net: ionic: Create an auxiliary device for rdma driver

To support RDMA capable ethernet device, create an auxiliary device in
the ionic Ethernet driver. The RDMA device is modeled as an auxiliary
device to the Ethernet device.

Reviewed-by: Shannon Nelson <shannon.nelson@amd.com>
Signed-off-by: Abhijit Gangurde <abhijit.gangurde@amd.com>
Link: https://patch.msgid.link/20250903061606.4139957-2-abhijit.gangurde@amd.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>

Documentation/networking/device_drivers/ethernet/pensando/ionic.rst

@@ -13,6 +13,7 @@ Contents
 - Identifying the Adapter
 - Enabling the driver
 - Configuring the driver
+- RDMA Support via Auxiliary Device
 - Statistics
 - Support
 
@@ -105,6 +106,15 @@ XDP
 Support for XDP includes the basics, plus Jumbo frames, Redirect and
 ndo_xmit.  There is no current support for zero-copy sockets or HW offload.
 
+RDMA Support via Auxiliary Device
+=================================
+
+The ionic driver supports RDMA (Remote Direct Memory Access) functionality
+through the Linux auxiliary device framework when advertised by the firmware.
+RDMA capability is detected during device initialization, and if supported,
+the ethernet driver will create an auxiliary device that allows the RDMA
+driver to bind and provide InfiniBand/RoCE functionality.
+
 Statistics
 ==========
 

drivers/net/ethernet/pensando/Kconfig

@@ -24,6 +24,7 @@ config IONIC
 	select NET_DEVLINK
 	select DIMLIB
 	select PAGE_POOL
+	select AUXILIARY_BUS
 	help
 	  This enables the support for the Pensando family of Ethernet
 	  adapters.  More specific information on this driver can be

drivers/net/ethernet/pensando/ionic/Makefile

@@ -5,5 +5,5 @@ obj-$(CONFIG_IONIC) := ionic.o
 
 ionic-y := ionic_main.o ionic_bus_pci.o ionic_devlink.o ionic_dev.o \
 	   ionic_debugfs.o ionic_lif.o ionic_rx_filter.o ionic_ethtool.o \
-	   ionic_txrx.o ionic_stats.o ionic_fw.o
+	   ionic_txrx.o ionic_stats.o ionic_fw.o ionic_aux.o
 ionic-$(CONFIG_PTP_1588_CLOCK) += ionic_phc.o

drivers/net/ethernet/pensando/ionic/ionic_api.h

@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2018-2025, Advanced Micro Devices, Inc. */
+
+#ifndef _IONIC_API_H_
+#define _IONIC_API_H_
+
+#include <linux/auxiliary_bus.h>
+
+/**
+ * struct ionic_aux_dev - Auxiliary device information
+ * @lif:        Logical interface
+ * @idx:        Index identifier
+ * @adev:       Auxiliary device
+ */
+struct ionic_aux_dev {
+	struct ionic_lif *lif;
+	int idx;
+	struct auxiliary_device adev;
+};
+
+#endif /* _IONIC_API_H_ */

drivers/net/ethernet/pensando/ionic/ionic_aux.c

@@ -0,0 +1,80 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) 2018-2025, Advanced Micro Devices, Inc. */
+
+#include <linux/kernel.h>
+#include "ionic.h"
+#include "ionic_lif.h"
+#include "ionic_aux.h"
+
+static DEFINE_IDA(aux_ida);
+
+static void ionic_auxbus_release(struct device *dev)
+{
+	struct ionic_aux_dev *ionic_adev;
+
+	ionic_adev = container_of(dev, struct ionic_aux_dev, adev.dev);
+	ida_free(&aux_ida, ionic_adev->adev.id);
+	kfree(ionic_adev);
+}
+
+int ionic_auxbus_register(struct ionic_lif *lif)
+{
+	struct ionic_aux_dev *ionic_adev;
+	struct auxiliary_device *aux_dev;
+	int err, id;
+
+	if (!(le64_to_cpu(lif->ionic->ident.lif.capabilities) & IONIC_LIF_CAP_RDMA))
+		return 0;
+
+	ionic_adev = kzalloc(sizeof(*ionic_adev), GFP_KERNEL);
+	if (!ionic_adev)
+		return -ENOMEM;
+
+	aux_dev = &ionic_adev->adev;
+
+	id = ida_alloc(&aux_ida, GFP_KERNEL);
+	if (id < 0) {
+		dev_err(lif->ionic->dev, "Failed to allocate aux id: %d\n", id);
+		kfree(ionic_adev);
+		return id;
+	}
+
+	aux_dev->id = id;
+	aux_dev->name = "rdma";
+	aux_dev->dev.parent = &lif->ionic->pdev->dev;
+	aux_dev->dev.release = ionic_auxbus_release;
+	ionic_adev->lif = lif;
+	err = auxiliary_device_init(aux_dev);
+	if (err) {
+		dev_err(lif->ionic->dev, "Failed to initialize %s aux device: %d\n",
+			aux_dev->name, err);
+		ida_free(&aux_ida, id);
+		kfree(ionic_adev);
+		return err;
+	}
+
+	err = auxiliary_device_add(aux_dev);
+	if (err) {
+		dev_err(lif->ionic->dev, "Failed to add %s aux device: %d\n",
+			aux_dev->name, err);
+		auxiliary_device_uninit(aux_dev);
+		return err;
+	}
+
+	lif->ionic_adev = ionic_adev;
+	return 0;
+}
+
+void ionic_auxbus_unregister(struct ionic_lif *lif)
+{
+	mutex_lock(&lif->adev_lock);
+	if (!lif->ionic_adev)
+		goto out;
+
+	auxiliary_device_delete(&lif->ionic_adev->adev);
+	auxiliary_device_uninit(&lif->ionic_adev->adev);
+
+	lif->ionic_adev = NULL;
+out:
+	mutex_unlock(&lif->adev_lock);
+}

