h
+lib_LTLIBRARIES = libcxl.la
+
+libcxl_la_SOURCES =\
+	../libcxl.h \
+	private.h \
+	../../util/sysfs.c \
+	../../util/sysfs.h \
+	../../util/log.c \
+	../../util/log.h \
+	libcxl.c
+
+libcxl_la_LIBADD =\
+	$(UUID_LIBS) \
+	$(KMOD_LIBS)
+
+EXTRA_DIST += libcxl.sym
+
+libcxl_la_LDFLAGS = $(AM_LDFLAGS) \
+	-version-info $(LIBCXL_CURRENT):$(LIBCXL_REVISION):$(LIBCXL_AGE) \
+	-Wl,--version-script=$(top_srcdir)/cxl/lib/libcxl.sym
+libcxl_la_DEPENDENCIES = libcxl.sym
+
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = libcxl.pc
+EXTRA_DIST += libcxl.pc.in
+CLEANFILES += libcxl.pc
diff --git a/cxl/lib/libcxl.c b/cxl/lib/libcxl.c
new file mode 100644
index 0000000..c15e987
--- /dev/null
+++ b/cxl/lib/libcxl.c
@@ -0,0 +1,345 @@
+// SPDX-License-Identifier: LGPL-2.1
+// Copyright (C) 2020-2021, Intel Corporation. All rights reserved.
+#include <stdio.h>
+#include <errno.h>
+#include <limits.h>
+#include <libgen.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/sysmacros.h>
+#include <uuid/uuid.h>
+#include <ccan/list/list.h>
+#include <ccan/array_size/array_size.h>
+
+#include <util/log.h>
+#include <util/sysfs.h>
+#include <util/bitmap.h>
+#include <cxl/libcxl.h>
+#include "private.h"
+
+/**
+ * struct cxl_ctx - library user context to find "nd" instances
+ *
+ * Instantiate with cxl_new(), which takes an initial reference.  Free
+ * the context by dropping the reference count to zero with
+ * cxl_unref(), or take additional references with cxl_ref()
+ * @timeout: default library timeout in milliseconds
+ */
+struct cxl_ctx {
+	/* log_ctx must be first member for cxl_set_log_fn compat */
+	struct log_ctx ctx;
+	int refcount;
+	void *userdata;
+	int memdevs_init;
+	struct list_head memdevs;
+	struct kmod_ctx *kmod_ctx;
+	void *private_data;
+};
+
+static void free_memdev(struct cxl_memdev *memdev, struct list_head *head)
+{
+	if (head)
+		list_del_from(head, &memdev->list);
+	kmod_module_unref(memdev->module);
+	free(memdev->firmware_version);
+	free(memdev->dev_buf);
+	free(memdev->dev_path);
+	free(memdev);
+}
+
+/**
+ * cxl_get_userdata - retrieve stored data pointer from library context
+ * @ctx: cxl library context
+ *
+ * This might be useful to access from callbacks like a custom logging
+ * function.
+ */
+CXL_EXPORT void *cxl_get_userdata(struct cxl_ctx *ctx)
+{
+	if (ctx == NULL)
+		return NULL;
+	return ctx->userdata;
+}
+
+/**
+ * cxl_set_userdata - store custom @userdata in the library context
+ * @ctx: cxl library context
+ * @userdata: data pointer
+ */
+CXL_EXPORT void cxl_set_userdata(struct cxl_ctx *ctx, void *userdata)
+{
+	if (ctx == NULL)
+		return;
+	ctx->userdata = userdata;
+}
+
+CXL_EXPORT void cxl_set_private_data(struct cxl_ctx *ctx, void *data)
+{
+	ctx->private_data = data;
+}
+
+CXL_EXPORT void *cxl_get_private_data(struct cxl_ctx *ctx)
+{
+	return ctx->private_data;
+}
+
+/**
+ * cxl_new - instantiate a new library context
+ * @ctx: context to establish
+ *
+ * Returns zero on success and stores an opaque pointer in ctx.  The
+ * context is freed by cxl_unref(), i.e. cxl_new() implies an
+ * internal cxl_ref().
