@@ -8961,6 +8961,13 @@ L: linux-acpi@vger.kernel.org
S: Maintained
F: drivers/i2c/i2c-core-acpi.c
+I2C ADDRESS TRANSLATOR (ATR)
+M: Luca Ceresoli <luca@lucaceresoli.net>
+L: linux-i2c@vger.kernel.org
+S: Maintained
+F: drivers/i2c/i2c-atr.c
+F: include/linux/i2c-atr.h
+
I2C CONTROLLER DRIVER FOR NVIDIA GPU
M: Ajay Gupta <ajayg@nvidia.com>
L: linux-i2c@vger.kernel.org
@@ -71,6 +71,15 @@ config I2C_MUX
source "drivers/i2c/muxes/Kconfig"
+config I2C_ATR
+ tristate "I2C Address Translator (ATR) support"
+ help
+ Enable support for I2C Address Translator (ATR) chips.
+
+ An ATR allows accessing multiple I2C busses from a single
+ physical bus via address translation instead of bus selection as
+ i2c-muxes do.
+
config I2C_HELPER_AUTO
bool "Autoselect pertinent helper modules"
default y
@@ -13,6 +13,7 @@ i2c-core-$(CONFIG_OF) += i2c-core-of.o
obj-$(CONFIG_I2C_SMBUS) += i2c-smbus.o
obj-$(CONFIG_I2C_CHARDEV) += i2c-dev.o
obj-$(CONFIG_I2C_MUX) += i2c-mux.o
+obj-$(CONFIG_I2C_ATR) += i2c-atr.o
obj-y += algos/ busses/ muxes/
obj-$(CONFIG_I2C_STUB) += i2c-stub.o
obj-$(CONFIG_I2C_SLAVE_EEPROM) += i2c-slave-eeprom.o
new file mode 100644
@@ -0,0 +1,557 @@
+// SPDX-License-Identifier: GPL-2.0
+/**
+ * I2C Address Translator
+ *
+ * Copyright (c) 2019 Luca Ceresoli <luca@lucaceresoli.net>
+ *
+ * An I2C Address Translator (ATR) is a device with an I2C slave parent
+ * ("upstream") port and N I2C master child ("downstream") ports, and
+ * forwards transactions from upstream to the appropriate downstream port
+ * with a modified slave address. The address used on the parent bus is
+ * called the "alias" and is (potentially) different from the physical
+ * slave address of the child bus. Address translation is done by the
+ * hardware.
+ *
+ * An ATR looks similar to an i2c-mux except:
+ * - the address on the parent and child busses can be different
+ * - there is normally no need to select the child port; the alias used on
+ * the parent bus implies it
+ *
+ * The ATR functionality can be provided by a chip with many other
+ * features. This file provides a helper to implement an ATR within your
+ * driver.
+ *
+ * The ATR creates a new I2C "child" adapter on each child bus. Adding
+ * devices on the child bus ends up in invoking the driver code to select
+ * an available alias. Maintaining an appropriate pool of available aliases
+ * and picking one for each new device is up to the driver implementer. The
+ * ATR maintains an table of currently assigned alias and uses it to modify
+ * all I2C transactions directed to devices on the child buses.
+ *
+ * A typical example follows.
+ *
+ * Topology:
+ *
+ * Slave X @ 0x10
+ * .-----. |
+ * .-----. | |---+---- B
+ * | CPU |--A--| ATR |
+ * `-----' | |---+---- C
+ * `-----' |
+ * Slave Y @ 0x10
+ *
+ * Alias table:
+ *
+ * Client Alias
+ * -------------
+ * X 0x20
+ * Y 0x30
+ *
+ * Transaction:
+ *
+ * - Slave X driver sends a transaction (on adapter B), slave address 0x10
+ * - ATR driver rewrites messages with address 0x20, forwards to adapter A
+ * - Physical I2C transaction on bus A, slave address 0x20
+ * - ATR chip propagates transaction on bus B with address translated to 0x10
+ * - Slave X chip replies on bus B
+ * - ATR chip forwards reply on bus A
+ * - ATR driver rewrites messages with address 0x10
+ * - Slave X driver gets back the msgs[], with reply and address 0x10
+ *
+ * Usage:
+ *
+ * 1. In your driver (typically in the probe function) add an ATR by
+ * calling i2c_atr_new() passing your attach/detach callbacks
+ * 2. When the attach callback is called pick an appropriate alias,
+ * configure it in your chip and return the chosen alias in the
+ * alias_id parameter
+ * 3. When the detach callback is called, deconfigure the alias from
+ * your chip and put it back in the pool for later usage
+ *
+ * Originally based on i2c-mux.c
+ */
+
+#include <linux/i2c.h>
+#include <linux/i2c-atr.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/slab.h>
+
+/**
+ * struct i2c_atr_cli2alias_pair - Hold the alias assigned to a client.
