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diff --git a/Documentation/user/state.rst b/Documentation/user/state.rst new file mode 100644 index 0000000000..c401f105bd --- /dev/null +++ b/Documentation/user/state.rst @@ -0,0 +1,46 @@ +Barebox State Framework +======================= + +The state framework is build to exchange data between Barebox and Linux +userspace using a non-volatile storage. There are several components involved. +Barebox has a state driver to access the variables. For the Linux Userspace +there is a userspace tool. + +Devicetree +---------- + +Currently the devicetree defines the layout of the variables and data. +Variables are fixed size. Several types are supported, see the binding +documentation for details. + +Data Formats +------------ + +The state data can be stored in different ways. Currently two formats are +available, ``raw`` and ``dtb``. Both format the state data differently. +Basically these are serializers. The raw serializer additionally supports a +HMAC algorithm to detect manipulations. + +Storage Backends +---------------- + +The serialized data can be stored to different backends which are automatically +selected depending on the defined backend in the devicetree. Currently two +implementations exist, ``circular`` and ``direct``. ``circular`` writes the +data sequentially on the backend storage device. Each save is appended until +the storage area is full. It then erases the block and starts from offset 0. +``circular`` is used for MTD devices with erase functionality. ``direct`` +writes the data directly to the file without erasing. + +For all backends multiple copies are written to handle read errors. + +Commands +-------- + +The ``state`` command can be used to store and manipulate the state. Using +``state`` without argument lists you all available states with their name. +``devinfo STATE_NAME`` shows you all variables and their values. ``state -s`` +stores the state. + +Starting Barebox will automatically load the last written state. If loading the +state fails the defaults are used. |