From nobody Sun Feb 8 17:36:18 2026 Received: from mgamail.intel.com (mgamail.intel.com [192.198.163.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4981D47B42C; Wed, 21 Jan 2026 09:23:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=192.198.163.16 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768987423; cv=none; b=C1qvf7xPjSZPihBhX/NEyNXWQAQtFsnqHb2REtjJUKq0jAZbR+9pdVgFjp28JOv9KnFQVDOqSYlYXboDGxRe3fB+Rg1Sh9hy0ovdG2G5HR4ibfuUVDHHz4yHN9Dd41QyPSodEf+ho9JPjpqZ9IsmDN8huAVUGLKYD6PaJPsTglQ= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768987423; c=relaxed/simple; bh=xNWCmW31pGZmF7lTIVjzCHLl1hqt60gUK/dvIqhGBIo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=p8zzN4Prbj+yATyB0T+RSUH63qmOLdEjGVagBtjw9RBHHV9ssAnOnBsRrRgmIpfxVe6Y1bMlbU6dNJRRKDV1EHYonWtYZsf06V4tzrJLtHQAB6Xf0lZUwBZzIU7dUYz6wbbqMihJT9ere4VL7CzxyTYl3uQDCSKjor62Ywy+NsQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=linux.intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=LtCcDuK7; arc=none smtp.client-ip=192.198.163.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="LtCcDuK7" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1768987421; x=1800523421; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=xNWCmW31pGZmF7lTIVjzCHLl1hqt60gUK/dvIqhGBIo=; b=LtCcDuK7a7b2sva9u5w7oVRCcJxEx0fCqr3RF/8RFhgF3yguDoHqkqda WzGKVnau6kXCaNIgv/viBnq8/KzRGyegCulb1NHCATQheHtxyaBDpTDlb PU/6w6wuesXexZaLDTUP/4sjqMAjzzot8N5un3A1ZGvwPBU+EDl+k2F2K XSiiyshzgYQxbjzlyXXYYnF5Wf7NtvRzxdfSkBJKJ1qUPcKKuT/AQqAAx oqceeCm3C9LkvQgZpAGMTS2Rxz7uHjcyT9pIY3YtyhYizo/7C6S1rSeuM tXQSvtZAv27Ek/k3utSuj5Y5uey6th1w2KTDUJ+C5jeBBtwJcRXiBGt28 Q==; X-CSE-ConnectionGUID: V6LQ2jrXQAyJ7yExUbJj/A== X-CSE-MsgGUID: U0s324AETJetjDpFoIXXqw== X-IronPort-AV: E=McAfee;i="6800,10657,11677"; a="57773286" X-IronPort-AV: E=Sophos;i="6.21,242,1763452800"; d="scan'208";a="57773286" Received: from orviesa003.jf.intel.com ([10.64.159.143]) by fmvoesa110.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 21 Jan 2026 01:23:40 -0800 X-CSE-ConnectionGUID: Ydd0iDNfTzmreqfJY5KpAg== X-CSE-MsgGUID: MLLY5h18S8W26brRs1IpWg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.21,242,1763452800"; d="scan'208";a="210561009" Received: from black.igk.intel.com ([10.91.253.5]) by orviesa003.jf.intel.com with ESMTP; 21 Jan 2026 01:23:39 -0800 From: Heikki Krogerus To: Wolfram Sang Cc: Jeremy Kerr , Matt Johnston , linux-i2c@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 4/4] i2c: Add SMBus ARP target mode test driver Date: Wed, 21 Jan 2026 10:23:28 +0100 Message-ID: <20260121092328.2308705-5-heikki.krogerus@linux.intel.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260121092328.2308705-1-heikki.krogerus@linux.intel.com> References: <20260121092328.2308705-1-heikki.krogerus@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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. =20 +config I2C_TARGET_ARP + tristate "SMBus ARP target mode test driver" + help + This backend makes Linux respond to SMBus Address Resolution Protocol + commands. + endif =20 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 +=3D algos/ busses/ muxes/ obj-$(CONFIG_I2C_STUB) +=3D i2c-stub.o obj-$(CONFIG_I2C_SLAVE_EEPROM) +=3D