[PATCH] nvme-list: make verbose JSON output backward compatible

[PATCH] nvme-list: make verbose JSON output backward compatible

[Nilay Shroff]

The commit 64bed0a87a23 ("nvme-list: fix verbose JSON output for 'nvme
list' command") changed the JSON output format of the nvme list --verbose
command. While the new format is more structured, it introduced a
regression by breaking compatibility with tools and scripts relying on
the previous JSON schema.

So to restore backward compatibility, we now leverage the existing
--output-format-version option. With this patch,
1. The default --output-format-version=1 retains the original (legacy) JSON
format for nvme list --verbose.
2. If the user explicitly sets --output-format-version=2 then the newer
JSON structure introduced by commit 64bed0a87a23 ("nvme-list: fix verbose
JSON output for 'nvme list' command") is used.

This ensures that existing users and automation relying on the older format
do not break, while still supporting the newer schema for forward-looking
users.

Fixes: 64bed0a87a23 ("nvme-list: fix verbose JSON output for 'nvme list' command")
Signed-off-by: Nilay Shroff <nilay@linux.ibm.com>
---
 nvme-print-json.c | 117 ++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 113 insertions(+), 4 deletions(-)

diff --git a/nvme-print-json.c b/nvme-print-json.c
index 11b66616..829ba718 100644
--- a/nvme-print-json.c
+++ b/nvme-print-json.c
@@ -4519,7 +4519,7 @@ static void json_print_detail_list(nvme_subsystem_t s, struct json_object *jss)
 	obj_add_obj(jss, "Controllers", jctrls);
 }
 
-static void json_detail_list(nvme_root_t t)
+static void json_detail_list_v2(nvme_root_t t)
 {
 	struct json_object *r = json_create_object();
 	struct json_object *jdev = json_create_array();
@@ -4560,6 +4560,112 @@ static void json_detail_list(nvme_root_t t)
 	json_print(r);
 }
 
