[PATCH net-next v6 3/3] mctp i3c: MCTP I3C driver

Matt Johnston
2023-10-13T04:06:55Z

Provides MCTP network transport over an I3C bus, as specified in
DMTF DSP0233.

Each I3C bus (with "mctp-controller" devicetree property) gets an
"mctpi3cX" net device created. I3C devices are reachable as remote
endpoints through that net device. Link layer addressing uses the
I3C PID as a fixed hardware address for neighbour table entries.

The driver matches I3C devices that have the MIPI assigned DCR 0xCC for
MCTP.

Signed-off-by: Matt Johnston <matt@codeconstruct.com.au>
---

v6:

- Use multiple labels for error path handling
- Fix error handling from mctp_i3c_probe()
- Use spinlock_bh() instead for tx_lock
- Remove stale TODO comment (it had been tested)

v5:

- Use #define for constant initializer, fixes older gcc
- Wrap lines at 80 characters, fix parenthesis alignment

v4:

- Add asm/unaligned.h include

v3:

- Use get_unaligned_be48()
- Use kthread_run()
- Don't set net namespace

v2:

- Removed unnecessary pr_ printing
- Fixed reverse christmas tree ordering

drivers/net/mctp/Kconfig | 9 +
drivers/net/mctp/Makefile | 1 +
drivers/net/mctp/mctp-i3c.c | 755 ++++++++++++++++++++++++++++++++++++
3 files changed, 765 insertions(+)
create mode 100644 drivers/net/mctp/mctp-i3c.c

diff --git a/drivers/net/mctp/Kconfig b/drivers/net/mctp/Kconfig
index dc71657d9184..ce9d2d2ccf3b 100644
--- a/drivers/net/mctp/Kconfig
+++ b/drivers/net/mctp/Kconfig
@@ -33,6 +33,15 @@ config MCTP_TRANSPORT_I2C
from DMTF specification DSP0237. A MCTP protocol network device is
created for each I2C bus that has been assigned a mctp-i2c device.

+config MCTP_TRANSPORT_I3C
+ tristate "MCTP I3C transport"
+ depends on I3C
+ help
+ Provides a driver to access MCTP devices over I3C transport,
+ from DMTF specification DSP0233.
+ A MCTP protocol network device is created for each I3C bus
+ having a "mctp-controller" devicetree property.
+
endmenu