i2c-slave-eeprom.o obj-$(CONFIG_I2C_SLAVE_TESTUNIT) +=3D i2c-slave-testunit.o +obj-$(CONFIG_I2C_TARGET_ARP) +=3D i2c-target-arp.o =20 ccflags-$(CONFIG_I2C_DEBUG_CORE) :=3D -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 =3D I2C_SMBUS_DEFAULT_ADDR << 1; + u8 len =3D sizeof(arp->data); + u8 pec =3D 0; + + pec =3D i2c_smbus_pec(pec, &addr, 1); + pec =3D i2c_smbus_pec(pec, arp->buf, arp->write_count); + + if (read) { + addr |=3D 1; + pec =3D i2c_smbus_pec(pec, &addr, 1); + pec =3D i2c_smbus_pec(pec, &len, 1); + pec =3D i2c_smbus_pec(pec, (void *)&arp->data, len); + } + + return pec; +} + +static int i2c_target_arp_cb(struct i2c_client *target, enum i2c_slave_eve= nt event, u8 *val) +{ + struct arp_target *arp =3D container_of(target, struct arp_target, target= ); + + switch (event) { + case I2C_SLAVE_READ_PROCESSED: + if (arp->flag) + break; + + if (arp->read_count =3D=3D sizeof(arp->data)) + *val =3D i2c_arp_pec(arp, 1); + else + *val =3D ((u8 *)&arp->data)[arp->read_count]; + + arp->read_count++; + break; + case I2C_SLAVE_READ_REQUESTED: + if (arp->flag) + break; + + *val =3D sizeof(arp->data); + break; + case I2C_SLAVE_STOP: + switch (arp->buf[0]) { + case ARP_CMD_PREPARE_TO_ARP: + arp->flag =3D 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 =3D ARP_ADDRESS_VALID | ARP_ADDRESS_RESOLVED; + break; + default: + break; + } + + arp->read_count =3D 0; + arp->write_count =3D 0; + break; + case I2C_SLAVE_WRITE_REQUESTED: + arp->read_count =3D 0; + arp->write_count =3D 0; + break; + case I2C_SLAVE_WRITE_RECEIVED: + arp->buf[arp->write_count] =3D *val; + arp->write_count++; + break; + } + + return 0; +} + +static void i2c_notify_arp_controller(struct i2c_client *client) +{ + union i2c_smbus_data data =3D { }; + int ret; + + if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA)) + return; + + ret =3D 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 =3D devm_kzalloc(&client->dev, sizeof(*arp), GFP_KERNEL); + if (!arp) + return -ENOMEM; + + arp->client =3D client; + i2c_set_clientdata(client, arp); + + arp->target =3D *client; + arp->target.addr =3D I2C_SMBUS_DEFAULT_ADDR; + arp->target.flags |=3D 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 =3D 0xXXXX; + * arp->data.udid.device =3D 0xXXXX; + * + * The capabilities are also 0. That makes this a fixed address device + * without support for PEC. + */ + arp->data.udid.version =3D BIT(3); /* UDID Version 1 */ + arp->data.udid.interface =3D SMBUS_INTERFACE_SMBUS_V2_0; + arp->data.target_addr =3D 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 =3D 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 =3D i2c_get_clientdata(client); + i2c_slave_unregister(&arp->target); +} + +static const struct i2c_device_id i2c_target_arp_id[] =3D { + { "target-arp" }, + { } +}; +MODULE_DEVICE_TABLE(i2c, i2c_target_arp_id); + +static struct i2c_driver i2c_target_arp_driver =3D { + .driver =3D { + .name =3D "i2c-target-arp", + }, + .probe =3D i2c_target_arp_probe, + .remove =3D i2c_target_arp_remove, + .id_table =3D i2c_target_arp_id, +}; +module_i2c_driver(i2c_target_arp_driver); + +MODULE_DESCRIPTION("SMBus ARP target mode test driver"); +MODULE_LICENSE("GPL"); --=20 2.50.1