firmware: arm_scmi: Add common notifier helpers

Add a pair of notifier chains and generic empty notifier callbacks.
Currently they are still unused but they will be used to act properly
on device request and creation events.

Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
Link: https://lore.kernel.org/r/20221222185049.737625-5-cristian.marussi@arm.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>

diff --git a/drivers/firmware/arm_scmi/bus.c b/drivers/firmware/arm_scmi/bus.c
index 089957f5fb9bb482897b325b5759dab38f7a7a12..bed566f58029d613cfdfba7b78d83de52208ad00 100644 (file)
--- a/drivers/firmware/arm_scmi/bus.c
+++ b/drivers/firmware/arm_scmi/bus.c
@@ -15,6 +15,9 @@
 
 #include "common.h"
 
+BLOCKING_NOTIFIER_HEAD(scmi_requested_devices_nh);
+EXPORT_SYMBOL_GPL(scmi_requested_devices_nh);
+
 static DEFINE_IDA(scmi_bus_id);
 
 static const struct scmi_device_id *
@@ -94,12 +97,13 @@ static void scmi_dev_remove(struct device *dev)
                scmi_drv->remove(scmi_dev);
 }
 
-static struct bus_type scmi_bus_type = {
+struct bus_type scmi_bus_type = {
        .name = "scmi_protocol",
        .match = scmi_dev_match,
        .probe = scmi_dev_probe,
        .remove = scmi_dev_remove,
 };
+EXPORT_SYMBOL_GPL(scmi_bus_type);
 
 int scmi_driver_register(struct scmi_driver *driver, struct module *owner,
                         const char *mod_name)

diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
index 6a38244494fd4cd001187d472d811f0d4e69af1a..7ddae90eb945d808aad16eb25dac17063544c5de 100644 (file)
--- a/drivers/firmware/arm_scmi/common.h
+++ b/drivers/firmware/arm_scmi/common.h
@@ -105,6 +105,11 @@ void scmi_setup_protocol_implemented(const struct scmi_protocol_handle *ph,
 
 int __init scmi_bus_init(void);
 void __exit scmi_bus_exit(void);
+extern struct bus_type scmi_bus_type;
+
+#define SCMI_BUS_NOTIFY_DEVICE_REQUEST         0
+#define SCMI_BUS_NOTIFY_DEVICE_UNREQUEST       1
+extern struct blocking_notifier_head scmi_requested_devices_nh;
 
 int scmi_protocol_acquire(const struct scmi_handle *handle, u8 protocol_id);
 void scmi_protocol_release(const struct scmi_handle *handle, u8 protocol_id);

diff --git a/drivers/firmware/arm_scmi/driver.c b/drivers/firmware/arm_scmi/driver.c
index d1e32ea6d90a00f66a045ae0931df4996f288334..62760bed1645cb6acf8c06595cadbd09aa800a92 100644 (file)
--- a/drivers/firmware/arm_scmi/driver.c
+++ b/drivers/firmware/arm_scmi/driver.c
@@ -150,6 +150,9 @@ struct scmi_protocol_instance {
  * @notify_priv: Pointer to private data structure specific to notifications.
  * @node: List head
  * @users: Number of users of this instance
+ * @bus_nb: A notifier to listen for device bind/unbind on the scmi bus
+ * @dev_req_nb: A notifier to listen for device request/unrequest on the scmi
+ *             bus
  */
 struct scmi_info {
        struct device *dev;
@@ -169,9 +172,13 @@ struct scmi_info {
        void *notify_priv;
        struct list_head node;
        int users;
+       struct notifier_block bus_nb;
+       struct notifier_block dev_req_nb;
 };
 
 #define handle_to_scmi_info(h) container_of(h, struct scmi_info, handle)
+#define bus_nb_to_scmi_info(nb)        container_of(nb, struct scmi_info, bus_nb)
+#define req_nb_to_scmi_info(nb)        container_of(nb, struct scmi_info, dev_req_nb)
 
 static const int scmi_linux_errmap[] = {
        /* better than switch case as long as return value is continuous */
@@ -2509,6 +2516,60 @@ static void scmi_cleanup_txrx_channels(struct scmi_info *info)
        scmi_cleanup_channels(info, &info->rx_idr);
 }
 
