dibs: Define dibs_client_ops and dibs_dev_ops

Move the device add() and remove() functions from ism_client to
dibs_client_ops and call add_dev()/del_dev() for ism devices and
dibs_loopback devices. dibs_client_ops->add_dev() = smcd_register_dev() for
the smc_dibs_client. This is the first step to handle ism and loopback
devices alike (as dibs devices) in the smc dibs client.

Define dibs_dev->ops and move smcd_ops->get_chid to
dibs_dev_ops->get_fabric_id() for ism and loopback devices. See below for
why this needs to be in the same patch as dibs_client_ops->add_dev().

The following changes contain intermediate steps, that will be obsoleted by
follow-on patches, once more functionality has been moved to dibs:

Use different smcd_ops and max_dmbs for ism and loopback. Follow-on patches
will change SMC-D to directly use dibs_ops instead of smcd_ops.

In smcd_register_dev() it is now necessary to identify a dibs_loopback
device before smcd_dev and smcd_ops->get_chid() are available. So provide
dibs_dev_ops->get_fabric_id() in this patch and evaluate it in
smc_ism_is_loopback().

Call smc_loopback_init() in smcd_register_dev() and call
smc_loopback_exit() in smcd_unregister_dev() to handle the functionality
that is still in smc_loopback. Follow-on patches will move all smc_loopback
code to dibs_loopback.

In smcd_[un]register_dev() use only ism device name, this will be replaced
by dibs device name by a follow-on patch.

End of changes with intermediate parts.

Allocate an smcd event workqueue for all dibs devices, although
dibs_loopback does not generate events.

Use kernel memory instead of devres memory for smcd_dev and smcd->conn.
Since commit a72178cfe855 ("net/smc: Fix dependency of SMC on ISM") an ism
device and its driver can have a longer lifetime than the smc module, so
smc should not rely on devres to free its resources [1]. It is now the
responsibility of the smc client to free smcd and smcd->conn for all dibs
devices, ism devices as well as loopback. Call client->ops->del_dev() for
all existing dibs devices in dibs_unregister_client(), so all device
related structures can be freed in the client.

When dibs_unregister_client() is called in the context of smc_exit() or
smc_core_reboot_event(), these functions have already called
smc_lgrs_shutdown() which calls smc_smcd_terminate_all(smcd) and sets
going_away. This is done a second time in smcd_unregister_dev(). This is
analogous to how smcr is handled in these functions, by calling first
smc_lgrs_shutdown() and then smc_ib_unregister_client() >
smc_ib_remove_dev(), so leave it that way. It may be worth investigating,
whether smc_lgrs_shutdown() is still required or useful.

Remove CONFIG_SMC_LO. CONFIG_DIBS_LO now controls whether a dibs loopback
device exists or not.

Link: https://www.kernel.org/doc/Documentation/driver-model/devres.txt [1]
Signed-off-by: Alexandra Winter <wintera@linux.ibm.com>
Reviewed-by: Mahanta Jambigi <mjambigi@linux.ibm.com>
Link: https://patch.msgid.link/20250918110500.1731261-8-wintera@linux.ibm.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

1 files changed, 87 insertions, 2 deletions

diff --git a/include/linux/dibs.h b/include/linux/dibs.h
index c12db19c98c0..805ab33271b5 100644
--- a/include/linux/dibs.h
+++ b/include/linux/dibs.h
@@ -34,14 +34,45 @@
  * clients.
  */
 
