[PATCH v2 1/4] firmware: arm_scmi: Avoid protocol devices in exclusive raw mode

[Sudeep Holla]

Since standard protocol devices are created without a driver request,
rejecting SCMI driver registration is no longer enough to prevent them
from appearing when raw mode is enabled without coexistence.

When raw-mode debugfs setup succeeds, scmi_probe() returns success
before protocol enumeration, so it does not normally create those
devices. That early return is not sufficient: scmi_device_create() is
exported and can be called later.

Skip protocol-device creation in exclusive raw mode, including named
non-transport requests. Keep named transport devices so raw mode can
still set up its channels. Share the raw-mode condition and transport
name check with the existing bus paths.

Cc: Hans de Goede <johannes.goede at oss.qualcomm.com>
Fixes: aac4e67d6eb9 ("firmware: arm_scmi: Always create devices for standard protocols")
Reviewed-by: Hans de Goede <johannes.goede at oss.qualcomm.com>
Tested-by: Peng Fan <peng.fan at nxp.com> #i.MX95 EVK
Signed-off-by: Sudeep Holla <sudeep.holla at kernel.org>
---
 drivers/firmware/arm_scmi/bus.c | 23 +++++++++++++++++++----
 1 file changed, 19 insertions(+), 4 deletions(-)

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index 25197197db8e..f2e2ed56bc32 100644
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -36,6 +36,12 @@ struct scmi_requested_dev {
 /* Track globally the SCMI SystemPower protocol device. */
 static struct scmi_device *scmi_syspower_registered;
 
+static bool scmi_raw_mode_only(void)
+{
+	return IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT) &&
+	       !IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX);
+}
+
 /**
  * scmi_protocol_device_request  - Helper to request a device
  *
@@ -60,8 +66,7 @@ static int scmi_protocol_device_request(const struct scmi_device_id *id_table)
 	pr_debug("Requesting SCMI device (%s) for protocol %x\n",
 		 id_table->name, id_table->protocol_id);
 
-	if (IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT) &&
-	    !IS_ENABLED(CONFIG_ARM_SCMI_RAW_MODE_SUPPORT_COEX)) {
+	if (scmi_raw_mode_only()) {
 		pr_warn("SCMI Raw mode active. Rejecting '%s'/0x%02X\n",
 			id_table->name, id_table->protocol_id);
 		return -EINVAL;
@@ -210,12 +215,17 @@ scmi_protocol_table_unregister(const struct scmi_device_id *id_table)
 		scmi_protocol_device_unrequest(entry);
 }
 
-static bool scmi_device_is_transport(const struct scmi_device *scmi_dev)
+static bool scmi_device_name_is_transport(const char *name)
 {
-	return !strncmp(scmi_dev->name, SCMI_TRANSPORT_DEVNAME_PREFIX,
+	return !strncmp(name, SCMI_TRANSPORT_DEVNAME_PREFIX,
 			strlen(SCMI_TRANSPORT_DEVNAME_PREFIX));
 }
 
+static bool scmi_device_is_transport(const struct scmi_device *scmi_dev)
+{
+	return scmi_device_name_is_transport(scmi_dev->name);
+}
+
 static int __scmi_dev_match_by_id_table(struct scmi_device *scmi_dev,
 					const struct scmi_device_id *id_table,
 					bool skip_transport)
@@ -591,6 +601,11 @@ struct scmi_device *scmi_device_create(struct fwnode_handle *fwnode,
 	struct scmi_requested_dev *rdev;
 	struct scmi_device *sdev, *scmi_dev = NULL;
 
+	/* Exclusive raw mode still needs transport devices for its channels. */
+	if (scmi_raw_mode_only() &&
+	    (!name || !scmi_device_name_is_transport(name)))
+		return NULL;
+
 	if (name)
 		return _scmi_device_create(fwnode, parent, protocol, name);
 

-- 
2.43.0