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Tue, 09 Jun 2026 00:53:23 -0700 (PDT) Received: from QCOM-eG0v1AUPpu.na.qualcomm.com ([2a01:e0a:830:450:cc96:22ae:323b:9eff]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-68e64303892sm8121631a12.0.2026.06.09.00.53.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jun 2026 00:53:23 -0700 (PDT) From: Loic Poulain Date: Tue, 09 Jun 2026 09:52:29 +0200 Subject: [PATCH v4 4/8] block: implement NVMEM provider Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260609-block-as-nvmem-v4-4-45712e6b22c6@oss.qualcomm.com> References: <20260609-block-as-nvmem-v4-0-45712e6b22c6@oss.qualcomm.com> In-Reply-To: <20260609-block-as-nvmem-v4-0-45712e6b22c6@oss.qualcomm.com> To: Ulf Hansson , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Bjorn Andersson , Konrad Dybcio , Jens Axboe , Johannes Berg , Jeff Johnson , Bartosz Golaszewski , Marcel Holtmann , Luiz Augusto von Dentz , Balakrishna Godavarthi , Rocky Liao , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , Srinivas Kandagatla , Andrew Lunn , Heiner Kallweit , Russell King , Saravana Kannan Cc: linux-mmc@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-block@vger.kernel.org, linux-wireless@vger.kernel.org, ath10k@lists.infradead.org, linux-bluetooth@vger.kernel.org, netdev@vger.kernel.org, daniel@makrotopia.org, Loic Poulain X-Mailer: b4 0.14.2 X-Proofpoint-GUID: AaTPul4zq1xBzi3az7sPvKGzVQWqsHzR X-Proofpoint-ORIG-GUID: AaTPul4zq1xBzi3az7sPvKGzVQWqsHzR X-Authority-Analysis: v=2.4 cv=dIaWXuZb c=1 sm=1 tr=0 ts=6a27c674 cx=c_pps a=JbAStetqSzwMeJznSMzCyw==:117 a=xqWC_Br6kY4A:10 a=IkcTkHD0fZMA:10 a=FelO9ux0wxsA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=gowsoOTTUOVcmtlkKump:22 a=VT4XjZGOAAAA:8 a=EUspDBNiAAAA:8 a=0xOXAJtWE3glxeOP_3AA:9 a=QEXdDO2ut3YA:10 a=uxP6HrT_eTzRwkO_Te1X:22 a=6CpsfURP9XNmmWg3j1mJ:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNjA5MDA3MyBTYWx0ZWRfXx7NXANJURPjg mSeyuE7KPnnbhiQQCDVAwiPZtACJefEaDIEcRqvOosnATIDTLr72qrgmuaLLp5zV7O+b9l41HvT TV4DMy/nEOddPKClbBM+WF1O332/Fcbtvs8hMXsFdFG6yXJd463xnbUrNuaShuQEoDALPGLMLLO OdukTjMYiGbGuj3hYYCLOCK/MYGTFdckqIc/7HTOlpM3EPuFDxneQyh//sNzkNYuhFbt2OR7dE4 5Bt1O43CvQOS+mJBdokOlAefsXveHHJv5In6a9I1qBcGmURfptJOVnikzhLONu/gofpnvIZpsqq 9XTBn15DCYcd4z8YppGDlAXiosC733cDqbj0gpPOv2haUYMepwUKWvy0ze/HU1iVQ0oSHy0qcQl Bm8BIXGNXq1B0soqNJj2czcYvZl0k7s886Jnn/hEgeN5mN5nJGXCyXCfWur53uppFm0Jq8r9dLL V2L+f4iTv7q0Of8SMPA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.125,FMLib:17.12.100.49 definitions=2026-06-09_01,2026-06-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 spamscore=0 malwarescore=0 priorityscore=1501 impostorscore=0 phishscore=0 adultscore=0 bulkscore=0 clxscore=1015 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2605210000 definitions=main-2606090073 From: Daniel Golle On embedded devices using an eMMC it is common that one or more partitions on the eMMC are used to store MAC addresses and Wi-Fi calibration EEPROM data. Allow referencing the partition in device tree for the kernel and Wi-Fi drivers accessing it via the NVMEM layer. Signed-off-by: Daniel Golle Co-developed-by: Loic Poulain Signed-off-by: Loic Poulain --- block/Kconfig | 9 +++++ block/Makefile | 1 + block/blk-nvmem.c | 114 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 124 insertions(+) diff --git a/block/Kconfig b/block/Kconfig index 15027963472d7b40e27b9097a5993c457b5b3054..0b33747e16dc33473683706f75c92bdf8b648f7c 100644 --- a/block/Kconfig +++ b/block/Kconfig @@ -209,6 +209,15 @@ config BLK_INLINE_ENCRYPTION_FALLBACK by falling back to the kernel crypto API when inline encryption hardware is not present. +config BLK_NVMEM + bool "Block device NVMEM provider" + depends on OF + depends on NVMEM + help + Allow block devices (or partitions) to act as NVMEM providers, + typically used with eMMC to store MAC addresses or Wi-Fi + calibration data on embedded devices. + source "block/partitions/Kconfig" config BLK_PM diff --git a/block/Makefile b/block/Makefile index 7dce2e44276c4274c11a0a61121c83d9c43d6e0c..d7ac389e71902bc091a8800ea266190a43b3e63d 100644 --- a/block/Makefile +++ b/block/Makefile @@ -36,3 +36,4 @@ obj-$(CONFIG_BLK_INLINE_ENCRYPTION) += blk-crypto.o blk-crypto-profile.o \ blk-crypto-sysfs.o obj-$(CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK) += blk-crypto-fallback.o obj-$(CONFIG_BLOCK_HOLDER_DEPRECATED) += holder.o +obj-$(CONFIG_BLK_NVMEM) += blk-nvmem.o diff --git a/block/blk-nvmem.c b/block/blk-nvmem.c new file mode 100644 index 0000000000000000000000000000000000000000..a6e62fa98675ee9bcb9c7035a611b5a573ab9091 --- /dev/null +++ b/block/blk-nvmem.c @@ -0,0 +1,114 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * block device NVMEM provider + * + * Copyright (c) 2024 Daniel Golle + * Copyright (c) Qualcomm Technologies, Inc. and/or its subsidiaries. + * + * Useful on devices using a partition on an eMMC for MAC addresses or + * Wi-Fi calibration EEPROM data. + */ + +#include +#include +#include +#include +#include +#include + +#include "blk.h" + +static int blk_nvmem_reg_read(void *priv, unsigned int from, + void *val, size_t bytes) +{ + blk_mode_t mode = BLK_OPEN_READ | BLK_OPEN_RESTRICT_WRITES; + dev_t devt = (dev_t)(uintptr_t)priv; + size_t bytes_left = bytes; + loff_t pos = from; + int ret = 0; + + struct file *bdev_file __free(fput) = bdev_file_open_by_dev(devt, mode, priv, NULL); + if (IS_ERR(bdev_file)) + return PTR_ERR(bdev_file); + + while (bytes_left) { + pgoff_t f_index = pos >> PAGE_SHIFT; + struct folio *folio; + size_t folio_off; + size_t to_read; + + folio = read_mapping_folio(bdev_file->f_mapping, f_index, NULL); + if (IS_ERR(folio)) { + ret = PTR_ERR(folio); + break; + } + + folio_off = offset_in_folio(folio, pos); + to_read = min(bytes_left, folio_size(folio) - folio_off); + memcpy_from_folio(val, folio, folio_off, to_read); + pos += to_read; + bytes_left -= to_read; + val += to_read; + folio_put(folio); + } + + return ret; +} + +static int blk_nvmem_register(struct device *dev) +{ + struct block_device *bdev = dev_to_bdev(dev); + struct nvmem_config config = {}; + + /* skip devices which do not have a device tree node */ + if (!dev_of_node(dev)) + return 0; + + /* skip devices without an nvmem layout defined */ + struct device_node *child __free(device_node) = + of_get_child_by_name(dev_of_node(dev), "nvmem-layout"); + if (!child) + return 0; + + /* + * skip block device too large to be represented as NVMEM devices, + * the NVMEM reg_read callback uses an unsigned int offset + */ + if (bdev_nr_bytes(bdev) > UINT_MAX) { + dev_warn(dev, "block device too large to be an NVMEM provider\n"); + return -ENODEV; + } + + config.id = NVMEM_DEVID_NONE; + config.dev = dev; + config.name = dev_name(dev); + config.owner = THIS_MODULE; + config.priv = (void *)(uintptr_t)dev->devt; + config.reg_read = blk_nvmem_reg_read; + config.size = bdev_nr_bytes(bdev); + config.word_size = 1; + config.stride = 1; + config.read_only = true; + config.root_only = true; + config.ignore_wp = true; + config.of_node = to_of_node(dev->fwnode); + + return PTR_ERR_OR_ZERO(devm_nvmem_register(dev, &config)); +} + +static struct class_interface blk_nvmem_bus_interface __refdata = { + .class = &block_class, + .add_dev = &blk_nvmem_register, +}; + +static int __init blk_nvmem_init(void) +{ + int ret; + + ret = class_interface_register(&blk_nvmem_bus_interface); + if (ret) + return ret; + + return 0; +} +device_initcall(blk_nvmem_init); -- 2.34.1