endif
diff --git a/drivers/net/mctp/Makefile b/drivers/net/mctp/Makefile
index 1ca3e6028f77..e1cb99ced54a 100644
--- a/drivers/net/mctp/Makefile
+++ b/drivers/net/mctp/Makefile
@@ -1,2 +1,3 @@
obj-$(CONFIG_MCTP_SERIAL) += mctp-serial.o
obj-$(CONFIG_MCTP_TRANSPORT_I2C) += mctp-i2c.o
+obj-$(CONFIG_MCTP_TRANSPORT_I3C) += mctp-i3c.o
diff --git a/drivers/net/mctp/mctp-i3c.c b/drivers/net/mctp/mctp-i3c.c
new file mode 100644
index 000000000000..8e989c157caa
--- /dev/null
+++ b/drivers/net/mctp/mctp-i3c.c
@@ -0,0 +1,755 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implements DMTF specification
+ * "DSP0233 Management Component Transport Protocol (MCTP) I3C Transport
+ * Binding"
+ * https://www.dmtf.org/sites/default/files/standards/documents/DSP0233_1.0.0.pdf
+ *
+ * Copyright (c) 2023 Code Construct
+ */
+
+#include <linux/module.h>
+#include <linux/netdevice.h>
+#include <linux/i3c/device.h>
+#include <linux/i3c/master.h>
+#include <linux/if_arp.h>
+#include <asm/unaligned.h>
+#include <net/mctp.h>
+#include <net/mctpdevice.h>
+
+#define MCTP_I3C_MAXBUF 65536
+/* 48 bit Provisioned Id */
+#define PID_SIZE 6
+
+/* 64 byte payload, 4 byte MCTP header */
+static const int MCTP_I3C_MINMTU = 64 + 4;
+/* One byte less to allow for the PEC */
+static const int MCTP_I3C_MAXMTU = MCTP_I3C_MAXBUF - 1;
+/* 4 byte MCTP header, no data, 1 byte PEC */
+static const int MCTP_I3C_MINLEN = 4 + 1;
+
+/* Sufficient for 64kB at min mtu */
+static const int MCTP_I3C_TX_QUEUE_LEN = 1100;
+
+/* Somewhat arbitrary */
+static const int MCTP_I3C_IBI_SLOTS = 8;
+
+/* Mandatory Data Byte in an IBI, from DSP0233 */
+#define I3C_MDB_MCTP 0xAE
+/* From MIPI Device Characteristics Register (DCR) Assignments */
+#define I3C_DCR_MCTP 0xCC
+
+static const char *MCTP_I3C_OF_PROP = "mctp-controller";
+
+/* List of mctp_i3c_busdev */
+static LIST_HEAD(busdevs);
+/* Protects busdevs, as well as mctp_i3c_bus.devs lists */
+static DEFINE_MUTEX(busdevs_lock);
+
+struct mctp_i3c_bus {
+ struct net_device *ndev;
+
+ struct task_struct *tx_thread;
+ wait_queue_head_t tx_wq;
+ /* tx_lock protects tx_skb and devs */
+ spinlock_t tx_lock;
+ /* Next skb to transmit */
+ struct sk_buff *tx_skb;
+ /* Scratch buffer for xmit */
+ u8 tx_scratch[MCTP_I3C_MAXBUF];
+
+ /* Element of busdevs */
+ struct list_head list;
+
+ /* Provisioned ID of our controller */
+ u64 pid;
+
+ struct i3c_bus *bus;
+ /* Head of mctp_i3c_device.list. Protected by busdevs_lock */
+ struct list_head devs;
+};
+
+struct mctp_i3c_device {
+ struct i3c_device *i3c;
+ struct mctp_i3c_bus *mbus;
+ struct list_head list; /* Element of mctp_i3c_bus.devs */
+
+ /* Held while tx_thread is using this device */
+ struct mutex lock;
+
+ /* Whether BCR indicates MDB is present in IBI */
+ bool have_mdb;
+ /* I3C dynamic address */
+ u8 addr;
+ /* Maximum read length */
+ u16 mrl;
+ /* Maximum write length */
+ u16 mwl;
+ /* Provisioned ID */
+ u64 pid;
+};
+
+/* We synthesise a mac header using the Provisioned ID.
+ * Used to pass dest to mctp_i3c_start_xmit.
+ */
+struct mctp_i3c_internal_hdr {
