From bd66bfb0bf20919b07681a589bb2aa3f22b191b9 Mon Sep 17 00:00:00 2001 From: Marek Vasut Date: Sat, 30 May 2026 21:53:22 +0100 Subject: [PATCH] nvmem: core: Default to read-only if wp-gpios present 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 Signed-off-by: Srinivas Kandagatla Link: https://patch.msgid.link/20260530205333.117458-4-srini@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/nvmem/core.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/nvmem/core.c b/drivers/nvmem/core.c index e871181751f3..6bcb90760bee 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)