+struct dibs_dev;
+
 /* DIBS client
  * -----------
  */
 #define MAX_DIBS_CLIENTS	8
+/* All dibs clients have access to all dibs devices.
+ * A dibs client provides the following functions to be called by dibs layer or
+ * dibs device drivers:
+ */
+struct dibs_client_ops {
+	/**
+	 *  add_dev() - add a dibs device
+	 *  @dev: device that was added
+	 *
+	 * Will be called during dibs_register_client() for all existing
+	 * dibs devices and whenever a new dibs device is registered.
+	 * dev is usable until dibs_client.remove() is called.
+	 * *dev is protected by device refcounting.
+	 */
+	void (*add_dev)(struct dibs_dev *dev);
+	/**
+	 * del_dev() - remove a dibs device
+	 * @dev: device to be removed
+	 *
+	 * Will be called whenever a dibs device is removed.
+	 * Will be called during dibs_unregister_client() for all existing
+	 * dibs devices and whenever a dibs device is unregistered.
+	 * The device has already stopped initiative for this client:
+	 * No new handlers will be started.
+	 * The device is no longer usable by this client after this call.
+	 */
+	void (*del_dev)(struct dibs_dev *dev);
+};
 
 struct dibs_client {
 	/* client name for logging and debugging purposes */
 	const char *name;
+	const struct dibs_client_ops *ops;
 	/* client index - provided and used by dibs layer */
 	u8 id;
 };
@@ -52,6 +83,7 @@ struct dibs_client {
  * dibs_register_client() - register a client with dibs layer
  * @client: this client
  *
+ * Will call client->ops->add_dev() for all existing dibs devices.
  * Return: zero on success.
  */
 int dibs_register_client(struct dibs_client *client);
@@ -59,21 +91,74 @@ int dibs_register_client(struct dibs_client *client);
  * dibs_unregister_client() - unregister a client with dibs layer
  * @client: this client
  *
+ * Will call client->ops->del_dev() for all existing dibs devices.
  * Return: zero on success.
  */
 int dibs_unregister_client(struct dibs_client *client);
 
+/* dibs clients can call dibs device ops. */
+
 /* DIBS devices
  * ------------
  */
+
+/* Defined fabric id / CHID for all loopback devices:
+ * All dibs loopback devices report this fabric id. In this case devices with
+ * the same fabric id can NOT communicate via dibs. Only loopback devices with
+ * the same dibs device gid can communicate (=same device with itself).
+ */
+#define DIBS_LOOPBACK_FABRIC	0xFFFF
+
+/* A dibs device provides the following functions to be called by dibs clients.
+ * They are mandatory, unless marked 'optional'.
+ */
+struct dibs_dev_ops {
+	/**
+	 * get_fabric_id()
+	 * @dev: local dibs device
+	 *
+	 * Only devices on the same dibs fabric can communicate. Fabric_id is
+	 * unique inside the same HW system. Use fabric_id for fast negative
+	 * checks, but only query_remote_gid() can give a reliable positive
+	 * answer:
+	 * Different fabric_id: dibs is not possible
+	 * Same fabric_id: dibs may be possible or not
+	 *		   (e.g. different HW systems)
+	 * EXCEPTION: DIBS_LOOPBACK_FABRIC denotes an ism_loopback device
+	 *	      that can only communicate with itself. Use dibs_dev.gid
+	 *	      or query_remote_gid()to determine whether sender and
+	 *	      receiver use the same ism_loopback device.
+	 * Return: 2 byte dibs fabric id
+	 */
+	u16 (*get_fabric_id)(struct dibs_dev *dev);
+};
+
 struct dibs_dev {
 	struct list_head list;
+	/* To be filled by device driver, before calling dibs_dev_add(): */
+	const struct dibs_dev_ops *ops;
+	/* priv pointer for device driver */
+	void *drv_priv;
+
+	/* priv pointer per client; for client usage only */
+	void *priv[MAX_DIBS_CLIENTS];
 };
 
+static inline void dibs_set_priv(struct dibs_dev *dev,
+				 struct dibs_client *client, void *priv)
+{
+	dev->priv[client->id] = priv;
+}
+
+static inline void *dibs_get_priv(struct dibs_dev *dev,
+				  struct dibs_client *client)
+{
+	return dev->priv[client->id];
+}
+
 /* ------- End of client-only functions ----------- */
 
-/*
- * Functions to be called by dibs device drivers:
+/* Functions to be called by dibs device drivers:
  */
 /**
  * dibs_dev_alloc() - allocate and reference device structure