+ */
+CXL_EXPORT int cxl_new(struct cxl_ctx **ctx)
+{
+	struct kmod_ctx *kmod_ctx;
+	struct cxl_ctx *c;
+	int rc = 0;
+
+	c = calloc(1, sizeof(struct cxl_ctx));
+	if (!c)
+		return -ENOMEM;
+
+	kmod_ctx = kmod_new(NULL, NULL);
+	if (check_kmod(kmod_ctx) != 0) {
+		rc = -ENXIO;
+		goto out;
+	}
+
+	c->refcount = 1;
+	log_init(&c->ctx, "libcxl", "CXL_LOG");
+	info(c, "ctx %p created\n", c);
+	dbg(c, "log_priority=%d\n", c->ctx.log_priority);
+	*ctx = c;
+	list_head_init(&c->memdevs);
+	c->kmod_ctx = kmod_ctx;
+
+	return 0;
+out:
+	free(c);
+	return rc;
+}
+
+/**
+ * cxl_ref - take an additional reference on the context
+ * @ctx: context established by cxl_new()
+ */
+CXL_EXPORT struct cxl_ctx *cxl_ref(struct cxl_ctx *ctx)
+{
+	if (ctx == NULL)
+		return NULL;
+	ctx->refcount++;
+	return ctx;
+}
+
+/**
+ * cxl_unref - drop a context reference count
+ * @ctx: context established by cxl_new()
+ *
+ * Drop a reference and if the resulting reference count is 0 destroy
+ * the context.
+ */
+CXL_EXPORT void cxl_unref(struct cxl_ctx *ctx)
+{
+	struct cxl_memdev *memdev, *_d;
+
+	if (ctx == NULL)
+		return;
+	ctx->refcount--;
+	if (ctx->refcount > 0)
+		return;
+
+	list_for_each_safe(&ctx->memdevs, memdev, _d, list)
+		free_memdev(memdev, &ctx->memdevs);
+
+	kmod_unref(ctx->kmod_ctx);
+	info(ctx, "context %p released\n", ctx);
+	free(ctx);
+}
+
+/**
+ * cxl_set_log_fn - override default log routine
+ * @ctx: cxl library context
+ * @log_fn: function to be called for logging messages
+ *
+ * The built-in logging writes to stderr. It can be overridden by a
+ * custom function, to plug log messages into the user's logging
+ * functionality.
+ */
+CXL_EXPORT void cxl_set_log_fn(struct cxl_ctx *ctx,
+		void (*cxl_log_fn)(struct cxl_ctx *ctx, int priority,
+			const char *file, int line, const char *fn,
+			const char *format, va_list args))
+{
+	ctx->ctx.log_fn = (log_fn) cxl_log_fn;
+	info(ctx, "custom logging function %p registered\n", cxl_log_fn);
+}
+
+/**
+ * cxl_get_log_priority - retrieve current library loglevel (syslog)
+ * @ctx: cxl library context
+ */
+CXL_EXPORT int cxl_get_log_priority(struct cxl_ctx *ctx)
+{
+	return ctx->ctx.log_priority;
+}
+
+/**
+ * cxl_set_log_priority - set log verbosity
+ * @priority: from syslog.h, LOG_ERR, LOG_INFO, LOG_DEBUG
+ *
+ * Note: LOG_DEBUG requires library be built with "configure --enable-debug"
+ */
+CXL_EXPORT void cxl_set_log_priority(struct cxl_ctx *ctx, int priority)
+{
+	ctx->ctx.log_priority = priority;
+}
+
+static void *add_cxl_memdev(void *parent, int id, const char *cxlmem_base)
+{
+	const char *devname = devpath_to_devname(cxlmem_base);
+	char *path = calloc(1, strlen(cxlmem_base) + 100);
+	struct cxl_ctx *ctx = parent;
+	struct cxl_memdev *memdev, *memdev_dup;
+	char buf[SYSFS_ATTR_SIZE];
+	struct stat st;
+
+	if (!path)
+		return NULL;
+	dbg(ctx, "%s: base: \'%s\'\n", devname, cxlmem_base);
+
+	memdev = calloc(1, sizeof(*memdev));
+	if (!memdev)
+		goto err_dev;
+	memdev->id = id;
+	memdev->ctx = ctx;
+
+	sprintf(path, "/dev/cxl/%s", devname);
+	if (stat(path, &st) < 0)
+		goto err_read;
+	memdev->major = major(st.st_rdev);
+	memdev->minor = minor(st.st_rdev);
+
+	sprintf(path, "%s/pmem/size", cxlmem_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		goto err_read;