+ u8 dest[PID_SIZE];
+ u8 source[PID_SIZE];
+} __packed;
+
+static int mctp_i3c_read(struct mctp_i3c_device *mi)
+{
+ struct i3c_priv_xfer xfer = { .rnw = 1, .len = mi->mrl };
+ struct net_device_stats *stats = &mi->mbus->ndev->stats;
+ struct mctp_i3c_internal_hdr *ihdr = NULL;
+ struct sk_buff *skb = NULL;
+ struct mctp_skb_cb *cb;
+ int net_status, rc;
+ u8 pec, addr;
+
+ skb = netdev_alloc_skb(mi->mbus->ndev,
+ mi->mrl + sizeof(struct mctp_i3c_internal_hdr));
+ if (!skb) {
+ stats->rx_dropped++;
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ skb->protocol = htons(ETH_P_MCTP);
+ /* Create a header for internal use */
+ skb_reset_mac_header(skb);
+ ihdr = skb_put(skb, sizeof(struct mctp_i3c_internal_hdr));
+ put_unaligned_be48(mi->pid, ihdr->source);
+ put_unaligned_be48(mi->mbus->pid, ihdr->dest);
+ skb_pull(skb, sizeof(struct mctp_i3c_internal_hdr));
+
+ xfer.data.in = skb_put(skb, mi->mrl);
+
+ rc = i3c_device_do_priv_xfers(mi->i3c, &xfer, 1);
+ if (rc < 0)
+ goto err;
+
+ if (WARN_ON_ONCE(xfer.len > mi->mrl)) {
+ /* Bad i3c bus driver */
+ rc = -EIO;
+ goto err;
+ }
+ if (xfer.len < MCTP_I3C_MINLEN) {
+ stats->rx_length_errors++;
+ rc = -EIO;
+ goto err;
+ }
+
+ /* check PEC, including address byte */
+ addr = mi->addr << 1 | 1;
+ pec = i2c_smbus_pec(0, &addr, 1);
+ pec = i2c_smbus_pec(pec, xfer.data.in, xfer.len - 1);
+ if (pec != ((u8 *)xfer.data.in)[xfer.len - 1]) {
+ stats->rx_crc_errors++;
+ rc = -EINVAL;
+ goto err;
+ }
+
+ /* Remove PEC */
+ skb_trim(skb, xfer.len - 1);
+
+ cb = __mctp_cb(skb);
+ cb->halen = PID_SIZE;
+ put_unaligned_be48(mi->pid, cb->haddr);
+
+ net_status = netif_rx(skb);
+
+ if (net_status == NET_RX_SUCCESS) {
+ stats->rx_packets++;
+ stats->rx_bytes += xfer.len - 1;
+ } else {
+ stats->rx_dropped++;
+ }
+
+ return 0;
+err:
+ kfree_skb(skb);
+ return rc;
+}
+
+static void mctp_i3c_ibi_handler(struct i3c_device *i3c,
+ const struct i3c_ibi_payload *payload)
+{
+ struct mctp_i3c_device *mi = i3cdev_get_drvdata(i3c);
+
+ if (WARN_ON_ONCE(!mi))
+ return;
+
+ if (mi->have_mdb) {
+ if (payload->len > 0) {
+ if (((u8 *)payload->data)[0] != I3C_MDB_MCTP) {
+ /* Not a mctp-i3c interrupt, ignore it */
+ return;
+ }
+ } else {
+ /* The BCR advertised a Mandatory Data Byte but the
+ * device didn't send one.
+ */
+ dev_warn_once(i3cdev_to_dev(i3c), "IBI with missing MDB");
+ }
+ }
+
+ mctp_i3c_read(mi);
+}
+
+static int mctp_i3c_setup(struct mctp_i3c_device *mi)
+{
+ const struct i3c_ibi_setup ibi = {
+ .max_payload_len = 1,
+ .num_slots = MCTP_I3C_IBI_SLOTS,
+ .handler = mctp_i3c_ibi_handler,
+ };
+ struct i3c_device_info info;
+ int rc;
+
+ i3c_device_get_info(mi->i3c, &info);
+ mi->have_mdb = info.bcr & BIT(2);
+ mi->addr = info.dyn_addr;
+ mi->mwl = info.max_write_len;
+ mi->mrl = info.max_read_len;
+ mi->pid = info.pid;
+
+ rc = i3c_device_request_ibi(mi->i3c, &ibi);
+ if (rc == -ENOTSUPP) {
+ /* This driver only supports In-Band Interrupt mode.
+ * Support for Polling Mode could be added if required.
+ * (ENOTSUPP is from the i3c layer, not EOPNOTSUPP).
+ */
