[PATCH v2 2/2] firmware: arm_scmi: request modules for discovered protocols

[Bjorn Andersson <bjorn.andersson@oss.qualcomm.com>]

SCMI client devices are created from SCMI driver id tables. If such a
driver is modular, the core does not know the driver's client name until
the module has already loaded, so normal device uevent based autoloading
cannot break the dependency cycle.

Emit a protocol-level alias for each SCMI device id table entry and
request that alias when the SCMI core discovers an implemented protocol.
This loads modules that have registered interest in the protocol; their
normal SCMI driver registration then requests the concrete client device
and the SCMI bus matches it by protocol and name.

This allows e.g. ARM_SCMI_CPUFREQ=m to autoload on systems that expose
only the SCMI Performance protocol node, where the cpufreq client name
is Linux-internal and not available from firmware before loading the
module.

Assisted-by: Codex:GPT-5.5
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Bjorn Andersson <bjorn.andersson@oss.qualcomm.com>
---
 drivers/firmware/arm_scmi/driver.c | 2 ++
 include/linux/mod_devicetable.h    | 1 +
 scripts/mod/file2alias.c           | 4 +++-
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index 0fd6a947499e..7d33fab94e28 100644
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -48,6 +48,7 @@
 #include <trace/events/scmi.h>
 
 #define SCMI_VENDOR_MODULE_ALIAS_FMT	"scmi-protocol-0x%02x-%s"
+#define SCMI_MODULE_ALIAS_FMT		SCMI_PROTOCOL_MODULE_PREFIX "0x%02x"
 
 static DEFINE_IDA(scmi_id);
 
@@ -3363,6 +3364,7 @@ static int scmi_probe(struct platform_device *pdev)
 		}
 
 		of_node_get(child);
+		request_module_nowait(SCMI_MODULE_ALIAS_FMT, prot_id);
 		scmi_create_protocol_devices(child, info, prot_id, NULL);
 	}
 
diff --git a/include/linux/mod_devicetable.h b/include/linux/mod_devicetable.h
index 769382f2eadd..2cc7e78e35a3 100644
--- a/include/linux/mod_devicetable.h
+++ b/include/linux/mod_devicetable.h
@@ -477,6 +477,7 @@ struct rpmsg_device_id {
 
 #define SCMI_NAME_SIZE		32
 #define SCMI_MODULE_PREFIX	"scmi:"
+#define SCMI_PROTOCOL_MODULE_PREFIX	"scmi-protocol-"
 
 struct scmi_device_id {
 	__u8 protocol_id;
diff --git a/scripts/mod/file2alias.c b/scripts/mod/file2alias.c
index a5283f4c8e6f..40a37b6bf1ad 100644
--- a/scripts/mod/file2alias.c
+++ b/scripts/mod/file2alias.c
@@ -852,7 +852,7 @@ 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 */
+/* Looks like: scmi:NN:S and scmi-protocol-0xNN */
 static void do_scmi_entry(struct module *mod, void *symval)
 {
 	DEF_FIELD(symval, scmi_device_id, protocol_id);
@@ -860,6 +860,8 @@ static void do_scmi_entry(struct module *mod, void *symval)
 
 	module_alias_printf(mod, false, SCMI_MODULE_PREFIX "%02x:%s",
 			    protocol_id, *name);
+	module_alias_printf(mod, false, SCMI_PROTOCOL_MODULE_PREFIX "0x%02x",
+			    protocol_id);
 }
 
 /* Looks like: i2c:S */

-- 
2.53.0