+ * @node: List node
+ * @client: Pointer to the client on the child bus
+ * @alias: I2C alias address assigned by the driver.
+ * This is the address that will be used to issue I2C transactions
+ * on the parent (physical) bus.
+ */
+struct i2c_atr_cli2alias_pair {
+ struct list_head node;
+ const struct i2c_client *client;
+ u16 alias;
+};
+
+/*
+ * Data for each channel (child bus)
+ */
+struct i2c_atr_chan {
+ struct i2c_adapter adap;
+ struct i2c_atr *atr;
+ u32 chan_id;
+
+ struct list_head alias_list;
+
+ u16 *orig_addrs;
+ unsigned int orig_addrs_size;
+ struct mutex orig_addrs_lock; /* Lock orig_addrs during xfer */
+};
+
+static struct i2c_atr_cli2alias_pair *
+i2c_atr_find_mapping_by_client(const struct list_head *list,
+ const struct i2c_client *client)
+{
+ struct i2c_atr_cli2alias_pair *c2a;
+
+ list_for_each_entry(c2a, list, node) {
+ if (c2a->client == client)
+ return c2a;
+ }
+
+ return NULL;
+}
+
+static struct i2c_atr_cli2alias_pair *
+i2c_atr_find_mapping_by_addr(const struct list_head *list,
+ u16 phys_addr)
+{
+ struct i2c_atr_cli2alias_pair *c2a;
+
+ list_for_each_entry(c2a, list, node) {
+ if (c2a->client->addr == phys_addr)
+ return c2a;
+ }
+
+ return NULL;
+}
+
+/*
+ * Replace all message addresses with their aliases, saving the original
+ * addresses.
+ *
+ * This function is internal for use in i2c_atr_master_xfer(). It must be
+ * followed by i2c_atr_unmap_msgs() to restore the original addresses.
+ */
+static int i2c_atr_map_msgs(struct i2c_atr_chan *chan,
+ struct i2c_msg msgs[], int num)
+
+{
+ struct i2c_atr *atr = chan->atr;
+ static struct i2c_atr_cli2alias_pair *c2a;
+ int i;
+
+ /* Ensure we have enough room to save the original addresses */
+ if (unlikely(chan->orig_addrs_size < num)) {
+ void *new_buf = kmalloc(num * sizeof(chan->orig_addrs[0]),
+ GFP_KERNEL);
+ if (new_buf == NULL)
+ return -ENOMEM;
+
+ kfree(chan->orig_addrs);
+ chan->orig_addrs = new_buf;
+ chan->orig_addrs_size = num;
+ }
+
+ for (i = 0; i < num; i++) {
+ chan->orig_addrs[i] = msgs[i].addr;
+
+ c2a = i2c_atr_find_mapping_by_addr(&chan->alias_list,
+ msgs[i].addr);
+ if (c2a) {
+ msgs[i].addr = c2a->alias;
+ } else {
+ dev_err(atr->dev, "client 0x%02x not mapped!\n",
+ msgs[i].addr);
+ return -ENXIO;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Restore all message address aliases with the original addresses.
+ *
+ * This function is internal for use in i2c_atr_master_xfer().