+static int scmi_bus_notifier(struct notifier_block *nb,
+                            unsigned long action, void *data)
+{
+       struct scmi_info *info = bus_nb_to_scmi_info(nb);
+       struct scmi_device *sdev = to_scmi_dev(data);
+
+       /* Skip transport devices and devices of different SCMI instances */
+       if (!strncmp(sdev->name, "__scmi_transport_device", 23) ||
+           sdev->dev.parent != info->dev)
+               return NOTIFY_DONE;
+
+       switch (action) {
+       case BUS_NOTIFY_BIND_DRIVER:
+               break;
+       case BUS_NOTIFY_UNBOUND_DRIVER:
+               break;
+       default:
+               return NOTIFY_DONE;
+       }
+
+       dev_dbg(info->dev, "Device %s (%s) is now %s\n", dev_name(&sdev->dev),
+               sdev->name, action == BUS_NOTIFY_BIND_DRIVER ?
+               "about to be BOUND." : "UNBOUND.");
+
+       return NOTIFY_OK;
+}
+
+static int scmi_device_request_notifier(struct notifier_block *nb,
+                                       unsigned long action, void *data)
+{
+       struct device_node *np;
+       struct scmi_device_id *id_table = data;
+       struct scmi_info *info = req_nb_to_scmi_info(nb);
+
+       np = idr_find(&info->active_protocols, id_table->protocol_id);
+       if (!np)
+               return NOTIFY_DONE;
+
+       dev_dbg(info->dev, "%sRequested device (%s) for protocol 0x%x\n",
+               action == SCMI_BUS_NOTIFY_DEVICE_REQUEST ? "" : "UN-",
+               id_table->name, id_table->protocol_id);
+
+       switch (action) {
+       case SCMI_BUS_NOTIFY_DEVICE_REQUEST:
+               break;
+       case SCMI_BUS_NOTIFY_DEVICE_UNREQUEST:
+               break;
+       default:
+               return NOTIFY_DONE;
+       }
+
+       return NOTIFY_OK;
+}
+
 static int scmi_probe(struct platform_device *pdev)
 {
        int ret;
@@ -2528,6 +2589,8 @@ static int scmi_probe(struct platform_device *pdev)
 
        info->dev = dev;
        info->desc = desc;
+       info->bus_nb.notifier_call = scmi_bus_notifier;
+       info->dev_req_nb.notifier_call = scmi_device_request_notifier;
        INIT_LIST_HEAD(&info->node);
        idr_init(&info->protocols);
        mutex_init(&info->protocols_mtx);
@@ -2563,10 +2626,19 @@ static int scmi_probe(struct platform_device *pdev)
        if (ret)
                return ret;
 
-       ret = scmi_xfer_info_init(info);
+       ret = bus_register_notifier(&scmi_bus_type, &info->bus_nb);
        if (ret)
                goto clear_txrx_setup;
 
+       ret = blocking_notifier_chain_register(&scmi_requested_devices_nh,
+                                              &info->dev_req_nb);
+       if (ret)
+               goto clear_bus_notifier;
+
+       ret = scmi_xfer_info_init(info);
+       if (ret)
+               goto clear_dev_req_notifier;
+
        if (scmi_notification_init(handle))
                dev_err(dev, "SCMI Notifications NOT available.\n");
 
@@ -2624,6 +2696,11 @@ static int scmi_probe(struct platform_device *pdev)
 
 notification_exit:
        scmi_notification_exit(&info->handle);
+clear_dev_req_notifier:
+       blocking_notifier_chain_unregister(&scmi_requested_devices_nh,
+                                          &info->dev_req_nb);
+clear_bus_notifier:
+       bus_unregister_notifier(&scmi_bus_type, &info->bus_nb);
 clear_txrx_setup:
        scmi_cleanup_txrx_channels(info);
        return ret;
@@ -2652,6 +2729,10 @@ static int scmi_remove(struct platform_device *pdev)
                of_node_put(child);
        idr_destroy(&info->active_protocols);
 
+       blocking_notifier_chain_unregister(&scmi_requested_devices_nh,
+                                          &info->dev_req_nb);
+       bus_unregister_notifier(&scmi_bus_type, &info->bus_nb);
+
        /* Safe to free channels since no more users */
        scmi_cleanup_txrx_channels(info);