Custom Kconfig Preprocessor Functions

Kconfiglib supports custom Kconfig preprocessor functions written in Python. These functions are defined in scripts/kconfig/kconfigfunctions.py.

Note

The official Kconfig preprocessor documentation can be found here.

Most of the custom preprocessor functions are used to get devicetree information into Kconfig. For example, the default value of a Kconfig symbol can be fetched from a devicetree reg property.

Devicetree-related Functions

The functions listed below are used to get devicetree information into Kconfig. See the Python docstrings in scripts/kconfig/kconfigfunctions.py for detailed documentation.

The *_int version of each function returns the value as a decimal integer, while the *_hex version returns a hexadecimal value starting with 0x.

$(dt_chosen_reg_addr_int,<property in /chosen>[,<index>,<unit>])
$(dt_chosen_reg_addr_hex,<property in /chosen>[,<index>,<unit>])
$(dt_chosen_reg_size_int,<property in /chosen>[,<index>,<unit>])
$(dt_chosen_reg_size_hex,<property in /chosen>[,<index>,<unit>])
$(dt_node_reg_addr_int,<node path>[,<index>,<unit>])
$(dt_node_reg_addr_hex,<node path>[,<index>,<unit>])
$(dt_node_reg_size_int,<node path>[,<index>,<unit>])
$(dt_node_reg_size_hex,<node path>[,<index>,<unit>])
$(dt_compat_enabled,<compatible string>)
$(dt_chosen_enabled,<property in /chosen>)
$(dt_node_has_bool_prop,<node path>,<prop>)
$(dt_node_has_prop,<node path>,<prop>)

Example Usage

Assume that the devicetree for some board looks like this:

{
     soc {
             #address-cells = <1>;
             #size-cells = <1>;

             spi0: spi@10014000 {
                     compatible = "sifive,spi0";
                     reg = <0x10014000 0x1000 0x20010000 0x3c0900>;
                     reg-names = "control", "mem";
                     ...
             };
};

The second entry in reg in spi@1001400 (<0x20010000 0x3c0900>) corresponds to mem, and has the address 0x20010000. This address can be inserted into Kconfig as follows:

config FLASH_BASE_ADDRESS
     default $(dt_node_reg_addr_hex,/soc/spi@1001400,1)

After preprocessor expansion, this turns into the definition below:

config FLASH_BASE_ADDRESS
     default 0x20010000