[PATCH v3 1/3] module: add SCMI device table alias support

[Hans de Goede]

From: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>

SCMI client drivers already describe their bus match data with
MODULE_DEVICE_TABLE(scmi, ...), but modpost does not know how to consume
SCMI device tables. As a result, SCMI modules do not get generated module
aliases from their id tables.

Move struct scmi_device_id to mod_devicetable.h so it has a fixed layout
visible to modpost, add the corresponding generated offsets and teach
file2alias to emit scmi:<protocol>:<name> aliases.

Use the same stable alias format for SCMI device uevents and sysfs
modaliases. The previous string included the instance-specific device
name, which is not useful for matching modules.

Assisted-by: Codex:GPT-5.5
Reviewed-by: Hans de Goede <johannes.goede@xxxxxxxxxxxxxxxx>
Tested-by: Hans de Goede <johannes.goede@xxxxxxxxxxxxxxxx>
Signed-off-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxxxxxxxx>
Signed-off-by: Hans de Goede <johannes.goede@xxxxxxxxxxxxxxxx>
---
Changes in v3:
- Adjust for ad428f5811bd ("mod_devicetable.h: Split into per subsystem
  headers")
- Add '\n' to modalias_show() output, matching other subsystems' modalias
- Link to v2: https://lore.kernel.org/all/20260618-scmi-modalias-v2-1-8c7547c1be21@xxxxxxxxxxxxxxxx/

Changes in v2:
- Drop #include <linux/mod_devicetable.h> from scmi_protocol.h
- Link to v1: https://patch.msgid.link/20260616-scmi-modalias-v1-0-662b8dd52ab2@xxxxxxxxxxxxxxxx
---
 MAINTAINERS                       |  1 +
 drivers/firmware/arm_scmi/bus.c   | 21 ++++++++++-----------
 include/linux/device-id/scmi.h    | 19 +++++++++++++++++++
 include/linux/mod_devicetable.h   |  1 +
 include/linux/scmi_protocol.h     |  6 +-----
 scripts/mod/devicetable-offsets.c |  4 ++++
 scripts/mod/file2alias.c          | 11 +++++++++++
 7 files changed, 47 insertions(+), 16 deletions(-)
 create mode 100644 include/linux/device-id/scmi.h

diff --git a/MAINTAINERS b/MAINTAINERS
index fc6ca082106f..ee5beee606fc 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26334,6 +26334,7 @@ F:	drivers/pmdomain/arm/
 F:	drivers/powercap/arm_scmi_powercap.c
 F:	drivers/regulator/scmi-regulator.c
 F:	drivers/reset/reset-scmi.c
+F:	include/linux/device-id/scmi.h
 F:	include/linux/sc[mp]i_protocol.h
 F:	include/trace/events/scmi.h
 F:	include/uapi/linux/virtio_scmi.h
diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index 793be9eabaed..d12d5de15a1a 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -13,11 +13,12 @@
 #include <linux/of.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
+#include <linux/string.h>
 #include <linux/device.h>
 
 #include "common.h"
 
-#define SCMI_UEVENT_MODALIAS_FMT	"%s:%02x:%s"
+#define SCMI_UEVENT_MODALIAS_FMT	SCMI_MODULE_PREFIX "%02x:%s"
 
 BLOCKING_NOTIFIER_HEAD(scmi_requested_devices_nh);
 EXPORT_SYMBOL_GPL(scmi_requested_devices_nh);
@@ -141,7 +142,7 @@ static int scmi_protocol_table_register(const struct scmi_device_id *id_table)
 	int ret = 0;
 	const struct scmi_device_id *entry;
 
-	for (entry = id_table; entry->name && ret == 0; entry++)
+	for (entry = id_table; entry->name[0] && ret == 0; entry++)
 		ret = scmi_protocol_device_request(entry);
 
 	return ret;
@@ -197,18 +198,18 @@ scmi_protocol_table_unregister(const struct scmi_device_id *id_table)
 {
 	const struct scmi_device_id *entry;
 
-	for (entry = id_table; entry->name; entry++)
+	for (entry = id_table; entry->name[0]; entry++)
 		scmi_protocol_device_unrequest(entry);
 }
 
 static int scmi_dev_match_by_id_table(struct scmi_device *scmi_dev,
 				      const struct scmi_device_id *id_table)
 {
-	if (!id_table || !id_table->name)
+	if (!id_table || !id_table->name[0])
 		return 0;
 
 	/* Always skip transport devices from matching */
-	for (; id_table->protocol_id && id_table->name; id_table++)
+	for (; id_table->protocol_id && id_table->name[0]; id_table++)
 		if (id_table->protocol_id == scmi_dev->protocol_id &&
 		    strncmp(scmi_dev->name, "__scmi_transport_device", 23) &&
 		    !strcmp(id_table->name, scmi_dev->name))
@@ -245,7 +246,7 @@ static struct scmi_device *scmi_child_dev_find(struct device *parent,
 	struct device *dev;
 
 	id_table[0].protocol_id = prot_id;
-	id_table[0].name = name;
+	strscpy(id_table[0].name, name, sizeof(id_table[0].name));
 
 	dev = device_find_child(parent, &id_table, scmi_match_by_id_table);
 	if (!dev)
@@ -282,8 +283,7 @@ static int scmi_device_uevent(const struct device *dev, struct kobj_uevent_env *
 	const struct scmi_device *scmi_dev = to_scmi_dev(dev);
 
 	return add_uevent_var(env, "MODALIAS=" SCMI_UEVENT_MODALIAS_FMT,
-			      dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
-			      scmi_dev->name);
+			      scmi_dev->protocol_id, scmi_dev->name);
 }
 
 static ssize_t modalias_show(struct device *dev,
@@ -291,9 +291,8 @@ static ssize_t modalias_show(struct device *dev,
 {
 	struct scmi_device *scmi_dev = to_scmi_dev(dev);
 