drivers/net/ethernet/pensando/ionic/ionic_aux.h

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (C) 2018-2025, Advanced Micro Devices, Inc. */
+
+#ifndef _IONIC_AUX_H_
+#define _IONIC_AUX_H_
+
+int ionic_auxbus_register(struct ionic_lif *lif);
+void ionic_auxbus_unregister(struct ionic_lif *lif);
+
+#endif /* _IONIC_AUX_H_ */

drivers/net/ethernet/pensando/ionic/ionic_bus_pci.c

@@ -9,6 +9,7 @@
 #include "ionic.h"
 #include "ionic_bus.h"
 #include "ionic_lif.h"
+#include "ionic_aux.h"
 #include "ionic_debugfs.h"
 
 /* Supported devices */
@@ -375,6 +376,8 @@ static int ionic_probe(struct pci_dev *pdev, const struct pci_device_id *ent)
 		goto err_out_deregister_devlink;
 	}
 
+	ionic_auxbus_register(ionic->lif);
+
 	mod_timer(&ionic->watchdog_timer,
 		  round_jiffies(jiffies + ionic->watchdog_period));
 	ionic_queue_doorbell_check(ionic, IONIC_NAPI_DEADLINE);
@@ -416,6 +419,7 @@ static void ionic_remove(struct pci_dev *pdev)
 
 		if (ionic->lif->doorbell_wa)
 			cancel_delayed_work_sync(&ionic->doorbell_check_dwork);
+		ionic_auxbus_unregister(ionic->lif);
 		ionic_lif_unregister(ionic->lif);
 		ionic_devlink_unregister(ionic);
 		ionic_lif_deinit(ionic->lif);
@@ -445,6 +449,7 @@ static void ionic_reset_prepare(struct pci_dev *pdev)
 	timer_delete_sync(&ionic->watchdog_timer);
 	cancel_work_sync(&lif->deferred.work);
 
+	ionic_auxbus_unregister(ionic->lif);
 	mutex_lock(&lif->queue_lock);
 	ionic_stop_queues_reconfig(lif);
 	ionic_txrx_free(lif);

drivers/net/ethernet/pensando/ionic/ionic_lif.c

@@ -19,6 +19,7 @@
 #include "ionic_bus.h"
 #include "ionic_dev.h"
 #include "ionic_lif.h"
+#include "ionic_aux.h"
 #include "ionic_txrx.h"
 #include "ionic_ethtool.h"
 #include "ionic_debugfs.h"
@@ -3293,6 +3294,7 @@ int ionic_lif_alloc(struct ionic *ionic)
 
 	mutex_init(&lif->queue_lock);
 	mutex_init(&lif->config_lock);
+	mutex_init(&lif->adev_lock);
 
 	spin_lock_init(&lif->adminq_lock);
 
@@ -3349,6 +3351,7 @@ err_out_free_lif_info:
 	lif->info = NULL;
 	lif->info_pa = 0;
 err_out_free_mutex:
+	mutex_destroy(&lif->adev_lock);
 	mutex_destroy(&lif->config_lock);
 	mutex_destroy(&lif->queue_lock);
 err_out_free_netdev:
@@ -3384,6 +3387,7 @@ static void ionic_lif_handle_fw_down(struct ionic_lif *lif)
 
 	netif_device_detach(lif->netdev);
 
+	ionic_auxbus_unregister(ionic->lif);
 	mutex_lock(&lif->queue_lock);
 	if (test_bit(IONIC_LIF_F_UP, lif->state)) {
 		dev_info(ionic->dev, "Surprise FW stop, stopping queues\n");
@@ -3446,6 +3450,8 @@ int ionic_restart_lif(struct ionic_lif *lif)
 	netif_device_attach(lif->netdev);
 	ionic_queue_doorbell_check(ionic, IONIC_NAPI_DEADLINE);
 
+	ionic_auxbus_register(ionic->lif);
+
 	return 0;
 
 err_txrx_free:
@@ -3528,6 +3534,7 @@ void ionic_lif_free(struct ionic_lif *lif)
 
 	mutex_destroy(&lif->config_lock);
 	mutex_destroy(&lif->queue_lock);
+	mutex_destroy(&lif->adev_lock);
 
 	/* free netdev & lif */
 	ionic_debugfs_del_lif(lif);

drivers/net/ethernet/pensando/ionic/ionic_lif.h

@@ -10,6 +10,7 @@
 #include <linux/dim.h>
 #include <linux/pci.h>
 #include "ionic_rx_filter.h"
+#include "ionic_api.h"
 
 #define IONIC_ADMINQ_LENGTH	16	/* must be a power of two */
 #define IONIC_NOTIFYQ_LENGTH	64	/* must be a power of two */
@@ -225,6 +226,8 @@ struct ionic_lif {
 	dma_addr_t info_pa;
 	u32 info_sz;
 	struct ionic_qtype_info qtype_info[IONIC_QTYPE_MAX];
+	struct ionic_aux_dev *ionic_adev;
+	struct mutex adev_lock;	/* lock for aux_dev actions */
 
 	u8 rss_hash_key[IONIC_RSS_HASH_KEY_SIZE];
 	u8 *rss_ind_tbl;