+ *
+ * @see i2c_atr_map_msgs()
+ */
+static void i2c_atr_unmap_msgs(struct i2c_atr_chan *chan,
+ struct i2c_msg msgs[], int num)
+{
+ int i;
+
+ for (i = 0; i < num; i++)
+ msgs[i].addr = chan->orig_addrs[i];
+}
+
+static int i2c_atr_master_xfer(struct i2c_adapter *adap,
+ struct i2c_msg msgs[], int num)
+{
+ struct i2c_atr_chan *chan = adap->algo_data;
+ struct i2c_atr *atr = chan->atr;
+ struct i2c_adapter *parent = atr->parent;
+ int ret = 0;
+
+ /* Switch to the right atr port */
+ if (atr->ops->select) {
+ ret = atr->ops->select(atr, chan->chan_id);
+ if (ret < 0)
+ goto out;
+ }
+
+ /* Translate addresses */
+ mutex_lock(&chan->orig_addrs_lock);
+ ret = i2c_atr_map_msgs(chan, msgs, num);
+ if (ret < 0) {
+ mutex_unlock(&chan->orig_addrs_lock);
+ goto out;
+ }
+
+ /* Perform the transfer */
+ ret = i2c_transfer(parent, msgs, num);
+
+ /* Restore addresses */
+ i2c_atr_unmap_msgs(chan, msgs, num);
+ mutex_unlock(&chan->orig_addrs_lock);
+
+out:
+ if (atr->ops->deselect)
+ atr->ops->deselect(atr, chan->chan_id);
+
+ return ret;
+}
+
+static int i2c_atr_smbus_xfer(struct i2c_adapter *adap,
+ u16 addr, unsigned short flags,
+ char read_write, u8 command,
+ int size, union i2c_smbus_data *data)
+{
+ struct i2c_atr_chan *chan = adap->algo_data;
+ struct i2c_atr *atr = chan->atr;
+ struct i2c_adapter *parent = atr->parent;
+ struct i2c_atr_cli2alias_pair *c2a;
+ int err = 0;
+
+ c2a = i2c_atr_find_mapping_by_addr(&chan->alias_list, addr);
+ if (!c2a) {
+ dev_err(atr->dev, "client 0x%02x not mapped!\n", addr);
+ return -ENXIO;
+ }
+
+ if (atr->ops->select)
+ err = atr->ops->select(atr, chan->chan_id);
+ if (!err)
+ err = i2c_smbus_xfer(parent, c2a->alias, flags,
+ read_write, command, size, data);
+ if (atr->ops->deselect)
+ atr->ops->deselect(atr, chan->chan_id);
+
+ return err;
+}
+
+static u32 i2c_atr_functionality(struct i2c_adapter *adap)
+{
+ struct i2c_atr_chan *chan = adap->algo_data;
+ struct i2c_adapter *parent = chan->atr->parent;
+
+ return parent->algo->functionality(parent);
+}
+
+static void i2c_atr_lock_bus(struct i2c_adapter *adapter, unsigned int flags)
+{
+ struct i2c_atr_chan *chan = adapter->algo_data;
+ struct i2c_atr *atr = chan->atr;
+
+ mutex_lock(&atr->lock);
+}
+
+static int i2c_atr_trylock_bus(struct i2c_adapter *adapter, unsigned int flags)
+{
+ struct i2c_atr_chan *chan = adapter->algo_data;
+ struct i2c_atr *atr = chan->atr;
+
+ return mutex_trylock(&atr->lock);
+}
+
+static void i2c_atr_unlock_bus(struct i2c_adapter *adapter, unsigned int flags)
+{
+ struct i2c_atr_chan *chan = adapter->algo_data;
+ struct i2c_atr *atr = chan->atr;
+
+ mutex_unlock(&atr->lock);
+}
+
+static const struct i2c_lock_operations i2c_atr_lock_ops = {
+ .lock_bus = i2c_atr_lock_bus,
+ .trylock_bus = i2c_atr_trylock_bus,
+ .unlock_bus = i2c_atr_unlock_bus,
+};
+
+static int i2c_atr_attach_client(struct i2c_adapter *adapter,
+ const struct i2c_board_info *info,
+ const struct i2c_client *client)
+{
+ struct i2c_atr_chan *chan = adapter->algo_data;
+ struct i2c_atr *atr = chan->atr;
+ struct i2c_atr_cli2alias_pair *c2a;
+ u16 alias_id = 0;
+ int err = 0;
+
+ c2a = kzalloc(sizeof(struct i2c_atr_cli2alias_pair), GFP_KERNEL);
+ if (!c2a) {
+ err = -ENOMEM;
+ goto err_alloc;
+ }
+
+ err = atr->ops->attach_client(atr, chan->chan_id, info, client,
+ &alias_id);
+ if (err)
+ goto err_attach;
+ if (alias_id == 0) {
+ err = -EINVAL;
+ goto err_attach;
+ }
+
+ c2a->client = client;
+ c2a->alias = alias_id;
+ list_add(&c2a->node, &chan->alias_list);
+
+ return 0;
+
+err_attach:
+ kfree(c2a);
+err_alloc:
+ return err;
+}
+
+static void i2c_atr_detach_client(struct i2c_adapter *adapter,
+ const struct i2c_client *client)
+{
+ struct i2c_atr_chan *chan = adapter->algo_data;
+ struct i2c_atr *atr = chan->atr;
+ struct i2c_atr_cli2alias_pair *c2a;
+
+ atr->ops->detach_client(atr, chan->chan_id, client);
+
+ c2a = i2c_atr_find_mapping_by_client(&chan->alias_list, client);
+ if (c2a != NULL) {
+ list_del(&c2a->node);
+ kfree(c2a);
+ }
+}
+
+static const struct i2c_attach_operations i2c_atr_attach_ops = {
+ .attach_client = i2c_atr_attach_client,
+ .detach_client = i2c_atr_detach_client,
+};
+
+/**
+ * i2c_atr_add_adapter - Create a child ("downstream") I2C bus.
