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 B3C12126C02; Sun, 26 Apr 2026 02:45:17 +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=1777171519; cv=none; b=dRuxRWhOmOlxcqN+ftiQ4BBxehf0WlntQQON1EKQuTq6rN1vxahbWQGQ5YCkNRuvh0AhoHOK6cdmkVP9ns7m7GfOrmUjCZT0DXM/63AzeGwiJwNsJBX8LQyzR7lrfqEVwBO4DkgVbb9g+21VnvFtPSdDCqCCw4vUmquyE7UDlDs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777171519; c=relaxed/simple; bh=P6vg/u8mtaOqDTc++MuUp6HgFqxSPaUF8GiwXM2ZEw0=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Kvoc7f+4/6CZsTTrtRFNO/75/oIKNR5v0SA2uCpz+8kCbhy++It0hc4tl7FIQFyfkyjQtxDkMeDIr4OCwQSRFMY95EZhVAQLXnXN+iLRxnc/0tj1XCeKS46m7mOl9xXl6vPkdN3gxk063lYB/iFvos9N9x4iosRE0OBUKFwmkSE= 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=gJk3nKDC; 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="gJk3nKDC" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 655AA114D3D; Sun, 26 Apr 2026 04:45:14 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nabladev.com; s=dkim; t=1777171515; h=from:subject:date:message-id:to:cc:mime-version: content-transfer-encoding; bh=OCw1cmmN/s4IqyAwm6S/ENA1IUWW4c1JPYW+MdOnM6w=; b=gJk3nKDC0OQ5FIOvLERMM5dIY8XkXJSsCGm5gd0ljl36aByaPr4oo0mmHtDs43ym+00OIN Svqcjo7LF696g3B9CLdQucNrmMtmoT3vxK3h3c2tYQto/ib1muGj5MUM0zjWPFTwn/yhu7 /o6GLXhvHZdLsgdRmy3ZXkgDFTjMPbjExmRDPO0EjxTTc8aYslugZNQieYED8kTLMnD/Ec J6LAh3T+cR7TsqMYm3SR6GraNJokNy1Yr0V/NXx3B9BA0VzqpB5WwugEUFQqCLxgQ9f1jT 5FtvRn+GZ7IUMumLrI5kUPU9Jj1G3w5pue4bWWx+ePHp01bFEQoAA+auh1u4dQ== From: Marek Vasut To: linux-i2c@vger.kernel.org Cc: Marek Vasut , Arnd Bergmann , Bartosz Golaszewski , Greg Kroah-Hartman , Srinivas Kandagatla , linux-kernel@vger.kernel.org Subject: [PATCH v2] nvmem: core: Default to read-only if wp-gpios present Date: Sun, 26 Apr 2026 04:44:32 +0200 Message-ID: <20260426024507.597480-1-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 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 " 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 --- drivers/nvmem/core.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index 311cb2e5a5c02..0b1942e389113 100644 --- a/drivers/nvmem/core.c +++ b/drivers/nvmem/core.c @@ -1019,6 +1019,12 @@ 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; + gpiod_set_value_cansleep(nvmem->wp_gpio, 1); + } + #ifdef CONFIG_NVMEM_SYSFS rval = nvmem_populate_sysfs_cells(nvmem); if (rval) -- 2.53.0