+ dev_warn(i3cdev_to_dev(mi->i3c),
+ "Failed, bus driver doesn't support In-Band Interrupts");
+ goto err;
+ } else if (rc < 0) {
+ dev_err(i3cdev_to_dev(mi->i3c),
+ "Failed requesting IBI (%d)\n", rc);
+ goto err;
+ }
+
+ rc = i3c_device_enable_ibi(mi->i3c);
+ if (rc < 0) {
+ /* Assume a driver supporting request_ibi also
+ * supports enable_ibi.
+ */
+ dev_err(i3cdev_to_dev(mi->i3c), "Failed enabling IBI (%d)\n", rc);
+ goto err_free_ibi;
+ }
+
+ return 0;
+
+err_free_ibi:
+ i3c_device_free_ibi(mi->i3c);
+
+err:
+ return rc;
+}
+
+/* Adds a new MCTP i3c_device to a bus */
+static int mctp_i3c_add_device(struct mctp_i3c_bus *mbus,
+ struct i3c_device *i3c)
+__must_hold(&busdevs_lock)
+{
+ struct mctp_i3c_device *mi = NULL;
+ int rc;
+
+ mi = kzalloc(sizeof(*mi), GFP_KERNEL);
+ if (!mi) {
+ rc = -ENOMEM;
+ goto err;
+ }
+ mi->mbus = mbus;
+ mi->i3c = i3c;
+ mutex_init(&mi->lock);
+ list_add(&mi->list, &mbus->devs);
+
+ i3cdev_set_drvdata(i3c, mi);
+ rc = mctp_i3c_setup(mi);
+ if (rc < 0)
+ goto err_free;
+
+ return 0;
+
+err_free:
+ list_del(&mi->list);
+ kfree(mi);
+
+err:
+ dev_warn(i3cdev_to_dev(i3c), "Error adding mctp-i3c device, %d\n", rc);
+ return rc;
+}
+
+static int mctp_i3c_probe(struct i3c_device *i3c)
+{
+ struct mctp_i3c_bus *b = NULL, *mbus = NULL;
+
+ /* Look for a known bus */
+ mutex_lock(&busdevs_lock);
+ list_for_each_entry(b, &busdevs, list)
+ if (b->bus == i3c->bus) {
+ mbus = b;
+ break;
+ }
+ mutex_unlock(&busdevs_lock);
+
+ if (!mbus) {
+ /* probably no "mctp-controller" property on the i3c bus */
+ return -ENODEV;
+ }
+
+ return mctp_i3c_add_device(mbus, i3c);
+}
+
+static void mctp_i3c_remove_device(struct mctp_i3c_device *mi)
+__must_hold(&busdevs_lock)
+{
+ /* Ensure the tx thread isn't using the device */
+ mutex_lock(&mi->lock);
+
+ /* Counterpart of mctp_i3c_setup */
+ i3c_device_disable_ibi(mi->i3c);
+ i3c_device_free_ibi(mi->i3c);
+
+ /* Counterpart of mctp_i3c_add_device */
+ i3cdev_set_drvdata(mi->i3c, NULL);
+ list_del(&mi->list);
+
+ /* Safe to unlock after removing from the list */
+ mutex_unlock(&mi->lock);
+ kfree(mi);
+}
+
+static void mctp_i3c_remove(struct i3c_device *i3c)
+{
+ struct mctp_i3c_device *mi = i3cdev_get_drvdata(i3c);
+
+ /* We my have received a Bus Remove notify prior to device remove,
+ * so mi will already be removed.
+ */
+ if (!mi)
+ return;
+
+ mutex_lock(&busdevs_lock);
+ mctp_i3c_remove_device(mi);
+ mutex_unlock(&busdevs_lock);
+}
+
+/* Returns the device for an address, with mi->lock held */
+static struct mctp_i3c_device *
+mctp_i3c_lookup(struct mctp_i3c_bus *mbus, u64 pid)
+{
+ struct mctp_i3c_device *mi = NULL, *ret = NULL;
+
+ mutex_lock(&busdevs_lock);
+ list_for_each_entry(mi, &mbus->devs, list)
+ if (mi->pid == pid) {
+ ret = mi;
+ mutex_lock(&mi->lock);
+ break;
+ }
+ mutex_unlock(&busdevs_lock);
+ return ret;
+}
+
+static void mctp_i3c_xmit(struct mctp_i3c_bus *mbus, struct sk_buff *skb)
+{
+ struct net_device_stats *stats = &mbus->ndev->stats;
+ struct i3c_priv_xfer xfer = { .rnw = false };
+ struct mctp_i3c_internal_hdr *ihdr = NULL;