+	memdev->pmem_size = strtoull(buf, NULL, 0);
+
+	sprintf(path, "%s/ram/size", cxlmem_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		goto err_read;
+	memdev->ram_size = strtoull(buf, NULL, 0);
+
+	sprintf(path, "%s/payload_max", cxlmem_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		goto err_read;
+	memdev->payload_max = strtoull(buf, NULL, 0);
+	if (memdev->payload_max < 0)
+		goto err_read;
+
+	memdev->dev_path = strdup(cxlmem_base);
+	if (!memdev->dev_path)
+		goto err_read;
+
+	sprintf(path, "%s/firmware_version", cxlmem_base);
+	if (sysfs_read_attr(ctx, path, buf) < 0)
+		goto err_read;
+
+	memdev->firmware_version = strdup(buf);
+	if (!memdev->firmware_version)
+		goto err_read;
+
+	memdev->dev_buf = calloc(1, strlen(cxlmem_base) + 50);
+	if (!memdev->dev_buf)
+		goto err_read;
+	memdev->buf_len = strlen(cxlmem_base) + 50;
+
+	cxl_memdev_foreach(ctx, memdev_dup)
+		if (memdev_dup->id == memdev->id) {
+			free_memdev(memdev, NULL);
+			free(path);
+			return memdev_dup;
+		}
+
+	list_add(&ctx->memdevs, &memdev->list);
+	free(path);
+	return memdev;
+
+ err_read:
+	free(memdev->firmware_version);
+	free(memdev->dev_buf);
+	free(memdev->dev_path);
+	free(memdev);
+ err_dev:
+	free(path);
+	return NULL;
+}
+
+static void cxl_memdevs_init(struct cxl_ctx *ctx)
+{
+	if (ctx->memdevs_init)
+		return;
+
+	ctx->memdevs_init = 1;
+
+	sysfs_device_parse(ctx, "/sys/bus/cxl/devices", "mem", ctx,
+			   add_cxl_memdev);
+}
+
+CXL_EXPORT struct cxl_ctx *cxl_memdev_get_ctx(struct cxl_memdev *memdev)
+{
+	return memdev->ctx;
+}
+
+CXL_EXPORT struct cxl_memdev *cxl_memdev_get_first(struct cxl_ctx *ctx)
+{
+	cxl_memdevs_init(ctx);
+
+	return list_top(&ctx->memdevs, struct cxl_memdev, list);
+}
+
+CXL_EXPORT struct cxl_memdev *cxl_memdev_get_next(struct cxl_memdev *memdev)
+{
+	struct cxl_ctx *ctx = memdev->ctx;
+
+	return list_next(&ctx->memdevs, memdev, list);
+}
+
+CXL_EXPORT int cxl_memdev_get_id(struct cxl_memdev *memdev)
+{
+	return memdev->id;
+}
+
+CXL_EXPORT const char *cxl_memdev_get_devname(struct cxl_memdev *memdev)
+{
+	return devpath_to_devname(memdev->dev_path);
+}
+
+CXL_EXPORT int cxl_memdev_get_major(struct cxl_memdev *memdev)
+{
+	return memdev->major;
+}
+
+CXL_EXPORT int cxl_memdev_get_minor(struct cxl_memdev *memdev)
+{
+	return memdev->minor;
+}
+
+CXL_EXPORT unsigned long long cxl_memdev_get_pmem_size(struct cxl_memdev *memdev)
+{
+	return memdev->pmem_size;
+}
+
+CXL_EXPORT unsigned long long cxl_memdev_get_ram_size(struct cxl_memdev *memdev)
+{
+	return memdev->ram_size;
+}
+
+CXL_EXPORT const char *cxl_memdev_get_firmware_verison(struct cxl_memdev *memdev)
+{
+	return memdev->firmware_version;
+}
diff --git a/cxl/lib/libcxl.pc.in b/cxl/lib/libcxl.pc.in
new file mode 100644
index 0000000..949fcdc
--- /dev/null
+++ b/cxl/lib/libcxl.pc.in
@@ -0,0 +1,11 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: libcxl
+Description: Manage CXL devices
+Version: @VERSION@
+Libs: -L${libdir} -lcxl
+Libs.private:
+Cflags: -I${includedir}
diff --git a/cxl/lib/libcxl.sym b/cxl/lib/libcxl.sym
new file mode 100644
index 0000000..2616e5c
--- /dev/null
+++ b/cxl/lib/libcxl.sym
@@ -0,0 +1,25 @@
+LIBCXL_1 {
+global:
+	cxl_get_userdata;
+	cxl_set_userdata;
+	cxl_get_private_data;
