From patchwork Wed Jul 26 15:08:49 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhang Xiaoxu X-Patchwork-Id: 708252 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 21399C001E0 for ; Wed, 26 Jul 2023 07:14:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232167AbjGZHOm (ORCPT ); Wed, 26 Jul 2023 03:14:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48582 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232141AbjGZHON (ORCPT ); Wed, 26 Jul 2023 03:14:13 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 521542705; Wed, 26 Jul 2023 00:10:32 -0700 (PDT) Received: from dggpeml100024.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4R9lPN2n6pzVk3X; Wed, 26 Jul 2023 15:08:56 +0800 (CST) Received: from china (10.175.101.107) by dggpeml100024.china.huawei.com (7.185.36.115) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Wed, 26 Jul 2023 15:10:29 +0800 From: Zhang Xiaoxu To: , , , CC: , , , Subject: [PATCH v2 -next 3/3] spi: mockup: Add documentation Date: Wed, 26 Jul 2023 15:08:49 +0000 Message-ID: <20230726150849.28407-4-zhangxiaoxu5@huawei.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230726150849.28407-1-zhangxiaoxu5@huawei.com> References: <20230726150849.28407-1-zhangxiaoxu5@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.175.101.107] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpeml100024.china.huawei.com (7.185.36.115) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org From: Wei Yongjun Add documentation for the SPI mockup controller driver. This include the tutorial for how to mockup a api device. Signed-off-by: Wei Yongjun Signed-off-by: Zhang Xiaoxu --- Documentation/spi/index.rst | 1 + Documentation/spi/spi-mockup.rst | 174 +++++++++++++++++++++++++++++++ 2 files changed, 175 insertions(+) create mode 100644 Documentation/spi/spi-mockup.rst diff --git a/Documentation/spi/index.rst b/Documentation/spi/index.rst index 06c34ea11bcf..a8f4f5cd0f09 100644 --- a/Documentation/spi/index.rst +++ b/Documentation/spi/index.rst @@ -13,6 +13,7 @@ Serial Peripheral Interface (SPI) pxa2xx spi-lm70llp spi-sc18is602 + spi-mockup .. only:: subproject and html diff --git a/Documentation/spi/spi-mockup.rst b/Documentation/spi/spi-mockup.rst new file mode 100644 index 000000000000..5e720de19991 --- /dev/null +++ b/Documentation/spi/spi-mockup.rst @@ -0,0 +1,174 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========== +spi-mockup +========== + +Description +=========== + +This module is a very simple fake SPI controller driver. It implements +a BPF based interface to mockup SPI device. + +No hardware is needed nor associated with this module. It will respond +spi message by BPF program attached to spi_transfer_writeable tracepoint +by reading from or writing BPF maps. + +The typical use-case is like this: + 1. load EBPF program as device's backend + 2. create target chip device + +Example +======= + +This example show how to mock a MTD device by using spi-mockup driver. + +Compile your copy of the kernel source. Make sure to configure the spi-mockup +and the target chip driver as a module. + +Write a BPF program as device's backup. + +:: + + #define MCHP23K256_CMD_WRITE_STATUS 0x01 + #define MCHP23K256_CMD_WRITE 0x02 + #define MCHP23K256_CMD_READ 0x03 + + #define CHIP_REGS_SIZE 0x20000 + + #define MAX_CMD_SIZE 4 + + struct { + __uint(type, BPF_MAP_TYPE_ARRAY); + __uint(max_entries, CHIP_REGS_SIZE); + __type(key, __u32); + __type(value, __u8); + } regs_mchp23k256 SEC(".maps"); + + static unsigned int chip_reg = 0; + + static int spi_transfer_read(struct spi_msg_ctx *msg, unsigned int len) + { + int i, key; + u8 *reg; + + for (i = 0; i < len && i < sizeof(msg->data); i++) { + key = i + chip_reg; + + reg = bpf_map_lookup_elem(®s_mchp23k256, &key); + if (!reg) { + bpf_printk("key %d not exists", key); + return -EINVAL; + } + + msg->data[i] = *reg; + } + + return 0; + } + + static int spi_transfer_write(struct spi_msg_ctx *msg, unsigned int len) + { + u8 opcode = msg->data[0], value; + int i, key; + + switch (opcode) { + case MCHP23K256_CMD_READ: + case MCHP23K256_CMD_WRITE: + if (len < 2) + return -EINVAL; + + chip_reg = 0; + for (i = 0; i < MAX_CMD_SIZE && i < len - 1; i++) + chip_reg = (chip_reg << 8) + msg->data[1 + i]; + + return 0; + case MCHP23K256_CMD_WRITE_STATUS: + // ignore write status + return 0; + default: + break; + } + + for (i = 0; i < len && i < sizeof(msg->data); i++) { + value = msg->data[i]; + key = chip_reg + i; + + if (bpf_map_update_elem(®s_mchp23k256, &key, &value, + BPF_EXIST)) { + bpf_printk("key %d not exists", key); + return -EINVAL; + } + } + + return 0; + } + + SEC("raw_tp.w/spi_transfer_writeable") + int BPF_PROG(mtd_mchp23k256, struct spi_msg_ctx *msg, u8 chip, unsigned int len) + { + int ret = 0; + + if (msg->tx_nbits) + ret = spi_transfer_write(msg, len); + else if (msg->rx_nbits) + ret = spi_transfer_read(msg, len); + + return ret; + } + + char LICENSE[] SEC("license") = "GPL"; + +Use bpftool to load the BPF program. + +:: + + bpftool prog load mtd-mchp23k256.o /sys/fs/bpf/mtd_mchp23k256 autoattach + + +This is accomplished by executing the following command: + +:: + + $ echo mchp23k256 0 > /sys/class/spi_master/spi0/new_device + + +The name of the target driver and its chip select were used to instantiate +the device. + +Now, the mchp23k256 MTD device named /dev/mtd0 has been created successfully. + +:: + + $ ls /sys/bus/spi/devices/spi0.0/mtd/ + mtd0 mtd0ro + + $ cat /sys/class/mtd/mtd0/name + spi0.0 + + $ hexdump /dev/mtd0 + 0000000 0000 0000 0000 0000 0000 0000 0000 0000 + * + 0008000 + + $echo aaaa > /dev/mtd0 + + $ hexdump /dev/mtd0 + 0000000 6161 6161 000a 0000 0000 0000 0000 0000 + 0000010 0000 0000 0000 0000 0000 0000 0000 0000 + * + 0008000 + + $ bpftool map update name regs_mchp23k256 key 0 0 0 0 value 0 + + $ hexdump /dev/mtd0 + 0000000 6100 6161 000a 0000 0000 0000 0000 0000 + 0000010 0000 0000 0000 0000 0000 0000 0000 0000 + * + 0008000 + +Remove the mockup device by executing the following command: + +:: + + $echo 0 > /sys/class/spi_master/spi0/delete_device