+ * @atr: The I2C ATR
+ * @chan_id: Index of the new adapter (0 .. max_adapters-1). This value is
+ * passed to the callbacks in `struct i2c_atr_ops`.
+ *
+ * After calling this function a new i2c bus will appear. Adding and
+ * removing devices on the downstream bus will result in calls to the
+ * `attach_client` and `detach_client` callbacks for the driver to assign
+ * an alias to the device.
+ *
+ * If there is a device tree node under "i2c-atr" whose "reg" property
+ * equals chan_id, the new adapter will receive that node and perhaps start
+ * adding devices under it. The callbacks for those additions will be made
+ * before i2c_atr_add_adapter() returns.
+ *
+ * Call i2c_atr_del_adapter() to remove the adapter.
+ *
+ * Return: 0 on success, a negative error code otherwise.
+ */
+int i2c_atr_add_adapter(struct i2c_atr *atr, u32 chan_id)
+{
+ struct i2c_adapter *parent = atr->parent;
+ struct device *dev = atr->dev;
+ struct i2c_atr_chan *chan;
+ char symlink_name[20];
+ int err;
+
+ if (chan_id >= atr->max_adapters)
+ return -EINVAL;
+
+ if (atr->adapter[chan_id]) {
+ dev_err(dev, "Adapter %d already present\n", chan_id);
+ return -EEXIST;
+ }
+
+ chan = kzalloc(sizeof(*chan), GFP_KERNEL);
+ if (!chan)
+ return -ENOMEM;
+
+ chan->atr = atr;
+ chan->chan_id = chan_id;
+ INIT_LIST_HEAD(&chan->alias_list);
+ mutex_init(&chan->orig_addrs_lock);
+
+ snprintf(chan->adap.name, sizeof(chan->adap.name),
+ "i2c-%d-atr-%d", i2c_adapter_id(parent), chan_id);
+ chan->adap.owner = THIS_MODULE;
+ chan->adap.algo = &atr->algo;
+ chan->adap.algo_data = chan;
+ chan->adap.dev.parent = dev;
+ chan->adap.retries = parent->retries;
+ chan->adap.timeout = parent->timeout;
+ chan->adap.quirks = parent->quirks;
+ chan->adap.lock_ops = &i2c_atr_lock_ops;
+ chan->adap.attach_ops = &i2c_atr_attach_ops;
+
+ if (dev->of_node) {
+ struct device_node *atr_node;
+ struct device_node *child;
+ u32 reg;
+
+ atr_node = of_get_child_by_name(dev->of_node, "i2c-atr");
+
+ for_each_child_of_node(atr_node, child) {
+ err = of_property_read_u32(child, "reg", ®);
+ if (err)
+ continue;
+ if (chan_id == reg)
+ break;
+ }
+
+ chan->adap.dev.of_node = child;
+ of_node_put(atr_node);
+ }
+
+ err = i2c_add_adapter(&chan->adap);
+ if (err) {
+ dev_err(dev, "failed to add atr-adapter %u (error=%d)\n",
+ chan_id, err);
+ goto err_add_adapter;
+ }
+
+ WARN(sysfs_create_link(&chan->adap.dev.kobj, &dev->kobj, "atr_device"),
+ "can't create symlink to atr device\n");
+ snprintf(symlink_name, sizeof(symlink_name), "channel-%u", chan_id);
+ WARN(sysfs_create_link(&dev->kobj, &chan->adap.dev.kobj, symlink_name),
+ "can't create symlink for channel %u\n", chan_id);
+
+ dev_info(dev, "Added ATR child bus %d\n", i2c_adapter_id(&chan->adap));
+
+ atr->adapter[chan_id] = &chan->adap;
+ return 0;
+
+err_add_adapter:
+ mutex_destroy(&chan->orig_addrs_lock);
+ kfree(chan);
+ return err;
+}
+EXPORT_SYMBOL_GPL(i2c_atr_add_adapter);
+
+/**
+ * i2c_atr_del_adapter - Remove a child ("downstream") I2C bus added by
+ * i2c_atr_del_adapter().
