{"id":2225725,"url":"http://patchwork.ozlabs.org/api/patches/2225725/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260421140755.54222-1-marex@nabladev.com/","project":{"id":35,"url":"http://patchwork.ozlabs.org/api/projects/35/?format=json","name":"Linux I2C development","link_name":"linux-i2c","list_id":"linux-i2c.vger.kernel.org","list_email":"linux-i2c@vger.kernel.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260421140755.54222-1-marex@nabladev.com>","list_archive_url":null,"date":"2026-04-21T14:06:49","name":"nvmem: core: eeprom: at24: Handle EEPROM with both read-only and wp-gpios","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"c69e05a74191239d3eafedee22ff0424f64a5424","submitter":{"id":91452,"url":"http://patchwork.ozlabs.org/api/people/91452/?format=json","name":"Marek Vasut","email":"marex@nabladev.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-i2c/patch/20260421140755.54222-1-marex@nabladev.com/mbox/","series":[{"id":500813,"url":"http://patchwork.ozlabs.org/api/series/500813/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-i2c/list/?series=500813","date":"2026-04-21T14:06:49","name":"nvmem: core: eeprom: at24: Handle EEPROM with both read-only and wp-gpios","version":1,"mbox":"http://patchwork.ozlabs.org/series/500813/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2225725/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2225725/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-i2c@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=nabladev.com header.i=@nabladev.com header.a=rsa-sha256\n header.s=dkim header.b=SKXpzINo;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c09:e001:a7::12fc:5321; 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c=relaxed/simple;\n\tbh=U3S/azcYtoK8lqyCMrjeJ/KYEZqdHpjzdHxJ59k4dfM=;\n\th=From:To:Cc:Subject:Date:Message-ID:MIME-Version;\n b=bTy2xQSItL8pwUlqY+fV2qaJkIXJcZu93yNvuvukwZxrz7Hps4o4A0PaaReCXg07oDczsnxdWS5qU0r02QBPYAytK+8zAycjIE6ddSz0nbCaddzb0msQShXGpP3VFfOiGKCAPPz50Dr+j99/xznFVD093BrGyEM6FFdkxcNgTws=","ARC-Authentication-Results":"i=1; smtp.subspace.kernel.org;\n dmarc=pass (p=reject dis=none) header.from=nabladev.com;\n spf=pass smtp.mailfrom=nabladev.com;\n dkim=pass (2048-bit key) header.d=nabladev.com header.i=@nabladev.com\n header.b=SKXpzINo; arc=none smtp.client-ip=178.251.229.89","DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=nabladev.com;\n\ts=dkim; t=1776780478; h=from:subject:date:message-id:to:cc:mime-version:\n\t content-transfer-encoding; bh=ONHip1GbFzvZ4cejM52KSuI+49tZZL0UydKXrafRDOQ=;\n\tb=SKXpzINoETov8u3ksehh8NnLGkKRkat+0/W/iCk6kpxpKqDThTVnyISyVYkZOvY3SBS8Pv\n\t3tyV/6VCbGZ2GKw5DC4TW1wPLX5N3OPVgIoWAhESfDaeC1fAunBSAK3Nde8vufCTbu7xLI\n\t/r8dF46xPERu2Cu6s/jU0JFCNYCUdMLXZHq0y5nq9th70APWZY52ZdEYUmhz/jq9aM3WBh\n\t+bKHpqXhCCsjI5wHuUq8MVlvxbFgup1CDI47hhBWr4T2Vvh8gmNLjbi/pc99vzX1hO7Gqh\n\tKIvYzBhDRA7CukSE1+hylC1wCtrTvYaPeolxWjh2v9wn0EHl9s7S2phgzmSOJg==","From":"Marek Vasut ","To":"linux-i2c@vger.kernel.org","Cc":"Marek Vasut ,\n\tArnd Bergmann ,\n\tBartosz Golaszewski ,\n\tGreg Kroah-Hartman ,\n\tSrinivas Kandagatla ,\n\tlinux-kernel@vger.kernel.org","Subject":"[PATCH] nvmem: core: eeprom: at24: Handle EEPROM with both read-only\n and wp-gpios","Date":"Tue, 21 Apr 