Backend that the hosts can enumerate by using the SMBus Address Resolution Protocol. Signed-off-by: Heikki Krogerus --- drivers/i2c/Kconfig | 6 ++ drivers/i2c/Makefile | 1 + drivers/i2c/i2c-target-arp.c | 201 +++++++++++++++++++++++++++++++++++ 3 files changed, 208 insertions(+) create mode 100644 drivers/i2c/i2c-target-arp.c diff --git a/drivers/i2c/Kconfig b/drivers/i2c/Kconfig index c232054fddd6..4b97a66fc698 100644 --- a/drivers/i2c/Kconfig +++ b/drivers/i2c/Kconfig @@ -134,6 +134,12 @@ config I2C_SLAVE_TESTUNIT multi-master, SMBus Host Notify, etc. Please read Documentation/i2c/slave-testunit-backend.rst for further details. +config I2C_TARGET_ARP + tristate "SMBus ARP target mode test driver" + help + This backend makes Linux respond to SMBus Address Resolution Protocol + commands. + endif config I2C_DEBUG_CORE diff --git a/drivers/i2c/Makefile b/drivers/i2c/Makefile index 4fdb37b94aa4..3ea292dab065 100644 --- a/drivers/i2c/Makefile +++ b/drivers/i2c/Makefile @@ -19,5 +19,6 @@ obj-y += algos/ busses/ muxes/ obj-$(CONFIG_I2C_STUB) += i2c-stub.o obj-$(CONFIG_I2C_SLAVE_EEPROM) += i2c-slave-eeprom.o obj-$(CONFIG_I2C_SLAVE_TESTUNIT) += i2c-slave-testunit.o +obj-$(CONFIG_I2C_TARGET_ARP) += i2c-target-arp.o ccflags-$(CONFIG_I2C_DEBUG_CORE) := -DDEBUG diff --git a/drivers/i2c/i2c-target-arp.c b/drivers/i2c/i2c-target-arp.c new file mode 100644 index 000000000000..458749e4681e --- /dev/null +++ b/drivers/i2c/i2c-target-arp.c @@ -0,0 +1,201 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * SMBus Address Resolution Protocol target mode test driver + * + * Copyright (C) 2026 Intel Corporation + */ +#include +#include +#include +#include +#include +#include +#include + +#define ARP_ADDRESS_VALID BIT(0) +#define ARP_ADDRESS_RESOLVED BIT(1) + +#define I2C_SMBUS_HOST 0x08 +#define I2C_SMBUS_DEFAULT_ADDR 0x61 + +#define ARP_CMD_PREPARE_TO_ARP 0x01 +#define ARP_CMD_RESET_DEVICE 0x02 +#define ARP_CMD_GET_UDID 0x03 +#define ARP_CMD_ASSIGN_ADDRESS 0x04 + +struct get_udid_data { + struct i2c_arp_udid udid; + u8 target_addr; +} __packed; + +struct arp_target { + struct i2c_client target; + struct i2c_client *client; + + int read_count; + int write_count; + unsigned char buf[24]; + + struct get_udid_data data; + unsigned char flag; +}; + +static u8 i2c_arp_pec(struct arp_target *arp, bool read) +{ + u8 addr = I2C_SMBUS_DEFAULT_ADDR << 1; + u8 len = sizeof(arp->data); + u8 pec = 0; + + pec = i2c_smbus_pec(pec, &addr, 1); + pec = i2c_smbus_pec(pec, arp->buf, arp->write_count); + + if (read) { + addr |= 1; + pec = i2c_smbus_pec(pec, &addr, 1); + pec = i2c_smbus_pec(pec, &len, 1); + pec = i2c_smbus_pec(pec, (void *)&arp->data, len); + } + + return pec; +} + +static int i2c_target_arp_cb(struct i2c_client *target, enum i2c_slave_event event, u8 *val) +{ + struct arp_target *arp = container_of(target, struct arp_target, target); + + switch (event) { + case I2C_SLAVE_READ_PROCESSED: + if (arp->flag) + break; + + if (arp->read_count == sizeof(arp->data)) + *val = i2c_arp_pec(arp, 1); + else + *val = ((u8 *)&arp->data)[arp->read_count]; + + arp->read_count++; + break; + case I2C_SLAVE_READ_REQUESTED: + if (arp->flag) + break; + + *val = sizeof(arp->data); + break; + case I2C_SLAVE_STOP: + switch (arp->buf[0]) { + case ARP_CMD_PREPARE_TO_ARP: + arp->flag = 0; + break; + case ARP_CMD_ASSIGN_ADDRESS: + /* If the UDID matches, this address is for us. */ + if (!memcmp(&arp->buf[2], &arp->data.udid, sizeof(arp->data.udid))) + arp->flag = ARP_ADDRESS_VALID | ARP_ADDRESS_RESOLVED; + break; + default: + break; + } + + arp->read_count = 0; + arp->write_count = 0; + break; + case I2C_SLAVE_WRITE_REQUESTED: + arp->read_count = 0; + arp->write_count = 0; + break; + case I2C_SLAVE_WRITE_RECEIVED: + arp->buf[arp->write_count] = *val; + arp->write_count++; + break; + } + + return 0; +} + +static void i2c_notify_arp_controller(struct i2c_client *client) +{ + union i2c_smbus_data data = { }; + int ret; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) + return; + + ret = i2c_smbus_xfer(client->adapter, I2C_SMBUS_HOST, client->flags, + I2C_SMBUS_WRITE, client->addr, + I2C_SMBUS_WORD_DATA, &data); + if (ret) + dev_warn(&client->dev, "Failed to Notify ARP Controller (%d)\n", ret); +} + +static int i2c_target_arp_probe(struct i2c_client *client) +{ + struct arp_target *arp; + int ret; + + arp = devm_kzalloc(&client->dev, sizeof(*arp), GFP_KERNEL); + if (!arp) + return -ENOMEM; + + arp->client = client; + i2c_set_clientdata(client, arp); + + arp->target = *client; + arp->target.addr = I2C_SMBUS_DEFAULT_ADDR; + arp->target.flags |= I2C_CLIENT_SLAVE; + + /* + * The vendor and device ID are left undefined. Some hosts may not + * support this. If that's the case, supply values for them. + * + * arp->data.udid.vendor = 0xXXXX; + * arp->data.udid.device = 0xXXXX; + * + * The capabilities are also 0. That makes this a fixed address device + * without support for PEC. + */ + arp->data.udid.version = BIT(3); /* UDID Version 1 */ + arp->data.udid.interface = SMBUS_INTERFACE_SMBUS_V2_0; + arp->data.target_addr = client->addr; + + /* + * NOTE: This target is only for the ARP. After the address has been + * assigned, another target should be registered for the actual device, + * but this test code does _not_ register it. + */ + ret = i2c_slave_register(&arp->target, i2c_target_arp_cb); + if (ret) + return ret; + + i2c_notify_arp_controller(client); + + return 0; +} + +static void i2c_target_arp_remove(struct i2c_client *client) +{ + struct arp_target *arp; + + if (IS_ERR_OR_NULL(client)) + return; + + arp = i2c_get_clientdata(client); + i2c_slave_unregister(&arp->target); +} + +static const struct i2c_device_id i2c_target_arp_id[] = { + { "target-arp" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, i2c_target_arp_id); + +static struct i2c_driver i2c_target_arp_driver = { + .driver = { + .name = "i2c-target-arp", + }, + .probe = i2c_target_arp_probe, + .remove = i2c_target_arp_remove, + .id_table = i2c_target_arp_id, +}; +module_i2c_driver(i2c_target_arp_driver); + +MODULE_DESCRIPTION("SMBus ARP target mode test driver"); +MODULE_LICENSE("GPL"); -- 2.50.1