+	cxl_set_private_data;
+	cxl_ref;
+	cxl_get_log_priority;
+	cxl_set_log_fn;
+	cxl_unref;
+	cxl_set_log_priority;
+	cxl_new;
+	cxl_memdev_get_first;
+	cxl_memdev_get_next;
+	cxl_memdev_get_id;
+	cxl_memdev_get_devname;
+	cxl_memdev_get_major;
+	cxl_memdev_get_minor;
+	cxl_memdev_get_ctx;
+	cxl_memdev_get_pmem_size;
+	cxl_memdev_get_ram_size;
+	cxl_memdev_get_firmware_verison;
+local:
+        *;
+};
diff --git a/cxl/lib/private.h b/cxl/lib/private.h
new file mode 100644
index 0000000..fc88fa1
--- /dev/null
+++ b/cxl/lib/private.h
@@ -0,0 +1,29 @@
+/* SPDX-License-Identifier: LGPL-2.1 */
+/* Copyright (C) 2020-2021, Intel Corporation. All rights reserved. */
+#ifndef _LIBCXL_PRIVATE_H_
+#define _LIBCXL_PRIVATE_H_
+
+#include <libkmod.h>
+
+#define CXL_EXPORT __attribute__ ((visibility("default")))
+
+struct cxl_memdev {
+	int id, major, minor;
+	void *dev_buf;
+	size_t buf_len;
+	char *dev_path;
+	char *firmware_version;
+	struct cxl_ctx *ctx;
+	struct list_node list;
+	unsigned long long pmem_size;
+	unsigned long long ram_size;
+	int payload_max;
+	struct kmod_module *module;
+};
+
+static inline int check_kmod(struct kmod_ctx *kmod_ctx)
+{
+	return kmod_ctx ? 0 : -ENXIO;
+}
+
+#endif /* _LIBCXL_PRIVATE_H_ */
diff --git a/cxl/libcxl.h b/cxl/libcxl.h
new file mode 100644
index 0000000..fd06790
--- /dev/null
+++ b/cxl/libcxl.h
@@ -0,0 +1,55 @@
+/* SPDX-License-Identifier: LGPL-2.1 */
+/* Copyright (C) 2020-2021, Intel Corporation. All rights reserved. */
+#ifndef _LIBCXL_H_
+#define _LIBCXL_H_
+
+#include <stdarg.h>
+#include <unistd.h>
+
+#ifdef HAVE_UUID
+#include <uuid/uuid.h>
+#else
+typedef unsigned char uuid_t[16];
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+struct cxl_ctx;
+struct cxl_ctx *cxl_ref(struct cxl_ctx *ctx);
+void cxl_unref(struct cxl_ctx *ctx);
+int cxl_new(struct cxl_ctx **ctx);
+void cxl_set_log_fn(struct cxl_ctx *ctx,
+		void (*log_fn)(struct cxl_ctx *ctx, int priority,
+			const char *file, int line, const char *fn,
+			const char *format, va_list args));
+int cxl_get_log_priority(struct cxl_ctx *ctx);
+void cxl_set_log_priority(struct cxl_ctx *ctx, int priority);
+void cxl_set_userdata(struct cxl_ctx *ctx, void *userdata);
+void *cxl_get_userdata(struct cxl_ctx *ctx);
+void cxl_set_private_data(struct cxl_ctx *ctx, void *data);
+void *cxl_get_private_data(struct cxl_ctx *ctx);
+
+struct cxl_memdev;
+struct cxl_memdev *cxl_memdev_get_first(struct cxl_ctx *ctx);
+struct cxl_memdev *cxl_memdev_get_next(struct cxl_memdev *memdev);
+int cxl_memdev_get_id(struct cxl_memdev *memdev);
+const char *cxl_memdev_get_devname(struct cxl_memdev *memdev);
+int cxl_memdev_get_major(struct cxl_memdev *memdev);
+int cxl_memdev_get_minor(struct cxl_memdev *memdev);
+struct cxl_ctx *cxl_memdev_get_ctx(struct cxl_memdev *memdev);
+unsigned long long cxl_memdev_get_pmem_size(struct cxl_memdev *memdev);
+unsigned long long cxl_memdev_get_ram_size(struct cxl_memdev *memdev);
+const char *cxl_memdev_get_firmware_verison(struct cxl_memdev *memdev);
+
+#define cxl_memdev_foreach(ctx, memdev) \
+        for (memdev = cxl_memdev_get_first(ctx); \
+             memdev != NULL; \
+             memdev = cxl_memdev_get_next(memdev))
+
+#ifdef __cplusplus
+} /* extern "C" */
+#endif
+
+#endif