+ struct mctp_i3c_device *mi = NULL;
+ unsigned int data_len;
+ u8 *data = NULL;
+ u8 addr, pec;
+ int rc = 0;
+ u64 pid;
+
+ skb_pull(skb, sizeof(struct mctp_i3c_internal_hdr));
+ data_len = skb->len;
+
+ ihdr = (void *)skb_mac_header(skb);
+
+ pid = get_unaligned_be48(ihdr->dest);
+ mi = mctp_i3c_lookup(mbus, pid);
+ if (!mi) {
+ /* I3C endpoint went away after the packet was enqueued? */
+ stats->tx_dropped++;
+ goto out;
+ }
+
+ if (WARN_ON_ONCE(data_len + 1 > MCTP_I3C_MAXBUF))
+ goto out;
+
+ if (data_len + 1 > (unsigned int)mi->mwl) {
+ /* Route MTU was larger than supported by the endpoint */
+ stats->tx_dropped++;
+ goto out;
+ }
+
+ /* Need a linear buffer with space for the PEC */
+ xfer.len = data_len + 1;
+ if (skb_tailroom(skb) >= 1) {
+ skb_put(skb, 1);
+ data = skb->data;
+ } else {
+ /* Otherwise need to copy the buffer */
+ skb_copy_bits(skb, 0, mbus->tx_scratch, skb->len);
+ data = mbus->tx_scratch;
+ }
+
+ /* PEC calculation */
+ addr = mi->addr << 1;
+ pec = i2c_smbus_pec(0, &addr, 1);
+ pec = i2c_smbus_pec(pec, data, data_len);
+ data[data_len] = pec;
+
+ xfer.data.out = data;
+ rc = i3c_device_do_priv_xfers(mi->i3c, &xfer, 1);
+ if (rc == 0) {
+ stats->tx_bytes += data_len;
+ stats->tx_packets++;
+ } else {
+ stats->tx_errors++;
+ }
+
+out:
+ if (mi)
+ mutex_unlock(&mi->lock);
+}
+
+static int mctp_i3c_tx_thread(void *data)
+{
+ struct mctp_i3c_bus *mbus = data;
+ struct sk_buff *skb;
+
+ for (;;) {
+ if (kthread_should_stop())
+ break;
+
+ spin_lock_bh(&mbus->tx_lock);
+ skb = mbus->tx_skb;
+ mbus->tx_skb = NULL;
+ spin_unlock_bh(&mbus->tx_lock);
+
+ if (netif_queue_stopped(mbus->ndev))
+ netif_wake_queue(mbus->ndev);
+
+ if (skb) {
+ mctp_i3c_xmit(mbus, skb);
+ kfree_skb(skb);
+ } else {
+ wait_event_idle(mbus->tx_wq,
+ mbus->tx_skb || kthread_should_stop());
+ }
+ }
+
+ return 0;
+}
+
+static netdev_tx_t mctp_i3c_start_xmit(struct sk_buff *skb,
+ struct net_device *ndev)
+{
+ struct mctp_i3c_bus *mbus = netdev_priv(ndev);
+ netdev_tx_t ret;
+
+ spin_lock(&mbus->tx_lock);
+ netif_stop_queue(ndev);
+ if (mbus->tx_skb) {
+ dev_warn_ratelimited(&ndev->dev, "TX with queue stopped");
+ ret = NETDEV_TX_BUSY;
+ } else {
+ mbus->tx_skb = skb;
+ ret = NETDEV_TX_OK;
+ }
+ spin_unlock(&mbus->tx_lock);
+
+ if (ret == NETDEV_TX_OK)
+ wake_up(&mbus->tx_wq);
+
+ return ret;
+}
+
+static void mctp_i3c_bus_free(struct mctp_i3c_bus *mbus)
+__must_hold(&busdevs_lock)
+{
+ struct mctp_i3c_device *mi = NULL, *tmp = NULL;
+
+ if (mbus->tx_thread) {
+ kthread_stop(mbus->tx_thread);
+ mbus->tx_thread = NULL;
+ }
+
+ /* Remove any child devices */
+ list_for_each_entry_safe(mi, tmp, &mbus->devs, list) {
+ mctp_i3c_remove_device(mi);
+ }
+
+ kfree_skb(mbus->tx_skb);
+ list_del(&mbus->list);
+}
+
+static void mctp_i3c_ndo_uninit(struct net_device *ndev)
+{
+ struct mctp_i3c_bus *mbus = netdev_priv(ndev);
+
+ /* Perform cleanup here to ensure there are no remaining references */
+ mctp_i3c_bus_free(mbus);
+}
+
+static int mctp_i3c_header_create(struct sk_buff *skb, struct net_device *dev,
