On Sun, Jun 23, 2024 at 05:15:47AM +0200, Marek Vasut wrote: > Implement "force_ro" sysfs attribute to allow users to set read-write > devices as read-only and back to read-write from userspace. The choice > of the name is based on MMC core 'force_ro' attribute. > > This solves a situation where an AT24 I2C EEPROM with GPIO based nWP > signal may have to be occasionally updated. Such I2C EEPROM device is > usually set as read-only during most of the regular system operation, > but in case it has to be updated in a controlled manner, it could be > unlocked using this new "force_ro" sysfs attribute and then re-locked > again. > > The "read-only" DT property and config->read_only configuration is > respected and is used to set default state of the device, read-only > or read-write, for devices which do implement .reg_write function. > For devices which do not implement .reg_write function, the device > is unconditionally read-only and the "force_ro" attribute is not > visible. > > Signed-off-by: Marek Vasut <marex@xxxxxxx> > --- > Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx> > Cc: Arnd Bergmann <arnd@xxxxxxxx> > Cc: Bartosz Golaszewski <brgl@xxxxxxxx> > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> > Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxxx> > Cc: linux-i2c@xxxxxxxxxxxxxxx > --- > V2: - Document the force_ro attribute > - Use sysfs_emit() > --- > Documentation/ABI/stable/sysfs-bus-nvmem | 13 +++++++ > drivers/nvmem/core.c | 44 ++++++++++++++++++++++++ > drivers/nvmem/internals.h | 1 + > 3 files changed, 58 insertions(+) > > diff --git a/Documentation/ABI/stable/sysfs-bus-nvmem b/Documentation/ABI/stable/sysfs-bus-nvmem > index 0e3a8492a1082..c713c4e6cecb1 100644 > --- a/Documentation/ABI/stable/sysfs-bus-nvmem > +++ b/Documentation/ABI/stable/sysfs-bus-nvmem > @@ -1,3 +1,16 @@ > +What: /sys/bus/nvmem/devices/.../force_ro > +Date: June 2024 > +KernelVersion: 6.11 > +Contact: Marek Vasut <marex@xxxxxxx> > +Description: > + This read/write attribute allows users to set read-write > + devices as read-only and back to read-write from userspace. > + This can be used to unlock and relock write-protection of > + devices which are generally locked, except during sporadic > + programming operation. > + Note: This file is only present if CONFIG_NVMEM_SYSFS > + is enabled And what exactly are the values that can be read or written here? thanks, greg k-h