diff --git a/cxl/list.c b/cxl/list.c
new file mode 100644
index 0000000..043d20c
--- /dev/null
+++ b/cxl/list.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2020-2021 Intel Corporation. All rights reserved. */
+#include <stdio.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <limits.h>
+#include <util/json.h>
+#include <util/filter.h>
+#include <json-c/json.h>
+#include <cxl/libcxl.h>
+#include <util/parse-options.h>
+#include <ccan/array_size/array_size.h>
+
+static struct {
+	bool memdevs;
+	bool idle;
+	bool human;
+} list;
+
+static unsigned long listopts_to_flags(void)
+{
+	unsigned long flags = 0;
+
+	if (list.idle)
+		flags |= UTIL_JSON_IDLE;
+	if (list.human)
+		flags |= UTIL_JSON_HUMAN;
+	return flags;
+}
+
+static struct {
+	const char *memdev;
+} param;
+
+static int did_fail;
+
+#define fail(fmt, ...) \
+do { \
+	did_fail = 1; \
+	fprintf(stderr, "cxl-%s:%s:%d: " fmt, \
+			VERSION, __func__, __LINE__, ##__VA_ARGS__); \
+} while (0)
+
+static int num_list_flags(void)
+{
+	return list.memdevs;
+}
+
+int cmd_list(int argc, const char **argv, struct cxl_ctx *ctx)
+{
+	const struct option options[] = {
+		OPT_STRING('m', "memdev", &param.memdev, "memory device name",
+			   "filter by CXL memory device name"),
+		OPT_BOOLEAN('M', "memdevs", &list.memdevs,
+			    "include CXL memory device info"),
+		OPT_BOOLEAN('i', "idle", &list.idle, "include idle devices"),
+		OPT_BOOLEAN('u', "human", &list.human,
+				"use human friendly number formats "),
+		OPT_END(),
+	};
+	const char * const u[] = {
+		"cxl list [<options>]",
+		NULL
+	};
+	struct json_object *jdevs = NULL;
+	unsigned long list_flags;
+	struct cxl_memdev *memdev;
+	int i;
+
+	argc = parse_options(argc, argv, options, u, 0);
+	for (i = 0; i < argc; i++)
+		error("unknown parameter \"%s\"\n", argv[i]);
+
+	if (argc)
+		usage_with_options(u, options);
+
+	if (num_list_flags() == 0) {
+		/*
+		 * TODO: We likely want to list regions by default if nothing
+		 * was explicitly asked for. But until we have region support,
+		 * print this error asking for devices explicitly.
+		 * Once region support is added, this TODO can be removed.
+		 */
+		error("please specify entities to list, e.g. using -m/-M\n");
+		usage_with_options(u, options);
+	}
+
+	list_flags = listopts_to_flags();
+
+	cxl_memdev_foreach(ctx, memdev) {
+		struct json_object *jdev = NULL;
+
+		if (!util_cxl_memdev_filter(memdev, param.memdev))
+			continue;
+
+		if (list.memdevs) {
+			if (!jdevs) {
+				jdevs = json_object_new_array();
+				if (!jdevs) {
+					fail("\n");
+					continue;
+				}
+			}
+
+			jdev = util_cxl_memdev_to_json(memdev, list_flags);
+			if (!jdev) {
+				fail("\n");
+				continue;
+			}
+			json_object_array_add(jdevs, jdev);
+		}
+	}
+
+	if (jdevs)
+		util_display_json_array(stdout, jdevs, list_flags);
+
+	if (did_fail)
+		return -ENOMEM;
+	return 0;
+}
diff --git a/util/filter.c b/util/filter.c
index 8b4aad3..d81dade 100644
--- a/util/filter.c
+++ b/util/filter.c
@@ -12,6 +12,7 @@
 #include <util/filter.h>
 #include <ndctl/libndctl.h>
 #include <daxctl/libdaxctl.h>
+#include <cxl/libcxl.h>
 
 struct ndctl_bus *util_bus_filter(struct ndctl_bus *bus, const char *__ident)
 {
@@ -339,6 +340,25 @@ struct daxctl_region *util_daxctl_region_filter(struct daxctl_region *region,
