From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx.nabladev.com (mx.nabladev.com [178.251.229.89]) (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 CF3E7423A61; Fri, 8 May 2026 17:00:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.251.229.89 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778259642; cv=none; b=fpKRD5Qyu68NmryGu2Y6Lt1UohIinH2aR3NAzf4gll79xySUQi2ZW/yTXKUdLjDB2yQjmZ/9ZBOSMO7nXOeKeCswZDois21fKrLznY9jb0NNGi8XqRtUmR+6wthemx+rMEro0sqI8jNkSl97Y5vvTWHfi3ma4mwkwJVmcjeq814= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778259642; c=relaxed/simple; bh=6GWnrhPtCt8z+xja1vhQtIKnmHl+KDzASgdjiNRokls=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=N3CX6WAomv7Q2Hsp8mwR5UjMt6A7vHwVg0aMwmXln4k0EsAXOjXG55Ui7eHOeUOMBTSy8HydnfYt/PWIWq2BdwEM0RwaL/JmD9a4dkPaHHz3+bxqF0cB/Y/zQxIhxiwV4Jwh+EajptzReaTu95m37nqF8bUQQtzihuHVOKag1XQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nabladev.com; spf=pass smtp.mailfrom=nabladev.com; dkim=pass (2048-bit key) header.d=nabladev.com header.i=@nabladev.com header.b=h5toUFH5; arc=none smtp.client-ip=178.251.229.89 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nabladev.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=nabladev.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=nabladev.com header.i=@nabladev.com header.b="h5toUFH5" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id E1D4D11246D; Fri, 8 May 2026 19:00:33 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nabladev.com; s=dkim; t=1778259636; h=from:subject:date:message-id:to:cc:mime-version: content-transfer-encoding; bh=liaZ+ZDZEG4iFeXBJPKtXIAuHGGnhSNYt+fPUomNifE=; b=h5toUFH54koOrtaVvDI3YdPOMz+X/PdrETp+jdUI+kuukzTyRQvg7yXazolARljycw6/TR 8rQ5XtL9y31LeEqSEtqyaJ20ui7xOEHser4a1fhlhC7pX2waq6GFWJNu3Po5Kc3zNYHP/w S+OoYisBggFbLqS1/9NhRdRkvSGf7FnVAVhAxkw7bn6CswBZcF7TtxyKzAL4o63H+4LP62 USH7Idlyn4MaAM0ZTgKIiJaDiV7yUzQ5SQKIF4F1QK1vy6SLUDk9k3ZdU9YWw28DiArdca XoHVlXK406fV6i9lfklARSRWLa0wGd33L86PPb0L6q9962PqQOcWHS7DC5sLgw== From: Marek Vasut To: linux-i2c@vger.kernel.org Cc: Marek Vasut , Bartosz Golaszewski , Arnd Bergmann , Bartosz Golaszewski , Greg Kroah-Hartman , Srinivas Kandagatla , linux-kernel@vger.kernel.org Subject: [PATCH v4] nvmem: core: Default to read-only if wp-gpios present Date: Fri, 8 May 2026 19:00:20 +0200 Message-ID: <20260508170032.560650-1-marex@nabladev.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Last-TLS-Session-Version: TLSv1.3 In case the nvmem DT node contains "wp-gpios" DT property, the device currently defaults to read-write and the force_ro sysfs attribute reads 0. Switch to the default read-only, which is both safer, and aligned with eMMC HW BOOT partition force_ro sysfs attribute behavior, which also defaults to read-only. The adjustment of nvmem->read_only value to read-only in case wp-gpios DT property is present must be done only after the device_add() got called because device_add() does internally call nvmem_bin_attr_get_umode(), which configures the permissions of 'nvmem' bin attr based on the value of nvmem->read_only that is only parsed from DT property 'read-only', without any adjustment. This way, if DT property 'read-only' is present, the 'nvmem' attribute is always read-only. Otherwise, if the device is writeable, then 'nvmem' attribute is writeable, and nvmem->read_only defaults to read-only, but can be switched to read-write at runtime via the 'force_ro' attribute. The updated behavior can be tested as follows: Current content: " $ cat /sys/bus/nvmem/devices/logging7/force_ro 1 $ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem 00000000 66 6f 6f 0a ff ff ff ff " Write into default-read-only device: " $ echo bar > /sys/bus/nvmem/devices/logging7/nvmem bash: echo: write error: Operation not permitted $ cat /sys/bus/nvmem/devices/logging7/force_ro 1 " Unlock and write into device: " $ echo 0 > /sys/bus/nvmem/devices/logging7/force_ro $ cat /sys/bus/nvmem/devices/logging7/force_ro 0 $ echo bar > /sys/bus/nvmem/devices/logging7/nvmem $ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem 00000000 62 61 72 0a ff ff ff ff " Relock and write into device, fails because device is read-only again: " $ echo 1 > /sys/bus/nvmem/devices/logging7/force_ro $ echo baz > /sys/bus/nvmem/devices/logging7/nvmem bash: echo: write error: Operation not permitted $ hexdump -C /sys/bus/nvmem/devices/logging7/nvmem 00000000 62 61 72 0a ff ff ff ff " Reviewed-by: Bartosz Golaszewski Signed-off-by: Marek Vasut --- Cc: Arnd Bergmann Cc: Bartosz Golaszewski Cc: Greg Kroah-Hartman Cc: Srinivas Kandagatla Cc: linux-i2c@vger.kernel.org Cc: linux-kernel@vger.kernel.org --- V2: Simplify the implementation, make devices with wp-gpios default to read-only and let users unlock those devices via force_ro sysfs attribute, just like eMMC HW BOOT partitions V3: Drop unnecessary gpiod_set_value_cansleep() V4: Add RB from Bartosz --- drivers/nvmem/core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index 311cb2e5a5c02..be28a366f6031 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -1019,6 +1019,10 @@ struct nvmem_device *nvmem_register(const struct nvmem_config *config) if (rval) goto err_remove_dev; + /* If the device has WP GPIO, default to read-only */ + if (nvmem->wp_gpio) + nvmem->read_only = true; + #ifdef CONFIG_NVMEM_SYSFS rval = nvmem_populate_sysfs_cells(nvmem); if (rval) -- 2.53.0