+ * @atr: The I2C ATR
+ * @chan_id: Index of the `adapter to be removed (0 .. max_adapters-1)
+ */
+void i2c_atr_del_adapter(struct i2c_atr *atr, u32 chan_id)
+{
+ char symlink_name[20];
+
+ struct i2c_adapter *adap = atr->adapter[chan_id];
+ struct i2c_atr_chan *chan = adap->algo_data;
+ struct device_node *np = adap->dev.of_node;
+ struct device *dev = atr->dev;
+
+ if (atr->adapter[chan_id] == NULL) {
+ dev_err(dev, "Adapter %d does not exist\n", chan_id);
+ return;
+ }
+
+ dev_info(dev, "Removing ATR child bus %d\n", i2c_adapter_id(adap));
+
+ atr->adapter[chan_id] = NULL;
+
+ snprintf(symlink_name, sizeof(symlink_name),
+ "channel-%u", chan->chan_id);
+ sysfs_remove_link(&dev->kobj, symlink_name);
+ sysfs_remove_link(&chan->adap.dev.kobj, "atr_device");
+
+ i2c_del_adapter(adap);
+ of_node_put(np);
+ mutex_destroy(&chan->orig_addrs_lock);
+ kfree(chan);
+}
+EXPORT_SYMBOL_GPL(i2c_atr_del_adapter);
+
+/**
+ * i2c_atr_new() - Allocate and initialize an I2C ATR helper.
+ * @parent: The parent (upstream) adapter
+ * @dev: The device acting as an ATR
+ * @ops: Driver-specific callbacks
+ * @max_adapters: Maximum number of child adapters
+ *
+ * The new ATR helper is connected to the parent adapter but has no child
+ * adapters. Call i2c_atr_add_adapter() to add some.
+ *
+ * Call i2c_atr_delete() to remove.
+ *
+ * Return: pointer to the new ATR helper object, or ERR_PTR
+ */
+struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
+ const struct i2c_atr_ops *ops, int max_adapters)
+{
+ struct i2c_atr *atr;
+
+ if (!ops || !ops->attach_client || !ops->detach_client)
+ return ERR_PTR(-EINVAL);
+
+ atr = devm_kzalloc(dev, sizeof(*atr)
+ + max_adapters * sizeof(atr->adapter[0]),
+ GFP_KERNEL);
+ if (!atr)
+ return ERR_PTR(-ENOMEM);
+
+ mutex_init(&atr->lock);
+
+ atr->parent = parent;
+ atr->dev = dev;
+ atr->ops = ops;
+ atr->max_adapters = max_adapters;
+
+ if (parent->algo->master_xfer)
+ atr->algo.master_xfer = i2c_atr_master_xfer;
+ if (parent->algo->smbus_xfer)
+ atr->algo.smbus_xfer = i2c_atr_smbus_xfer;
+ atr->algo.functionality = i2c_atr_functionality;
+
+ return atr;
+}
+EXPORT_SYMBOL_GPL(i2c_atr_new);
+
+/**
+ * i2c_atr_delete - Delete an I2C ATR helper.
+ * @atr: I2C ATR helper to be deleted.
+ *
+ * Precondition: all the adapters added with i2c_atr_add_adapter() mumst be
+ * removed by calling i2c_atr_del_adapter().
+ */
+void i2c_atr_delete(struct i2c_atr *atr)
+{
+ mutex_destroy(&atr->lock);
+}
+EXPORT_SYMBOL_GPL(i2c_atr_delete);
+
+MODULE_AUTHOR("Luca Ceresoli <luca@lucaceresoli.net>");
+MODULE_DESCRIPTION("I2C Address Translator");
+MODULE_LICENSE("GPL v2");
new file mode 100644
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/**
+ * drivers/i2c/i2c-atr.h -- I2C Address Translator
+ *
+ * Copyright (c) 2019 Luca Ceresoli <luca@lucaceresoli.net>
+ *
+ * Based on i2c-mux.h
+ */
+
+#ifndef _LINUX_I2C_ATR_H
+#define _LINUX_I2C_ATR_H
+
+#ifdef __KERNEL__
+
+#include <linux/i2c.h>
+#include <linux/mutex.h>
+
+struct i2c_atr;
+
+/**
+ * struct i2c_atr_ops - Callbacks from ATR to the device driver.