 	return NULL;
 }
 
+struct cxl_memdev *util_cxl_memdev_filter(struct cxl_memdev *memdev,
+					  const char *ident)
+{
+	int memdev_id;
+
+	if (!ident || strcmp(ident, "all") == 0)
+		return memdev;
+
+	if (strcmp(ident, cxl_memdev_get_devname(memdev)) == 0)
+		return memdev;
+
+	if ((sscanf(ident, "%d", &memdev_id) == 1
+			|| sscanf(ident, "mem%d", &memdev_id) == 1)
+			&& cxl_memdev_get_id(memdev) == memdev_id)
+		return memdev;
+
+	return NULL;
+}
+
 enum ndctl_namespace_mode util_nsmode(const char *mode)
 {
 	if (!mode)
diff --git a/util/filter.h b/util/filter.h
index 1e1a41c..9a80d65 100644
--- a/util/filter.h
+++ b/util/filter.h
@@ -29,6 +29,8 @@ struct daxctl_dev *util_daxctl_dev_filter(struct daxctl_dev *dev,
 		const char *ident);
 struct daxctl_region *util_daxctl_region_filter(struct daxctl_region *region,
 		const char *ident);
+struct cxl_memdev *util_cxl_memdev_filter(struct cxl_memdev *memdev,
+		const char *ident);
 
 enum ndctl_namespace_mode util_nsmode(const char *mode);
 const char *util_nsmode_name(enum ndctl_namespace_mode mode);
diff --git a/util/json.c b/util/json.c
index a8d2412..3be3a92 100644
--- a/util/json.c
+++ b/util/json.c
@@ -9,6 +9,7 @@
 #include <json-c/printbuf.h>
 #include <ndctl/libndctl.h>
 #include <daxctl/libdaxctl.h>
+#include <cxl/libcxl.h>
 #include <ccan/array_size/array_size.h>
 #include <ccan/short_types/short_types.h>
 #include <ndctl.h>
@@ -1440,3 +1441,28 @@ struct json_object *util_badblock_rec_to_json(u64 block, u64 count,
 	json_object_put(jerr);
 	return NULL;
 }
+
+struct json_object *util_cxl_memdev_to_json(struct cxl_memdev *memdev,
+		unsigned long flags)
+{
+	const char *devname = cxl_memdev_get_devname(memdev);
+	struct json_object *jdev, *jobj;
+
+	jdev = json_object_new_object();
+	if (!devname || !jdev)
+		return NULL;
+
+	jobj = json_object_new_string(devname);
+	if (jobj)
+		json_object_object_add(jdev, "memdev", jobj);
+
+	jobj = util_json_object_size(cxl_memdev_get_pmem_size(memdev), flags);
+	if (jobj)
+		json_object_object_add(jdev, "pmem_size", jobj);
+
+	jobj = util_json_object_size(cxl_memdev_get_ram_size(memdev), flags);
+	if (jobj)
+		json_object_object_add(jdev, "ram_size", jobj);
+
+	return jdev;
+}
diff --git a/util/json.h b/util/json.h
index 0f09e36..91918c8 100644
--- a/util/json.h
+++ b/util/json.h
@@ -55,4 +55,7 @@ struct json_object *util_dimm_health_to_json(struct ndctl_dimm *dimm);
 struct json_object *util_dimm_firmware_to_json(struct ndctl_dimm *dimm,
 		unsigned long flags);
 struct json_object *util_region_capabilities_to_json(struct ndctl_region *region);
+struct cxl_memdev;
+struct json_object *util_cxl_memdev_to_json(struct cxl_memdev *memdev,
+		unsigned long flags);
 #endif /* __NDCTL_JSON_H__ */
diff --git a/util/main.h b/util/main.h
index c89a843..80b55c4 100644
--- a/util/main.h
+++ b/util/main.h
@@ -10,16 +10,19 @@
 enum program {
 	PROG_NDCTL,
 	PROG_DAXCTL,
+	PROG_CXL,
 };
 
 struct ndctl_ctx;
 struct daxctl_ctx;
+struct cxl_ctx;
 
 struct cmd_struct {
 	const char *cmd;
 	union {
 		int (*n_fn)(int, const char **, struct ndctl_ctx *ctx);
 		int (*d_fn)(int, const char **, struct daxctl_ctx *ctx);
+		int (*c_fn)(int, const char **, struct cxl_ctx *ctx);
 	};
 };
 
-- 
2.27.0