-	return sysfs_emit(buf, SCMI_UEVENT_MODALIAS_FMT,
-			  dev_name(&scmi_dev->dev), scmi_dev->protocol_id,
-			  scmi_dev->name);
+	return sysfs_emit(buf, SCMI_UEVENT_MODALIAS_FMT "\n",
+			  scmi_dev->protocol_id, scmi_dev->name);
 }
 static DEVICE_ATTR_RO(modalias);
 
diff --git a/include/linux/device-id/scmi.h b/include/linux/device-id/scmi.h
new file mode 100644
index 000000000000..4150481524d4
--- /dev/null
+++ b/include/linux/device-id/scmi.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+#ifndef LINUX_DEVICE_ID_SCMI_H
+#define LINUX_DEVICE_ID_SCMI_H
+
+#ifdef __KERNEL__
+#include <linux/types.h>
+typedef unsigned long kernel_ulong_t;
+#endif
+
+#define SCMI_NAME_SIZE		32
+#define SCMI_MODULE_PREFIX	"scmi:"
+
+struct scmi_device_id {
+	__u8 protocol_id;
+	char name[SCMI_NAME_SIZE];
+	kernel_ulong_t driver_data;
+};
+
+#endif /* ifndef LINUX_DEVICE_ID_SCMI_H */
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index a397213bedac..d241421c36aa 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -49,6 +49,7 @@
 #include "device-id/pnp.h"
 #include "device-id/rio.h"
 #include "device-id/rpmsg.h"
+#include "device-id/scmi.h"
 #include "device-id/sdio.h"
 #include "device-id/sdw.h"
 #include "device-id/serio.h"
diff --git a/include/linux/scmi_protocol.h b/include/linux/scmi_protocol.h
index 5ab73b1ab9aa..ba53302d95f5 100644
--- a/include/linux/scmi_protocol.h
+++ b/include/linux/scmi_protocol.h
@@ -9,6 +9,7 @@
 #define _LINUX_SCMI_PROTOCOL_H
 
 #include <linux/bitfield.h>
+#include <linux/device-id/scmi.h>
 #include <linux/device.h>
 #include <linux/notifier.h>
 #include <linux/types.h>
@@ -951,11 +952,6 @@ struct scmi_device {
 
 #define to_scmi_dev(d) container_of_const(d, struct scmi_device, dev)
 
-struct scmi_device_id {
-	u8 protocol_id;
-	const char *name;
-};
-
 struct scmi_driver {
 	const char *name;
 	int (*probe)(struct scmi_device *sdev);
diff --git a/scripts/mod/devicetable-offsets.c b/scripts/mod/devicetable-offsets.c
index b4178c42d08f..da5bd712c8da 100644
--- a/scripts/mod/devicetable-offsets.c
+++ b/scripts/mod/devicetable-offsets.c
@@ -144,6 +144,10 @@ int main(void)
 	DEVID(rpmsg_device_id);
 	DEVID_FIELD(rpmsg_device_id, name);
 
+	DEVID(scmi_device_id);
+	DEVID_FIELD(scmi_device_id, protocol_id);
+	DEVID_FIELD(scmi_device_id, name);
+
 	DEVID(i2c_device_id);
 	DEVID_FIELD(i2c_device_id, name);
 
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index 8d36c74dec2d..a5283f4c8e6f 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -852,6 +852,16 @@ static void do_rpmsg_entry(struct module *mod, void *symval)
 	module_alias_printf(mod, false, RPMSG_DEVICE_MODALIAS_FMT, *name);
 }
 
+/* Looks like: scmi:NN:S */
+static void do_scmi_entry(struct module *mod, void *symval)
+{
+	DEF_FIELD(symval, scmi_device_id, protocol_id);
+	DEF_FIELD_ADDR(symval, scmi_device_id, name);
+
+	module_alias_printf(mod, false, SCMI_MODULE_PREFIX "%02x:%s",
+			    protocol_id, *name);
+}
+
 /* Looks like: i2c:S */
 static void do_i2c_entry(struct module *mod, void *symval)
 {
@@ -1491,6 +1501,7 @@ static const struct devtable devtable[] = {
 	{"virtio", SIZE_virtio_device_id, do_virtio_entry},
 	{"vmbus", SIZE_hv_vmbus_device_id, do_vmbus_entry},
 	{"rpmsg", SIZE_rpmsg_device_id, do_rpmsg_entry},
+	{"scmi", SIZE_scmi_device_id, do_scmi_entry},
 	{"i2c", SIZE_i2c_device_id, do_i2c_entry},
 	{"i3c", SIZE_i3c_device_id, do_i3c_entry},
 	{"slim", SIZE_slim_device_id, do_slim_entry},
-- 
2.55.0