+ * @select: Ask the driver to select a child bus (optional)
+ * @deselect: Ask the driver to deselect a child bus (optional)
+ * @attach_client: Notify the driver of a new device connected on a child
+ * bus. The driver must choose an I2C alias, configure the
+ * hardware to use it and return it in `alias_id`.
+ * @detach_client: Notify the driver of a device getting disconnected. The
+ * driver must configure the hardware to stop using the
+ * alias.
+ *
+ * All these functions return 0 on success, a negative error code otherwise.
+ */
+struct i2c_atr_ops {
+ int (*select)(struct i2c_atr *atr, u32 chan_id);
+ int (*deselect)(struct i2c_atr *atr, u32 chan_id);
+ int (*attach_client)(struct i2c_atr *atr, u32 chan_id,
+ const struct i2c_board_info *info,
+ const struct i2c_client *client,
+ u16 *alias_id);
+ void (*detach_client)(struct i2c_atr *atr, u32 chan_id,
+ const struct i2c_client *client);
+};
+
+/**
+ * Helper to add I2C ATR features to a device driver.
+ */
+struct i2c_atr {
+ /* private: internal use only */
+
+ struct i2c_adapter *parent;
+ struct device *dev;
+ const struct i2c_atr_ops *ops;
+
+ void *priv;
+
+ struct i2c_algorithm algo;
+ struct mutex lock;
+ int max_adapters;
+
+ struct i2c_adapter *adapter[0];
+};
+
+struct i2c_atr *i2c_atr_new(struct i2c_adapter *parent, struct device *dev,
+ const struct i2c_atr_ops *ops, int max_adapters);
+void i2c_atr_delete(struct i2c_atr *atr);
+
+static inline void i2c_atr_set_clientdata(struct i2c_atr *atr, void *data)
+{
+ atr->priv = data;
+}
+
+static inline void *i2c_atr_get_clientdata(struct i2c_atr *atr)
+{
+ return atr->priv;
+}
+
+int i2c_atr_add_adapter(struct i2c_atr *atr, u32 chan_id);
+void i2c_atr_del_adapter(struct i2c_atr *atr, u32 chan_id);
+
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_I2C_ATR_H */
An ATR is a device that looks similar to an i2c-mux: it has an I2C slave "upstream" port and N master "downstream" ports, and forwards transactions from upstream to the appropriate downstream port. But is is different in that the forwarded transaction has a different slave address. The address used on the upstream bus is called the "alias" and is (potentially) different from the physical slave address of the downstream chip. Add a helper file (just like i2c-mux.c for a mux or switch) to allow implementing ATR features in a device driver. The helper takes care or adapter creation/destruction and translates addresses at each transaction. Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net> --- Changes RFCv2 -> v3: - fix const-related warnings Changes RFCv1 -> RFCv2: RFCv1 was implemented inside i2c-mux.c and added yet more complexity there. RFCv2 creates a new file on its own, i2c-atr.c. Since many ATR features are not in a MUX and vice versa, the overlapping is low. This was almost a complete rewrite, but for the records here are the main differences from the old implementation: - change bus description - remove I2C_ATR_ARBITRATOR and I2C_ATR_GATE support - select() optional - rename i2c_atr_alloc -> i2c_atr_new, add i2c_atr_delete, move to bottom - lock the ATR, not the adapter or the muxes on the adapter - remove parent-locked code - remove I2C_MUX_LOCKED flag, now unused - remove I2C_ATR_ATR flag (always true) - translation in i2c_atr_smbus_xfer too - i2c_atr_map_msgs: don't ignore mapping errors - always require the "i2c-atr" DT node, no magic - remove ACPI support - one algo in the atrc, not one per adapter - remove unneeded i2c_atr_root_adapter - ditch force_nr - don't allocate private user memory, just provide a plain userdata pointer - consolidate all ops in a single struct, simplify naming - remove adapters individually, allocate in atrc->adapter[chan_id] --- MAINTAINERS | 7 + drivers/i2c/Kconfig | 9 + drivers/i2c/Makefile | 1 + drivers/i2c/i2c-atr.c | 557 ++++++++++++++++++++++++++++++++++++++++ include/linux/i2c-atr.h | 82 ++++++ 5 files changed, 656 insertions(+) create mode 100644 drivers/i2c/i2c-atr.c create mode 100644 include/linux/i2c-atr.h