2026 16:06:49 +0200","Message-ID":"<20260421140755.54222-1-marex@nabladev.com>","X-Mailer":"git-send-email 2.53.0","Precedence":"bulk","X-Mailing-List":"linux-i2c@vger.kernel.org","List-Id":"","List-Subscribe":"","List-Unsubscribe":"","MIME-Version":"1.0","Content-Transfer-Encoding":"8bit","X-Last-TLS-Session-Version":"TLSv1.3"},"content":"Handle special-case of AT24 EEPROM described in DT, which contains both\n\"read-only\" and \"wp-gpios\" properties. Interpret this configuration as\ndefault read-only, but with the possibility of unlock via force_ro sysfs\nattribute.\n\nFor this to work, the nvmem core must keep the \"nvmem\" sysfs bin attr as\nread-write, any writes into the bin attr which occur while the device is\nread-only are blocked in bin_attr_nvmem_write(). The AT24 EEPROM driver\nmust not mark the EEPROM as read-only if both \"read-only\" and \"wp-gpios\"\nDT properties are present.\n\nThe updated behavior can be tested as follows:\n\nCurrent content:\n\"\n$ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem\n00000000 66 6f 6f 0a ff ff ff ff\n\"\n\nWrite into default-read-only device:\n\"\n$ echo bar > /sys/bus/nvmem/devices/logging7/nvmem\nbash: echo: write error: Operation not permitted\n$ cat /sys/bus/nvmem/devices/logging7/force_ro\n1\n\"\n\nUnlock and write into device:\n\"\n$ echo 0 > /sys/bus/nvmem/devices/logging7/force_ro\n$ cat /sys/bus/nvmem/devices/logging7/force_ro\n0\n\n$ echo bar > /sys/bus/nvmem/devices/logging7/nvmem\n$ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem\n00000000 62 61 72 0a ff ff ff ff\n\"\n\nRelock and write into device, fails because device is read-only again:\n\"\n$ echo 1 > /sys/bus/nvmem/devices/logging7/force_ro\n$ echo baz > /sys/bus/nvmem/devices/logging7/nvmem\nbash: echo: write error: Operation not permitted\n\n$ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem\n00000000 62 61 72 0a ff ff ff ff\n\"\n\nSigned-off-by: Marek Vasut \n---\nCc: Arnd Bergmann \nCc: Bartosz Golaszewski \nCc: Greg Kroah-Hartman \nCc: Srinivas Kandagatla \nCc: linux-i2c@vger.kernel.org\nCc: linux-kernel@vger.kernel.org\n---\n drivers/misc/eeprom/at24.c | 3 ++-\n drivers/nvmem/core.c | 3 +++\n 2 files changed, 5 insertions(+), 1 deletion(-)","diff":"diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c\nindex 0200288d3a7ab..9ef00b0ce83d2 100644\n--- a/drivers/misc/eeprom/at24.c\n+++ b/drivers/misc/eeprom/at24.c\n@@ -627,7 +627,8 @@ static int at24_probe(struct i2c_client *client)\n \t\tpage_size = 1;\n \n \tflags = cdata->flags;\n-\tif (device_property_present(dev, \"read-only\"))\n+\tif (device_property_present(dev, \"read-only\") &&\n+\t !device_property_present(dev, \"wp-gpios\"))\n \t\tflags |= AT24_FLAG_READONLY;\n \tif (device_property_present(dev, \"no-read-rollover\"))\n \t\tflags |= AT24_FLAG_NO_RDROL;\ndiff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c\nindex 311cb2e5a5c02..c0eedfe8d706c 100644\n--- a/drivers/nvmem/core.c\n+++ b/drivers/nvmem/core.c\n@@ -282,6 +282,9 @@ static umode_t nvmem_bin_attr_get_umode(struct nvmem_device *nvmem)\n \tif (!nvmem->root_only)\n \t\tmode |= 0044;\n \n+\tif (nvmem->read_only && nvmem->reg_write)\n+\t\tmode |= 0200;\n+\n \tif (!nvmem->read_only)\n \t\tmode |= 0200;\n \n","prefixes":[]}