+ unsigned short type, const void *daddr,
+ const void *saddr, unsigned int len)
+{
+ struct mctp_i3c_internal_hdr *ihdr;
+
+ skb_push(skb, sizeof(struct mctp_i3c_internal_hdr));
+ skb_reset_mac_header(skb);
+ ihdr = (void *)skb_mac_header(skb);
+ memcpy(ihdr->dest, daddr, PID_SIZE);
+ memcpy(ihdr->source, saddr, PID_SIZE);
+ return 0;
+}
+
+static const struct net_device_ops mctp_i3c_ops = {
+ .ndo_start_xmit = mctp_i3c_start_xmit,
+ .ndo_uninit = mctp_i3c_ndo_uninit,
+};
+
+static const struct header_ops mctp_i3c_headops = {
+ .create = mctp_i3c_header_create,
+};
+
+static void mctp_i3c_net_setup(struct net_device *dev)
+{
+ dev->type = ARPHRD_MCTP;
+
+ dev->mtu = MCTP_I3C_MAXMTU;
+ dev->min_mtu = MCTP_I3C_MINMTU;
+ dev->max_mtu = MCTP_I3C_MAXMTU;
+ dev->tx_queue_len = MCTP_I3C_TX_QUEUE_LEN;
+
+ dev->hard_header_len = sizeof(struct mctp_i3c_internal_hdr);
+ dev->addr_len = PID_SIZE;
+
+ dev->netdev_ops = &mctp_i3c_ops;
+ dev->header_ops = &mctp_i3c_headops;
+}
+
+static bool mctp_i3c_is_mctp_controller(struct i3c_bus *bus)
+{
+ struct i3c_dev_desc *master = bus->cur_master;
+
+ if (!master)
+ return false;
+
+ return of_property_read_bool(master->common.master->dev.of_node,
+ MCTP_I3C_OF_PROP);
+}
+
+/* Returns the Provisioned Id of a local bus master */
+static int mctp_i3c_bus_local_pid(struct i3c_bus *bus, u64 *ret_pid)
+{
+ struct i3c_dev_desc *master;
+
+ master = bus->cur_master;
+ if (WARN_ON_ONCE(!master))
+ return -ENOENT;
+ *ret_pid = master->info.pid;
+
+ return 0;
+}
+
+/* Returns an ERR_PTR on failure */
+static struct mctp_i3c_bus *mctp_i3c_bus_add(struct i3c_bus *bus)
+__must_hold(&busdevs_lock)
+{
+ struct mctp_i3c_bus *mbus = NULL;
+ struct net_device *ndev = NULL;
+ char namebuf[IFNAMSIZ];
+ u8 addr[PID_SIZE];
+ int rc;
+
+ if (!mctp_i3c_is_mctp_controller(bus))
+ return ERR_PTR(-ENOENT);
+
+ snprintf(namebuf, sizeof(namebuf), "mctpi3c%d", bus->id);
+ ndev = alloc_netdev(sizeof(*mbus), namebuf, NET_NAME_ENUM,
+ mctp_i3c_net_setup);
+ if (!ndev) {
+ rc = -ENOMEM;
+ goto err;
+ }
+
+ mbus = netdev_priv(ndev);
+ mbus->ndev = ndev;
+ mbus->bus = bus;
+ INIT_LIST_HEAD(&mbus->devs);
+ list_add(&mbus->list, &busdevs);
+
+ rc = mctp_i3c_bus_local_pid(bus, &mbus->pid);
+ if (rc < 0) {
+ dev_err(&ndev->dev, "No I3C PID available\n");
+ goto err_free_uninit;
+ }
+ put_unaligned_be48(mbus->pid, addr);
+ dev_addr_set(ndev, addr);
+
+ init_waitqueue_head(&mbus->tx_wq);
+ spin_lock_init(&mbus->tx_lock);
+ mbus->tx_thread = kthread_run(mctp_i3c_tx_thread, mbus,
+ "%s/tx", ndev->name);
+ if (IS_ERR(mbus->tx_thread)) {
+ dev_warn(&ndev->dev, "Error creating thread: %pe\n",
+ mbus->tx_thread);
+ rc = PTR_ERR(mbus->tx_thread);
+ mbus->tx_thread = NULL;
+ goto err_free_uninit;
+ }
+
+ rc = mctp_register_netdev(ndev, NULL);
+ if (rc < 0) {
+ dev_warn(&ndev->dev, "netdev register failed: %d\n", rc);
+ goto err_free_netdev;
+ }
+ return mbus;
+
+err_free_uninit:
+ /* uninit will not get called if a netdev has not been registered,
+ * so we perform the same mbus cleanup manually.
+ */
+ mctp_i3c_bus_free(mbus);
+
+err_free_netdev:
+ free_netdev(ndev);
+
+err:
+ return ERR_PTR(rc);
+}
+
+static void mctp_i3c_bus_remove(struct mctp_i3c_bus *mbus)
+__must_hold(&busdevs_lock)
+{
+ /* Unregister calls through to ndo_uninit -> mctp_i3c_bus_free() */
+ mctp_unregister_netdev(mbus->ndev);
+
+ free_netdev(mbus->ndev);
+ /* mbus is deallocated */
+}
+
+/* Removes all mctp-i3c busses */
+static void mctp_i3c_bus_remove_all(void)
+{
+ struct mctp_i3c_bus *mbus = NULL, *tmp = NULL;
+
+ mutex_lock(&busdevs_lock);
+ list_for_each_entry_safe(mbus, tmp, &busdevs, list) {
+ mctp_i3c_bus_remove(mbus);
+ }
+ mutex_unlock(&busdevs_lock);
+}
+
+/* Adds a i3c_bus if it isn't already in the busdevs list.
+ * Suitable as an i3c_for_each_bus_locked callback.
+ */
+static int mctp_i3c_bus_add_new(struct i3c_bus *bus, void *data)
+{
+ struct mctp_i3c_bus *mbus = NULL, *tmp = NULL;
+ bool exists = false;
+
+ mutex_lock(&busdevs_lock);
+ list_for_each_entry_safe(mbus, tmp, &busdevs, list)
+ if (mbus->bus == bus)
+ exists = true;
+
+ /* It is OK for a bus to already exist. That can occur due to
+ * the race in mod_init between notifier and for_each_bus
+ */
+ if (!exists)
+ mctp_i3c_bus_add(bus);
+ mutex_unlock(&busdevs_lock);
+ return 0;
+}
+
+static void mctp_i3c_notify_bus_remove(struct i3c_bus *bus)
+{
+ struct mctp_i3c_bus *mbus = NULL, *tmp;
+
+ mutex_lock(&busdevs_lock);
+ list_for_each_entry_safe(mbus, tmp, &busdevs, list)
+ if (mbus->bus == bus)
+ mctp_i3c_bus_remove(mbus);
+ mutex_unlock(&busdevs_lock);
+}
+
+static int mctp_i3c_notifier_call(struct notifier_block *nb,
+ unsigned long action, void *data)
+{
+ switch (action) {
+ case I3C_NOTIFY_BUS_ADD:
+ mctp_i3c_bus_add_new((struct i3c_bus *)data, NULL);
+ break;
+ case I3C_NOTIFY_BUS_REMOVE:
+ mctp_i3c_notify_bus_remove((struct i3c_bus *)data);
+ break;
+ }
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block mctp_i3c_notifier = {
+ .notifier_call = mctp_i3c_notifier_call,
+};
+
+static const struct i3c_device_id mctp_i3c_ids[] = {
+ I3C_CLASS(I3C_DCR_MCTP, NULL),
+ { 0 },
+};
+
+static struct i3c_driver mctp_i3c_driver = {
+ .driver = {
+ .name = "mctp-i3c",
+ },
+ .probe = mctp_i3c_probe,
+ .remove = mctp_i3c_remove,
+ .id_table = mctp_i3c_ids,
+};
+
+static __init int mctp_i3c_mod_init(void)
+{
+ int rc;
+
+ rc = i3c_register_notifier(&mctp_i3c_notifier);
+ if (rc < 0) {
+ i3c_driver_unregister(&mctp_i3c_driver);
+ return rc;
+ }
+
+ i3c_for_each_bus_locked(mctp_i3c_bus_add_new, NULL);
+
+ rc = i3c_driver_register(&mctp_i3c_driver);
+ if (rc < 0)
+ return rc;
+
+ return 0;
+}
+
+static __exit void mctp_i3c_mod_exit(void)
+{
+ int rc;
+
+ i3c_driver_unregister(&mctp_i3c_driver);
+
+ rc = i3c_unregister_notifier(&mctp_i3c_notifier);
+ if (rc < 0)
+ pr_warn("MCTP I3C could not unregister notifier, %d\n", rc);
+
+ mctp_i3c_bus_remove_all();
+}
+
+module_init(mctp_i3c_mod_init);
+module_exit(mctp_i3c_mod_exit);
+
+MODULE_DEVICE_TABLE(i3c, mctp_i3c_ids);
+MODULE_DESCRIPTION("MCTP I3C device");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Matt Johnston <matt@codeconstruct.com.au>");