+static void json_detail_list(nvme_root_t t)
+{
+	struct json_object *r = json_create_object();
+	struct json_object *jdev = json_create_array();
+
+	nvme_host_t h;
+	nvme_subsystem_t s;
+	nvme_ctrl_t c;
+	nvme_path_t p;
+	nvme_ns_t n;
+
+	nvme_for_each_host(t, h) {
+		struct json_object *hss = json_create_object();
+		struct json_object *jsslist = json_create_array();
+		const char *hostid;
+
+		obj_add_str(hss, "HostNQN", nvme_host_get_hostnqn(h));
+		hostid = nvme_host_get_hostid(h);
+		if (hostid)
+			obj_add_str(hss, "HostID", hostid);
+
+		nvme_for_each_subsystem(h, s) {
+			struct json_object *jss = json_create_object();
+			struct json_object *jctrls = json_create_array();
+			struct json_object *jnss = json_create_array();
+
+			obj_add_str(jss, "Subsystem", nvme_subsystem_get_name(s));
+			obj_add_str(jss, "SubsystemNQN", nvme_subsystem_get_nqn(s));
+
+			nvme_subsystem_for_each_ctrl(s, c) {
+				struct json_object *jctrl = json_create_object();
+				struct json_object *jnss = json_create_array();
+				struct json_object *jpaths = json_create_array();
+
+				obj_add_str(jctrl, "Controller", nvme_ctrl_get_name(c));
+				obj_add_str(jctrl, "Cntlid", nvme_ctrl_get_cntlid(c));
+				obj_add_str(jctrl, "SerialNumber", nvme_ctrl_get_serial(c));
+				obj_add_str(jctrl, "ModelNumber", nvme_ctrl_get_model(c));
+				obj_add_str(jctrl, "Firmware", nvme_ctrl_get_firmware(c));
+				obj_add_str(jctrl, "Transport", nvme_ctrl_get_transport(c));
+				obj_add_str(jctrl, "Address", nvme_ctrl_get_address(c));
+				obj_add_str(jctrl, "Slot", nvme_ctrl_get_phy_slot(c));
+
+				nvme_ctrl_for_each_ns(c, n) {
+					struct json_object *jns = json_create_object();
+					int lba = nvme_ns_get_lba_size(n);
+					uint64_t nsze = nvme_ns_get_lba_count(n) * lba;
+					uint64_t nuse = nvme_ns_get_lba_util(n) * lba;
+
+					obj_add_str(jns, "NameSpace", nvme_ns_get_name(n));
+					obj_add_str(jns, "Generic", nvme_ns_get_generic_name(n));
+					obj_add_int(jns, "NSID", nvme_ns_get_nsid(n));
+					obj_add_uint64(jns, "UsedBytes", nuse);
+					obj_add_uint64(jns, "MaximumLBA", nvme_ns_get_lba_count(n));
+					obj_add_uint64(jns, "PhysicalSize", nsze);
+					obj_add_int(jns, "SectorSize", lba);
+
+					array_add_obj(jnss, jns);
+				}
+				obj_add_obj(jctrl, "Namespaces", jnss);
+
+				nvme_ctrl_for_each_path(c, p) {
+					struct json_object *jpath = json_create_object();
+
+					obj_add_str(jpath, "Path", nvme_path_get_name(p));
+					obj_add_str(jpath, "ANAState", nvme_path_get_ana_state(p));
+
+					array_add_obj(jpaths, jpath);
+				}
+				obj_add_obj(jctrl, "Paths", jpaths);
+
+				array_add_obj(jctrls, jctrl);
+			}
+			obj_add_obj(jss, "Controllers", jctrls);
+
+			nvme_subsystem_for_each_ns(s, n) {
+				struct json_object *jns = json_create_object();
+
+				int lba = nvme_ns_get_lba_size(n);
+				uint64_t nsze = nvme_ns_get_lba_count(n) * lba;
+				uint64_t nuse = nvme_ns_get_lba_util(n) * lba;
+
+				obj_add_str(jns, "NameSpace", nvme_ns_get_name(n));
+				obj_add_str(jns, "Generic", nvme_ns_get_generic_name(n));
+				obj_add_int(jns, "NSID", nvme_ns_get_nsid(n));
+				obj_add_uint64(jns, "UsedBytes", nuse);
+				obj_add_uint64(jns, "MaximumLBA", nvme_ns_get_lba_count(n));
+				obj_add_uint64(jns, "PhysicalSize", nsze);
+				obj_add_int(jns, "SectorSize", lba);
+
+				array_add_obj(jnss, jns);
+			}
+			obj_add_obj(jss, "Namespaces", jnss);
+
+			array_add_obj(jsslist, jss);
+		}
+
+		obj_add_obj(hss, "Subsystems", jsslist);
+		array_add_obj(jdev, hss);
+	}
+
+	obj_add_array(r, "Devices", jdev);
+
+	json_print(r);
+}
+
 static struct json_object *json_list_item_obj(nvme_ns_t n)
 {
 	struct json_object *r = json_create_object();
@@ -4622,9 +4728,12 @@ static void json_list_item(nvme_ns_t n)
 
 static void json_print_list_items(nvme_root_t t)
 {
-	if (verbose_mode())
-		json_detail_list(t);
-	else
+	if (json_print_ops.flags & VERBOSE) {
+		if (nvme_cfg.output_format_ver == 2)
+			json_detail_list_v2(t);
+		else
+			json_detail_list(t);
+	} else
 		json_simple_list(t);
 }
 
-- 
2.50.1

Re: [PATCH] nvme-list: make verbose JSON output backward compatible

[Daniel Wagner]

On Tue, 05 Aug 2025 15:50:50 +0530, Nilay Shroff wrote:
> The commit 64bed0a87a23 ("nvme-list: fix verbose JSON output for 'nvme
> list' command") changed the JSON output format of the nvme list --verbose
> command. While the new format is more structured, it introduced a
> regression by breaking compatibility with tools and scripts relying on
> the previous JSON schema.
> 
> So to restore backward compatibility, we now leverage the existing
> --output-format-version option. With this patch,
> 1. The default --output-format-version=1 retains the original (legacy) JSON
> format for nvme list --verbose.
> 2. If the user explicitly sets --output-format-version=2 then the newer
> JSON structure introduced by commit 64bed0a87a23 ("nvme-list: fix verbose
> JSON output for 'nvme list' command") is used.
> 
> [...]

Applied, thanks!

[1/1] nvme-list: make verbose JSON output backward compatible
      commit: 80ad62ba75f1f1dd5b99c6f56769141b48344485

Best regards,
-- 
Daniel Wagner <wagi@kernel.org>